CN1581976A - Video Compression Bit Rate Control Device for Fixed Image Quality - Google Patents

Abstract

The invention relates to a video compression bit rate control device with fixed image quality. According to the invention, the total activity of the current frame to be coded in a group of continuous frames is calculated, then the complexity of the current frame is estimated based on the total activity and the ratio of the activity to the complexity of the previously coded frames of the same type in the group of continuous frames, and the instantaneous complexity of the group of continuous frames is updated and the instantaneous bit rate is calculated according to the complexity, the instantaneous complexity and the instantaneous bit rate of the group of continuous frames, and the target bit limit is allocated to the current frame according to the complexity of the frame, the instantaneous complexity and the instantaneous bit rate of the group of continuous frames. After the picture is coded, the ratio of the activity to the complexity is calculated based on the total activity of the current picture, the actual number of bits consumed and the average of the actual quantization levels used.

Description

Video Compression Bit Rate Control Device for Fixed Image Quality

technical field

The present invention relates to the field of data compression, in particular to a device suitable for video coding system to implement variable bit rate control.

Background technique

As we all know, the electronic communication world is undergoing a digital revolution. The main advantage of representing information digitally is the data bit stream (bitstream) that can be stored, reproduced, transmitted, processed and utilized almost without error. For example, NTSC color video images have 29.97 frames per second, and each frame has about 480 visible scan lines, and each scan line requires about 480 pixels in red, green, and blue colors. , but if each color component is encoded in 8 bits, the resulting bit rate (bitrate) is about 168 megabits per second (Mbits/s), so the uncompressed bit rate of various video formats is very High and uneconomical, and therefore unsuitable for most applications.

The integration of digital audio and video with computers, telecommunication networks, and consumer products has further stimulated the progress of the information revolution, and the core of this revolution is the digital compression technology of audio and video. Many compression standards include algorithms based on the common essence of compression technology, such as: ITU-T (formerly CCITT) recommendations H.261 and H.263, and ISO/IEC MPEG-1, MPEG-2 and MPEG-4 standard. The MPEG algorithm was developed by the Moving Picture Experts Group (MPEG), which is a joint effort of the International Standards Organization (ISO) and the International Electrotechnical Commission (IEC). The Joint Technical Committee is committed to the development of video and audio compression and multi-channel transmission. These standards specify the syntax (syntax) and decoding method of the compressed bit stream, but for the algorithm used by the encoder, However, considerable degrees of freedom are reserved for coding novelty and diversity.

According to MPEG, a series of video pictures (pictures) are divided into a sequence of picture groups (group of picture, GOP), wherein each group of GOP starts with I-picture, followed by the arrangement of P-picture and B-picture, as shown in Figure 1 The sequence of shows a typical set of GOPs. The encoding of I-pictures does not need to refer to previous or future pictures. P-pictures are coded with reference to the closest I-picture or P-picture in time in a series of video pictures, and B-pictures are interspersed with I-pictures. and between P-pictures. And coded with immediately adjacent I-pictures and P-pictures, previous, future, or both. Although several B-pictures can appear in succession, B-pictures should never predict other pictures.

Each picture has three components: luminance value (luminance, represented by Y), red color difference (red color difference, represented by Cr), and blue color difference (blue color difference, represented by Cb). For the MPEG 4:2:0 format, the sampling points of each Cr and Cb component are only half of the Y component in the horizontal and vertical directions. Please refer to FIG. 2 , the basic building block of an MPEG picture is a macroblock (expressed in MB). Taking 4:2:0 video as an example, each MB contains an array of 16×16 sampling points for the Y component, and two blocks of 8×8 sampling points for the Cr and Cb components, of which the Y component is 16×16 sampling points The array of is actually composed of four blocks of 8×8 sampling points.

The role of the encoder is to determine which picture coding type and which prediction mode is the best. For each I-picture, each 8×8 block in the MB is subjected to discrete cosine transform (discrete cosine transform, DCT) to form an 8×8 transformation coefficient array, and the transformation coefficient is then quantized with a quantization matrix, and then zigzag (zig-zag) scans the quantized result of the DCT coefficients to obtain a series of DCT coefficients, and the DCT coefficient sequence is coded with a variable length code (variable length code, VLC). A P-picture must decide whether to encode each MB as an I-type MB or a P-type MB. The encoding of the I-type MB is performed in the above-mentioned way, and for each P-type MB, it is necessary to obtain the MB that was done in the previous picture. Prediction, this prediction is obtained by a motion vector (motion vector), the motion vector symbolizes the change between the MB to be coded in the current picture and the estimated MB in the previous picture, and the difference between the estimated MB and the current MB Prediction errors are coded in DCT, quantization, zigzag and VLC.

When processing B-pictures, one must decide in which of the following MB modes to encode each MB: I mode, F mode, B mode, and FB mode. I mode is coded by MB itself without motion compensation (like I-type MB); F-mode is unidirectional forward predictive coding, which is estimated by motion compensation from the previous picture (like P-type MB); On the contrary, the B mode is unidirectional backward predictive coding, which is to obtain motion-compensated estimation of the subsequent pictures. In particular, the FB mode is bi-directional predictive coding, using both the forward and backward motion compensation estimates for interpolation to obtain the motion compensation estimates of the FB mode. For F, B and FB modes, the prediction error can be coded using DCT, quantization, zigzag and VLC.

