JP2000059774A - Video coding control device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To control a video signal to be encoded at a minimum bit rate necessary to achieve a target quality. SOLUTION: An encoding parameter value F obtained as a result of encoding an input video signal by an encoding processing unit 1 in a predetermined processing unit.
A video signal feature deriving unit 3 for determining a feature T of the input video signal based on R, Q, and B; a feature T of the obtained input video signal; a feature of the input video previously obtained; And an optimal coding parameter value for the target quality S ₀ from the relationship between the coding quality and the subjective value S, and the coding processing is performed using the coding parameter value as a target value of the coding parameter of the input video signal in the next processing unit. An encoding control unit 5 to be provided to the unit 1 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal which is encoded by an encoding unit, and controls the encoding process of the encoding unit in consideration of the characteristics of an input video signal. The present invention relates to a video encoding control device that achieves a target subjective quality (hereinafter, referred to as a target quality).

[0002]

2. Description of the Related Art In the coding of video signals, the coding quality varies greatly depending on the physical characteristics of the input video. Therefore, in order to achieve a certain quality without depending on the input video, it is necessary to determine an encoding parameter value necessary for achieving the quality in consideration of characteristics of the input video. In general, the target quality can be achieved by using a sufficiently high bit rate. However, from the viewpoint of the transmission / storage efficiency of the video signal, it is desired to encode at a bit rate as low as possible. That is, it is important to perform coding control such that coding is performed at the minimum bit rate necessary to achieve the target quality.

Conventionally, as disclosed in, for example, JP-A-2-219388 and JP-A-3-124143, the amount of distortion of an encoded video signal is determined by a signal-to-noise ratio (S / N).
A technique has been proposed in which quantification is performed using a ratio, and coding control is performed based on the result. By performing such control, it is possible to encode a video signal at a necessary minimum bit rate while keeping the distortion amount within an allowable range.

[0004]

However, since the S / N ratio does not always correspond to the quality perceived by humans, that is, the subjective quality, it is necessary to achieve the target quality in the conventional control method for keeping the S / N ratio constant. Sufficient coding control cannot be performed.

[0005] It is an object of the present invention to perform encoding control so as to encode a video signal at a minimum bit rate necessary for achieving a target quality, and to achieve as high a quality as possible even when this is difficult. It is an object of the present invention to provide a video coding control device for performing such coding control.

[0006]

According to the present invention, the relationship between the coding parameter value and the subjective quality is previously determined for video having various characteristics, and the relationship is referred to based on the result of analyzing the characteristics of the input video. Thus, the main feature is to determine the coding parameter value that achieves the target quality at the lowest bit rate.

According to the present invention, the coding process of the coding unit is controlled based on the correspondence between the coding parameter value and the subjective quality which are determined in advance corresponding to the characteristics of the input video signal.
As long as this relationship is maintained, the target quality can be achieved at the lowest bit rate in the encoding processing control of the prepared encoding unit, or the highest subjective quality is achieved when this is not possible. can do.

[0008]

FIG. 1 is a block diagram of a first embodiment of the present invention. In the figure, 1 is an encoding processing unit (encoding unit), 2 is a video signal feature function database, 3 is a video signal feature deriving unit, 4 is a subjective quality database, and 5 is an encoding control unit.

[0009] encoding unit 1 in this embodiment, an input video signal IS, encoded at the target bit rate B ₀ obtained from the encoding processing unit 5 to be described later, and outputs the encoded signal OS. The encoding processing unit 1 autonomously determines the frame rate FR and the quantization accuracy parameter Q so that the generated bit rate B becomes the target bit rate B ₀ obtained from the encoding control unit 5. In the beginning of the encoding processing operation, using a predetermined value as an initial value of the target bit rate B _0.

The video signal feature function database 2 includes a code
Conversion unit 1 has target bit rate B₀ To input video signal
Encoding parameter value resulting from the encoding (here,
Based on frame rate FR, quantization accuracy parameter Q)
Function to derive the feature T of the input video signal
Number) F_B(FR, Q) is held. Video signal feature derivation unit
3 is obtained by referring to the video signal feature function database 2.
Feature derivation function F_B (FR, Q), the frame rate
Input by substituting FR and quantization accuracy parameter Q
The feature T of the video signal is derived. Specific feature derivation operation
Will be described later.

The subjective quality database 4 stores a bit rate and a subjective rate when the input video signal having the video feature T derived by the video signal feature deriving unit 3 is coded by changing the bit rate of the coding processing unit 1. A parameter derivation function g _T (S) representing a quality relationship is held. The encoding control unit 5 substitutes the target quality S ₀ into the parameter derivation function g _T (S) obtained from the subjective quality database 4 corresponding to the video feature T derived by the video signal feature derivation unit 3 to achieve the target. The bit rate B ₀ is derived. The specific operation of deriving the target bit rate will be described later.

