JP3914212B2 - Moving picture coding apparatus, moving picture coding method, moving picture coding program, and computer-readable recording medium recording the program - Google Patents

Description

  The present invention relates to a moving picture coding technique, and more particularly to a moving picture coding apparatus having an adaptive bit rate distribution function between a plurality of channels.

  A video encoding apparatus having an adaptive bit rate distribution function between multiple channels generally receives video of multiple channels, performs code amount distribution or bit rate distribution between channels according to the contents of each input video, Each encoding unit generates a variable bit rate encoded stream.

  The encoded stream output from the stream buffer of each encoding unit is multiplexed into one fixed bit rate or variable bit rate stream in a multiplexing unit in the apparatus or a multiplexing apparatus outside the apparatus.

  In such a case, the sum of the bit rates of the variable bit rate encoded streams output from the stream buffer of each encoding unit is always equal to or less than the bit rate after multiplexing. Is desirable. This means that if there is a moment when the sum of bit rates exceeds the bit rate after multiplexing, the bit rate of each encoded stream must be smoothed at the time of multiplexing, and the encoded data reception timing in the decoder can be controlled. This is because there are problems that become difficult.

  In order to ensure that the sum of the bit rates of the encoded streams output from the stream buffers of each encoding unit is always equal to or less than the bit rate after multiplexing, It is necessary to correctly distribute the bit rate and to match the output bit rate switching timing between the encoding units.

  As a method for realizing this, as a method that has been generally studied conventionally, there is a method in which switching of the output bit rate is instructed directly from one control unit to the stream buffer of each encoding unit at the same timing.

The following Patent Document 1 and Patent Document 2 describe a moving picture coding apparatus having a function for realizing adaptive bit rate distribution among a plurality of channels.
JP-A-6-62393 JP-A-7-303252

  In the method for instructing the switching of the output bit rate from the single control unit to the stream buffer of each encoding unit directly at the same timing, the encoded stream is output to each encoding unit at an arbitrary timing from the outside. An interface for receiving a bit rate switching instruction is required.

  Usually, as an implementation method of each encoding unit in such an encoding system, it is excellent in cost to use a video encoder LSI developed for general-purpose purposes. In many cases, the encoder LSI itself does not hold an interface that accepts an instruction to switch the output bit rate at an arbitrary timing.

  In this case, a method can be used in which an encoded stream is temporarily output from each encoder LSI to an external buffer, and the output bit rate of each encoded stream from the buffer and the switching timing of the output bit rate are controlled. However, this method requires a new external buffer circuit, which increases the circuit scale and is wasteful.

  In the method of instructing switching of the output bit rate at an arbitrary timing from the outside, there is a possibility that the output bit rate is switched while the encoded stream of the picture is being output. For this reason, there is no method for calculating the buffer occupancy by adding / subtracting the generated code amount and the encoded stream output code amount in units of pictures, which is adopted in a normal constant bit rate encoding control algorithm. For this reason, there is a problem that the constant bit rate algorithm in the normal encoder cannot be applied as it is, for example, it is necessary to always monitor the amount of data actually stored in the stream buffer.

  There are some moving picture coding apparatuses having a function of realizing adaptive bit rate allocation among a plurality of channels, which are described in Patent Document 1 and Patent Document 2 described above, all of which solve the above problems. Not done.

  An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a moving picture coding technique capable of appropriately controlling adaptive bit rate allocation among a plurality of channels without increasing the circuit scale. To do.

  In order to solve the above problem, in the present invention, the output bit rate of the encoded stream is changed in units of encoded streams for N (N is an integer of 1 or more) pictures in each encoding unit. At this time, the output start timing and output end timing of the encoded stream for N pictures are made to substantially coincide between the encoding units.

  With respect to the output start timing, the timing between the encoding units is matched by giving each encoding unit in common the time to start outputting encoded streams for N pictures. Regarding the output end timing, the output bit rate of the encoded stream for the N pictures of each encoding unit is determined so as to be proportional to the predicted value of the generated code amount for the N pictures in each encoding unit. , The time required to output the encoded streams for the same N pictures in each encoding unit is made to be substantially the same, and the output end timing is matched.

  The predicted value of the generated code amount in each encoding unit for N pictures is obtained from the encoding result of pre-encoding or the encoding result of past pictures. In each encoding unit, adjustments such as control of the code amount and insertion of zero data are performed based on the determined output bit rate so that the transmission / reception buffer does not fail in each encoding unit.