A video encoder must choose a quantization level for an entire frame in order to control visible artifacts at a given bit rate. However, the actual number of bits used to encode a frame at the chosen quantization level must It will be learned later that there is no inversion function in reality, which can determine in advance the actual number of bits used by a picture given the desired quantization level. A very important point of the encoder is the bit rate control. An important video encoder limitation in MPEG: the limitation of the number of bits used for each picture, especially in the case of fixed bit rate operation, this limitation is verified by Video Buffer Verifier (VBV) implement. If the input data rate of VBV is the same for each frame, the video can be said to be encoded with a constant bit rate (Constant Bitrate, CBR); otherwise, it is encoded with a variable bit rate (VBR). VBV is a virtual buffer and is a model of the input buffer at the decoder, the amount of bits allocated by the encoder to a picture at a fixed bit rate such that the VBV buffer does not overflow or starve; and For variable bit rates, the encoded bit stream enters the VBV buffer at a specified maximum bit rate until it saturates until no more bits are input, which can be interpreted as the number of bits entering the VBV buffer The rate is actually variable and can reach the maximum bit rate mentioned above. In terms of variable bit rate, it is only necessary to prevent VBV starvation.

The purpose of variable bit rate control is to improve the quality of the decoded video as much as possible while maintaining the output bit rate within the allowable range. Different from the method of fixed bit rate, the variable bit rate has greater flexibility to allocate extra bits to pictures with more complex scenes and more dramatic changes. This flexibility can make the reconstructed pictures evenly consistent , smooth and stable visual quality. For some applications, such as digital cinema, stable picture quality is the first consideration, which is better than other fixed bandwidth requirements. Such applications should use the bit rate control mechanism with variable bit rate and fixed image quality. . However, the traditional bit rate control method is quite complicated, and it usually takes several times to complete the video encoding process.

It can be seen that the above-mentioned existing video bit rate control device still has many defects, and further improvement is urgently needed.

In order to solve the problems existing in the video bit rate control device, a novel constant image quality bit rate control technology is developed, which can be used in a single-shot, real-time video encoder, and at the same time can provide a suitable for implementation in integrated circuits, with a picture Manufacturers of hierarchical-based fixed image quality bit rate control devices have tried their best to find a solution, but no suitable design has been developed for a long time, and there is no suitable structure for general products to solve the above problems , this is obviously a problem that relevant industry players are eager to solve.

In view of the defects existing in the above-mentioned existing video bit rate control device, the inventor actively researches and innovates based on rich practical experience and professional knowledge. After continuous research, design, and repeated trial production of samples and improvements, Finally create the present invention that really has practical value.

Contents of the invention

The main purpose of the present invention is to overcome the defects of the above-mentioned existing video bit rate control device, and provide a video compression bit rate control device with a new structure. The main technical problem to be solved is to make each picture The allocation of the target bits is based on the encoding result of the previous picture and the pre-analyzed activity of the current picture to be encoded. Through the analysis of the pre-analyzed activity of the current picture and the actual complexity of the previous encoded picture, By estimating the complexity of the current frame, the target bit quota can be allocated to each frame more accurately, so as to achieve stable visual quality between different frames in the video sequence.

The purpose of the present invention and the solution to its main technical problems are achieved by adopting the following technical solutions. According to the present invention, a fixed image quality video compression bit rate control device includes at least one motion estimation unit, which receives a current frame to be encoded in a group of continuous frames in a video sequence, to calculate the current frame a total activity of the picture; a complexity estimator for estimating the current picture based on the total activity of the current picture and the ratio of activity to complexity of previously coded pictures of the same type in the group of consecutive pictures a complexity of a target bit allocator, updating the instantaneous complexity of the group of continuous pictures with the complexity of the current picture, and based on a predetermined reference bit rate, a reference complexity and The instantaneous complexity is used to calculate the instantaneous bit rate of the group of continuous pictures, and according to the complexity of the current picture, the instantaneous complexity of the group of continuous pictures and the instantaneous bit rate, a target bit quota is allocated to The current picture; and a parameter updater, which calculates the activity of the current picture according to the total activity amount of the current picture, an actual consumed bit number of the current picture and the average value of the quantization scale actually used for encoding the current picture The ratio of the amount of activity to the complexity; wherein, the ratio of the amount of activity to the complexity of the current picture is proportional to the total activity of the current picture, and is related to the actual number of consumed bits of the current picture and the actual number of bits of the current picture. This average is inversely proportional to the quantization scale used.

The present invention also discloses a target bit allocator, which includes an instantaneous bit rate calculator, a quota calculator and a limit unit. The instantaneous bit rate calculator receives the complexity of the current picture to be encoded in a group of continuous pictures contained in the video sequence, and based on the complexity, updates the instantaneous complexity of this group of continuous pictures, and according to a function to calculate the instantaneous bit rate of the group of continuous pictures, wherein the function depends on the predetermined reference bit rate, reference complexity and instantaneous complexity of the group of continuous pictures. The quota calculator allocates the target bit quota to the current picture based on the complexity of the current picture, the instantaneous bit rate and the instantaneous complexity of this group of continuous pictures, and the limit unit is used to limit the target bit quota below the established limit.

The purpose of the present invention and the solution to its technical problems can also be further realized by adopting the following technical measures.

The aforementioned video compression bit rate control device includes at least one video encoder, which determines the plurality of quantization levels used by the above-mentioned current picture according to the above-mentioned target bit rate of the above-mentioned current picture, and these quantization levels are used as the above-mentioned current picture. For encoding each spatial region in a picture, the image encoder encodes the above-mentioned current picture according to the quantization levels, and the above-mentioned actual consumption bit number of the above-mentioned current picture and the above-mentioned average of the quantization levels actually used by the above-mentioned current picture Values are fed back to the above parameter updater.