Hereinafter, the operation of the present embodiment will be described in detail. Note that the following series of operations is performed for each encoded frame.

First, the configuration of the video signal feature function database 2 and the operation of the video signal feature deriving unit 3 using the database will be described. In the present embodiment, as shown in FIG. 2, a function f _B (FR, Q) for deriving the feature T of the input video signal from the FR, Q values when encoded at a certain bit rate B is stored in a video signal feature function database. Prepare in 2. The feature derivation function f _B (FR, Q) in this embodiment is shown below.

[0014]

(Equation 1)

The video signal feature deriving unit 3 includes an encoding processing unit 1
The feature derivation function f _B (FR, Q) corresponding to the bit rate B is obtained by referring to the video signal feature function database 2 from the value of the bit rate B obtained from. The frame rate F obtained from the encoding unit 1
By substituting the values of R and the quantization accuracy parameter Q, the characteristic T of the input video signal is determined. FIG. 3 shows the relationship among FR, Q, and T in the case where the function of Equation 1 is followed. In this embodiment, the characteristics of the input video are classified into four types (t0 to t).
Classified in 3).

Next, the configuration of the subjective quality database 4
Of the encoding control unit 5 that controls the bit rate by using
The work will be described. FIG. 4 shows the subjective quality database 4
2 shows a configuration. In this embodiment, the features t0 to t
Input video signals classified into 3
1 and subjective quality S and bit rate B when encoded in
Parameter derivation function g representing the relationship_T Hold (S)
You.

The coding control unit 5 searches for a parameter derivation function g _T (S) representing the relationship between the subjective quality S and the bit rate corresponding to the characteristic T of the current input video signal, and sets the target quality S ₀ to this. by substituting for, it outputs the bit rate B ₀ necessary to achieve the target quality. FIG. 5 schematically shows a procedure for determining the target bit rate B ₀ when the feature T of the input video signal is t1. When the target quality cannot be achieved at any of the bit rates that can be processed by the encoding processing unit 1, the highest bit rate B is output.

Generally, the generated bit rate B when encoding is performed with the same FR and Q values corresponds to the magnitude of the time / spatial information amount of the input video signal. The magnitude relationship corresponds to the magnitude of the bit rate required to encode these video signals with the same quality. In the present embodiment, the video signal feature deriving unit 3 groups the video features by focusing on the relative relationship between FR, Q, and B, so that the temporal and spatial information amounts of the videos belonging to each group are substantially equal. As a result, the bit rate required to encode these images at the target quality is almost constant. For such a reason, a relational expression as shown in FIG. 5 can be determined.

FIG. 6 is a block diagram of a second embodiment of the present invention. In the figure, 11 is an encoding processing unit (encoding unit), 12 is a video signal feature table, 13 is a video signal feature derivation unit, 14 is an encoding performance table, and 15 is an encoding control unit.

The encoding processing unit 11 in this embodiment encodes the input video signal IS based on the frame rate FR and the quantization accuracy parameter Q obtained from the encoding control unit 15, and encodes the encoded video signal OS. Is output.

The video signal characteristic table 12 is input based on the mutual relationship between the encoding parameter values (three in this example, the bit rate B, the frame rate FR, and the quantization precision parameter Q) obtained from the encoding processing unit 11. The result of pre-grouping the characteristics of the video signal is stored. The video signal feature deriving unit 13 derives the feature T of the input video signal with reference to the video signal feature table 12. A specific feature deriving operation will be described later.

The encoding processing performance table 14 is obtained when the input video signal having the video feature T derived by the video signal feature deriving unit 13 is encoded by changing the encoding parameter value of the encoding processing unit 11. Maintain the relationship between bit rate and subjective quality. The encoding control unit 15 refers to the encoding processing performance table 14 based on the video feature T and the target quality S ₀ derived by the video signal feature deriving unit 13, and codes that achieve the target quality at the lowest bit rate. The combination of the parameterization values (FR, Q) is selected. The configuration of the encoding processing performance table 14 and the operation of the encoding control unit 15 using the configuration will be described later.

Hereinafter, the operation of this embodiment will be described in detail. Note that also in the present embodiment, the following series of operations are performed for each encoded frame.

First, the structure of the video signal feature table 12 and the operation of deriving features in the video signal feature deriving unit 13 using the table will be described. In the present embodiment, the features T of the input video are grouped in advance based on the relative relationship among the three, the frame rate FR, the quantization accuracy parameter Q, and the bit rate B. Specifically, as shown in FIG.
For many combinations of the R and Q values, the video at that time that falls within a certain range is grouped, and the information is prepared as the video signal feature table 12. The video signal feature deriving unit 13 outputs the FR,
The characteristic T of the input video signal is determined by referring to the video signal characteristic table 12 from the Q and B values. In this embodiment, the characteristics T of the input video are classified into four types (t0 to t3).
It is classified into.

