Encoding system and encoding method

• US 20020012394A1
• Filed: 04/27/2001
• Published: 01/31/2002
• Est. Priority Date: 04/27/2000
• Status: Active Grant

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Nakao, Takashi, Sugiyama, Kazuhiro, Hatano, Yoshiko, Inamura, Mamoru, Kijima, Junko
• Granted Patent: US 6,792,046 B2
• Time in Patent Office: Days
• US Class Current: 375/240.02
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/15 by monitoring actual compressed data size at the memory before deciding storage at the transmission buffer
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/157 Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/18 the unit being a set of transform coefficients
• CPC Class Codes: H04N 19/196 being specially adapted for the computation of encoding parameters, e.g. by averaging previously computed encoding parameters processing of motion vectors H04N19/513
• CPC Class Codes: H04N 19/198 including smoothing of a sequence of encoding parameters, e.g. by averaging, by choice of the maximum, minimum or median value
• CPC Class Codes: H04N 19/20 using video object coding
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

An encoding system capable of preventing the overflow of a buffer and performing the encoding of a VOP within a predetermined time period even where the processing time period necessary for encoding each macroblock is not constant. In order to provide the encoding system, the maximum number of bits Tmax is set for each VOP, and the output of encoding unit and the output of fixed code output unit is switched and outputted so that the number of bits Sc of the VOP may not exceed the Tmax.

Claims

1. An encoding system comprising:

encoding unit for encoding external input signals of each macroblock, to output codes corresponding to said external input signals;

fixed code output unit for outputting fixed code;

s predetermined for each encoding type of a unit image;

storage unit for storing either said codes outputted from said encoding unit or said fixed codes outputted from said fixed code output unit; and

rate control unit for controlling either said codes or said fixed codes to be stored in said storage unit in accordance with the number of bits for said codes encoded by said encoding unit.

2. An encoding system according to claim 1,

wherein said rate control unit determines the maximum number of bits, as can be generated by encoding the unit image, for each of said unit image, to control either the codes outputted from said encoding unit or the fixed codes outputted from said fixed code output unit, for each of macroblocks constructing said unit image, on the basis of said maximum number of bits.

3. An encoding system according to claim 2,

wherein said rate control unit determines the maximum number of bits Tmax on the basis of the following relations:

Tmax≦

Bs−

B,

wherein Tmax designates the maximum number of bits, Bs designates the capacity of the storage unit, and B designates the occupancy in said storage unit.

4. An encoding system according to claim 2,

wherein said rate control unit determines the maximum number of bits Tmax on the basis of the following relations:

Tmax≦

vbv_bits+Rp,

wherein Rp=R/F, Tmax designates the maximum number of bits Rp designates the number of bits to be read from the storage unit for the unit image, R designates the bit rate to be read from said storage unit, F designates the rate of the unit image to be encoded, and vbv_bits designate the occupancy of the VBV buffer in the previous unit image.

5. An encoding system according to claim 2,

wherein said rate control unit determines the maximum number of bits Tmax on the basis of either the following relations or values for similar results:

Tmax≦

min (vbv_bits+Rp, Bs−

B),

wherein Rp=R/F, Tmax designates the maximum number of bits, Rp designates the number of bits to be read from the storage unit for the unit image, R designates the bit rate to be read from said storage unit, F designates the rate of the unit image to be encoded, vbv_bits designate an occupancy of the VBV buffer in the previous unit image, Bs designate the capacity of said storage unit, and B designates the occupancy of said storage unit.

6. An encoding system according to claim 4 or 5,

wherein the bit rate R to be read from said storage unit is variable.

7. An encoding system according to claim 2,

wherein said rate control unit makes a control to store in said storage unit said fixed code, as outputted by said fixed code output unit, for the current macroblock,

where the relations among the number of bits mb_bit of the codes outputted by the encoding unit for the current macroblock, the number of bits Sc to the previous macroblock constructing said unit image, the maximum number of bits Tmax of said unit image, the number M of the macroblocks to be encoded subsequent to the current macroblock constructing said unit image, the code length L of the fixed codes to be outputted by said fixed code output unit for said unit image, and the number of bits a of the additional codes to be generated at the unit of a video packet constructing said unit image are expressed by:

Sc+mb_bit+M×

L+α

>

Tmax

(wherein α

≧

0).

8. An encoding system according to claim 2,

wherein said rate control unit makes a control to store in said storage unit said fixed code, as outputted by said fixed code output unit, not only for the current macroblock but also for an M number of macroblocks to be encoded subsequent to sail current macroblock constructing said unit image,

where the relations among the number of bits mb_bit of the codes outputted by the encoding unit for said current macroblock, the number of bits Sc to the previous macrobloclk constructing said unit image, the maximum number of bits Tmax of said unit image, the number M of the macroblocks to be encoded subsequent to the current macroblock constructing said unit image, the code length L of the fixed codes to be outputted by said fixed code output unit for said unit image, and the number of bits α

of the additional codes to be generated at the unit of a video packet constructing said unit image are expressed by;

Sc+mb_bit+M×

L+α

>

Tmax

(wherein α

≧

0).

9. An encoding system according to claim 8,

wherein said rate control unit constructs a new video packet from the current macroblock,

where said following relation holds and where the encoding type of the unit image is intra:

Sc+mb_bit+M×

L+α

>

Tmax.

10. An encoding system according to claim 2,

wherein said fixed code output unit outputs a code corresponding to the macroblock, in which the number of bits is the minimum for the encoding type of the unit image.

11. An encoding system comprising:

encoding unit for encoding external input signals of each macroblock, to output codes corresponding to said external input signals;

fixed code output unit for outputting fixed codes predetermined for each encoding type of a unit image;

storage unit for storing either said codes outputted from said encoding unit or said fixed codes outputted from said fixed code output unit; and

rate control unit for controlling either said codes or said fixed codes to be stored in said storage unit on the basis of the elapsed time after the leading macroblock constructing the unit image was inputted.