In the aforementioned video compression bit rate control device, the above-mentioned complexity of the above-mentioned current picture estimated by the complexity estimator is based on an equation:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; est</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; ACR</span>}}$

Among them, C _est is the estimated complexity of the above-mentioned current picture, K is a predetermined weighted value, and its range is between 0 and 1, A is the above-mentioned total activity amount of the above-mentioned current picture, ACR is the above-mentioned same type The ratio of the amount of activity to the complexity of a previously encoded picture.

The aforementioned video compression bit rate control device, wherein the parameter updater calculates the ratio of the amount of activity to the complexity of the above-mentioned current picture, is based on:

$\mathrm{<span\; class="notranslate">\; ACR</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; AQ</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; UB</span>}}$

Among them, ACR represents the ratio of activity to complexity of the above-mentioned current picture, A is the above-mentioned total activity of the above-mentioned current picture, AQ is the above-mentioned average value of the quantization scale actually used in the above-mentioned current picture, and UB is the above-mentioned actual value of the above-mentioned current picture. Consumed bits.

The aforementioned video compression bit rate control device, wherein the target bit allocator is three types in the above-mentioned group of continuous pictures: I-picture, P-picture and B-picture respectively store their complexity C _I , complexity C _P and complexity C _B , and take the above-mentioned complexity of the above-mentioned current picture to update the complexity of the same-type picture among the three types.

The aforementioned video compression bit rate control device, wherein the target bit allocator at least includes:

an instant bit rate calculator, based on the above-mentioned complexity of the above-mentioned current picture, to update the above-mentioned instant complexity of the above-mentioned group of continuous pictures, and calculate the above-mentioned instant bit rate of the above-mentioned group of continuous pictures according to a function, Wherein the function depends on the above-mentioned predetermined reference bit rate, the above-mentioned instantaneous complexity and the above-mentioned reference complexity of the above-mentioned group of consecutive pictures;

a quota calculator for allocating the target bit quota based on the complexity of the current frame, the instantaneous bit rate and the instantaneous complexity of the group of consecutive frames; and

A limiting unit is used to limit the above-mentioned target bit quota below a predetermined upper limit.

In the aforementioned video compression bit rate control device, the above-mentioned instantaneous complexity of the above-mentioned group of continuous pictures obtained by the instantaneous bit rate calculator is based on:

INST_C＝N _I ×C _I +N _P ×C _P +N _B ×C _B

Wherein, INST_C represents the above-mentioned instantaneous complexity, N _I , N _P and N _B are respectively the numbers of the above-mentioned I-, P- and B-pictures in the above-mentioned group of continuous pictures.

The aforementioned video compression bit rate control device, wherein the instantaneous bit rate calculator calculates the above-mentioned instantaneous bit rate of the above-mentioned group of continuous pictures, is based on:

$\mathrm{<span\; class="notranslate">\; INST</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; SF</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; INST</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}}{\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Wherein, REF_R is the above-mentioned predetermined reference bit rate of the above-mentioned group of continuous pictures, SF is a scaling factor, and its range is between 0 and 1, INST_C, REF_C are the above-mentioned instantaneous complexity and the above-mentioned reference of the above-mentioned group of continuous pictures respectively. Complexity, INST_R represents the above instantaneous bit rate.

In the aforementioned video compression bit rate control device, the instantaneous bit rate is limited within the range of a predetermined maximum bit rate and a predetermined minimum bit rate of the above-mentioned group of continuous frames.

In the aforementioned video compression bit rate control device, the above-mentioned reference complexity of the group of continuous frames is as follows:

$\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; DQ</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; DQ</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; DQ</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; P</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}$

Among them, PB _I , PB _P and PB _B are used to specify that the coding bit ratio between the above-mentioned I-, P- and B-pictures in the above-mentioned group of continuous pictures is PB _I : PB _P : PB _B , DQ _I , DQ _P and DQ _B are respectively the target quantization levels of the above-mentioned I-, P- and B-pictures in the above-mentioned group of continuous pictures, and N _I , N _P and _NB are respectively the above-mentioned I-, P-pictures in the above-mentioned group of continuous pictures. - and the number of B-pictures.

Compared with the prior art, the present invention has obvious advantages and beneficial effects. As can be seen from the above technical solutions, in order to achieve the aforementioned object of the invention, the main technical contents of the present invention are as follows:

With regard to a video compression bit rate control device with fixed image quality, according to the present invention, first calculate the total amount of activity of the current picture to be encoded in a group of continuous pictures, and then based on the total amount of activity and the same type of pictures in the group of continuous pictures Estimate the complexity of the current picture based on the ratio of the amount of activity to the complexity of the previously coded pictures in the state, and update the instantaneous complexity of the group of continuous pictures with this complexity and calculate its instantaneous bit rate, and according to the picture complexity, the The instantaneous complexity and instantaneous bit rate of a group of consecutive images, and allocate the target bit quota to the current image. After the picture is encoded, the ratio of its activity to complexity is calculated according to the average of the total activity of the current picture, the actual number of consumed bits and the actual used quantization level.

Through the above invention, the various video formats existing in the existing video bit rate control device have been changed. The uncompressed bit rate is very high and uneconomical, and the traditional bit rate control method is quite complicated, and usually requires The defect of video coding can be completed several times. Through the analysis of the pre-analyzed activity of the current picture and the actual complexity of the previous encoded picture, the complexity of the current picture can be estimated, and the target bit quota can be allocated more accurately. Each frame to achieve uniform, smooth and stable visual quality between different frames in the video sequence.

To sum up, a video compression bit rate control device with a fixed image quality and a special structure of the present invention has the above-mentioned many advantages and practical value, and no similar structural design has been published or used in similar products. , it has great improvements in both structure and function, and has made great progress in technology, and has produced easy-to-use and practical effects, and indeed has enhanced efficacy, so it is more suitable for practical use. It is a novel, progressive and practical new design.

