JPH1127665A - Video data coder, its method and video data transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video data coder and its method by which statistical multiplexing is realized without causing overflow even for a program group where phases of group of picture(GOP) differ. SOLUTION: Encoders 21 , 22 ,...2n obtain coding difficulty information difficulty #1, difficulty #2,... difficulty #n for each GOP of n programs prog.1, prog.2,... prog.n, and provide their outputs, determine object coding rates based on target rate #1, target rate #2,... target rate #n fed from a controller 3 and provide an output of coded stream outputs stream #1, stream #2,... stream #n. In the case that the controller 3 assigns the object coding rates to the encoders 21 , 22 ,... 2n , the assignment to decrease values is made first and the assignment to increase values later. A multiplexer 4 multiplexes the coded stream outputs stream #1, stream #2,... stream #n.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video data encoding apparatus and method for compressing and encoding a plurality of video data and multiplexing the video data at a predetermined data rate or less, and a video data transmission method.

[0002]

2. Description of the Related Art In recent years, MPEG in which motion compensation processing (MC) and redundancy reduction processing by orthogonal transform such as discrete cosine transfer (DCT) are combined with compression coding of video data. (Mo
ving picture experts group) and MPEG2 have come to be widely used. In particular, digital broadcasting of video has been realized by combining the video compression coding technology of MPEG2 and the function of a communication satellite. In the future, digital broadcasting using terrestrial waves will be realized.

An advantage of digital broadcasting is that more programs can be transmitted on the same transmission path as compared with analog broadcasting. this is,
This is because the video can be compression-coded.

As a method of flowing more programs, a method called "statistical multiplexing" has been considered. Statistical multiplexing is a method of dynamically changing the transmission rate of each program and, for example, reducing the rate of a program in which image quality degradation is not conspicuous even if the transmission rate is reduced, thereby allowing many programs to flow.

FIG. 7 shows three programs for comparison.
For example, an example of multiplexing a weather forecast, news, and drama at a fixed rate will be described. The horizontal axis shows the flow of time, and the vertical axis shows the assigned coding rate for each program. In FIG. 7, each program remains at the coding rate assigned by the initial value and does not vary with time. Here, the initial assignment values are assigned so that the deterioration in the portion (time) where the image quality is conspicuous in each program falls within an allowable range. In other words, other than that part, an unnecessary coding rate is assigned.

On the other hand, FIG. 8 shows an example in which four programs are multiplexed using the above-described statistical multiplexing method. Here, the rates of weather forecast, news, drama 1 and drama 2 are dynamically changed. This takes advantage of the fact that portions (time) where the image quality of each program is noticeably deteriorated rarely overlap at the same time. Therefore, when a certain program is a part where the image quality degradation is conspicuous, other programs are not conspicuous even if the coding rate is reduced, so that the coding rate of the other program can be allocated more to the program where the image quality degradation is conspicuous. . In this way, more programs can be transmitted than usual.

As described above, in the statistical multiplexing, the coding rate is dynamically changed, and the time span of the change is determined by a group of pictures (hereinafter referred to as "group of pictures") which is a unit of moving image compression used in the MPEG2. GO
It is called P. ).

[0008] The GOP is an intra-frame coded image (I
Picture, an inter-frame forward predictive coded image (P picture), and a bidirectional predictive coded image (B picture). The I picture, the P picture, and the B picture are arranged in a predetermined order. ing. Generally, GOP
Has one I frame, for example, “IBBPBB”
PBBPBBPBB "is composed of 15 frames.

When the unit for dynamically changing the coding rate is the above GOP, TM5 [test model 5; ISO / IEC JTC / SC29, which is a rate control method generally used in the compression algorithm of the MPEG system, is generally used. (1993)] can be realized with only minor modifications. this is,
This is because TM5 originally performs control for each GOP by converting the coding rate into a code amount for each GOP.
In addition, if the image is of the order of GOP, it is possible to perform good rate control by pre-reading the image in advance.

[0010]

Incidentally, in the statistical multiplexing, when the coding rate is dynamically changed in the GOP unit, phase irregularity becomes a problem. There is no guarantee that the GOP phases of the programs multiplexed by the multiplexer are all the same. In addition, in the 2-3 pull-down processing often used for movie material, since the frame rate is not 30 frames / sec, a deviation from a moving image of 30 frames / sec occurs. This displacement may cause the screen to break down.