12. An encoding system comprising:

encoding unit for encoding external input signals at the unit of a macroblock, to output codes corresponding to said external input signals;

fixed code output unit for outputting fixed codes predetermined for each encoding type of a unit image;

storage unit for storing either said codes outputted from said encoding unit or said fixed codes outputted from said fixed code output unit; and

rate control unit for controlling either said codes or said fixed codes to be stored in said storage unit on the basis of the number of bits for said codes encoded by said encoding unit and the elapsed time after the leading macroblock constructing the unit image was inputted.

13. An encoding method comprising:

an encoding step for encoding external input signals of each macroblock, to output codes corresponding to said external input signals;

a fixed code output step for giving fixed codes predetermined for each encoding type of a unit image;

a storage step for storing either said codes given at said encoding step or said fixed codes given at said fixed code output step; and

a rate control step for controlling either of said codes or said fixed codes to be stored at said storage step in accordance with the number of bits for said codes encoded at said encoding step.

14. An encoding method according to claim 13,

wherein said rate control step determines the maximum number of bits, as can be generated by encoding the unit image, for each of said unit image, to control either the codes given at said encoding step or the fixed codes given at said fixed code output step, for each of macroblocks constructing said unit image, on the basis of said maximum number of bits.

15. An encoding method according to claim 14,

wherein said rate control step determines the maximum number of bits Tmax on the basis of the following relations:

Tmax≦

Bs−

B,

wherein Tmax designates the maximum number of bits, Bs designates the capacity allowed at the storage step, and B designates the occupancy allowed at said storage step.

16. An encoding method according to claim 14,

wherein said rate control step determines the maximum number of bits Tmax on the basis of the following relations:

Tmax≦

vbv_bits+Rp,

wherein Rp=R/F, Tmax designates the maximum number of bits, Rp designates the number of bits to be read at the storage step for the unit image, R designates the bit rate to be read at said storage step, F designates the rate of the unit image to be encoded, and vbv_bits designate the occupancy of the VBV buffer in the previous unit image.

17. An encoding method according to claim 14,

wherein said rate control step determines the maximum number of bits Tmax on the basis of either the following relations or values for similar results:

Tmax≦

min (vbv_bits+Rp, Bs−

B),

wherein Rp=R/F, Tmax designates the maximum number of bits, Rp designates the number of bits to be read at the storage step for the unit image, R designates the bit rate to be read at said storage step, F designates the rate of the unit image to be encoded, vbv_bits designate an occupancy of the VBV buffer in the unit previous image, Bs designate the capacity allowed at said storage step, and B designates the occupancy allowed at said storage step.

18. An encoding method according to claim 16 or 17,

wherein the bit rate R to be read at said storage step is variable.

19. An encoding method according to claim 14,

wherein said rate control step makes a control to store in said storage step said fixed code, as given at said fixed code output step, for the current macroblock,

where the relations among the number of bits mb_bit of the codes given at the encoding step for the current macroblock, the number of bits sc to the previous macroblock constructing said unit image, the maximum number of bits Tmax of said unit image, the number M of the macroblocks to be encoded subsequent to the current macroblock constructing said unit image, the code length L of the fixed codes to be given at said fixed code output step for said unit image, and the number of bits a of the additional codes to be generated at the unit of a video packet constructing said unit image are expressed by:

Sc+mb_bit+M×

L+α

>

Tmax

(wherein α

≧

0).

20. An encoding method according to claim 14,

wherein said rate control step makes a control to store said fixed code, as given at said fixed code output step, at said storage step not only for the current macroblock but also for an M number of macroblocks to be encoded subsequent to said current macroblock constructing said unit image,

where the relations among the number of bits mb_bit of the codes given at the encoding step for said current macroblock, the number of bits Sc to the previous macroblock constructing said unit image, the maximum number of bits Tmax of said unit image, the number M of the macroblocks to be encoded subsequent to the current macroblock constructing said unit image, the code length L of the fixed codes to be given at said fixed code output step for said unit image, and the number of bits α

of the additional codes to be generated at the unit of a video packet constructing said unit image are expressed by;

Sc+mb_bit+M×

L+α

>

Tmax

(wherein α

≧

0).

21. An encoding method according to claim 20,

wherein said rate control step constructs a new video packet from the current macroblock,

where said following relation holds and where the encoding type of the unit image is intra:

Sc+mb_bit+M×

L+α

>

Tmax.

22. An encoding method according to claim 14,

wherein said fixed code output step outputs a code corresponding to the macroblock, in which the number of bits is the minimum for the encoding type of the unit image.

23. An encoding method comprising:

an encoding step for encoding external input signals of each macroblock, to output codes corresponding to said external input signals;

a fixed code output step for outputting fixed codes predetermined for each encoding type of a unit image;

a storage step for storing either said codes given at said encoding step or said fixed codes given at said fixed code output step; and

a rate control step for controlling either said codes or said fixed codes to be stored at said storage step on the basis of the elapsed time after the leading macroblock constructing the unit image was inputted.

24. An encoding method comprising:

an encoding step for encoding external input signals at the unit of a macroblock, to output codes corresponding to said external input signals;

a fixed code output step for outputting fixed codes predetermined for each encoding type of a unit image;

a storage step for storing either said codes given at said encoding step or said fixed codes given at said fixed code output step; and

a rate control step for controlling either of said codes or said fixed codes to be stored at said storage step on the basis of the number of bits of said codes encoded at said encoding step and the elapsed time after the leading macroblock constructing the unit image was inputted.