  As described above, when the code amount is changed to avoid failure of the transmission / reception buffer, the generated code amount in each encoding unit may differ from the predicted value, so the output end timing is consistent between the encoding units. It is possible that you will not. Therefore, each encoding unit temporarily stops outputting the encoded stream after the output of the encoded streams for the N pictures is completed. Then, a time having a certain margin time from the latest output end timing among the encoding units is commonly given to each encoding unit as an output start time of the encoded stream of the subsequent pictures, and each encoding unit At this time, output of an encoded stream of subsequent pictures is started.

  Incidentally, the output end timing of each encoding unit can be obtained from the output bit rate of the encoded stream for the N pictures in each encoding unit and the generated code amount for the N pictures in each encoding unit. The output start time of the encoded stream of the subsequent pictures can be given in advance to each encoding unit before the end of the output of the encoded streams for the N pictures.

  In the present invention, as described above, the output bit rate of each encoding unit is changed in units of encoded streams for N pictures, but this N is made variable so that it is dynamically changed during encoding. Also good. The advantage of making N variable is that, for example, when a scene change occurs, the bit rate distribution between channels is changed at that time, so that buffer failure is less likely to occur and efficient code amount distribution becomes possible. That is.

  According to the present invention, each encoding unit generates a variable bit rate encoding stream corresponding to the content of the input image of each channel and multiplexes them into a single stream. The total sum of the bit rates of the encoded streams output from the stream buffer of the encoding unit can always be kept below a certain value without instructing the stream buffer of the unit directly to switch the output bit rate at the same timing. . Therefore, it becomes easier to implement a moving picture coding apparatus having an adaptive bit rate distribution function between a plurality of channels.

[First Embodiment]
FIG. 1 is a diagram showing a configuration of a moving picture coding apparatus according to the first embodiment of the present invention. Here, an example in which the number of input video channels is 3 will be described. The moving image encoding apparatus 1 includes pre-encoding units 16, 17, 18 for each channel, frame buffers 13, 14, 15, encoding units 10, 11, 12, and encoding units 10-12. A multiplexing unit 30 that multiplexes the encoded stream to be output and an overall control unit 10 that performs overall control thereof are provided.

  The overall control unit 19 includes a pre-encoding unit control unit (not shown) that controls the encoding of the entire pre-encoding units 16 to 18 and an encoding unit control unit that controls the encoding of the entire encoding units 10 to 12. (Not shown), in particular, in each encoding unit 10-12 in units of N picture encoded streams based on the result of pre-encoding in each pre-encoding unit 16-18 of each input video An output bit rate determination control unit 190 that determines an output bit rate and notifies each of the encoding units 10 to 12, and an output start that controls the output start timing of encoded streams for N pictures in each of the encoding units 10 to 12 A timing control unit 191.

  The encoding unit 10 includes a control unit 100, a stream generation unit 101, and a stream buffer 102. Similarly, the encoding units 11 and 12 include control units 110 and 120, stream generation units 111 and 121, and stream buffers 112 and 122, respectively. Similarly, the pre-encoding units 16, 17, and 18 include control units 160, 170, and 180, stream generation units 161, 171, and 181 and stream buffers 162, 172, and 182, respectively.

  Input video images A to C are input video images having different contents synchronized with each other. For example, it is assumed that one video image is divided into three. The moving image encoding apparatus 1 encodes input videos A to C, multiplexes the generated three encoded streams into one, and outputs the multiplexed streams. The bit rate of this multiplexed stream is a fixed bit rate, which is hereinafter referred to as the overall bit rate.

  The input videos A to C are input to the corresponding pre-encoding units 16 to 18 and are pre-encoded. In pre-encoding, the overall control unit 19 aggregates the picture encoding results of the pre-encoding units 16 to 18 in a picture cycle, and based on this, determines the target code amount or quantization parameter of the picture, It gives to each pre-encoding part 16-18. Here, unified coding control is performed so that the quantization parameters of pictures are almost equal between channels, and the total bit rate of the generated code amount becomes the total bit rate.

  For example, a fixed bit rate frame with the overall bit rate as the coding bit rate is obtained by calculating the overall complexity index based on the sum of the generated code amounts of the coding results of each channel and the average value of the average quantization parameter. The overall picture target code amount is determined by the inter-rate control algorithm. This overall picture target code amount is distributed to each channel in proportion to the picture complexity index for each channel, and is used as the picture target code amount for each channel.