For example, a specific example of multiplexing two programs is shown in FIGS. In both cases, the capacity of the transmission line is 10
It is assumed to be Mbps. The program prog.A was changed from 5Mbps to 7Mbps. On the other hand, program prog.B needed to change from 5 Mbps to 3 Mbps. At this time, as shown in FIG.
If the changing point of gA is the same as or later in time than the changing point of program prog.B, transmission can be performed without overflowing the transmission path. However, as shown in FIG. If the time is earlier than the change point, the transmission path overflows. This overflow significantly degrades the image quality, and in the worst case, the operation of the decoder may stop, which is very undesirable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a video data encoding apparatus and method capable of implementing statistical multiplexing without overflow for programs having different GOP phases. I do.

Further, the present invention has been made in view of the above-mentioned circumstances, and a video data transmission method capable of performing statistical multiplexing without overflowing even for a group of programs having different GOP phases and transmitting the same. The purpose is to provide.

[0014]

In order to solve the above-mentioned problems, the video data encoding apparatus according to the present invention is arranged such that the target encoding rate allocating means assigns a target encoding rate allocation order to a plurality of n video programs. Are performed in time prior to the allocation in which the value of the target coding rate is small, and the plurality of n coding units are configured to receive the target coding rate from the target coding rate allocating unit. Since the plurality of n video programs are encoded based on the target encoding rate, no overflow occurs.

Further, in the video data encoding method according to the present invention, in order to solve the above-mentioned problem, the target encoding rate allocating step includes the steps of: Priority is given to the assignment in which the value of the coding rate is small, and it is performed temporally before the assignment in which the value is large, and the coding step is performed based on the target coding rate from the target coding rate allocating step. Since a plurality of n video programs are encoded,
No overflow occurs.

In the video data transmission method according to the present invention, in order to solve the above-mentioned problem, the target coding rate allocating step includes the steps of: Priority is given to the assignment in which the value of the coding rate is small, and is performed temporally before the assignment in which the value is large, and the coding step is performed based on the target coding rate from the target coding rate allocating step. Since the n video programs are encoded and the multiplexing step multiplexes the encoded video programs from the encoding step, transmission that overflows the transmission path can be avoided.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a video data encoding apparatus and method and a video data transmission method according to the present invention will be described with reference to the drawings.

This embodiment is a video data transmission apparatus for compressing and encoding video data of a plurality of video programs, and then multiplexing and transmitting the video data. This video data transmission device has a configuration in which a multiplexing unit is provided in a video data encoding device to which the video data encoding method according to the present invention is applied.

In this embodiment, in order to transmit many video programs when the capacity of the transmission path is fixed, the transmission rate of each program is dynamically changed by statistical multiplexing and compressed. Transmit compression encoded data.
In particular, this video data transmission apparatus uses a span for dynamically changing the encoding rate as a GOP, which is a unit of moving image compression used in MPEG2.

[0020] The video data transmitting apparatus, as shown in FIG. 1, the input terminal 1 _1, 1 _2, ... and n-number of programs input through the 1 _n prog.1, PROG.2 ... And prog.n
Difficulty information for each GOP
, And difficulty # n are calculated and output, and the coding is performed based on target coding rates target_rate # 1, target_rate # 2, and target_rate # n supplied from the controller 3 described later. Determine the rate and output the encoded stream stream # 1, stream # 2 ... and stre
an encoder 2 _{1, 2} 2 ..., and 2 _n for outputting am # n,
.. And din from the encoders 2 ₁ , 2 ₂ ... And 2 _n.
Obtain fficulty # n and set the target coding rate ta for each encoder
rget_rate # 1, target_rate # 2 ... and target_rate # n
, And the controller 3 returning to the encoders, and the coded stream outputs stream # 1, stream # 2... And stream # _n from the encoders 2 ₁ , 2 _2. And a multiplexer 4 for supplying a multiplexed output MUXout to an output terminal 5.

The controller 3 includes the encoders 2 ₁ , 2 ₂
,... And 2 _n , the phase information of each GOP is correctly grasped, and each encoder gives priority to the assignment that lowers the allocation than the allocation that increases the target coding rate.

That is, the controller 3 includes a plurality n
When assigning the target coding rate to the encoders 2 ₁ , 2 _2, ..., And 2 _n , the video is assigned in such a manner that the smaller value is assigned earlier and the larger value is assigned later in time. Data compression method is applied. The details of this algorithm will be described later.

