Video encoding method and apparatus

• US 7,075,982 B2
• Filed: 06/28/2002
• Issued: 07/11/2006
• Est. Priority Date: 06/29/2001
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Koto, Shinichiro
• Primary Examiner(s): PHILIPPE, GIMS S
• Application Number:
  US10/183,516
• Publication Number:
  US 20030031251A1
• Time in Patent Office: 1,474 Days
• Field of Search: 375/240.03, 375/240.02, 375/240.08, 375/240.1, 382/236, 382/239, 348/419.1
• US Class Current: 375/240.03
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• 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 19/159 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 19/192 the adaptation method, adaptation tool or adaptation type being iterative or recursive
• CPC Class Codes: H04N 19/587 involving temporal sub-sampling or interpolation, e.g. decimation or subsequent interpolation of pictures in a video sequence
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

A video encoding method includes executing a first encoding of encoding an input video signal in units of one frame, determining at least one of the number-of-bits allocation and a quantization scale allocation for each frame according to statistical data, determining a frame skip allocation showing presence of execution of a frame skip for each frame according to the statistical data, and executing a second encoding of encoding the input video signal according to at least one of the number-of-bits allocation and a quantization scale allocation and a frame skip allocation, to generate a bitstream.

Claims

1. A video encoding method for encoding a video comprising:

executing a first encoding for encoding an input video signal in units of one frame at a constant frame rate to generate statistical data including the number of generated bits for each frame;

determining at least one of an allocation of the number of bits to each frame and an allocation of a quantization scale to each frame over a whole sequence of the input video signal, using the statistical data;

checking a condition of a video buffering verifier for each frame subjected to the allocation of the number of bits;

determining a frame skip allocation for a frame to be skipped when the condition of the video buffering verifier is not satisfied; and

executing a second encoding for encoding a same input video signal subjected to the first encoding, according to at least one of the allocation of the number-of-bits and the allocation of the quantization scale, and the frame skip allocation to generate a bitstream.

2. A video encoding method according to claim 1, wherein determining at least one of the allocation of the number of bits and the allocation of the quantization scale includes:

estimating a parameter based on the statistical data, the parameter being a parameter of a function indicating a relation between the number of generated bits and the quantization scale for each frame in the second encoding,

determining the allocation of the number-of-bits based on the parameter,

determining the frame skip allocation including an estimating a temporal change of occupation quantity of a virtual receiving buffer using at least one of the number-of-bits allocation and the quantization scale, and

determining the frame skip allocation to prevent underflow when the underflow of the virtual receiving buffer is estimated using a greatest quantization scale.

3. A video encoding method according to claim 1, wherein the first encoding and the second encoding includes:

selecting an encoding type for every frame, and

making the encoding type between the first encoding and the second encoding for the same frame of the input video signal coincide.

4. A video encoding method according to claim 1, wherein determining at least one of the allocation of the number-of-bits and the allocation of the quantization scale includes determining the allocation of the number of bits and the allocation of the quantization scale so that the second encoding encodes the video signal at a variable bit rate.

5. A video encoding method according to claim 4, wherein the first encoding and the second encoding includes:

selecting an encoding type for every frame, and

making the encoding type between the first encoding and the second encoding for the same frame of the input video signal coincide.

6. A video encoding method according to claim 2, wherein determining at least one of the allocation of the number of bits and the allocation of the quantization scale includes;

estimating a parameter based on the statistical data, the parameter being a parameter of a function indicating a relation between the number of generated bits and the quantization scale for each frame in the second encoding,

determining the allocation of the number-of-bits based on the parameter,

determining the frame skip allocation including estimating a temporal change of occupation quantity of a virtual receiving buffer using at least one of the number-of-bits allocation and the quantization scale, and

determining the frame skip allocation to prevent underflow when the underflow of the virtual receiving buffer is estimated using a greatest quantization scale.

7. A video encoding method according to claim 6, wherein the first encoding and the second encoding includes:

selecting an encoding type for every frame, and

making the encoding type between the first encoding and the second encoding for the same frame of the input video signal coincide.

8. A video encoding method according to claim 6, further comprising:

correcting at least one of the allocation of the number-of-bits and the quantization scale by changing the parameter of the function according to (a) the number of frames that the frame skip is determined, (b) a parameter of a function indicating a relation between the number of generated bits and a quantization scale for a skip determination frame determined as the frame skip, and (c) an encoding type of a frame to be encoded just after the skip determination frame, and wherein the parameter of the function indicates a relation between the number of generated bits and the quantization scale of the frame to be encoded just after the skip determination frame.

9. A video encoding method according to claim 6, wherein determining the frame skip allocation includes determining a frame skip allocation for a frame dated back in time from a frame from which he underflow is estimated.