  The above complexity index represents an amount of information of the original video normalized by the value of the quantization parameter. In general, the generated code amount can be changed by changing the quantization parameter. The two are generally in an inversely proportional relationship, and the product of both can be considered roughly constant. This product is called the complexity index. If the picture code amount is allocated in proportion to the complexity index, the quantization parameter becomes roughly constant. That is, encoding is performed so that the image quality at the time of decoding the video of each channel is approximately the same.

  The overall control unit 19 stores the encoding results in the pre-encoding units 16 to 18, stores the encoding results for each of the pre-encoding units 16 to 18, and stores the N pictures for each of the pre-encoding units 16 to 18. The code amount and the ratio to the total sum are calculated, and the overall bit rate is allocated based on the ratio, and the output bit rate of the encoded stream for N pictures in each of the encoding units 10 to 12 is determined.

  The input images A to C are also input to the corresponding frame buffers 13 to 15, delayed by (N + 1) pictures, and then input to the encoding units 10 to 12, respectively. Each of the encoding units 10 to 12 basically encodes the input images A to C based on the pre-encoding information given from the overall control unit 19 in the same manner as the pre-encoding units 16 to 18. Do. As the pre-encoding information, for example, information obtained at the time of pre-encoding such as a quantization parameter, a threshold used for motion search, and a threshold used for determining each encoding mode is received from the overall control unit 19.

  However, in the encoding in the encoding units 10 to 12, it is necessary to increase / decrease the code amount as necessary so that the transmission / reception buffer of the encoded stream does not fail under the determined output bit rate. There may be.

  This is because the output bit rate of each channel is not determined at the time of pre-encoding, so it is not possible to accurately determine the buffer failure at the time of pre-encoding, and the correct amount of zero stuffing or code amount clipping is performed. It is because it cannot be done. In such a case, when the encoder buffer (stream buffers 102 to 122) underflows, zero stuffing is newly added, and the decoder buffer (buffer on the receiving side video decoding device) underflows. Is encoded so as to reduce the code amount compared to the code amount in the case of pre-encoding.

  When the encoder buffer is likely to cause an underflow, the code amount is increased by zero stuffing, etc. If a code with a small code amount continues, the code amount input to the encoder buffer rather than the code amount output from the encoder buffer This is to avoid the underflow of the encoder buffer and the underflow of the encoder buffer.

  On the other hand, when the decoder buffer is likely to cause underflow, the amount of code at the time of encoding is reduced by the video decoding device (decoder) from the decoder buffer to the stream for each picture at a constant interval (frame or field). Since the data is extracted and decoded in order, and if a picture with a large amount of code continues, the amount of code extracted from the decoder buffer becomes larger than the amount of code input to the decoder buffer, which causes an underflow of the decoder buffer. This is to avoid this.

  By the encoding control as described above, an encoded stream is generated in the stream generation units 101 to 121 of the encoding units 10 to 12, and the encoded streams are respectively stream streams 102 to 102 of the encoding units 10 to 12. 122 is accumulated.

  The encoding units 10 to 12 obtain the time to start outputting encoded streams for N pictures from the overall control unit 19, and output the encoded streams for N pictures from the stream buffers 102 to 122 at that time. Start. At this time, the encoded stream is output from the stream buffers 102 to 122 at the output bit rate determined by the overall control unit 19.

  Each encoding unit 10-12 immediately transmits the generated code amount for the same picture to the overall control unit 19 after the generation of the encoded stream for N pictures, and the overall control unit 19 From the output bit rate and the generated code amount of the encoded stream for the N pictures, the time at which the encoding units 10 to 12 finish outputting the encoded stream for the N pictures is obtained. 12, the time when a certain margin time has elapsed from the time when the output of the encoded streams for N pictures ends is transmitted to the encoding units 10 to 12 as the time for starting the output of the encoded streams of the subsequent pictures.

  The encoding units 10 to 12 once stop outputting the encoded streams for the N pictures. The encoding units 10 to 12 obtain in advance a time to start output of the subsequent picture stream from the overall control unit 19, and resume output of the subsequent picture stream at that time (see FIG. 5). ).

  The multiplexing unit 30 multiplexes the variable bit rate encoded streams output from the encoding units 10 to 12. At this time, the sum of the bit rates of the respective encoded streams is always less than or equal to the total bit rate. At the time of switching the bit rate of the encoded stream in each of the encoding units 10 to 12, the output of the encoded stream from each of the encoding units 10 to 12 is temporarily stopped, so that the sum of the bit rates is significantly reduced. At 30, by inserting invalid data such as a null packet, it is output as a constant bit rate stream.