Next, the configuration of the encoding processing performance table 14 and the operation of the encoding control unit 15 for selecting and controlling encoding parameter values using the configuration will be described. FIG. 8 is a diagram showing a configuration of the encoding processing performance table 14. In this embodiment, the input video having the feature T is converted to the frame rate F
R and the subjective quality S when encoding by changing the value of the quantization accuracy parameter Q are held as a table. The encoding control unit 5 searches the encoding processing performance table 14 for an entry corresponding to the characteristic T of the current input video signal and having the lowest subjective quality S equal to or higher than the given target quality S _0. The FR and Q values at the time are output. Since the subjective quality and the bit rate have a monotonous relationship, the output FR,
The Q value is a parameter value that achieves the target quality S ₀ at the lowest bit rate. If the target quality cannot be achieved by any combination of FR and Q, the entry that achieves the highest subjective quality S is searched for, and the F at this time is searched.
Outputs R and Q values.

In the present embodiment, the video signal feature table 12 groups the features T of the input video on the basis of the relative relationship between FR, Q, and B. The FR and Q values required for encoding the video belonging to the target quality with the target quality are substantially constant. Therefore, as shown in FIG. 8, it is possible to determine a combination of the FR and Q values required to achieve the target quality for each video feature T.

In the first and second embodiments, the video signal feature deriving units 3 and 13 have the same parameters as the encoding parameters output from the encoding control units 5 and 15 among the encoding parameters obtained from the encoding processing units 1 and 11. For parameters whose values are always the same, the values can also be fed back from the encoding control units 5 and 15 directly to the video signal feature deriving units 3 and 13. FIG. 9 illustrates a case where the encoding processing unit 11 is operable with the frame rate FR and the quantization accuracy parameter Q as specified by the encoding control unit 15 in the second embodiment (that is, output from the encoding processing unit 11). FR, Q value and FR, output from the encoding control unit 15,
This is an example of a configuration applied to the case where the Q values match.

[0028]

As described above, according to the present invention,
In the video coding control, the target quality can be achieved at the lowest bit rate, or even when it is difficult, the quality closest to the target subjective quality can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a video signal feature function database used in the first embodiment of the present invention.

FIG. 3 is a diagram showing a feature derivation function constituting a video signal feature function database used in the first embodiment of the present invention.

FIG. 4 is a configuration diagram of a subjective quality database used in the first embodiment of the present invention.

FIG. 5 is a diagram showing parameter derivation functions constituting a subjective quality database used in the first embodiment of the present invention.

FIG. 6 is a block diagram of a second embodiment of the present invention.

FIG. 7 is a configuration diagram of a video signal feature table used in a second embodiment of the present invention.

FIG. 8 is a configuration diagram of an encoding processing performance table used in a second embodiment of the present invention.

FIG. 9 is a block diagram showing another aspect of the second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 encoding processing unit 2 video signal feature function database 3 video signal feature deriving unit 4 subjective quality database 5 encoding control unit 11 encoding processing unit 12 video signal feature table 13 video signal feature deriving unit 14 encoding processing performance table 15 code Control section

Continued on front page F term (reference) 5C059 KK01 KK47 LB07 MC11 SS06 SS11 TA00 TA07 TA46 TB04 TC00 TC37 TD13 TD15 UA02 UA38 5C078 AA04 BA12 BA21 CA00 CA27 DA01 DB07

Claims (4)

[Claims] 1. A video coding control device for controlling a coding process of a coding unit for coding a video signal in consideration of a feature of an input video signal, wherein the coding unit controls the video signal in a predetermined processing unit. A video signal feature deriving unit that determines a feature of the input video signal based on an encoding parameter value obtained as a result of encoding, and a feature of the input video signal obtained by the video signal feature deriving unit. From the characteristics of the input video, the relationship between the encoding parameter value and the subjective quality, determine the optimal encoding parameter value for the target quality, and set the encoding parameter value to the target value of the encoding parameter of the video signal of the next processing unit. A video coding control device, comprising: a coding control unit to be provided to a coding unit. 2. The video encoding control device according to claim 1, wherein the video encoding control device holds a database that associates encoding parameter values with features of the input video, and the video signal feature deriving unit refers to the database to input video data. A video encoding control device for determining characteristics of a signal. 3. The video coding control device according to claim 1, wherein the characteristics of the input video, the relationship between the coding parameter values and the subjective quality are stored as a database, and the coding control unit refers to the database. A video encoding control device that determines an optimal encoding parameter value corresponding to the characteristics of the input video signal. 4. The video encoding control device according to claim 1, wherein an encoding parameter value given from the encoding control unit to the encoding unit is fed back to the video signal feature deriving unit. Encoding control device.