Apparatus, articles of manufacture, and methods for improved adaptive loop filtering in video encoding

1 . An apparatus comprising:

interface circuitry instructions; and

at least one programmable circuit to be programmed based on the instructions to:

identify a first video frame as a critical video frame with respect to a previous video frame;

determine whether a latency associated with generation of filter coefficients of a video filter based on first pixel data of the first video frame satisfies a threshold;

based on a determination that the latency does not satisfy the threshold, generate the filter coefficients of the video filter based on the first pixel data of the first video frame;

based on a determination that the latency satisfies the threshold, generate the filter coefficients of the video filter based on second pixel data of a previous critical video frame; and

encode the first video frame with the filter coefficients.

2 . The apparatus of claim 1 , wherein one or more of the at least one programmable circuit is to restrict generation of video filters to be based on critical video frames.

3 . The apparatus of claim 1 , wherein one or more of the at least one programmable circuit is to:

select one or more types of the video filter to be applied to the first video frame;

identify a filter index corresponding to respective ones of the one or more types of the video filter;

encode the first video frame with the filter index; and

output the encoded first video frame.

4 . The apparatus of claim 1 , wherein the filter coefficients are first filter coefficients, and one or more of the at least one programmable circuit is to, based on a determination that a second video frame is not the critical video frame with respect to the previous video frame:

determine whether second filter coefficients associated with the previous critical video frame have been encoded in an adaptation parameter set data structure;

based on a determination that the second filter coefficients have been encoded in the adaptation parameter set data structure, select the second filter coefficients to be encoded in the second video frame; and

based on a determination that the second filter coefficients have not been encoded in the adaptation parameter set data structure, encode the second video frame with third filter coefficients stored in a decoded video frame buffer.

5 . The apparatus of claim 1 , wherein one or more of the at least one programmable circuit is to, based on a determination that a second video frame is not the critical video frame with respect to the previous video frame and a determination to turn off a chrominance adaptive loop filter:

generate a luminance adaptive loop filter;

identify a filter index corresponding to the luminance adaptive loop filter; and

encode the second video frame with the filter index.

6 . The apparatus of claim 1 , wherein one or more of the at least one programmable circuit is to, based on a determination that a second video frame is not the critical video frame with respect to the previous video frame and a determination to turn on a chrominance adaptive loop filter:

generate the chrominance adaptive loop filter, a luminance adaptive loop filter, and a cross-component adaptive loop filter;

identify a first filter index corresponding to the luminance adaptive loop filter, a second filter index corresponding to the chrominance adaptive loop filter, and a third filter index corresponding to the cross-component adaptive loop filter; and

encode the second video frame with the first filter index, the second filter index, and the third filter index.

7 . The apparatus of claim 1 , wherein one or more of the the at least one programmable circuit is to:

measure a temporal correlation difference between the first video frame and the previous video frame; and

identify the first video frame as the critical video frame based on the temporal correlation difference.

8 . The apparatus of claim 7 , wherein the threshold is a first threshold, and one or more of the at least one programmable circuit is to, based on a determination that the temporal correlation difference does not satisfy a second threshold:

determine a distance of the first video frame with respect to the previous video frame; and

identify the first video frame as the critical video frame based on the distance.

9 . An apparatus comprising:

means for identifying a first video frame as a critical video frame with respect to a previous video frame, the means for identifying to:

measure a temporal correlation difference between the first video frame and the previous video frame; and

identify the first video frame as the critical video frame based on the temporal correlation difference satisfying a threshold;

means for generating filter coefficients of a video filter based on first pixel data of the first video frame or second pixel data of a previous critical video frame; and

means for encoding the first video frame with the filter coefficients.

10 . The apparatus of claim 9 , wherein the means for generating is to restrict generation of video filters to be based on critical video frames.

11 . The apparatus of claim 9 , including:

means for determining whether a latency associated with generation of the filter coefficients based on the first pixel data of the first video frame satisfies a threshold; and

the means for generating to:

based on a determination that the latency does not satisfy the threshold, generate the filter coefficients based on the first pixel data; and

based on a determination that the latency satisfies the threshold, generate the filter coefficients based on the second pixel data.

12 . The apparatus of claim 9 , including:

means for selecting one or more types of the video filter to be applied to the first video frame; and

the means for encoding to:

identify a filter index corresponding to respective ones of the one or more types of the video filter;

encode the first video frame with the filter index; and

output the encoded first video frame.

