JPH11127127A - Information coding and multiplexing equipment - Google Patents

Abstract

(57) Abstract: Information encoding and multiplexing including a plurality of encoding means for inputting predetermined information, encoding the information, and outputting the information, and multiplexing encoded data output from each encoding means. In the conversion device, the data transmission rate of the transmission system is effectively used. A plurality of encoding units each having a different code generation amount are provided in each of a plurality of encoding units, and encoded data D20A to D20N output from the plurality of encoding units are provided. Based on the total value of the average code generation amount, each of the encoding units 20A to 20N selects one of the plurality of encoding units 30 and 40, and encodes the encoded data output from the selected encoding unit. By multiplexing the data as output data of the encoding units 20A to 20N, it is possible to realize a multiplex transmission apparatus having a simple configuration that can more effectively use the data transmission rate of the transmission system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Table of Contents] The present invention will be described in the following order.

BACKGROUND OF THE INVENTION Prior Art (FIG. 3) Problems to be Solved by the Invention Means for Solving the Problems Embodiments of the Invention (FIGS. 1 and 2) Effects of the Invention

[0003]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information coding and multiplexing apparatus, and is suitably applied to, for example, an information coding and multiplexing apparatus used for digital multiplex broadcasting.

[0004]

2. Description of the Related Art In recent years, various compression encoding methods have been proposed as methods for reducing the amount of video and audio information, and a typical one is MPEG2 (Moving Picture Experts).
There is a method called GroupPhase 2). MPEG
2. Description of the Related Art A digital broadcasting system has been started which compresses and encodes video and audio broadcast data using two methods and broadcasts using terrestrial or satellite waves. In a digital broadcasting system, coded broadcast data is compressed and coded, then is packetized for each predetermined block, and a packet sequence obtained as a result is transmitted (hereinafter, the packet is referred to as T).
S (Transport Stream) packet, and the sequence of the TS packet is called a transport stream). In the digital broadcasting system, the broadcast data is packetized as described above, whereby the broadcast data of a plurality of channels is multiplexed, whereby a plurality of channels can be broadcast on one line.

FIG. 3 shows a multiplex transmission apparatus 1 as a whole, and a plurality of encoding apparatuses 2A to 2N having the same configuration are connected to the multiplex apparatus 3. Encoding unit 2A-2
N includes image signals S2A to S2E for broadcasting from an image supply device (not shown) such as a video tape recorder.
Is supplied.

[0006] The image signals S2A to S2N are compression-encoded by the MPEG2 system in the corresponding encoding units 2A to 2N, are packetized at predetermined blocks, and are encoded data D2A to D formed of TS packets.
2N is supplied to the multiplexer unit 3.

In the multiplexing unit 3, the encoded data D
2A to 2N are multiplexed and transmitted to the transmitting unit 4 as multiplexed data D3 of a transport stream configuration, converted into a transmission signal D4 of a predetermined format, and transmitted.
Thus, the image signals S2A to S2E supplied from the plurality of image supply devices are encoded and multiplexed by the multiplexing transmission device 1, and transmitted as the transmission signal D4.

[0008]

By the way, the coding units 2A to 2A used in the multiplex transmission apparatus 1 are described.
When attention is paid to the generation amount of encoded data as N, two types of encoding methods, a fixed rate encoding method and a variable rate encoding method, are considered.

First, the fixed-rate encoding method changes the quantization step size in accordance with the amount of data generated by the encoding, whereby the GOP (Gr.
oupOf Pictures).

However, in the fixed-rate encoding method, control is performed such that the quantization step size is made coarser as the picture of the input image becomes more complicated, so that the picture quality is degraded in accordance with the complexity of the picture of the input image. However, there is a problem that the size becomes unsightly. On the other hand, when the pattern of the input image becomes flat, the amount of coded data is maintained by adding a large amount of unnecessary data which is originally unnecessary, and the transmission rate of the data is effectively reduced accordingly. There are problems that cannot be used.

Second, the variable rate coding method changes the amount of coded data generated depending on the complexity of the picture by fixing the quantization step size, thereby changing the picture quality. Not to be done.

However, when a variable rate coding method is used in a broadcasting system, it is difficult to accurately predict the complexity of a picture of an input image, and the coding generated in the plurality of coding units 2A to 2N is difficult. If the amount of data increases at the same time, the transmission rate when multiplexing and transmitting them may exceed the maximum allowable transmission rate of the multiplex transmission device 1, and in this case, it becomes difficult to broadcast. There was a problem.