The above description is only an overview of the technical solutions of the present invention. In order to understand the technical means of the present invention more clearly and implement them according to the contents of the description, the preferred embodiments of the present invention and accompanying drawings are described in detail below.

The specific embodiment of the present invention is given in detail by the following examples and accompanying drawings.

Description of drawings

Figure 1 presents a typical group of pictures (GOP) in the order shown;

Fig. 2 is a big block of MPEG;

3 is a schematic block diagram of a preferred embodiment of the video compression bit rate control device of the present invention;

Fig. 4 is the operation flowchart of the present invention;

FIG. 5 is a block diagram of the target bit allocator of the present invention.

300. Video compression bit rate control device 310. Motion estimation unit

312. Signal line 320. Complexity estimator

330. Target bit dispatcher 340. Parameter updater

350. Video encoder 510. Instantaneous bit rate calculator

520. Quota calculator 530. Limit unit

P ⁽ⁱ⁾ , screen A ⁽ⁱ⁾ , total activity

C _est ⁽ⁱ⁾ , estimated complexity ACR ⁽ⁱ⁾ , ratio of activity to complexity

EB, excess bits TB ⁽ⁱ⁾ , target bit quota

AQ ⁽ⁱ⁾ , the average value of the actual quantization scale used UB ⁽ⁱ⁾ , the actual number of consumed bits

CD, encoded data INST_R, instantaneous bit rate

INST_C, instantaneous complexity

Detailed ways

The specific implementation, structure, features and functions of a video compression bit rate control device with fixed image quality according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

Please refer to Fig. 1, Fig. 2, Fig. 3, Fig. 4, and Fig. 5, a video compression bit rate control device with fixed image quality of the present invention mainly includes: a motion estimation unit, a complexity estimator, A target bit allocator, a parameter updater.

Initially, the I-pictures and P-pictures used for prediction must be decoded in the MPEG encoder. By calculating the root mean square (root mean square) error between the original picture and the decoded picture, an objective estimate of the quality of the decoded picture can be obtained. measure. Taking the root mean square error as the distortion degree of the solution picture, the complexity (complex)-C of the solution picture is defined as follows:

C=r×d

where r is the bit rate required to encode the picture, and d is the distortion of the decoded picture. Theoretically, there is a proportional relationship between the average quantization step size and the degree of distortion. Therefore, the complexity of the picture can be defined as:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; \&ap;</span>\frac{\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; q</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}$

where q is the average quantization scale of the picture. After the picture is encoded, the bit rate (the actual number of consumed bits) and the average quantization level can be obtained, and the complexity of the picture is obtained accordingly.

The complexity of the picture depends on the nature of the picture and its encoding form. The prior art uses the complexity of the most recent coded picture to represent the complexity of the current picture, and maintains its complexity for I-, P- and B-pictures respectively to mitigate the impact of different coding forms, if the content of the picture in the video sequence is smooth changes, this method can achieve quite good results. However, due to the inconsistency between the target bit quota of frame coding and the actual consumed bits, the above method is not suitable for achieving consistent visual quality if the content of the video sequence changes greatly.

According to the present invention, the complexity of the current picture can be estimated by pre-analyzing the ratio of the activity of the current picture and the actual complexity of the previously coded picture. The amount of activity is an attempt to measure the bit rate and quality of a picture after encoding. Assuming that the total amount of activity A of a whole picture is proportional to the complexity C, then

$\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; \&ap;</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; k</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; q</span>}$

where k is a constant of proportionality. If k' is the activity-to-complexity ratio (activity-to-complexity ratio, ACR), then the total activity A can also be expressed by the following formula:

A=ACR×r×q

According to the present invention, ACR can be estimated from previously coded pictures of the same type. Conceptually, before encoding a picture, calculate its total activity A, and then estimate the complexity C _est ^{(i ) of the picture P (i} ) to be encoded as follows:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; est</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; ACR</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}$

Wherein, A ⁽ⁱ⁾ is the total activity of the picture P ⁽ⁱ⁾ , and ACR ^(i-1) is the ratio of the activity to the complexity of the previously coded picture of the same type. In the following, a superscript ⁽ⁱ⁾ in a symbol or variable indicates that the symbol or variable is related to the current picture to be coded; similarly, a superscript ^(i-1) in a symbol or variable is related to the previous coded picture .

The estimated complexity C _est ⁽ⁱ⁾ can be used to update the complexity of the appropriate type of frame, so the complexities C _I , _CP and C _B of the three types of frames are stored for subsequent processing. The ins tantaneous complexity of a sequence of pictures is also updated as follows:

INST_C＝N _I ×C _I +N _P ×C _P +N _B ×C _B

Wherein, N _I , N _P and N _B are respectively the numbers of I-, P- and B-pictures in the group of continuous pictures, and the group of continuous pictures referred to here includes at least one group of GOP.