13 . The apparatus of claim 9 , wherein the filter coefficients are first filter coefficients, and including:

means for selecting to, based on a determination that a second video frame is not the critical video frame with respect to the previous video frame:

determine whether second filter coefficients associated with the previous critical video frame have been encoded in an adaptation parameter set data structure; and

based on a determination that the second filter coefficients have been encoded in the adaptation parameter set data structure, select the second filter coefficients to be encoded in the second video frame; and

the means for encoding to, based on a determination that the second filter coefficients have not been encoded in the adaptation parameter set data structure, encode the second video frame with third filter coefficients stored in a decoded video frame buffer.

14 . The apparatus of claim 9 , wherein, based on a determination that a second video frame is not the critical video frame with respect to the previous video frame and a determination to turn off a chrominance adaptive loop filter:

the means for generating is to generate a luminance adaptive loop filter; and

the means for encoding is to:

identify a filter index corresponding to the luminance adaptive loop filter; and

encode the second video frame with the filter index.

15 . The apparatus of claim 9 , wherein, based on a determination that a second video frame is not the critical video frame with respect to the previous video frame and a determination to turn on a chrominance adaptive loop filter:

the means for generating is to generate the chrominance adaptive loop filter, a luminance adaptive loop filter, and a cross-component adaptive loop filter; and

the means for encoding is to:

identify a first filter index corresponding to the luminance adaptive loop filter, a second filter index corresponding to the chrominance adaptive loop filter, and a third filter index corresponding to the cross-component adaptive loop filter; and

encode the second video frame with the first filter index, the second filter index, and the third filter index.

16 . The apparatus of claim 9 , wherein the threshold is a first threshold, and, based on a determination that the temporal correlation difference does not satisfy the threshold, the means for identifying is to:

determine a distance of the first video frame with respect to the previous video frame; and

based on a determination that the distance satisfies a second threshold, identify the first video frame as the critical video frame.

17 . At least one non-transitory computer readable storage medium comprising instructions to cause at least one programmable circuit to at least:

determine a first video frame is not a critical video frame; and

based on a determination to turn on a chrominance adaptive loop filter:

generate the chrominance adaptive loop filter, a luminance adaptive loop filter, and a cross-component adaptive loop filter;

identify a first filter index corresponding to the luminance adaptive loop filter, a second filter index corresponding to the chrominance adaptive loop filter, and a third filter index corresponding to the cross-component adaptive loop filter; and

encode the first video frame with the first filter index, the second filter index, and the third filter index.

18 . The at least one non-transitory computer readable storage medium of claim 17 , wherein the instructions are to cause one or more of the at least one programmable circuit to limit generation of video to be based on critical video frames.

19 . The at least one non-transitory computer readable storage medium of claim 17 , wherein the instructions are to cause one or more of the at least one programmable circuit to:

identify a second video frame as the critical video frame;

determine whether a latency associated with generating filter coefficients of a video filter based on first pixel data of the second video frame satisfies a threshold;

based on determining that the latency does not satisfy the threshold, generate the filter coefficients based on the first pixel data; and

based on determining that the latency satisfies the threshold, generate the filter coefficients based on second pixel data of a previous critical video frame.

20 . The at least one non-transitory computer readable storage medium of claim 19 , wherein the instructions are to cause one or more of the at least one programmable circuit to:

select one or more types of the video filter to be applied to the second video frame;

identify a filter index corresponding to respective ones of the one or more types of the video filter;

encode the second video frame with the filter index; and

output the encoded second video frame.

21 . The at least one non-transitory computer readable storage medium of claim 17 , wherein the instructions are to cause one or more of the at least one programmable circuit to:

determine whether first filter coefficients associated with an intra-coded video frame have been encoded in an adaptation parameter set data structure;

based on a determination that the first filter coefficients have been encoded in the adaptation parameter set data structure, select the first filter coefficients to be encoded in the first video frame; and

based on a determination that the first filter coefficients have not been encoded in the adaptation parameter set data structure, encode the first video frame with second filter coefficients stored in a decoded video frame buffer.

22 . The at least one non-transitory computer readable storage medium of claim 17 , wherein the instructions are to cause one or more of the at least one programmable circuit to, based on a determination to turn off the chrominance adaptive loop filter:

generate the luminance adaptive loop filter;

identify the first filter index corresponding to the luminance adaptive loop filter; and

encode the first video frame with the first filter index.