  FIG. 2 is a diagram showing a process flow for determining an output bit rate of an encoded stream through pre-encoding. When the input images A to C are taken into the pre-encoding units 16 to 18 for each picture (step S1), the overall control unit 19 first determines the overall picture target code amount (step S2). The overall picture target code amount is distributed to each channel in proportion to the picture complexity index for each channel, and the picture target code amount of each pre-encoding unit 16 to 18 is determined (step S3).

  Each of the pre-encoding units 16 to 18 performs picture encoding of the input videos A to C in accordance with the picture target encoding amount determined by the overall control unit 19 (step S4). The overall control unit 19 aggregates the picture encoding results (step S5), and updates the overall complexity index, generated code amount, buffer occupancy, etc. (step S6). The encoding results of the respective pre-encoding units 16 to 18 are stored (step S7), and it is determined whether encoding for N pictures has been completed (step S8). Encoding for N pictures has not been completed. In the case, the process proceeds to step S11.

  When the encoding for N pictures is completed, the generated code amounts for N pictures of the pre-encoding units 16 to 18 are totaled (step S9), and the N pictures for each of the pre-encoding units 16 to 18 are tabulated. The amount of generated code and the ratio to the total sum are calculated, the overall bit rate is allocated based on the ratio, and the output bit rate of the encoded stream for N pictures in each encoding unit 10-12 is determined. (Step S10). Then, the processes from step S1 to step S10 are repeated until the encoding is completed (step S11).

  FIG. 3 is a diagram showing the flow of the encoded stream generation process. Input video images A to C are respectively input to the corresponding frame buffers 13 to 15 and taken into the encoding units 10 to 12 at a timing delayed by N + 1 pictures from the input to the pre-encoding units 16 to 18 ( Step S21).

  In each of the encoding units 10 to 12, when the input video is the first picture of N pictures (step S22), the output bit rate determined by the overall control unit 19 is captured (step S23). If it is not the first N picture, step S23 is skipped.

  Each of the encoding units 10 to 12 takes in pre-encoding information of a picture to be encoded, which is given from the overall control unit 19 (step S24), and each pre-code corresponding to each of the encoding units 10 to 12 The input images A to C are encoded in the same manner as the encoding units 16 to 18. At this time, encoding is performed according to the following determination (step S25) so that the transmission / reception buffer of the encoded stream does not fail under the determined output bit rate.

  First, if the next picture is encoded in the same way as the pre-encoding, it is determined whether or not the buffer fails under the determined output bit rate (step S25). The picture is encoded as shown (step S26).

  If the encoder buffer underflows, the picture is encoded according to pre-encoding, and then new zero stuffing is added (step S27). If the decoder buffer underflows, pre-encoding The picture is encoded so as to reduce the code amount as compared with the code amount (step S28).

  Through the encoding control as described above, an encoding stream is generated in the stream generation units 101 to 121 of the encoding units 10 to 12, and the encoded streams are stream buffers 102 to 122 of the encoding units 10 to 12, respectively. (Step S29).

  The encoding units 10 to 12 determine whether or not generation of encoded streams for N pictures has been completed (step S30). If encoding for N pictures has not been completed, the process proceeds to step S33, where encoding is performed. Repeat the process until the process is completed.

  When the encoding for N pictures is completed (step S30), the generated code amount for the N pictures is immediately transmitted to the overall control unit 19, and the overall control unit 19 outputs the same N pictures for the encoding units 10 to 12. From the output bit rate of the encoded stream and the amount of generated code, the time when the output of the encoded streams for the same N pictures of the encoding units 10 to 12 ends is calculated (step S31). The overall control unit 19 sets the time when a certain margin time has elapsed from the time when the output of the encoded stream for the N pictures is the latest among all the encoding units 10 to 12 to the encoded stream of the subsequent pictures. The output time is calculated and transmitted to the encoding units 10 to 12 (step S32). The processing from step S21 to step S32 is repeated until the encoding is completed (step S33).

  FIG. 4 is a diagram showing an encoded stream output processing flow in each of the encoding units 10 to 12. When the encoding units 10 to 12 are notified by the overall control unit 19 of the start time of output of encoded streams for the current N pictures (step S41), the notified encoded stream output start time is reached. (Step S42), and starts outputting encoded streams for the same N pictures from the stream buffers 102 to 122 at the output start time at the output bit rate determined by the overall control unit 19 (step S43).

