[FFmpeg-trac] #6307(undetermined:new): detected tbr different past 3.1.7 (1080i H.264)

[FFmpeg]

#6307: detected tbr different past 3.1.7 (1080i H.264)
-------------------------------------+-------------------------------------
             Reporter:  korylprince  |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 The tbr of a 1080i H.264 clip is detected differently with versions 3.1.7
 and early detecting '''29.97 tbr''' (which should be correct) and versions
 after 3.1.7 (I've tested 3.2, 3.2.4, and current 3.3-dev) detecting
 '''59.94 tbr'''.

 I don't want to say either is wrong, because I don't know what the correct
 answer is; The behavior is definitely different. I don't know exactly how
 interlaced video works, but the fps should be 29.97 for this clip.

 The clip in question is recorded from a Panasonic HDC-TM700.

 This was discovered because newer versions of blender (including 3.2+
 versions of ffmpeg) detect the given clip at 59.94 fps instead of 29.97
 fps, meaning the video is imported twice as long as the audio. The bug
 report is here: https://developer.blender.org/T51153

 I am attaching logs for versions 3.1.7, 3.2, 3.2.4, and 3.3-dev (commit
 efa89a8), and the clip used, 1080i_29.97.mts .

 Command used:
 {{{
 ffprobe -v 9 -loglevel 99 -report 1080i_29.97.mts
 }}}


 Here is the relevant output from each ffprobe command:

 3.1.7:

 {{{
 Stream #0:0[0x1011]: Video: h264 (High) (HDMV / 0x564D4448), yuv420p,
 1920x1080 [SAR 1:1 DAR 16:9], 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
 }}}

 3.2:

 {{{
 Stream #0:0[0x1011]: Video: h264 (High) (HDMV / 0x564D4448), yuv420p(top
 first), 1920x1080 [SAR 1:1 DAR 16:9], 29.97 fps, 59.94 tbr, 90k tbn, 59.94
 tbc
 }}}

 3.2.4:

 {{{
 Stream #0:0[0x1011]: Video: h264 (High) (HDMV / 0x564D4448), yuv420p(top
 first), 1920x1080 [SAR 1:1 DAR 16:9], 29.97 fps, 59.94 tbr, 90k tbn, 59.94
 tbc
 }}}

 3.3-dev:

 {{{
 Stream #0:0[0x1011]: Video: h264 (High) (HDMV / 0x564D4448), yuv420p(top
 first), 1920x1080 [SAR 1:1 DAR 16:9], 29.97 fps, 59.94 tbr, 90k tbn, 59.94
 tbc
 }}}


 As you can see, 3.1.7 has 29.97 tbr, and the reset are identical and 59.94
 tbr. My guess is this is incorrect, and it should be detected as 29.97
 tbr.

 I think the problem is in libavformat judging from the comments on the
 blender bug.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/6307>
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