[0023] Each of the encoders 2 _{1, 2} 2,... And 2 _n is,
The configuration is as shown in FIG. Here, encoder 2
₁ will be described as a representative. The encoder 2 _1, the image rearrangement circuit 9, the scan conversion macroblock forming circuit 10,
Addition circuit 11, DCT circuit 12, quantization circuit 13, variable length coding circuit (VLC) 14, buffer 15, code amount control circuit 16, inverse quantization circuit 17, inverse DCT circuit 18, addition circuit 19, motion compensation circuit This is a general video data compression encoder composed of a motion detection circuit 20 and a motion detection circuit 21.

The image rearranging circuit 9 rearranges video signal inputs in the order of encoding. The scan conversion / macroblock conversion circuit 10 performs field-frame conversion to form a macroblock. For example, when the video signal input is a movie video signal, 3: 2 pull-down processing or the like is performed.

The addition circuit 11 subtracts the output data of the addition circuit 19 from the input video signal passed through the scan conversion / macroblock conversion circuit 10 and outputs the result to the DCT circuit 12.

The DCT circuit 12 performs a discrete cosine transform (DCT) process on the video data input from the adder circuit 11, for example, in units of 16 × 16 pixel macroblocks.
The data in the time domain is converted into data in the frequency domain and output to the quantization circuit 13.

The quantization circuit 13 quantizes the data in the frequency domain input from the DCT circuit 12 with a fixed or arbitrary quantization value, and generates the variable-length coding circuit 1 as quantized data.
4 and the inverse quantization circuit 17.

The variable-length encoding circuit 14 includes a quantization circuit 13
The variable-length encoding is performed on the quantized data input from the CPU, and the compressed video data obtained as a result of the variable-length encoding is supplied to the buffer 15. The buffer 15 buffers the compressed video data and outputs a bit stream stream # 1 via the output terminal 24.

The inverse quantization circuit 17 inversely quantizes the quantized data input from the quantization circuit 13 and outputs it to the inverse DCT circuit 18 as inversely quantized data.

The inverse DCT circuit 18 performs inverse DCT processing on the inversely quantized data input from the inverse quantization circuit 17 and outputs the result to the adding circuit 19.

The addition circuit 19 adds the output data of the motion compensation circuit 20 and the output data of the inverse DCT circuit 18 and outputs the result to the addition circuit 19 and the motion compensation circuit 20.

The motion compensating circuit 20 performs a motion compensating process on the output data of the adding circuit 19 based on the motion vector calculated for the reference frame by the motion detecting circuit 21, and outputs the result to the adding circuit 11. .

[0033] The encoder 2 _1, first, the case of obtaining the coding difficulty difficulty is to pre-play the program, and the quantization step of the quantization circuit 13 to a fixed value, the generated code amount of the buffer 15 Measure. The generated code amount data is supplied to the controller 3 via the output terminal 22 as the above-mentioned encoding difficulty difficulty.

The target code amount target_rate # 1 determined by the controller 3 by an algorithm described later is supplied to the code amount control circuit 16 via the input terminal 23. The code amount control circuit 16 controls an arbitrary quantization value in the quantization circuit 13.

The controller 3 comprises a ROM 26, a CPU 27 and a RAM 28, for example, as shown in FIG. The CPU 27 receives the encoding difficulty information difficulty from each encoder via an input terminal 29, and sends a target_rate to each encoder via an output terminal 30 from the CPU 27. The CPU 27 executes the algorithms and tables stored in the ROM 26 while using the RAM 28 as a work area.

The algorithm stored in the ROM 26 will be described with reference to the flowchart of FIG.

This process is performed when a new rate is assigned to each program. Here, it is assumed that the newly assigned program number is i.

First, in step S1, a new allocation rate candidate New_Rate (i) for the program i is calculated using the encoding difficulty information difficulty. Next, in step S2, the new allocation rate candidate New_Rate
Curr_Rate (i) containing (i) and the previous assigned rate
Compare with Here, if New_Rate (i) is large, the process proceeds to step S3, and this time, New_Rate (i) is compared with the rate obtained by subtracting the sum of the rates of programs other than i from the rate of the entire transmission channel torall_rate. Where New_Ra
If te (i) is larger, the process proceeds to step S4, where the previous assigned rate Curr_Rate (i) is determined as a new rate, and Curr_Rat is determined.
Substitute for e (i) and exit.

In step S2, New_Rate (i) is Curr_Rate.
(i) If it is equal to or less than, or if New_Rate (i) is equal to or less than in step S3, the process proceeds to step S5, where the calculated allocation rate candidate New_Rate (i) is determined as a new rate, and Curr_Rate (i) is determined. ) And exit.