  The encoding units 10 to 12 continue to output the encoded streams for the N pictures while the encoded streams for the N pictures are in the stream buffers 102 to 122 (steps S44 and S45). When the output of the encoded stream for the picture is completed (step S46), it is determined whether or not the entire encoding is completed (step S47), and the process returns to step S41 until the encoding is completed and the process is repeated in the same manner.

  FIG. 5 is a diagram illustrating an example of output start / end timing and output bit rate of an encoded stream. In the example of FIG. 5, N = 15. 5 represents the output bit rate of each encoded stream output from the stream buffers 102 to 122 of the respective encoding units 10 to 12, and the horizontal axis represents time t.

At time t ₀ , the overall control unit 19 sends a picture No. to each encoding unit 10 to 12. The encoded stream output start time t ₁ of 0 to 14 is notified. At time t ₁ , each of the encoding units 10 to 12 uses a picture No. 1 at an output bit rate notified from the overall control unit 19. Output of 0 to 14 encoded streams is started. No. in all encoding units 10-12. 0 to No. At time t ₂ when encoding of 15 pictures up to 14 is completed, the overall control unit 19 calculates the time required to output the encoded stream by summing up the generated code amounts. The output of the encoded streams of 0-14 seek time t ₃ when finishes, the time t ₄ when allowance has elapsed time period that is from the time t _3, the picture No. It is calculated as the start time of output of 15 to 29 encoded streams, and is notified to each of the encoding units 10 to 12.

Each encoding unit 10-12 receives the next picture No. When encoded streams 15 to 29 are generated and the notified output start time t ₄ is reached, the picture No. Output of encoded streams 15 to 29 is started. When 15 pictures of encoded becomes a time instant t ₅ ended, the overall control unit 19, the picture No. The time t ₇ when a certain margin time has elapsed from the time t ₆ when the output of the encoded streams 15 to 29 ends is designated as the picture No. It is calculated as the start time of output of encoded streams 30 to 44, and is notified to the encoding units 10 to 12. Thereafter, output for 15 pictures is repeated in the same manner.

[Second Embodiment]
FIG. 6 is a diagram showing a configuration of a moving picture coding apparatus according to the second embodiment of the present invention. The moving image encoding apparatus 2 includes encoding units 20 to 22, an overall control unit 23, and a multiplexing unit 24. The overall control unit 23 includes an encoding unit control unit (not shown) that controls the encoding of the entire encoding units 20 to 22, and in particular, past encoding in each encoding unit 20 to 22 of each input video. Based on the result, an output bit rate determination control unit 230 that determines an output bit rate in each of the encoding units 20 to 22 in units of encoded streams for N pictures, and an amount of N pictures in each of the encoding units 20 to 22 An output start timing control unit 231 that controls the output start timing of the encoded stream.

  The input videos A to C are input videos having different contents synchronized, and the moving image encoding device 2 encodes the input videos A to C, multiplexes the generated three encoded streams into one, Outputs multiplexed stream. The bit rate of this multiplexed stream is a fixed bit rate, which is hereinafter referred to as the overall bit rate.

  The input images A to C are input to the encoding units 20 to 22 corresponding to the input images A to C, respectively, and are encoded. Based on the past picture encoding results of the encoding units 20 to 22, the overall control unit 19 calculates the predicted value of the generated code amount for N pictures to be encoded and its ratio to the total sum. Based on the ratio, the total bit rate is distributed to each of the encoding units 20 to 22, and the output bit rate of the encoded stream in each of the encoding units 20 to 22 is determined.

  In encoding, the overall control unit 23 is unified so that the quantization parameters of pictures are almost equal among the encoding units 20 to 22 and the sum of the bit rates of generated code amounts becomes the overall bit rate. Encoding control is performed. Therefore, the overall control unit 23 aggregates the picture encoding results of the encoding units 20 to 22 in a picture cycle, determines a target code amount or a quantization parameter for the next picture, and supplies the result to each encoding unit 20 to 22 .

  For example, a fixed bit rate frame with the overall bit rate as the coding bit rate is obtained by calculating the overall complexity index based on the sum of the generated code amounts of the coding results of each channel and the average value of the average quantization parameter. The overall picture target code amount is determined by inter-rate control. The overall picture target code amount is distributed to each channel in proportion to the complexity index for each channel, and is used as the picture target code amount for each channel.

  At the same time, in each of the encoding units 20 to 22, the encoder buffer underflows under the current output bit rate determined by the overall control unit 23 so that the transmission / reception buffer of the encoded stream does not break down. In this case, zero stuffing is added, and if the decoder buffer underflows, encoding is performed so as to reduce the target code amount.