The present invention has been made in view of the above points, and it is an object of the present invention to propose an information coding and multiplexing apparatus having a simple configuration capable of effectively utilizing the data transmission rate of a transmission system.

[0014]

According to the present invention, in order to solve the above-mentioned problems, a plurality of encoding units each having a different code generation amount are provided in each of the plurality of encoding units, and output from the plurality of encoding units is provided. Each of the encoding means selects one of the plurality of encoding units based on the total value of the average code generation amount of the encoded data, and encodes the encoded data output from the selected encoding unit. By multiplexing the data as output data of the means, the data transmission rate of the transmission system can be used more effectively.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a multiplex transmitting apparatus 10 as a whole, and a plurality of (N [number]) encoding apparatus sections 20A to 20N having the same configuration are connected to a multiplexing apparatus section 50. Image signals S1A to S1N are supplied to the encoding device units 20A to 20N from an image supply device (not shown) such as a video tape recorder. Image signals S1A-S
1N is, for example, an MPEG (Moving Picture Experts Group) in the corresponding encoding device units 20A to 20N.
2 based on the TS (Transport Strea
m) Encoded data in packet units (D20A to D20N)
The multiplexed data is transmitted to the multiplexing device section 50, and then multiplexed, supplied to the transmitting section 60 as multiplexed data D50 in a transport stream configuration, and transmitted as a transmission signal D60.

In the encoding unit 20A, the image signal S
1A is supplied to the variable rate coding unit 30 and the fixed rate coding unit 40. The variable rate encoding unit 30 inputs the image signal S11A to the encoder 31, performs DCT (Discrete Cosine Transform) processing on a predetermined block basis, and converts the DCT coefficients obtained thereby into the encoding control unit 11.
Is quantized at a fixed quantization step size based on the variable rate coding control signal S53 supplied from the CDMA, and is further subjected to variable length coding to obtain variable rate coded data D31.

As described above, the variable rate coded data D31 quantized at a fixed quantization step size varies in data generation amount according to the complexity of the picture of the image signal S1A. The variable-rate coded data D31 is temporarily stored in the following buffer 32, and the first data of the selection circuit 12 is selected in response to the output control signal S54 supplied from the coding control unit 11.
To the switching input terminal 12A.

On the other hand, the fixed-rate encoding unit 40 inputs the image signal S1A to the encoder 41, performs DCT (Discrete Cosine Transform) processing on a predetermined block basis, and encodes the DCT coefficients obtained by this. Based on the fixed rate coding control signal S55 supplied from the control unit 11, quantization is performed with a variable quantization step size, and this is further subjected to variable length coding to obtain fixed rate coded data D41.

In this case, the fixed rate coding control signal S5
The quantization step size designated by 5 is a variable step size value such that the amount of data generated in the encoder 41 becomes a predetermined constant amount. The fixed-rate coded data D41 quantized with the variable quantization step size has a fixed data amount regardless of the complexity of the picture of the image signal S1A, and is temporarily stored in the subsequent buffer 42. The signal is transmitted to the second switching input terminal 12B of the selection circuit 12 in response to the output control signal S56 supplied from the encoding control unit 11.

The selection circuit 12 is switched to the first switching input terminal 12A side in the initial state, and outputs from the variable rate coding section 30 in response to the output control signal S54 supplied from the coding control section 11. The variable rate coded data D31 is output to the multiplexing unit 51 of the multiplexing unit 50 as selected output data D20A.

Here, the encoding control unit 11 includes a buffer 32.
The data amount of the variable-rate encoded data D31 stored therein and the average code generation rate per GOP (Group Of Picture) unit are constantly monitored by the code information S32, and similarly stored in the buffer 42. Of the fixed rate encoded data D41 and the GOP (Group Of Pi
cture) The average code generation rate per unit is represented by code information S4.
2 is always monitoring. And the encoding control unit 1
1 represents the code information S32 and S42 as code information S11A.
To the multiplexing control unit 53 of the multiplexing unit 50.