In order to achieve fixed image quality between different frames, the three types of I, P, and B in the same group of continuous frames are quantized at different quantization levels, so the target quantization bits of I-, P-, and B-pictures The order is preset as DQ _I , DQ _P and DQ _B respectively. If a reference bit rate and the coding bit ratio between the three picture types I, P and B are specified for a group of continuous pictures, the The reference complexity, REF_C, is as follows:

$\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; DQ</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; DQ</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; DQ</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}$

Among them, PB _I , PB _P and PB _B are used to specify the coding bit ratio between I-, P- and B-pictures in a group of continuous pictures as PB _I : _{PB P} : PB _B , and REF_R is the group of continuous pictures The established reference bit rate for . The coding bit ratio between I-, P- and B-pictures can be a predetermined constant or calculated from the most recently coded picture. According to the aforementioned formula, REF_C represents the reference complexity of encoding a group of continuous pictures with the reference bit rate REF_R and the target quantization levels DQ _I , DQ _P and DQ _B. In this way, the instantaneous bit rate of the group of continuous pictures It can be calculated by the following formula:

$\mathrm{<span\; class="notranslate">\; INST</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; SF</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; INSF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}}{\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>$

Wherein, SF is a scaling factor, and its range is between 0 and 1. Using the scaling factor SF can make the instantaneous bit rate INST_R change smoothly with the instantaneous complexity INST_C, which can form a better bit rate distribution among different frames. If the maximum and minimum bit rates of a group of continuous pictures have been determined in advance according to the reference bit rate, the instantaneous bit rate INST_R must be further limited to: ER _min ≤ INST_R ≤ _{ER max} .

Once the instantaneous complexity INST_C and the instantaneous bit rate INST_R have been determined, the target bit quota TB ⁽ⁱ⁾ of the current picture P ⁽ⁱ⁾ is

${\mathrm{<span\; class="notranslate">\; TB</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; est</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}{\mathrm{<span\; class="notranslate">\; INST</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; INST</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}$

It can be known from the above formula that the target bit quota TB ⁽ⁱ⁾ is directly proportional to the complexity C _est ⁽ⁱ⁾ and the instantaneous bit rate INST_R, and is inversely proportional to the instantaneous complexity INST_C. All MPEG-2 data bitstreams must follow the VBV rules of the MPEG-2 standard, and the allocated target quota must be limited so that the VBV buffer will not overflow or underflow. After the target bit quota of the current picture is determined, many different types of image encoders, such as TestModel 5 described in the MPEG-2 standard, can be used to complete picture compression according to the target bit quota. .

After the encoding of the current picture is completed, its actual complexity will be known, and the relationship between the total activity of the current picture and the actual complexity is that ACR ⁽ⁱ⁾ can be obtained from the following calculation

${\mathrm{<span\; class="notranslate">\; ACR</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; AQ</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; UB</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}$

Wherein, ACR ⁽ⁱ⁾ is directly proportional to the total activity A ⁽ⁱ⁾ , and inversely proportional to the actual consumed bit number UB ⁽ⁱ⁾ and the average quantization level AQ ⁽ⁱ⁾ of the current frame. This ACR ⁽ⁱ⁾ can be used to estimate the complexity of the next frame of the same type. ACR ⁽ⁱ⁾ can be linearly combined with ACR ^(i-1) to avoid the influence of those images rich in noise.

For the single-pass video encoding of the present invention, please refer to the preferred embodiment in FIG. 3 and explain it with the operation flowchart in FIG. 4 . As shown in FIG. 3 , the video compression bit rate control device 300 includes a motion estimation unit 310 , a complexity estimator 320 , a target bit allocator 330 , a parameter updater 340 and an image encoder 350 . The motion estimation unit 310 receives the current frame P ⁽ⁱ⁾ to be encoded in a group of consecutive frames in the video sequence, and is used to calculate the total activity A of the current frame P ⁽ⁱ⁾ when performing block matching for motion estimation ⁽ⁱ⁾ (step S410). Based on the total activity A ⁽ⁱ⁾ and the ACR ^(i-1) of the same type of previously coded pictures in this group of consecutive pictures, the complexity estimator 320 can be used to estimate the complexity C _est ⁽ⁱ⁾ of the current picture (step S420 ). The target bit allocator 330 updates the instantaneous complexity INST_C of this group of continuous pictures with the estimated complexity C _est ⁽ⁱ⁾ , and calculates the instantaneous complexity INST_C according to the predetermined reference bit rate REF_R, reference complexity REF_C and instantaneous complexity INST_C The instantaneous bit rate INST_R of the group of continuous pictures (step S430).

The target bit allocator 330 then allocates the target bit quota TB ^{(i) to the current frame P (i} ) based on the instantaneous bit rate INST_R, the complexity C _est ^{( i)} and the instantaneous complexity INST_C (step S440 ). Therefore, the image encoder 350 determines all the quantization levels used by the current picture P (i) according to the target bit quota TB ^{(i) ,} and these quantization levels are used as each spatial region in the picture P ⁽ⁱ⁾ : large block (MB) encoding use. The video encoder 350 encodes the current picture P ⁽ⁱ⁾ according to these quantization levels (step S450). After the encoding of the current picture is completed, the video encoder 350 reports the actual consumed bit number UB ^{(i ) of the picture P (i)} and the average value AQ ⁽ⁱ⁾ of the actually used quantization scale to the parameter updater 340 . Then based on the total activity amount A ⁽ⁱ⁾ , the actual consumed bit number UB ⁽ⁱ⁾ and the average value AQ ⁽ⁱ⁾ of the actual quantization scale used, the parameter updater 340 calculates the activity amount for the current picture P ⁽ⁱ⁾ to the complexity ratio ACR ⁽ⁱ⁾ (step S460).

The preferred embodiment of FIG. 3 can be considered to be implemented by hardware and/or software. According to the present invention, the motion estimation unit 310 and other components in FIG. 3 can operate in a pipeline mode. Before the complexity estimator 320 starts to calculate the complexity of the current picture, the motion estimation unit 310 must first complete the current picture to be encoded. Calculation of all motions of the frame and estimation of motion vectors, and when the motion estimation unit 310 is preparing for the next frame, the complexity estimator 320 and other components are still busy completing all operations related to the current frame. Next, each component in the preferred embodiment will be described in detail.