FIG. 5 shows an example using this algorithm.
Here, the horizontal axis indicates time, and the vertical axis indicates the occupation of the actual rate of each program. It is assumed that the capacity of the transmission path is 10 Mbps.

The length of the GOP of the program prog.3 is shorter than the length of the GOP of the programs prog.1 and prog.2. In the figure, “()” represents the step S in FIG.
This is the value of the new allocation rate candidate New_Rate () calculated in step 1. Immediately before “()”, the actual rate determined by the algorithm described above is used. “#”
The numbers following GOP are the numbers of the GOPs in each program added for easy understanding. It is assumed that there are three programs, and the program prog.1 is stable at 5 Mbps, the program prog.2 is 2 Mbps, and the program prog.3 is 3 Mbps as an initial state.

The following describes the order in which the above algorithm is applied. First, priority is given to those that change quickly. Next, when the changing points of the GOPs of the program are the same, priority is given to the one whose rate decreases. The next priority is the one with the lowest program number. Since the initial state is stable, the above processing is performed from GOP # 2 of the program prog.2 where a change occurs. In each GOP, a GOP whose numerical value is shown diagonally to the upper right is targeted. The description will be made in the order of the numerical values at the upper right.

1. The calculated rate of GOP # 2 of program prog.2 is 4, but the rate is higher than before, and the remainder after subtracting the use of other programs from the total rate of the channel is 2, so it is actually The rate taken is 2.

2. The calculated rate of GOP # 2 of program prog.3 is 2, and the actual rate is 2 because the rate is smaller than before.

3. The calculated rate of GOP # 2 of program prog.1 is 4, and the actual rate is 4, because the rate is smaller than before.

4. GOP # 3 of program prog.2 has a calculated rate of 4 and the rate is higher than before, but the remainder obtained by subtracting the usage of other programs from the total rate of the channel is 4, Actual rate is 4
Becomes

5. GOP # 3 of program prog.3 has the calculated rate of 2 and the same rate as before, so the actual rate taken is 2.

6 GOP # 3 of program prog.1 has a calculated rate of 4 and the same rate as before, so the actual rate taken is 4.

7. GOP # 4 of program prog.2 has a calculated rate of 4 and the rate is the same as before, so the actual rate taken is 4.

8. GOP # 4 of program prog.3 has the calculated rate of 2 and the same rate as before, so the actual rate taken is 2.

9. GOP # 4 of the program prog.1 has the calculated rate of 4 and the same rate as before, so the actual rate taken is 4.

10. GOP # 5 of program prog.3 has a calculated rate of 3, but the rate increases from before,
Since the remainder obtained by subtracting the usage of other programs from the total rate of the channel is 2, the actual rate taken is 2
Becomes

11. The calculated rate of GOP # 5 of program prog.2 is 3, and the actual rate is 3, because the rate is smaller than before.

12. GOP # 5 of program prog.1 has a calculated rate of 4 and the same rate as before, so the actual rate taken is 4.

13. GOP # 6 of program prog.3 has a calculated rate of 3, but the rate increases from before,
In addition, since the remainder obtained by subtracting the usage of other programs from the total rate of the channel is 3, the rate actually taken is 3
Becomes

14. The calculated rate of GOP # 6 of program prog.2 is 3, which is the same as before, so the actual rate taken is 3.

15. The calculated rate of GOP # 7 of program prog.3 is 3, and the rate is the same as before, so the actual rate taken is 3.

16. The calculated rate of GOP # 6 of program prog.1 is 4, and the rate is the same as before, so the actual rate taken is 4.

17. GOP # 7 of program prog.2 has a calculated rate of 4, but the rate increases from before,
In addition, since the remainder obtained by subtracting the usage of other programs from the total rate of the channel is 3, the rate actually taken is 3
Becomes

18. GOP # 8 of program prog.3 has a calculated rate of 3 and the rate is the same as before, so the actual rate taken is 3.

19. The calculated rate of GOP # 7 of program prog.1 is 3, and the actual rate is 3 because the rate is smaller than before.

20. GOP # 8 of program prog.2 has a calculated rate of 4, but the rate increases from before,
In addition, since the remainder obtained by subtracting the usage of other programs from the total rate of the channel is 4, the rate actually taken is 4
Becomes

21. The calculated rate of GOP # 9 of program prog.3 is 3, and the rate is the same as before, so the actual rate taken is 3.