The above description has been made with respect to the first encoding unit 20A, but a plurality of encoding units 20A to 20A
N have the same configuration, and each of the encoding device units 20A to 20A
20N performs variable rate coding and fixed rate coding of the input image signals S1A to S1N, and calculates the amount of data generated by each coding in code information S11A to S11A.
In step S11N, the variable rate coded data D31 generated in each of the coder units 20A to 20N is selected as an initial state by each of the selection circuits 12, while being supplied to the multiplexing control unit 53 of the multiplexing unit 50 as S11N. Is supplied to the multiplexing unit 51 of the multiplexing unit 50 as the selected output data D20A to D20N.

Accordingly, the multiplexing unit 51 multiplexes the variable rate coded data D31 output from each of the coding units 20A to 20N as an initial state based on the control signal S74 supplied from the multiplexing control unit 53. Thus, the multiplexed data D50 is obtained, and is temporarily stored in the main buffer 52. Multiplexed data D50 stored in main buffer 52
Is an output control signal S7 supplied from the multiplexing control unit 53.
5 is output to the transmitting unit 60 in response to the number 5.

Here, the multiplexing control unit 53 generates code information S11A to S11A supplied from each of the encoding device units 20A to 20N.
Based on S11N, each code generation amount of the variable rate coded data D31 and the fixed rate coded data D41 generated in each of the encoders 20A to 20N is monitored, and is supplied to the multiplexing unit 51 at this time. The sum of the average code generation rates per GOP unit of each of the encoded data (variable encoded data D31 or fixed encoded data D41) selected as the selected output data D20A to D20N is the main buffer of the multiplexer unit 50. It is determined whether or not the transmission output rate that can be output from the transmission rate 52 exceeds the allowable value R [bits / sec].

Based on the result of the determination and the data occupancy of the main buffer 52, a failure due to the overflow of the main buffer 52 is predicted, and the selected output data output from the encoding units 20A to 20N is predicted based on the prediction result. D2
0A to D20N (ie, variable rate encoded data D3
Control is performed such that any one of the methods 1) is switched to the fixed rate encoded data D41 and supplied to the multiplexing unit 51.

That is, the multiplexing control section 53 enters the data switching processing procedure from step SP1 in FIG. 2, and in step SP2, each of the encoding apparatus sections 20A to 20A.
The total of the average code generation rates per GOP unit of the selected output data D20A to D20N output from each of the encoding device units 20A to 20N based on the code information S11A to S11N supplied from the 20N is an allowable value R [bits / sec]. It is determined whether or not: In this case, in this case, the selected output data D20A output from each of the encoding device units 20A to 20N.
ＤD20N are all variable rate encoded data D31 as an initial state.

If a positive result is obtained here, this means that the average of the selected output data D20A to D20N (in this case, all of the variable rate coded data D31) output from each of the coding units 20A to 20N. It indicates that the code generation amount does not exceed the allowable value R [bits / sec],
At this time, the multiplexing control unit 53 proceeds to the next step SP3, and at this time, continuously outputs the variable rate encoded data D31 output as the selected output data D20A to D20N from each of the encoding device units 20A to 20N.

On the other hand, if a negative result is obtained in step SP2, this means that each of the encoder units 20A to 20A.
20N selected output data D20A-D
20N (in this case, all variable rate encoded data D3
1) exceeds the allowable value R [bits / sec], which indicates that the main buffer 52 is predicted to fail. At this time, the multiplexing control unit 53 sets the step SP5
The average code generation rate per GOP among the variable rate encoded data D31 output as the selected output data D20A to D20N from the encoding device units 20A to 20N is R / N [bits / sec]. Detecting the encoder section that exceeds. Incidentally, R is an allowable value of the transmission rate [b
its / sec], and N represents the number of encoder units 20A to 20N.

In this way, when the encoding unit outputting the variable rate encoded data D31 exceeding R / N [bits / sec] to the multiplexing unit 51 is detected, the multiplexing control unit 53
Moves to step SP6, and selects one or a plurality of encoding device sections of the encoding device section detected in step SP5.
Then, a switching control signal (any of S56A to S56N) is transmitted to the second control signal. As a result, the designated selection circuit 12 is switched to the first switching input terminal 12B side, and in the subsequent step SP3, the fixed rate encoded data D41 is selected as the selected output data (any of D20A to D20N). Is output to

Here, in each of the variable rate coding sections 30 of each of the coding apparatus sections 20A to 20N, the average code generation rate when the input image signal is a simple picture is R
/ N [bits / sec], and a certain quantum value such that the average code generation rate becomes higher than R / N [bits / sec] when the input image signal has a complicated picture. Step size is assigned. On the contrary,
In each of the fixed rate coding sections 40 of each of the coding apparatus sections 20A to 20N, the average code generation rate is constant at R / N [bits / sec] regardless of the complexity of the picture of the input image signal. Are controlled by the encoding control unit 11.