  Through the above encoding, an encoded stream is generated in the stream generation units 201 to 221 of the encoding units 20 to 22, and the encoded streams are respectively stored in the stream buffers 202 to 222 of the encoding units 20 to 22, respectively. Accumulated.

  The encoding units 20 to 22 obtain the time to start outputting encoded streams for N pictures from the overall control unit 23, and output the encoded streams for N pictures from the stream buffers 202 to 222 at that time. Start. At this time, the encoded stream is output from the stream buffers 202 to 222 at the output bit rate determined by the overall control unit 23.

  The encoding units 20 to 22 immediately transmit the generated code amount for the N pictures to the overall control unit 23 immediately after the generation of the encoded stream for N pictures, and the overall control unit 23 From the output bit rate and the generated code amount of the encoded stream for the 22 N-pictures, the time at which the output of the encoded stream for the N-picture of each of the encoding units 20 to 22 ends is obtained, and all the encoding units In each of the encoding units 20 to 22, the time when a certain margin time has elapsed from the time when output of encoded streams for the same N pictures ends in 20 to 22 is set as the time when output of encoded streams of subsequent pictures is started. Tell 22.

  Each encoding unit 20 to 22 temporarily stops the output after the output of encoded streams for N pictures is completed. Each of the encoding units 20 to 22 obtains in advance a time to start outputting the encoded stream of the subsequent picture from the overall control unit 23, and resumes output of the encoded stream of the subsequent picture at that time. To do. These timings are the same as those in the first embodiment, and are as described with reference to FIG.

  The multiplexing unit 24 multiplexes the variable bit rate encoded streams output from the encoding units 20 to 22. At this time, the sum of the bit rates of the respective encoded streams is always less than or equal to the total bit rate. At the time of switching the bit rate of the encoded stream in each of the encoding units 20 to 22, since the output of the encoded stream from each of the encoding units 20 to 22 is temporarily stopped, the sum of the bit rates is significantly reduced, but the multiplexing unit 24 , By inserting invalid data such as a null packet, it is output as a constant bit rate stream.

  FIG. 7 is a diagram illustrating the flow of the encoded stream generation process. The input videos A to C are taken into the corresponding encoding units 20 to 22 (step S51). The overall control unit 23 determines the overall picture target code amount (step S52), and distributes the overall picture target code amount in proportion to the complexity index for each channel, so that each encoding unit 20˜ 22 picture target code amounts are determined (step S53).

  Next, it is determined whether or not a failure occurs in the transmission / reception buffer of the encoded stream under the current output bit rate determined by the overall control unit 23 (step S54). If the picture is encoded according to the target code amount (step S55) and the encoder buffer underflows, after the picture is encoded according to the target code amount, zero stuffing is added (step S56), and the decoder buffer is under In the case of flow, the picture is encoded with the target code amount lowered (step S57).

  Through the above encoding, an encoded stream is generated in the stream generation units 201 to 221 of the encoding units 20 to 22, and the encoded streams are respectively stored in the stream buffers 202 to 222 of the encoding units 20 to 22, respectively. Accumulated (step S58).

  The overall control unit 23 aggregates the picture encoding results of the encoding units 20 to 22 (step S59), and updates the overall complexity index, generated code amount, buffer occupancy amount, and the like (step S60). Further, the overall control unit 23 stores the encoding results of the encoding units 20 to 22 (step S61). Thereafter, it is determined whether encoding for N pictures has been completed (step S62). If encoding for N pictures has not been completed, the process proceeds to step S66.

  When the encoding for N pictures is completed, the encoding units 20 to 22 immediately transmit the generated code amount for the N pictures to the overall control unit 23, and the overall control unit 23 determines the generated code amount. Aggregate (step S63). The overall control unit 23 outputs the encoded stream of the N pictures of the encoding units 20 to 22 from the output bit rate and the generated code amount of the encoded streams of the N pictures of the encoding units 20 to 22. Is calculated, and the time when a certain margin time has elapsed from the time when output of encoded streams for the same N pictures in all the encoding units 20 to 22 ends is output as encoded streams of subsequent pictures. Is transmitted to each of the encoding units 20 to 22 (step S64).

