On 2021-03-04 09:36, Michael Koch wrote:
Am 03.03.2021 um 23:57 schrieb Mark Filipak (ffmpeg):
I've tried transcoding a 2:21:19 movie via this script:
SET prep23=settb=expr=1/720000,setpts=N*30030
SET cfr23=setpts=N*1001/24000/TB,fps=24000/1001
SET codecs=-codec:v libx265 -x265-params crf=16:qcomp=1.00 -codec:a copy
-codec:s copy -dn
ffmpeg -i i:\BDMV\STREAM\00303.m2ts -vf %prep23%,%cfr23% %codecs% test.mkv
Isn't the first setpts filter useless, because it's overwritten by the second
setpts filter?
Not useless.
The 'TB' set by 'prep23' produces 'PTS's based on it -- 'PTS' is a function of 'TB' & 'N'. If the
'TB' in that function doesn't have enough resolution to produce valid 'PTS's throughout the video,
if it gets truncated in some internal step, then for those 'PTS's toward the end of the video,
frames will have bogus 'PTS's and will be dropped. On the other hand, if all is well within the
filter pipeline and 'TB' is not truncated in some internal step, then, Yes, the test seems
superfluous. My command line determines which of those is the case.
If the output, 'test.mkv', wound up shortened (due to dropped frames), then I could conclude that
calculations that included 'TB' got truncated in some internal step. Essentially, what I did was
indirectly test the resolution of 'TB'.
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