One of the main purposes of the motion estimation unit 310 is to decide which prediction mode to use to encode each MB in a picture, and if necessary, to perform forward and backward motion prediction, and also from the block matching operation Information about the amount of screen activity is extracted. First, the intra-activity of each MB is calculated, and the pixel intensity of four 8x8 luminance value blocks in one MB is expressed as Y _m,n ,m=0,...,7,n=0, ..., 7 to represent, and the average value of each 8x8 block is Y, then the amount of activity within each MB IntraAct:

$\mathrm{<span\; class="notranslate">\; IntraAct</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}$

in

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; =</span>\sqrt{\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 7</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 7</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Y</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

If lower computational complexity is required, it can be replaced by the absolute difference relative to Y:

$\mathrm{<span\; class="notranslate">\; IntraAct</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}$

in

${\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 7</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 7</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Y</span>}}<span\; class="notranslate">\; |</span>$

Since the MB in the I-picture has only one mode: I-mode, IntraAct is the activity amount of each MB of the I-picture.

If the picture is a P- or B-picture, motion estimation is required. The most commonly used technique to find the best motion vector is block matching. For nonintra coding (e.g. P- and B-pictures), selection of forward, backward, bidirectional prediction or no motion compensation. Once the MB mode for each MB in the P- or B-picture is determined, the variance of the 4 8x8 blocks in each motion-compensated difference MB is also obtained. The motion-compensated difference MB is the MB to be processed and Estimates the pixel-by-pixel difference between MBs; the absolute sum of distortions is usually more computationally efficient and can therefore be used instead of the variance. Add the variance or absolute value of distortion of 4 8x8 blocks to obtain the inter-activity (inter-activity) of each MB in the non-intra-coded picture, InterAct, and then calculate the IntraAct of each MB in the non-intra-coded picture and its InterAct are used for comparison to determine whether the InterAct is small, if so, use InterAct as the activity of the MB, and encode the MB in inter-mode; otherwise use IntraAct as the activity of the MB, And encode the MB in intra-mode. Finally, for the current I-, P- or B-picture, the total activity A ⁽ⁱ⁾ is obtained by adding the activity of all MBs, and the motion estimation unit 310 sends the entire activity A ⁽ⁱ⁾ to the complexity An estimator 320 and a parameter updater 340 .

Next, the complexity estimator 320 estimates the complexity of a certain type of current picture P ⁽ⁱ⁾ , and introduces weighting coefficients to the estimated complexity C _est ⁽ⁱ⁾ according to the three picture types. Since B-pictures can never be used to predict other pictures, the weight coefficients of B-pictures can be reduced to allocate less bits to B-pictures and reserve more bits to I- and P-pictures; generally In other words, encoding I-pictures produces the most bits, so the weighting coefficients of P-pictures are smaller than those of I-pictures. The complexity estimator 320 updates one of the complexity C _I , C _P or C _B according to the type of the current picture, and the complexity C _est (i ^{) of the current picture P (i )} is estimated as follows:

if(I-picture)

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; est</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&times;</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; ACR</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}$

else if(P-picture)

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; est</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; \&times;</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; ACR</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}$

else if(B-picture)

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; est</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&times;</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; ACR</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}$

Among them, ACR _I ^(i-1) , ACR _P ^(i-1) and ACR _B ^(i-1) are the respective activity versus complexity of previously coded pictures of I, P and B types in a group of consecutive pictures Ratio. These ACR _I ^(i-1) , ACR _P ^(i-1) and ACR _B ^(i-1) are stored in the parameter updater 340, and the complexity estimator 320 reads the corresponding The ratio of activity to complexity. K _I , K _P and K _B are weighting coefficients of I-, P- and B-pictures respectively, and their ranges are generally between 0 and 1.0. As for I-pictures, a preferred embodiment may use K _I =1.0.

The target bit allocator 330 can store the complexity C _I , the complexity C _P and the complexity C _B of three types of consecutive pictures: I-picture, P-picture and B-picture respectively. When C _est ⁽ⁱ⁾ is received, depending on the type of the current picture P(i), only one of the complexity C _I , C _P , and C _B is updated each time, as follows:

if(I-picture)

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; est</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}$

else if(P-picture)

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; est</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}$

else if(B-picture)

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; est</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}$

Please refer to the preferred embodiment shown in FIG. 5 , the target bit allocator 330 is composed of an instantaneous bit rate calculator 510 , a quota calculator 520 and a limit unit 530 . The instantaneous bit rate calculator 510 updates the instantaneous complexity INST_C for the group of continuous pictures as follows:

INST_C＝N _I ×C _I +N _P ×C _P +N _B ×C _B

Wherein, N _I , N _P and N _B are respectively the numbers of I-, P- and B-pictures in a group of consecutive pictures. In addition to C _I , C _P and C _B , the instantaneous bit rate calculator 510 also stores five other parameters: the reference bit rate REF_R of this group of continuous pictures, the maximum bit rate ER _max , and the minimum bit rate ER _min , reference complexity REF_C, and scaling factor SF. The coding bit ratio between I-, P- and B-pictures in a group of consecutive pictures can be obtained from the latest coded picture, so the reference complexity REF_C is:

$\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; \&CenterDot;</span>\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; DQ</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; DQ</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; DQ</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}$

Among them, PB _I , PB _P and PB _B are used to specify the coding bit ratio between I-, P- and B-pictures in a group of continuous pictures as PB _I : PB _P : PB _B , DQ _I , DQ _P and DQ _B are respectively the target quantization levels of the I-, P- and B-pictures in the group of consecutive pictures. Once the instantaneous complexity and the reference complexity are determined, the instantaneous bit rate calculator 510 can calculate the instantaneous bit rate INST_R of a group of consecutive frames by the following formula:

$\mathrm{<span\; class="notranslate">\; INST</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; SF</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; INST</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}}{\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>$

Wherein, the range of the scaling factor SF is set between 0 and 1 (for example, 0.8), and the instantaneous bit rate INST_R is preferably limited between the maximum and minimum bit rates ER _max and ER _min of the group of continuous pictures.