  In addition, the overall control unit 23 counts the predicted values of the generated code amounts for the subsequent N pictures and the ratio of the sum to the total sum based on the picture encoding results in the encoding units 20 to 22. Based on the ratio, the overall bit rate is allocated to each of the encoding units 20 to 22, and the output bit rate of the encoded stream in each of the encoding units 20 to 22 is determined (step S65). Then, the processes in steps S51 to S65 are repeated until the encoding is completed (step S66).

  FIG. 8 is a diagram showing an encoded stream output processing flow in each of the encoding units 20 to 22. When the encoding units 20 to 22 are notified by the overall control unit 23 of the time to start outputting encoded streams for the current N pictures (step S71), the notified encoded stream output start time is reached. (Step S72), and at the output start time, output of encoded streams for the same N pictures is started from the stream buffers 202 to 222 at the output bit rate determined by the overall control unit 23 (step S73).

  The encoding units 20 to 22 continue to output the encoded streams for the N pictures while the encoded streams for the N pictures are in the stream buffers 202 to 222 (steps S74 and S75). When the output of the encoded stream for the picture is completed (step S76), it is determined whether or not the entire encoding is completed (step S77), and the process returns to step S71 until the encoding is completed, and the same process is repeated.

[Third Embodiment]
In the first and second embodiments described above, the output bit rate is changed in units of encoded streams for N pictures, and the value of N is determined in advance. In the third embodiment, this N is made variable during encoding. By making N variable, for example, when a scene change occurs, the bit rate distribution between channels is changed at that time. As a result, it is difficult to cause a buffer failure, and more efficient code amount distribution can be realized.

  As a method of making N variable, for example, a method of detecting a scene change of an input image and the whole control unit changing the bit rate distribution before and after that can be used. When there is a pre-encoder, the scene change is detected by the pre-encoder. If there is no pre-encoder, the scene change is detected at the input part of the encoder (encoding unit) or at the preceding stage.

  In the above embodiment, an example in which the number of channels is three has been described. Of course, the present invention is not limited to the encoding of a video with three channels, and the same applies to the case with two or more channels. Can be applied to.

  The processing of the overall control unit and each encoding unit for moving image encoding described above can also be realized by a computer and a software program, and the program is recorded on a computer-readable recording medium and provided. Can also be provided through a network.

It is a figure which shows the structure of a moving image encoder. It is a figure which shows the output bit rate determination processing flow of the encoding stream through pre-encoding. It is a figure which shows an encoding stream production | generation process flow. It is a figure which shows an encoding stream output process flow. It is a figure which shows the output start / end timing etc. of an encoding stream. It is a figure which shows the structure of a moving image encoder. It is a figure which shows an encoding stream production | generation process flow. It is a figure which shows an encoding stream output process flow.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Moving image encoder 10,20 Encoding part 11,21 Encoding part 12,22 Encoding part 13 Frame buffer 14 Frame buffer 15 Frame buffer 16 Pre-encoding part 17 Pre-encoding part 18 Pre-encoding part 19, 23 Overall control unit 24, 30 Multiplexing unit 100, 110, 120, 160, 170, 180, 200, 210, 220 Control unit 101, 111, 121, 161, 171, 181, 2011, 211, 221 Stream generation Units 102, 112, 122, 162, 172, 182, 202, 212, 222 Stream buffers 190, 230 Output bit rate determination control units 191, 231 Output start timing control unit

Claims (16)

