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Old 18th January 2021, 11:31   #1  |  Link
dvbrain
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Bad macro block when using cavlc encoding

When using x264 do intra encoding with tune fastdecode, we found some frames got wrong outputs.

When using command line:
x264 -o x264_test_sample_2.264 --input-fmt raw --input-res 3840x2160 --fps 50 --input-depth 10 --input-csp i422 --output-depth 10 --output-csp i422 --preset ultrafast --tune fastdecode --qp 12 --keyint 1 --slices 8 --no-cabac --threads 1 x264_test_sample_2.yuv
We got this:
When using command line:
x264 -o x264_test_sample_2.264 --input-fmt raw --input-res 3840x2160 --fps 50 --input-depth 10 --input-csp i422 --output-depth 10 --output-csp i422 --preset ultrafast --tune fastdecode --qp 11 --keyint 1 --slices 8 --no-cabac --threads 1 x264_test_sample_2.yuv
We got this:
It seems the first micro block of slice 6 is corrupt encoded. The gray bar will disappear if we modify the Y value of pixel (0, 1344) from 721 to 711.

The source YUV file:
https://drive.google.com/file/d/1Wx3...ew?usp=sharing

Hope somebody can help us to fix this problem.
Thanks.
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Old 21st January 2021, 11:34   #2  |  Link
dvbrain
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Below is the differences between qp 11 and qp 12:

Dequantized for qp 11:


Dequantized for qp 12:


Transform for qp 11:


Transform for qp 12:


Residual for qp 11:


Residual for qp 12:


Decoded for qp 11:


Decoded for qp 12:


Hope these can help to solve the problem.
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Old 21st January 2021, 17:18   #3  |  Link
jpsdr
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I suggest you post here the issue, if it's not allready posted.
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Old 22nd January 2021, 07:33   #4  |  Link
dvbrain
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The bug has been fixed with patch BugMaster/x264@133c700b.

Thanks.
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Old 23rd January 2021, 23:34   #5  |  Link
Emulgator
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Good find !
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Old 24th January 2021, 11:25   #6  |  Link
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Not merged yet, probably in the next official release.
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