Reference picture management and list construction
Techniques for encoding video with motion compensation include a compressed bitstream syntax that includes a list of all motion prediction reference frames without distinguishing between short-term reference frame and long-term reference frames. The list of reference frames may be provided in a slice header and may apply to encoded data video data within the corresponding slice. The list may be prefaced with a single number indicating the total number of reference frames. In an aspect delta POC reference numbers may be encoded with a flag indicating the sign of the delta POC when the absolute value of the POC is not equal to zero. In another aspect, a flag may be encoded for every reference frame indicating if POC information should be used when scaling prediction references, and a weighting parameter may be included when POC information should be used.
1. A method for managing a decoded picture buffer (DPB) comprising:
responsive to a bitstream of a coded sequence of pictures, deriving a list of all reference pictures used in decoding of a portion of bitstream syntax essentially consisting of a single list of reference pictures including single number indicating a total number of all reference pictures;
decoding a picture in the coded sequence of pictures including predicting a portion of the picture from reference pictures in the list; and
parsing, from the bitstream syntax for entries in the list of reference pictures, an identification of a reference picture by a difference in a picture order count (POC) between a current picture and the identified reference picture, including:
parsing a magnitude of the difference;
determining if the magnitude of the difference is greater than zero;
when the magnitude is determined to be greater than zero, parsing a flag indicating a sign of the difference.
2. The method of claim 1 , further comprising:
evicting decoded pictures from a DPB that are not in the list.
3. The method of claim 1 , wherein the bitstream syntax for the difference in POC includes:
for a first reference picture in the list, a magnitude of the difference, and always includes a flag indicating a sign of the difference; and
for subsequent reference pictures in the list, a magnitude of the difference, and, only if the magnitude is not zero, a flag indicating a sign of the difference.
4. The method of claim 1 , wherein the bitstream syntax for entries in the list of reference pictures includes a flag indicating if an absolute POC is used and an indicator of the reference picture, wherein
if the flag indicates an absolute reference is used, the indicator of the reference picture includes least significant bits of the POC of the reference picture, and
if the flag indicates an absolute reference picture is not used, the indicator of the reference picture includes a difference in a POC between a current picture and the reference picture.
5. The method of claim 1 , wherein the bitstream syntax for entries in the list of reference pictures includes a weighting derivations flag for each entry indicating if the POC of a corresponding reference picture should be considered for derivations of a weighting for the corresponding reference picture.
6. The method of claim 5 , wherein:
when the weighting derivations flag is true, the bitstream syntax for corresponding entry include a weighting parameter for the corresponding reference picture.
7. A non-transitory computer readable medium containing instructions that, when executed on a processor, cause:
responsive to a bitstream of a coded sequence of pictures, deriving a list of all reference pictures used in decoding of a portion of bitstream syntax essentially consisting of a single list of reference pictures including single number indicating a total number of all reference pictures;
decoding a picture in the coded sequence of pictures including predicting a portion of the picture from reference pictures in the list; and
parsing, from the bitstream syntax for entries in the list of reference pictures, an identification of a reference picture by a difference in a picture order count (POC) between a current picture and the identified reference picture, including:
parsing a magnitude of the difference;
determining if the magnitude of the difference is greater than zero;
when the magnitude is determined to be greater than zero, parsing a flag indicating a sign of the difference.
8. The medium of claim 7 , wherein the instructions further cause:
evicting decoded pictures from a DPB that are not in the list.
9. The medium of claim 7 , wherein the bitstream syntax for the difference in POC includes:
for a first reference picture in the list, a magnitude of the difference, and always includes a flag indicating a sign of the difference; and
for subsequent reference pictures in the list, a magnitude of the difference, and, only if the magnitude is not zero, a flag indicating a sign of the difference.
10. The medium of claim 7 , wherein the bitstream syntax for entries in the list of reference pictures includes a flag indicating if an absolute POC is used and an indicator of the reference picture, wherein
if the flag indicates an absolute reference is used, the indicator of the reference picture includes least significant bits of the POC of the reference picture, and
if the flag indicates an absolute reference picture is not used, the indicator of the reference picture includes a difference in a POC between a current picture and the reference picture.
11. The medium of claim 7 , wherein the bitstream syntax for entries in the list of reference pictures includes a weighting derivations flag for each entry indicating if the POC of a corresponding reference picture should be considered for derivations of a weighting for the corresponding reference picture.
12. The medium of claim 11 , wherein:
when the weighting derivations flag is true, the bitstream syntax for corresponding entry include a weighting parameter for the corresponding reference picture.
13. A video decoder comprising:
a decoded picture buffer (DPB);
a decoder for decoding compressed video and storing reference pictures in the DPB;
a predictor for predicting from reference pictures in the DPB; and
a controller with instructions that cause the decoder to:
responsive to a bitstream of a coded sequence of pictures, deriving a list of all reference pictures used in decoding of a portion of bitstream syntax essentially consisting of a single list of reference pictures including single number indicating a total number of all reference pictures;
decoding a picture in the coded sequence of pictures including predicting a portion of the picture from reference pictures in the list; and
parsing, from the bitstream syntax for entries in the list of reference pictures, an identification of a reference picture by a difference in a picture order count (POC) between a current picture and the identified reference picture, including:
parsing a magnitude of the difference;
determining if the magnitude of the difference is greater than zero; and,
when the magnitude is determined to be greater than zero, parsing a flag indicating a sign of the difference.
14. The decoder of claim 13 , wherein the instructions further cause:
evicting decoded pictures from a DPB that are not in the list.
15. The decoder of claim 13 , wherein the bitstream syntax for the difference in POC includes:
for a first reference picture in the list, a magnitude of the difference, and always includes a flag indicating a sign of the difference; and
for subsequent reference pictures in the list, a magnitude of the difference, and, only if the magnitude is not zero, a flag indicating a sign of the difference.
16. The decoder of claim 13 , wherein the bitstream syntax for entries in the list of reference pictures includes a flag indicating if an absolute POC is used and an indicator of the reference picture, wherein
if the flag indicates an absolute reference is used, the indicator of the reference picture includes least significant bits of the POC of the reference picture, and
if the flag indicates an absolute reference picture is not used, the indicator of the reference picture includes a difference in a POC between a current picture and the reference picture.
17. The decoder of claim 13 , wherein the bitstream syntax for entries in the list of reference pictures includes a weighting derivations flag for each entry indicating if the POC of a corresponding reference picture should be considered for derivations of a weighting for the corresponding reference picture.
18. The decoder of claim 17 , wherein:
when the weighting derivations flag is true, the bitstream syntax for corresponding entry include a weighting parameter for the corresponding reference picture.