22. The calculated rate of GOP # 8 of program prog.1 is 3, which is the same as before, so the actual rate taken is 3.

23. The calculated rate of GOP # 10 of program prog.3 is 3, and the rate is the same as before, so the actual rate taken is 3.

24. The calculated rate of GOP # 9 of program prog.2 is 4, and the rate is the same as before, so the actual rate taken is 4.

25. The calculated rate of GOP # 11 of program prog.3 is 2, and the actual rate is 2 because the calculated rate is smaller than before.

26. GOP # 8 of program prog.1 has a calculated rate of 5, but the rate increases from before,
In addition, since the remainder obtained by subtracting the usage of other programs from the total rate of the channel is 3, the rate actually taken is 3
Becomes

27. The calculated rate of GOP # 10 of program prog.2 is 3, and the actual rate is 3 because the rate is smaller than before.

28. GOP # 12 of program prog.3 has a calculated rate of 2 and the same rate as before, so the actual rate taken is 2.

29. GOP # 10 of program prog.1 has a calculated rate of 5, but since the rate is higher than before and the remainder obtained by subtracting the use of other programs from the total rate of the channel is 5, the actual rate is 5. The rate taken is 5.

30. The calculated rate of GOP # 11 of program prog.2 is 3, and the rate is the same as before, so the actual rate taken is 3.

31. The calculated rate of GOP # 13 of program prog.3 is 2, and the rate is the same as before, so the actual rate taken is 2.

32. The calculated rate of GOP # 11 of program prog.1 is 5, and the rate is the same as before, so the actual rate taken is 5.

33. The calculated rate of GOP # 12 of program prog.2 is 3, and the rate is the same as before, so the actual rate taken is 3.

34. GOP # 14 of program prog.3 has a calculated rate of 2 and the same rate as before, so the actual rate taken is 2.

Here, the dead space (de) shown in FIG.
ad space) is the surplus in terms of rate. Although there is a surplus part, no overflow occurs when the above algorithm is used.

That is, according to the video data transmission apparatus according to the above-described embodiment, when three groups of programs having different GOP phases are transmitted via a fixed capacity transmission path,
Statistical multiplexing can be realized and transmitted without overflow.

In the above-described embodiment, the encoding difficulty information difficulty is obtained for each program by the same encoder that actually performs the encoding. However, the encoding difficulty information obtained by using a fixed quantization encoder separately is obtained. Difficulty difficulty
A target encoding rate may be assigned based on ty, and the actual encoding may be delayed by an appropriate FIFO for processing.

FIG. 6 shows a specific example of a video data compression apparatus using two encoders in one program system. The video data compression apparatus shown in FIG. 6 converts the difficulty data of the compressed video data obtained by preliminary compression encoding of the non-compressed video data into the encoding difficulty information di of the non-compressed video data.
Calculates the fficulty and calculates the compression difficulty of the uncompressed video data delayed by a predetermined time by a FIFO memory or the like, based on the encoding difficulty calculated by the preliminary compression encoding. Encoding method is applied.

If this simple two-pass encoding method is used, it is possible to adaptively compress and encode the non-compressed video data almost in real time based on the degree of difficulty of the picture of the non-compressed video data. It can be applied to applications that require real-time performance, and is suitable for transmission of a plurality of programs using the above-described statistical multiplexing method.

This video data compression apparatus multiplexes n input programs prog.1, prog.2... Prog.n. Each program has input terminals 101 ₁ , 101 _2.
Through 01 _n, encoders # A102 _1, 102 ₂ ···
And 102 _n . Each encoder # A102 ₁ , 1
02 ₂ ..., and 102 _n fixed quantizing steps FixedQ
# 1 Difficulty # 1, # 2 ... # when quantized by
Measure n. The measured code amount difficulty # 1,
.. #N are sent to the controller 103. In the controller 103, each code amount difficulty #
Each program prog.1, pro based on 1, # 2 ... # n
g.2 ... allocation rate of prog.n target_rate # 1, # 2
· · #N was calculated by applying the algorithm described above, and sends to each encoder _{# B104 1, 104 2 ··· 104} n.

Encoder #B 104 ₁ , 104 ₂ ... 10
At 4 _n , the data actually encoded is delayed by the FIFO 105 ₁ , 105 ₂ ... 105 _n by the look-ahead time. Encoder # B104 ₁ , 104 ₂ ... 104
_{In n} , given rates target_rate # 1, # 2 ... #
input program prog.1, prog.2 ... pro based on n
encode gn. Each encoded stream s
.. #n are multiplexed by the multiplexer 106, and output terminals 1 as multiplexed output MUXout.
07.