Therefore, the average code generation rate is R / N [bit
[s / sec] or more, the encoding device unit that outputs the variable rate encoded data D41 as the selected output data, by the processing of step SP5 and step SP6, converts the variable rate encoded data D31 output at this time. Is switched to fixed-rate encoded data D41 which is set in advance so that the code generation rate becomes R / N [bits / sec], and is output to the multiplexing unit 51 as selected output data.

In this control, in step SP5 and step SP6, the average code generation rate is R / N [bits /
[sec], the average code generation rate is R / N [bits / sec].
The variable rate encoded data D31 described above is all switched to the fixed rate encoded data D41.

As a result, a plurality of encoding units 20A-2A
0N, selected output data D20A to D20N
Means that all the average code generation rates are R / N [bits / se
c], the selected output data D20A
The sum of the average code generation rates of all the codes from D to N is R [b
its / sec]. Therefore, the multiplexed data D5 obtained by multiplexing these selected output data D20A to D20N.
Since the average code generation rate of 0 is also not more than R [bits / sec], the transmission rate of the multiplexed data D50 output from the main buffer 52 to the transmission system is reduced.
2, the maximum transmission output rate R [bits / sec] or less.

In the above configuration, since the image signals S1A to S1N input to the plurality of encoder units 20A to 20N are different images, the complexity of each picture changes every moment without correlation.

Each of the encoding units 20A to 20N initially selects the variable rate encoded data D31 obtained by the variable rate encoding unit 30 as the selected output data D20A to 20N.
The signal is output to the multiplexing unit 51 as D20N. Accordingly, in the initial state, each of the encoding devices 20A to 20N quantizes the image signals S1A to S1N at a fixed quantization step size, thereby selecting and outputting the selected output data D20A to D20N regardless of the pattern of the input image. Keeps the image quality constant.

In this case, when the complexity of the picture increases,
Although the average code generation rate of the selected output data (variable rate encoded data D31) increases, the average code generation rate of one selected output data (variable rate encoded data D31) is R / N [bits / sec]. ], The selected output data D20 output from all (N) encoder units 20A to 20N when the complexity of the other input image is low.
The sum of the average code generation rates of A to D20N does not always exceed the allowable value (the transmission output rate of the main buffer 52) R [bits / sec].

Accordingly, the multiplexing control unit 53 of the multiplexing unit 50 monitors the sum of the average code generation amounts of all the coder units 20A to 20N, and the sum indicates the allowable value R [bits / sec].
Is exceeded, the average code generation rate of the selected output data (variable rate encoded data D31) is R / N [bits / se
c], and converts the encoded data output from the encoding unit as selected output data from the variable rate encoded data D31 to the fixed rate encoded data D.
Switch to 41.

As described above, the multiplexing control unit 53 outputs the selected output data D20 output from the encoding device units 20A to 20N.
By monitoring the sum of the average code generation rates of A to D20N, the average code generation amount of the variable rate coded data D31 is R / N [bits / se
c], the sum of the overall average code generation rates is R [b
As long as the value does not exceed its / sec], the encoding device unit can output the result (variable-rate encoded data D31) obtained by performing quantization with a fixed quantization step size to the multiplexing unit 51 as selected output data. As a result, coded data having a constant image quality can be obtained regardless of the complexity of the picture of the input image.

Accordingly, each of the coding units 20A to 20N has an average code generation rate of R / R
Even if it exceeds N [bits / sec], as long as the sum of the entire average code generation rates does not exceed R [bits / sec], the variable rate encoded data D31 can be output to the multiplexing unit 51 as selected output data. The frequency of image quality changes caused by switching to fixed rate coding can be reduced.

Each of the encoding units 20A to 20N
Even if the sum of the entire code generation rates does not exceed R [bits / sec], the variable rate coding section 30 and the fixed rate coding section 40 perform the fixed rate coding (R / N [bits / se]).
c]) are performed simultaneously, and the average code generation rate of the selected output data D20A to D20N (variable rate encoded data D31) output from all the encoding device units 20A to 20N is calculated. The total is R [bits / se
c], among the encoding units 20A to 20N,
Only those in which the average code generation rate of the variable rate encoded data D31 output as the selected output data D20A to D20N exceeds R / N [bits / sec] are immediately switched to the fixed rate encoded data D41 and output. .