In a video encoding device that encodes video of a plurality of channels with a corresponding encoding unit and outputs or multiplexes the encoded streams,
Control the encoding of each encoding unit, change the output bit rate in units of encoded streams for N (N is an integer of 1 or more) pictures in each encoding unit, and output the encoded stream It has an overall control unit to control,
The overall control unit
Determine an output bit rate of each encoding unit based on a prediction value of a generated code amount of encoded data for N pictures in each encoding unit, and determine an output bit rate to be notified to each encoding unit A control unit;
The time when a predetermined margin time has elapsed from the time when output of encoded streams for N pictures ends in all the encoding units is calculated, and the time is set as the output start time of encoded streams for the next N pictures. An output start timing control unit configured to notify each of the encoding units, and to control each of the encoding units to simultaneously start output of encoded streams for the next N pictures. apparatus. In the moving image encoding device according to claim 1,
The output start timing control unit
After the generation of the encoded streams for N pictures in each encoding unit, the encoded streams for the N pictures are obtained from the output bit rate and the generated code amount of the encoded streams for the N pictures of the encoding units. Is output, and the time when a predetermined margin time has elapsed from the time when output of the encoded stream of the N picture ends in all the encoding units is output of the encoded stream of the subsequent pictures. Is transmitted to each of the encoding units in advance as an output start time at which to resume the video encoding apparatus. In the moving image encoding device according to claim 1 or 2,
The output bit rate determination control unit
A moving image characterized by determining an output bit rate of the encoded stream for the N pictures of each encoding unit in proportion to a predicted value of the generated code amount for the N pictures of each encoding unit. Encoding device. In the moving picture encoding device according to claim 1, claim 2 or claim 3,
The output bit rate determination control unit
A moving picture coding apparatus, wherein a predicted value of a generated code amount for the N pictures of each coding unit is obtained from a coding result of a past picture in each coding unit. In the moving picture encoding device according to claim 1, claim 2 or claim 3,
A plurality of pre-encoding units that perform pre-encoding of input video for each channel corresponding to each of the encoding units,
The output bit rate determination control unit
The moving picture coding apparatus using the generated code amount for the N pictures by the pre-encoding in each pre-encoding unit as a predicted value of the generated code amount for the N pictures of each encoding unit . In the moving image encoding device according to claim 5,
The overall control unit
The pre-encoding information in the pre-encoding unit is notified to each of the corresponding encoding units, and each encoding unit performs the same encoding as the pre-encoding in the pre-encoding unit,
Each of the encoding units is
Based on the output bit rate of the encoded stream for the N pictures determined by the output bit rate determination control unit, with respect to the code amount at the time of the pre-encoding so that the stream transmission / reception buffer does not fail, A moving picture coding apparatus that performs coding for the N pictures while reducing a code amount and adding a code amount. In the moving image encoder according to any one of claims 1 to 6,
The overall control unit
A moving image encoding apparatus comprising: means for dynamically changing the N during encoding. In a video encoding method in which video of a plurality of channels is encoded by an encoding unit corresponding to each channel, and an encoded stream is output or multiplexed, respectively,
A process of encoding an input video for each channel in each encoding unit;
The output bit rate allocated to each encoding unit in units of encoded streams for N (N is an integer of 1 or more) pictures in each encoding unit is encoded data for N pictures in each encoding unit. A process of determining based on a predicted value of the generated code amount of
Calculating a time when a predetermined margin time has elapsed from the time when output of encoded streams for N pictures ends in all the encoding units as output start time of all the encoding units;
And a step of simultaneously starting output of encoded streams for the next N pictures based on the calculated output start time in each of the encoding units. In the moving image encoding method according to claim 8,
In the process of calculating the output start time,
After the generation of the encoded streams for N pictures in each encoding unit, the encoded streams for the N pictures are obtained from the output bit rate and the generated code amount of the encoded streams for the N pictures of the encoding units. Is output, and the time when a predetermined margin time has elapsed from the time when output of the encoded stream of the N picture ends in all the encoding units is output of the encoded stream of the subsequent pictures. Is calculated as an output start time at which to start. In the moving image encoding method according to claim 8 or 9,
In the process of determining the output bit rate,
A moving image characterized by determining an output bit rate of the encoded stream for the N pictures of each encoding unit in proportion to a predicted value of the generated code amount for the N pictures of each encoding unit. Encoding method. In the moving image encoding method according to claim 8, claim 9, or claim 10,
In the process of determining the output bit rate,
A moving picture coding method, wherein a predicted value of a generated code amount for the N pictures of each coding unit is obtained from a coding result of a past picture in each coding unit. In the moving image encoding method according to claim 8, claim 9, or claim 10,
A process of pre-encoding an input video for each channel by a pre-encoding unit corresponding to each of the encoding units;
In the process of determining the output bit rate,
A moving picture encoding method, wherein the generated code amount for N pictures by the pre-encoding is used as a predicted value of the generated code amount for N pictures of each encoding unit. The moving image encoding method according to claim 12,
Notifying pre-encoding information in the pre-encoding to each of the corresponding encoding units;
In the process of encoding in each encoding unit,
Under the output bit rate of the encoded stream for N pictures, the code amount is reduced and the code amount is added to the code amount at the time of the pre-encoding so that the stream transmission / reception buffer does not fail. A moving picture coding method characterized in that the coding for the N pictures is performed. In the moving image encoding method according to any one of claims 8 to 13,
A moving image encoding method comprising the step of dynamically changing N during encoding.   A moving picture coding program for causing a computer to execute the moving picture coding method according to any one of claims 8 to 14.   A computer-readable recording medium having recorded thereon a moving image encoding program for causing a computer to execute the moving image encoding method according to any one of claims 8 to 14.

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