Line-based video rate control
A method for line-based video rate control is provided. The line based video rate control method includes system feedback to change system operating parameters, including on a packet-by-packet basis and also on a line-by-line basis. Also provided is a method for line-based compression. The method includes basic elements of an arithmetic coder to improve Golomb coding performance. By inverting operations in the method for line-based compression, the corresponding decoder can be obtained. The method also provides a heuristic-driven method for generating prediction residuals from quantized data, wherein prediction is driven in the direction of maximum correlation so that it is unnecessary to supply the decoder with additional data specifying this direction at each array element.
1. A method for video rate control, comprising the steps of:
receiving a first active line of a video frame;
determining a plurality of quantization parameters for active video data associated with the first active line;
providing the plurality of quantization parameters to a coding system, wherein, the plurality of quantization parameters are used to encode at least a portion of the first active line so that a video rate of the encoded first active line does not exceed a maximum video rate; and
receiving a second active line of the video frame, wherein the step of determining a plurality of quantization parameters for active video data associated with the first active line is at least partially performed during a horizontal blanking portion of the second active line of the video frame.
2. The method of claim 1 , wherein said receiving a first active line includes receiving a low-pass portion of said first active line and receiving a high-pass portion of said first active line.
3. The method of claim 2 , wherein said determining a plurality of quantization parameters for active video data associated with the first active line includes determining at least one low-pass quantization parameter for the low-pass portion of said first active line and determining at least one high-pass quantization parameter for the high-pass portion of said first active line.
4. The method of claim 3 , further comprising receiving a high-pass maximum encoded line size for said high-pass portion of said first active line and receiving a low-pass maximum encoded line size for said low-pass portion of said first active line, and wherein determining said low-pass quantization parameter for said low-pass portion of said first active line includes comparing whether a low-pass coded length of said low-pass portion of said first active line is smaller than said low-pass maximum encoded line size and wherein determining said high-pass quantization parameter for said high-pass portion of said first active line includes comparing whether a high-pass coded length of said high-pass portion of said first active line is smaller than said high-pass maximum encoded line size.
5. The method of claim 1 wherein determining said plurality of optimal quantization parameters includes:
receiving a bitrate requirement for the first active line;
receiving an initial throughput estimate;
determining an initial compression ratio;
determining a second compression ratio that is greater than said initial compression ratio; and
detecting over-compression.
6. The method of claim 5 further comprising:
receiving a compressed video packet size;
wherein said detecting over-compression includes monitoring said received compressed video packet size.
7. The method of claim 5 further comprising:
receiving a compressed line size;
wherein, said detecting over-compression includes monitoring said compressed line size.
8. The method of claim 5 wherein detecting over-compression includes:
determining an actual encoded low-pass line size;
determining an actual encoded high-pass line size;
comparing said actual encoded low-pass line size with a previous encoded low-pass line size; and
comparing said actual encoded high-pass line size with a previous encoded high-pass line size.
9. The method of claim 8 wherein said previous encoded low-pass line size includes a maximum encoded low-pass line size and where said previous encoded high-pass line size includes a maximum encoded high-pass line size.
10. The method of claim 2 further comprising:
estimating a low-pass pixel domain distortion associated with the low-pass portion of said first active line; and
estimating a high-pass pixel domain distortion associated with the high-pass portion of said first active line.
11. The method of claim 10 further comprising:
providing a high-pass transform coefficient; and
providing a low-pass transform coefficient, wherein estimating the low-pass pixel domain distortion includes scaling said low-pass transform coefficient, and inverting said scaling after performing a low-pass inverse transform, and wherein estimating the high-pass pixel domain distortion includes scaling said high-pass transform coefficient, and inverting said scaling after performing a high-pass inverse transform.
12. The method of claim 2 further comprising determining a low-pass coded length of the low-pass portion of said first active line by predicting data for at least one quantization level.