Accordingly, each of the encoding units 20A to 20N performs predetermined encoding (in this embodiment, two types of variable rate encoding and fixed rate encoding).
Only the code amount need be performed, and there is no need to perform complicated code amount control in accordance with the code generation amount of the other encoding device units.

According to the above configuration, each encoding unit 20
A to 20N simultaneously perform the variable rate coding and the fixed rate coding, respectively.
Selected output data D20A-D output from A-20N
20N (variable rate encoded data D31), the variable rate encoded data D3
1 or the fixed-rate encoded data D41 by switching and outputting the encoded data, so that the encoding apparatus units 20A to 20N can easily control the entire code generation rate based on variable rate encoding without any change in image quality. And the multiplexing device unit 50.

In the above-described embodiment, a case has been described where the threshold for switching from variable rate coding to fixed rate coding is uniformly R / N [bits / sec], but the present invention is not limited to this. The total rate is R [bits / sec]
Then, the threshold is set to R / according to the program content of each channel.
Various settings may be made above or below N [bits / sec]. For example, for programs requiring high image quality such as movies, the threshold is set to R / N
[bits / sec] or more, and for a program that does not require high image quality such as news, by setting the threshold value to R / N [bits / sec] or less, an image having an image quality corresponding to the program content can be provided.

Also, in the above-described embodiment, the variable-rate encoding section 30 in the encoding apparatus sections 20A to 20N.
Although the case where two types of coding units of the fixed rate coding unit 40 are provided has been described, the present invention is not limited to this, and two or more coding units may be provided. In this case, by providing a plurality of variable rate coding units having different fixed quantization step sizes and / or providing a plurality of fixed rate coding units having different fixed code generation rates, the overall average code generation rate can be improved. To a predetermined value (eg, R [bits /
[sec]).

[0046]

As described above, according to the present invention, a plurality of encoding units each having a different code generation amount are provided in each of the plurality of encoding units, and an average of encoded data output from the plurality of encoding units is provided. Based on the total value of the code generation amounts, each of the plurality of encoding units is selected in each encoding unit, and encoded data output from the selected encoding unit is used as output data of the encoding unit. By multiplexing, it is possible to realize a multiplex transmission apparatus having a simple configuration that can more effectively use the data transmission rate of the transmission system.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a multiplex transmission apparatus according to the present invention.

FIG. 2 is a flowchart showing internal processing of a multiplex processing unit.

FIG. 3 is a block diagram showing a conventional multiplex transmission apparatus.

[Explanation of symbols]

1, 10 ... multiplex transmission apparatus, 2A-2N, 20A-2
0N: coding device section, 3, 50: multiplexing device section, 1
2 ... selection circuit, 30 ... variable rate coding unit, 31,
41 ... encoding unit, 32, 42 ... buffer, 40 ...
Fixed-rate encoding unit 51 51 Multiplexing unit 52 Main buffer 53 Multiplexing control unit

Claims (3)

[Claims] An information coding and multiplexing apparatus comprising a plurality of coding means for inputting predetermined information, coding the information and outputting the information, and multiplexing coded data output from each of the coding means. The encoding means each having a plurality of encoding units having different code generation amounts, and the encoding means based on the code generation amounts of the encoded data output from the plurality of encoding means, respectively. Selecting means for selecting any one of the plurality of encoding units and multiplexing encoded data output from the selected encoding unit as encoded data of the encoding means. Information coding and multiplexing device. 2. A plurality of encoding units included in each of the encoding means, wherein a fixed-rate encoding unit in which a generated code amount is constant, and a generated code amount changes according to the input information. The information coding and multiplexing apparatus according to claim 1, wherein the information coding and multiplexing apparatus is a variable rate coding unit. 3. The encoding device according to claim 2, wherein the selecting unit is configured to, when a total value of an average code generation amount of the encoded data output from the plurality of encoding units is equal to or less than a predetermined allowable value, select all of the encoding units. Selecting a variable rate coding unit, when the total value of the average code generation amount of the coded data output from the plurality of coding means exceeds the allowable value,
The information coding and multiplexing apparatus according to claim 2, wherein the fixed rate coding unit is selected in some or all of the plurality of coding units.