10. A video encoding method according to claim 9, wherein the first encoding and the second encoding includes:

selecting an encoding type for every frame, and

making the encoding type between the first encoding and the second encoding for the same frame of the input video signal coincide.

11. A video encoding method according to claim 9, further comprising:

correcting at least one of the allocation of the number-of-bits and the quantization scale by changing the parameter of the function according to (a) the number of frames that the frame skip is determined, (b) a parameter of a function indicating a relation between the number of generated bits and a quantization scale for a skip determination frame determined as the frame skip, and (c) an encoding type of a frame to be encoded just after the skip determination frame, and wherein the parameter of the function indicates a relation between the number of generated bits and the quantization scale of the frame to be encoded just after the skip determination frame.

12. A video encoding method according to claim 11, wherein the first encoding and the second encoding includes:

selecting an encoding type for every frame, and

making the encoding type between the first encoding and the second encoding for the same frame of the input video signal coincide.

13. A video encoding method for encoding a video by encoding an input video signal a plurality of times, the method comprising:

executing a first encoding for encoding an input video signal at a constant bit rate;

generating statistical data including the number of generated bits for each frame in the first encoding;

determining at least one of the number of bits and a quantization scale that are to be allocated to each frame over a whole sequence of the input video scale, using the statistical data;

checking a condition of a video buffering verifier for each frame subjected to allocation of the number of bits;

determining a frame skip allocation for a frame to be skipped when the condition of the video buffering verifier is not satisfied;

executing a second encoding for encoding a same input video signal subjected to the first encoding, according to at least one of the number of bits and the quantization scale, and the frame to be skipped.

14. A video encoding method according to claim 13, wherein determining the at least one of the number of bits and the quantization scale includes determining the number of bits and the quantization scale so that the second encoding encodes the video signal at a variable bit rate.

15. A video encoding apparatus which encodes an input video signal, comprising:

an encoder configured to encode an input video signal in units of one frame at a constant frame rate to obtain statistical data including the number of generated bits for every frame;

a first determination part configured to determine at least one of an allocation of the number of bits and an allocation of a quantization scale for each frame over a whole sequence of the input video signal according to the statistical data;

a checker configured to check a condition of a video buffering verifier for each frame subjected to the allocation of the number of bits; and

a second determination part configured to determine a frame skip allocation for a frame to be skipped when the condition of the video buffering verifier is not satisfied, wherein

the encoder encodes a same input video signal subjected to encoding to obtain the statistical data, according to the frame skip allocation and at least one of the allocation of the number-of-bits and the allocation of the quantization scale, to output encoded video data.

16. A video encoding apparatus according to claim 15, wherein the first determination part includes:

a estimation part configured to estimate a parameter based on the statistical data, the parameter being a parameter of a function indicating a relation between the number of generated bits and the quantization scale for each frame in the second encoding,

a determination part configured to determine the allocation of the number-of-bits based on the parameter, and the second determination part includes an estimation part configured to estimate a temporal change of occupation quantity of a virtual receiving buffer using at least one of the number-of-bits allocation and the quantization scale, and

a determination part configured to determine the frame skip allocation to prevent underflow when the underflow of the virtual receiving buffer is estimated using a greatest quantization scale.

17. A video encoding apparatus according to claim 15, wherein the encoder includes:

a selection part configured to select an encoding type for every frame, and

a coincidence part configured to make the encoding type between the first encoding and the second encoding for the same frame of the input video signal coincide.

18. A video encoding apparatus according to claim 15, wherein the first determination part includes a determination part configured to determine the allocation of the number of bits and the allocation of the quantization scale so that the second encoding encodes the video signal at a variable bit rate.

19. A video encoding program recorded on a computer readable medium, for encoding a video at least two times, the program comprising:

means for instructing a computer to encode an input video signal input in units of one frame at a constant frame rate to obtain statistical data including the number of generated bits for every frame;

means for instructing the computer to determine at least one of an allocation of the number-of-bits and an allocation of a quantization scale for each frame over a whole sequence of the input video signal according to the statistical data;

means for instructing the computer to check a condition of a video buffering verifier for each frame subjected to the allocation of the number of bits;

means for instructing the computer to determine a frame skip allocation for a frame skip when the condition of the video buffering verifier is not satisfied; and

means for instructing the computer to encode a same input video signal subjected to encoding to obtain the statistical data, according to the frame skip allocation and at least one of the allocation of the number-of-bits, and the allocation of the quantization scale.

20. A video encoding program according to claim 19, further comprising:

means for instructing the computer to select an encoding type for every frame, and making the encoding type between the first encoding and the second encoding for the same frame of the input video signal coincide.