Also, one encoder for each program system is used to calculate the sum of flatness in frame units, the sum of intra ACs,
The DC value and the ME residual may be pre-read as parameter information, the code amount difficult of the image may be estimated, and supplied to the controller.

Here, the controller uses the code amount of the image to execute each program pro according to the above algorithm.
g.1, prog.2 ... prog.n allocation rate target_rate #
.., #N are calculated and sent to each encoder.

[0086]

According to the video data encoding apparatus of the present invention, statistical multiplexing can be realized without overflowing even for a group of programs having different GOP phases.

Further, according to the video data encoding method of the present invention, statistical multiplexing can be realized without overflowing even for a group of programs having different GOP phases.
Further, according to the video data transmission method according to the present invention, GO
A program group having different P phases can be transmitted after performing statistical multiplexing without overflowing.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a video data compression apparatus and method according to the present invention.

FIG. 2 is a block diagram illustrating a detailed configuration of an encoder used in the embodiment.

FIG. 3 is a block diagram illustrating a detailed configuration of a controller used in the embodiment.

FIG. 4 is a flowchart illustrating an algorithm executed by the controller.

FIG. 5 is a timing chart for explaining an operation example of the embodiment.

FIG. 6 is a block diagram of another embodiment in which two encoders are used for one program system.

FIG. 7 is a diagram for explaining multiplexing at a fixed rate.

FIG. 8 is a diagram for explaining multiplexing by statistical multiplexing.

FIG. 9 is a diagram showing a case where overflow does not occur due to multiplexing.

FIG. 10 is a diagram showing a case where overflow occurs due to multiplexing.

[Explanation of symbols]

2 ₁ , 2 ₂ ... And 2 _n encoders, 3 controllers, 4 multiplexers

Claims (9)

[Claims] In order to reduce the transmission rate when a plurality of n (n ≧ 2) video programs are multiplexed and transmitted, the transmission rate is not more than a predetermined value. A video data encoding device that allocates and encodes encoding rates, wherein the order of assigning target encoding rates to the plurality of n video programs is prioritized in such an order that the value of the target encoding rate decreases. A target coding rate allocating unit that performs time prior to the allocation in which the value increases, and a plurality of units that encode the plurality of n video programs based on the target coding rate from the target coding rate allocating unit. A video data encoding device comprising: n encoding units. 2. The image processing apparatus according to claim 1, wherein each of the plurality of n encoding units includes a predetermined number of intra-coded images, inter-frame forward predicted coded images, and bidirectional predicted coded images. 2. The video data encoding apparatus according to claim 1, wherein the video data of the video program is encoded. 3. The video data encoding apparatus according to claim 2, wherein the plurality of n image encoding groups have different phases. 4. In order to reduce a transmission rate when a plurality of n (n ≧ 2) video programs are multiplexed and transmitted to a predetermined value or less, independent targets are set for the plurality of n video programs. A video data coding method for allocating and coding a coding rate, wherein the order of allocating target coding rates to the plurality of n video programs is prioritized in such a way that the value of the target coding rate becomes smaller. A target coding rate allocating step to be performed earlier than the allocation in which the value increases, and a code for coding the plurality of n video programs based on the target coding rate from the target coding rate allocating step. And a video data encoding method. 5. The video data of the video program in a video coding group unit including a predetermined number of intra-frame coded images, inter-frame forward prediction coded images, and bidirectional prediction coded images. 5. The video data encoding method according to claim 4, wherein 6. The video data encoding method according to claim 5, wherein the plurality of n image encoding groups have different phases. 7. In order to reduce the transmission rate to a predetermined value or less, a plurality of n (n ≧ 2) video programs are assigned and encoded with independent target encoding rates, and then multiplexed and transmitted. Video data transmission method, wherein the order of assigning the target coding rate to the plurality of n video programs is set to be shorter than the assignment in which the value of the target coding rate becomes smaller, giving priority to the assignment in which the value of the target coding rate becomes smaller. A target encoding rate allocating step to be performed first, an encoding step of encoding the plurality of n video programs based on the target encoding rate from the target encoding rate allocating step, A multiplexing step of multiplexing the encoded video program. 8. The image processing apparatus according to claim 8, wherein the encoding step includes the steps of: 8. The video data transmission method according to claim 7, wherein 9. The video data transmission method according to claim 8, wherein the plurality of n image encoding groups have different phases.