13. The method of claim 12 wherein predicting said data for said at least one quantization level includes predicting based on a neighbor of said low-pass portion of said first active line.
14. An apparatus for video rate control, the apparatus comprising:
means for receiving a first active line of a video frame;
means for determining a plurality of quantization parameters for active video data associated with the first active line;
means for providing the plurality of quantization parameters to a coding system, wherein, the plurality of quantization parameters is used to encode at least a portion of the first active line so that a video rate of the encoded first active line does not exceed a maximum video rate; and
means for receiving a second active line of the video frame, wherein the means for determining a plurality of quantization parameters for active video data associated with the first active line is at least partially performed during a horizontal blanking portion of the second active line of the video frame.
15. The apparatus of claim 14 , wherein said means for receiving a first active line includes means for receiving a low-pass portion of said first active line and means for receiving a high-pass portion of said first active line.
16. The apparatus of claim 15 , wherein said means for determining a plurality of quantization parameters for active video data associated with the first active line includes means for determining at least one low-pass quantization parameter for the low-pass portion of said first active line and means for determining at least one high-pass quantization parameter for the high-pass portion of said first active line.
17. The apparatus of claim 16 , further comprising means for receiving a high-pass maximum encoded line size for said high-pass portion of said first active line and means for receiving a low-pass maximum encoded line size for said low-pass portion of said first active line, wherein the means for determining said low-pass quantization parameter for said low-pass portion of said first active line includes means for comparing whether a low-pass coded length of said low-pass portion of said first active line is smaller than said low-pass maximum encoded line size, and wherein the means for determining said high-pass quantization parameter for said high-pass portion of said first active line includes means for comparing whether a high-pass coded length of said high-pass portion of said first active line is smaller than said high-pass maximum encoded line size.
18. The apparatus of claim 15 , further comprising:
means for estimating a low-pass pixel domain distortion associated with the low-pass portion of said first active line; and
means for estimating a high-pass pixel domain distortion associated with the high-pass portion of said first active line.
19. The apparatus of claim 18 , further comprising:
means for providing a high-pass transform coefficient; and
means for providing a low-pass transform coefficient, wherein the means for estimating the low-pass pixel domain distortion includes means for scaling said low-pass transform coefficient and inverting said scaling after performing a low-pass inverse transform, and wherein the means for estimating the high-pass pixel domain distortion includes means for scaling said high-pass transform coefficient and inverting said scaling after performing a high-pass inverse transform.
20. The apparatus of claim 15 , further comprising means for determining a low-pass coded length of the low-pass portion of said first active line by predicting data for at least one quantization level.
21. The apparatus of claim 20 , wherein predicting said data for said at least one quantization level includes predicting based on a neighbor of said low-pass portion of said first active line.
22. The apparatus of claim 14 , wherein the means for determining said plurality of optimal quantization parameters includes:
means for receiving a bitrate requirement for the first active line;
means for receiving an initial throughput estimate;
means for determining an initial compression ratio;
means for determining a second compression ratio that is greater than said initial compression ratio; and
means for detecting over-compression.
23. The apparatus of claim 22 , further comprising:
means for receiving a compressed video packet size, wherein said means for detecting over-compression includes means for monitoring said received compressed video packet size.
24. The apparatus of claim 22 , further comprising:
means for receiving a compressed line size, wherein, said means for detecting over-compression includes monitoring said compressed line size.
25. The apparatus of claim 22 , wherein the means for detecting over-compression includes:
means for determining an actual encoded low-pass line size;
means for determining an actual encoded high-pass line size;
means for comparing said actual encoded low-pass line size with a previous encoded low-pass line size; and
means for comparing said actual encoded high-pass line size with a previous encoded high-pass line size.
26. The apparatus of claim 25 , wherein said previous encoded low-pass line size includes a maximum encoded low-pass line size and where said previous encoded high-pass line size includes a maximum encoded high-pass line size.