The quota calculator 520 then allocates the target bit quota TB ⁽ⁱ⁾ to the current picture P ⁽ⁱ⁾ , and the target bit quota TB ⁽ⁱ⁾ is based on

${\mathrm{<span\; class="notranslate">\; TB</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; est</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}{\mathrm{<span\; class="notranslate">\; INST</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; INST</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}$

However, the actual number of consumed bits will not be exactly equal to the expected bit quota, so a feedback strategy is developed to make the actual consumed bit number of the picture close to the target bit quota. In a preferred embodiment, The excess bits encoded so far can be amortized by the current picture being encoded:

TB ⁽ⁱ⁾ =TB ⁽ⁱ⁾ -AR×EB

Wherein, EB is the excess bit amount transmitted from the parameter updater 340, and AR is a predetermined amortization rate, and its range is generally between 0.05 and 0.2. According to the previous formula, the target bit quota TB ⁽ⁱ⁾ is proportional to the complexity C _est ⁽ⁱ⁾ of the current picture and the instantaneous bit rate INST_R of a group of continuous pictures, and is proportional to the instantaneous complexity of a group of continuous pictures INST_C is inversely proportional. The limit unit 530 can be used to adjust the target bit amount TB ⁽ⁱ⁾ to comply with the VBV specification, so the upper limit (U_bound) and the lower limit (L_bound) of the amount are set in advance. For constant bit rate (CBR) operation, the target bit quota allocated to a frame must be such that the VBV buffer does not overflow or starve, so limit unit 530 limits the target bit quota TB ⁽ⁱ⁾ to Within the upper and lower limits:

if (TB ⁽ⁱ⁾ > U_bound) then TB ⁽ⁱ⁾ = U_bound

if (TB ⁽ⁱ⁾ < L_bound) then TB ⁽ⁱ⁾ = L_bound

If it is variable bit rate (VBR), it is only necessary to prevent the lack of VBV, so:

if (TB ⁽ⁱ⁾ > U_bound) then TB ⁽ⁱ⁾ = U_bound

Then, the target bit quota TB ⁽ⁱ⁾ is sent to the parameter updater 340 and the video encoder 350 .

Referring to FIG. 3 , the video encoder 350 receives the frame data, the motion vector of each MB and the MB pattern from the motion estimation unit 310 through the signal line 312 . In order to achieve the best quality of the picture as possible, the video encoder 350 determines the quantization level used for encoding each MB of the current picture according to the target bit quota TB ⁽ⁱ⁾ . Based on these data, the video encoder 350 starts Encode the current picture P ⁽ⁱ⁾ and output the encoded data CD. After the current picture P ⁽ⁱ⁾ is encoded, the video encoder 350 averages the used quantization levels and calculates the actual number of consumed bits UB ⁽ⁱ⁾ , and then returns the UB ⁽ⁱ⁾ of the current picture and the actual used quantization levels The average value AQ ⁽ⁱ⁾ is given to the parameter updater 340 .

The difference between the target bit quota TB ⁽ⁱ⁾ of the picture P ⁽ⁱ⁾ and the actual consumed bit number UB ⁽ⁱ⁾ will be accumulated by the parameter updater 340 so as to obtain the excess bit amount after the picture P ⁽ⁱ⁾ is encoded EB:

EB＝EB×(1-AR)+UB ⁽ⁱ⁾ -TB ⁽ⁱ⁾

Among them, AR is the established amortization rate. Therefore, the relationship between the amount of activity and the actual complexity is, ACR ⁽ⁱ⁾ , which can be calculated from

${\mathrm{<span\; class="notranslate">\; ACR</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; AQ</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; UB</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}$

The ACR ⁽ⁱ⁾ to which the just encoded picture P ⁽ⁱ⁾ belongs can be used to estimate the complexity of the next picture of the same type. In order to make ACR ⁽ⁱ⁾ unaffected by noisy pictures, a preferred embodiment utilizes a linear combination of ACR ⁽ⁱ⁾ and ACR ^(i-1) , for example:

if(I-picture)

${\mathrm{<span\; class="notranslate">\; ACR</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; ACR</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; CW</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; ACR</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; CW</span>}$

else if(P-picture)

${\mathrm{<span\; class="notranslate">\; ACR</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; ACR</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; CW</span>}<span\; class="notranslate">\; )</span>{<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; ACR</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; CW</span>}$

else if(B-picture)

${\mathrm{<span\; class="notranslate">\; ACR</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; ACR</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; CW</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; ACR</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; CW</span>}$

Among them, CW is the predetermined weighting coefficient of the linear combination. The updated ACR _I ⁽ⁱ⁾ , ACR _P ⁽ⁱ⁾ and ACR _B ⁽ⁱ⁾ will be sent to the complexity estimator 320, so as to estimate the complexity of the next picture with a suitable type. In addition, the overuse bits The amount EB is sent to the target bit allocator 330 for bit allocation.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention are still valid. It belongs to the scope of the technical solutions of the present invention.

