[FFmpeg-trac] #8590(undetermined:closed): 'telecine=pattern' error for p24, soft telecined sources
FFmpeg
trac at avcodec.org
Thu Apr 2 04:56:39 EEST 2020
#8590: 'telecine=pattern' error for p24, soft telecined sources
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Reporter: markfilipak | Owner:
Type: defect | Status: closed
Priority: normal | Component:
| undetermined
Version: unspecified | Resolution: invalid
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Comment (by markfilipak):
I'm heartened that this is now getting the attention it deserves... Thank
you.
May I reitterate that 'telecine=pattern=5555' works correctly for p24
progressive (BD) video (i.e., 24/1.001 FPS video).
The problem is with p24 soft telecined (DVD) video (i.e., 24/1.001 FPS
video that has metadata that specifies 30/1.001 FPS playback). The
transcoded DVD video (but not the audio) runs 20% fast because the
'telecine' filter calculates PTS advance as 20/8*30/1.001 (incorrect)
instead of 20/8*24/1.001 (correct). This mistake is probably due to a
developer misunderstanding regarding what the 'frame_rate_code' MPEG flag
means. The flag specifies playback (30/1.001), not what the stream
actually is (24/1.001).
"There is 24.000 and 23.976, how are you fixing for this?"
BDs don't require any correction because 'telecine' correctly calculates
PTS advance.
DVDs require a '-r:v 24000/1001' directive (as a workaround) to force
ffmpeg to 24/1.001 (i.e., to ignore the 30/1.001 MPEG flag). With the
workaround, ffmpeg passes 24/1.001 to 'telecine', and 'telecine' then
calculates the correct PTS advance. In my opinion, the workaround should
not be more than a workaround. In my opinion, the best solution is for
'telecine' to look at the interlace metadata, to recognize that the source
is soft telecined, to recognize that 30/1.001 is bogus, and to apply
24/1.001 on its own without being forced.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/8590#comment:19>
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