[FFmpeg-trac] #3902(undetermined:closed): FFmpeg MD5 output different with same data #3

[FFmpeg]

#3902: FFmpeg MD5 output different with same data #3
-------------------------------------+-------------------------------------
             Reporter:               |                    Owner:
  ahthovaikied                       |                   Status:  closed
                 Type:  defect       |                Component:
             Priority:  normal       |  undetermined
              Version:  git-master   |               Resolution:  duplicate
             Keywords:  mpeg2video   |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Changes (by cehoyos):

 * keywords:  md5 mpeg2 ac3 mkv => mpeg2video
 * resolution:   => duplicate
 * status:  new => closed
 * component:  avformat => undetermined


Comment:

 {{{
 $ ffmpeg -i cut.mkv -map v -map a -c:v copy -c:a copy -f md5 -
 }}}
 The expected output for this command line is
 0b0257acc6662c99b71e879d27705ce9 (for current FFmpeg git head - b627385b -
 I suspect this could change in the future as it has changed - once - in
 the past).
 As explained in ticket #3871, the output of above command line generally
 depends on the enabled decoders. If the mpeg2video decoder gets disabled,
 the output becomes 726d4f2a3d79e000e0bbde6397311bb2 and the console output
 changes:
 {{{
     Stream #0:0(eng): Video: mpeg2video (Main), yuv420p(tv), 720x576 [SAR
 64:45 DAR 16:9], max. 7500 kb/s, 25 fps, 25 tbr, 1k tbn, 50 tbc (default)
 }}}
 {{{
     Stream #0:0(eng): Video: mpeg2video, 720x576, max. 7500 kb/s, SAR
 64:45 DAR 16:9, 25 fps, 25 tbr, 1k tbn, 50 tbc (default)
 }}}
 The console output change does not directly correspond to the md5 output
 change, it is just a more visible difference between the different
 configurations.
 As explained in ticket #3871 both changes are not unexpected, demuxers can
 depend on decoders.

 At least on all Linux systems, you can always disable the mpeg2video
 decoder with {{{--disable-decoders --disable-hwaccels}}}, it makes no
 difference if you specify {{{--disable-vdpau}}}, {{{--disable-vaapi}}} or
 {{{--disable-xvmc}}} or not. Your original configure line only contained
 {{{--disable-decoders}}} but not {{{--disable-hwaccels}}}. On your corei7
 system at least one hardware acceleration library including its header is
 present (vdpau, vaapi or xvmc) meaning the mpeg2video decoder was enabled
 because it is required by all mpegvideo hwaccels, on the atom system none
 of the hardware acceleration libraries is present with an appropriate
 header meaning the mpeg2video decoder was not enabled. This explains the
 different output (for different binaries!) that you saw on different
 systems.

 The md5 output changed with ac293b66 / 194be1f4 just as for ticket #3871.
 If whatever you are trying to do makes sense for you, please compile one
 static binary that you share across systems. It took considerable time to
 solve this riddle and I don't think anybody has learned anything relevant
 from it.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/3902#comment:39>
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