Claims (10)

1. A video compression bit rate control device with a fixed image quality, characterized in that: at least comprising: a motion estimation unit, receiving a current picture to be encoded in a group of continuous pictures in a video sequence, to calculate the The total amount of activity in the current screen; a complexity estimator for estimating a complexity of the current picture based on the total activity of the current picture and a ratio of activity to complexity of previously coded pictures of the same type in the group of consecutive pictures; a target bit allocator for updating the instantaneous complexity of the group of continuous pictures with the complexity of the current picture, and based on a predetermined reference bit rate, a reference complexity and the instantaneous complexity of the group of continuous pictures calculating a momentary bit rate of the group of continuous pictures, and allocating a target bit quota to the current picture according to the complexity of the current picture, the momentary complexity of the group of continuous pictures and the momentary bit rate; and A parameter updater for calculating the activity-to-complexity of the current picture based on the total activity of the current picture, an actual consumed bit number of the current picture, and an average value of the quantization scale actually used to encode the current picture Ratio; Wherein, the ratio of the activity amount to the complexity of the current frame is directly proportional to the total amount of activity in the current frame, and is the average of the actual consumed bits of the current frame and the actual quantization scale used in the current frame. The value is inversely proportional to. 2. The video compression bit rate control device according to claim 1, characterized in that it comprises at least one video encoder, which determines the plurality of quantization levels used in the current picture according to the target bit rate of the current picture , these quantization levels are used for encoding each spatial region in the above-mentioned current picture, the image encoder encodes the above-mentioned current picture according to these quantization levels, and the above-mentioned actual consumption bit number of the above-mentioned current picture and the above-mentioned The above-mentioned average value of the quantization scale actually used in the current picture is fed back to the above-mentioned parameter updater. 3. The video compression bit rate control device according to claim 1, wherein the complexity of the current picture estimated by the complexity estimator is based on an equation: ${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; est</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; ACR</span>}}$ Among them, C _est is the estimated complexity of the above-mentioned current picture, K is a predetermined weighted value, and its range is between 0 and 1, A is the above-mentioned total activity amount of the above-mentioned current picture, ACR is the above-mentioned same type The ratio of the amount of activity to the complexity of a previously encoded picture. 4. The video compression bit rate control device according to claim 2, wherein said parameter updater calculates the ratio of the amount of activity to the complexity of the above-mentioned current picture based on: $\mathrm{<span\; class="notranslate">\; ACR</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; AQ</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; UB</span>}}$ Among them, ACR represents the ratio of activity to complexity of the above-mentioned current picture, A is the above-mentioned total activity of the above-mentioned current picture, AQ is the above-mentioned average value of the quantization scale actually used in the above-mentioned current picture, and UB is the above-mentioned actual value of the above-mentioned current picture. Consumed bits. 5. The video compression bit rate control device according to claim 1, wherein said target bit allocator is of three types in said group of continuous pictures: I-picture, P-picture and The B-picture stores its complexity C _I , complexity C _P and complexity C _B respectively, and uses the above-mentioned complexity of the above-mentioned current picture to update the complexity of the same-type picture among the three types. 6. The video compression bit rate control device according to claim 5, wherein said target bit allocator at least includes: an instant bit rate calculator, based on the above-mentioned complexity of the above-mentioned current picture, to update the above-mentioned instant complexity of the above-mentioned group of continuous pictures, and calculate the above-mentioned instant bit rate of the above-mentioned group of continuous pictures according to a function, Wherein the function depends on the above-mentioned predetermined reference bit rate, the above-mentioned instantaneous complexity and the above-mentioned reference complexity of the above-mentioned group of consecutive pictures; a quota calculator for allocating the target bit quota based on the complexity of the current frame, the instantaneous bit rate and the instantaneous complexity of the group of consecutive frames; and A limiting unit is used to limit the above-mentioned target bit quota below a predetermined upper limit. 7. The video compression bit rate control device according to claim 6, wherein the instantaneous complexity of the above-mentioned group of continuous pictures obtained by the instantaneous bit rate calculator is based on: INST_C＝N _I ×C _I +N _P ×C _P +N _B ×C _B Wherein, INST_C represents the above-mentioned instantaneous complexity, N _I , N _P and N _B are respectively the numbers of the above-mentioned I-, P- and B-pictures in the above-mentioned group of continuous pictures. 8. The video compression bit rate control device according to claim 6, wherein said instantaneous bit rate calculator calculates said instantaneous bit rate of said group of continuous pictures according to: $\mathrm{<span\; class="notranslate">\; INST</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; SF</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; INST</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}}{\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>$ Wherein, REF_R is the above-mentioned predetermined reference bit rate of the above-mentioned group of continuous pictures, SF is a scaling factor, and its range is between 0 and 1, INST_C, REF_C are the above-mentioned instantaneous complexity and the above-mentioned reference of the above-mentioned group of continuous pictures respectively. Complexity, INST_R represents the above instantaneous bit rate. 9. The video compression bit rate control device according to claim 8, wherein said instantaneous bit rate is limited to a predetermined maximum bit rate and a predetermined minimum bit rate of said group of continuous pictures In the range. 10. The video compression bit rate control device according to claim 8, wherein said reference complexity of said group of continuous pictures is as follows: $\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; REF</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; D.</span>}{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; DQ</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; DQ</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PB</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}$ Among them, PB _I , PB _P and PB _B are used to specify that the coding bit ratio between the above-mentioned I-, P- and B-pictures in the above-mentioned group of continuous pictures is PB _I : PB _P : PB _B , DQ _I , DQ _P and DQ _B are respectively the target quantization levels of the above-mentioned I-, P- and B-pictures in the above-mentioned group of continuous pictures, and N _I , N _P and _NB are respectively the above-mentioned I-, P-pictures in the above-mentioned group of continuous pictures. - and the number of B-pictures.

Images