[FFmpeg-trac] #9560(undetermined:new): SSIM result will be lower than expected when use .mkv

[FFmpeg]

#9560: SSIM result will be lower than expected when use .mkv
-------------------------------------+-------------------------------------
             Reporter:  rxf91        |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:  git-
  undetermined                       |  master
             Keywords:  ssim         |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Hello.

 Summary of the bug:

 When using '''ssim''' filter, If I use .mkv file for main, other format
 (eg mp4) for reference, SSIM will be lower than expected.



 How to reproduce:

 Results when not using mkv container
 {{{
 ffmpeg -i origin.m2ts -c:v copy copied.mkv
 ffmpeg -i copied.mkv -i origin.m2ts -an -lavfi "[0:v]settb=AVTB,setpts
 =PTS-STARTPTS[main];[1:v]settb=AVTB,setpts=PTS-
 STARTPTS[ref];[main][ref]ssim" -f null -
 [Parsed_ssim_4 @ 00000148654eedc0] SSIM Y:0.922225 (11.091597) U:0.985489
 (18.383000) V:0.989469 (19.775481) All:0.943976 (12.516286)
 }}}

 {{{
 ffmpeg -i origin.m2ts -an -c:v libx264 -ssim 1 x264.mkv
 SSIM Mean Y:0.9828054 (17.646db)
 ffmpeg -i x264.mkv -i origin.m2ts -an -lavfi "[0:v]settb=AVTB,setpts=PTS-
 STARTPTS[main];[1:v]settb=AVTB,setpts=PTS-STARTPTS[ref];[main][ref]ssim"
 -f null -
 [Parsed_ssim_4 @ 0000017f8d025740] SSIM Y:0.915586 (10.735878) U:0.982084
 (17.467682) V:0.986489 (18.693172) All:0.938487 (12.110299)
 }}}

 Results when not using mkv container
 Note the x264 ssim, It's same as mkv.
 {{{
 ffmpeg -i origin.m2ts -an -c:v copy copied.mp4
 ffmpeg -i copied.mp4 -i origin.m2ts -an -lavfi "[0:v]settb=AVTB,setpts
 =PTS-STARTPTS[main];[1:v]settb=AVTB,setpts=PTS-
 STARTPTS[ref];[main][ref]ssim" -f null -
 [Parsed_ssim_4 @ 000002bb515c7800] SSIM Y:1.000000 (inf) U:1.000000 (inf)
 V:1.000000 (inf) All:1.000000 (inf)
 }}}

 {{{
 ffmpeg -i origin.m2ts -an -c:v libx264 -ssim 1 x264.mp4
 [libx264 @ 000002c587d34600] SSIM Mean Y:0.9828054 (17.646db)
 ffmpeg -i x264.mp4 -i origin.m2ts -an -lavfi "[0:v]settb=AVTB,setpts=PTS-
 STARTPTS[main];[1:v]settb=AVTB,setpts=PTS-STARTPTS[ref];[main][ref]ssim"
 -f null -
 [Parsed_ssim_4 @ 0000019be0469840] SSIM Y:0.983138 (17.731021) U:0.992124
 (21.037030) V:0.993634 (21.961672) All:0.986385 (18.659951)
 }}}
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9560>
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