Selective reference block generation without full reference frame generation
A motion vector for a current block of a current frame is decoded from a compressed bitstream. A location of a reference block within an un-generated reference frame is identified. The reference block is generated using a forward reference frame and a backward reference frame without generating the un-generated reference frame. The reference block is generated by identifying an extended reference block by extending the reference block at each boundary of the reference block by a number of pixels related to a filter length of a filter used in sub-pixel interpolation; and generating pixel values of only the extended reference block by performing a projection using the forward reference frame and the backward reference frame without generating the whole of the un-generated reference frame. The current block is then decoded based on the reference block and the motion vector.
1. A method, comprising:
decoding, from a compressed bitstream, a motion vector for a current block of a current frame;
identifying a location of a reference block within an un-generated reference frame;
generating the reference block using a forward reference frame and a backward reference frame without generating the un-generated reference frame by:
identifying an extended reference block by extending the reference block at each boundary of the reference block by a number of pixels related to a filter length of a filter used in sub-pixel interpolation; and
generating pixel values of only the extended reference block by performing a projection using the forward reference frame and the backward reference frame without generating the whole of the un-generated reference frame; and
decoding the current block based on the reference block and the motion vector.
2. The method of claim 1 , further comprising:
decoding, from the compressed bitstream, a flag indicating that the current block is encoded using the un-generated reference frame.
3. The method of claim 2 , further comprising:
omitting decoding from the compressed bitstream an index of a reference frame to be used for decoding the current block in response to the flag indicating that the current block is encoded using the un-generated reference frame.
4. The method of claim 1 , wherein the un-generated reference frame is temporally co-located with the current frame.
5. The method of claim 1 , further comprising:
determining that motion prediction using the un-generated reference frame is available for the current frame.
6. The method of claim 5 , wherein the motion prediction using the un-generated reference frame is determined to be available in response to determining that a reference frame buffer includes the forward reference frame and the backward reference frame.
7. The method of claim 1 , wherein the number of the pixels is equal to half of the filter length.
8. A device comprising:
a processor configured to:
decode, from a compressed bitstream, a motion vector for a current block of a current frame;
identify a location of a reference block within an un-generated reference frame;
generate the reference block using a forward reference frame and a backward reference frame without generating the un-generated reference frame, wherein to generate the reference block comprises to:
identify an extended reference block by extending the reference block at each boundary of the reference block by a number of pixels related to a filter length of a filter used in sub-pixel interpolation; and
generate pixel values of only the extended reference block by performing a projection using the forward reference frame and the backward reference frame without generating the whole of the un-generated reference frame; and
decode the current block based on the reference block and the motion vector.
9. The device of claim 8 , wherein the processor is further configured to:
decode, from the compressed bitstream, a flag indicating that the current block is encoded using the un-generated reference frame.
10. The device of claim 9 , wherein the processor is further configured to:
omit decoding from the compressed bitstream an index of a reference frame to be used for decoding the current block in response to the flag indicating that the current block is encoded using the un-generated reference frame.
11. The device of claim 8 , wherein the un-generated reference frame is temporally co-located with the current frame.
12. The device of claim 8 , wherein the processor is further configured to:
determine that motion prediction using the un-generated reference frame is available for the current frame.
13. The device of claim 12 , wherein the motion prediction using the un-generated reference frame is determined to be available in response to determining that a reference frame buffer includes the forward reference frame and the backward reference frame.
14. The device of claim 8 , wherein the number of the pixels is equal to half of the filter length.
15. A non-transitory computer-readable storage medium having stored thereon a compressed bitstream, wherein the compressed bitstream is configured for decoding by operations comprising:
decoding, from the compressed bitstream, a motion vector for a current block of a current frame;
identifying a location of a reference block within an un-generated reference frame;
generating the reference block using a forward reference frame and a backward reference frame without generating the un-generated reference frame by:
identifying an extended reference block by extending the reference block at each boundary of the reference block by a number of pixels related to a filter length of a filter used in sub-pixel interpolation; and
generating pixel values of only the extended reference block by performing a projection using the forward reference frame and the backward reference frame without generating the whole of the un-generated reference frame; and
decoding the current block based on the reference block and the motion vector.
16. The non-transitory computer-readable storage medium of claim 15 , wherein the operations further comprise:
decoding, from the compressed bitstream, a flag indicating that the current block is encoded using the un-generated reference frame.
17. The non-transitory computer-readable storage medium of claim 16 , wherein the operations further comprise:
omitting decoding from the compressed bitstream an index of a reference frame to be used for decoding the current block in response to the flag indicating that the current block is encoded using the un-generated reference frame.
18. The non-transitory computer-readable storage medium of claim 15 , wherein the un-generated reference frame is temporally co-located with the current frame.
19. The non-transitory computer-readable storage medium of claim 15 , wherein the operations further comprise:
determining that motion prediction using the un-generated reference frame is available for the current frame.
20. The non-transitory computer-readable storage medium of claim 19 , wherein the motion prediction using the un-generated reference frame is determined to be available in response to determining that a reference frame buffer includes the forward reference frame and the backward reference frame.