[FFmpeg-trac] #7839(avcodec:new): QVBR breaks mpeg2_qsv

[FFmpeg]

#7839: QVBR breaks mpeg2_qsv
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             Reporter:  atorp        |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  important    |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  qsv          |               Blocked By:
  regression                         |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by atorp):

 Hi lizhong1008,

 Regarding the problem, I think I have one idea to solve it:

 - If you check in the Intel Media SDK for Linux (Open Source) you can
 review the MPEG2 ENCODER implementation. See this part of the code:
 - https://github.com/Intel-Media-
 SDK/MediaSDK/blob/fcb7e6bf4c6b3acbc2698ecb45926be6ac8cd911/_studio/mfx_lib/encode_hw/mpeg2/src/mfx_mpeg2_encode_utils_hw.cpp#L602

 - As you can note, inside the initialization of the Encoder the code tries
 to check the Hardware, with the function CheckHwCaps(), and after it
 checks the buffer capabilities, with the function CheckExtendedBuffers().

 - My assumption is this: The MPEG2 encoder doesn't support the CO3
 extension, even if the H264 encoder does it. Or perhaps it depends on the
 Intel CPU running, or the driver version. In any case, AT RUNTIME it's
 possible that the use of the CO3 extension will generate a failed
 initialization of the MFX context. This last is for sure true, because the
 only difference between the patch pointed is the inclusion of the CO3 in
 the code. And my proposed workaround needs to disable both QVBR and CO3.
 So the problem is the CO3 extension. And not because the API, but because
 the refuse to initialize the MFX context when configuring the MPEG2
 encoder. So the only viable solution is to check it at runtime or not use
 it at all when configuring the MPEG2 encoder.

 You agree?

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Ticket URL: <https://trac.ffmpeg.org/ticket/7839#comment:19>
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