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

[FFmpeg]

#7839: QVBR breaks mpeg2_qsv
-------------------------------------+-------------------------------------
             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            |
-------------------------------------+-------------------------------------

Comment (by atorp):

 Replying to [comment:21 lizhong1008]:
 > Please help to verify https://patchwork.ffmpeg.org/patch/12935/.
 > (Changing QSV_HAVE_QVBR and CO3 to be zero is not a correct way IMHO,
 they are pre-complie marco, not runtime checking )
 > Thanks!

 Hi lizhong1008,

 Thank you! I'll check it.

 However I feel your patch is unfinished. See this part of the code:
 https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/qsvenc.c#L346

 {{{
     else if (avctx->global_quality > 0 && !avctx->rc_max_rate) {
         rc_mode = MFX_RATECONTROL_ICQ;
         rc_desc = "intelligent constant quality (ICQ)";
     }
 ...
 #if QSV_HAVE_QVBR
     else if (avctx->global_quality > 0) {
         rc_mode = MFX_RATECONTROL_QVBR;
         rc_desc = "constant quality with VBR algorithm (QVBR)";
     }
 #endif
 }}}

 When selecting MPEG2 encoding, and Global Quality Control and a MAX-
 BITRATE... which RC is selected then? As the QVBR is not functional with
 MPEG2 but enabled in the compilation.

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Ticket URL: <https://trac.ffmpeg.org/ticket/7839#comment:22>
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