[FFmpeg-user] Force target DTS == source DTS -- How?

[Andrew Randrianasulu]

пт, 12 янв. 2024 г., 05:18 Mark Filipak <markfilipak.imdb at gmail.com>:

> On 1/10/24 16:50, Devin Heitmueller wrote:
> > On Wed, Jan 10, 2024 at 4:26 PM Mark Filipak <markfilipak.imdb at gmail.com>
> wrote:
> >> The change from 1048560 to 1174560 has to be happening inside the
> muxer, wouldn't you say? We now
> >> know that what's going into the muxer is right. Here is what went to
> the target file in the last run:
> >>
> >> 0,    1170806,    1174560,     3753,   640646, 0x900a1a7a, S=1,        1
> >
> > Try setting -muxdelay 0 on the output options.  If not specified it
> > defaults to 0.7, and the delta between 1174560 and 1048560 is exactly
> > 1.4 seconds.  I don't know why you're getting exactly 2x the mux delay
> > rather than just being off by 0.7s, but I suspect it's the muxdelay
> > that is causing you to get PTS values which are not what you would
> > expect.
> >
> > Devin
> >
>
> When I wrote "That did it", I 'spoke' too soon. I'm still being driven
> nuts.
> There are 4 questions at the end.
> -- Mark.
>
> set TRIM=-ss 20.061708333 -to 40.123416666
> set SOURCE=h:\BDMV\STREAM\00305.m2ts
> set CODE=-c copy -sn -dn
> set TARGET=c:\FANNY AND ALEXANDER [1982(1983)] 1of4.mp4
> ffmpeg -report %TRIM% -copyts -i %SOURCE% -map 0 %CODE% -muxdelay 0
> "%TARGET%"
> (The report is attached.)
>
> ___ THE INPUT M2TS (the cut is PTS=2854113)
> :
> 0,    2839098,    2839098,     3753,    25719, 0x6f77b9b6
> 1,    2839920,    2839920,      960,     1084, 0xe54d2b6f
> 1,    2840880,    2840880,      960,     1084, 0xe54d2b6f
> 1,    2841840,    2841840,      960,     1084, 0xe54d2b6f
> 1,    2842800,    2842800,      960,     1084, 0xe54d2b6f
> 0,    2842852,    2842852,     3753,    22455, 0xaa9655b8
> 1,    2843760,    2843760,      960,     1084, 0xe54d2b6f
> 1,    2844720,    2844720,      960,     1084, 0xe54d2b6f
> 1,    2845680,    2845680,      960,     1084, 0xe54d2b6f
> -cut-           +---------+
> 0,    2846606,  ¦ 2854113 ¦    3753,   640646, 0x3a5a0c45
> 1,    2846640,  +---------+     960,     1084, 0xe54d2b6f
> 1,    2847600,    2847600,      960,     1084, 0xe54d2b6f
> 1,    2848560,    2848560,      960,     1084, 0xe54d2b6f
> 1,    2849520,  +---------+     960,     1084, 0xe54d2b6f
> 0,    2850360,  ¦ 2850360 ¦    3753,   640646, 0xfed1d09a <= TO BE CUT
> 1,    2850480,  +---------+     960,     1084, 0xe54d2b6f
> 1,    2851440,    2851440,      960,     1084, 0xe54d2b6f
> 1,    2852400,    2852400,      960,     1084, 0xe54d2b6f
> 1,    2853360,    2853360,      960,     1084, 0xe54d2b6f
> 0,    2854113,    2861621,     3753,   640646, 0x02208727
> :
>
> ___ THE OUTPUT MP4 (the cut is PTS=2854080)
> 1,    1492608,    1492608,      512,       60, 0xec16103f
> : 50 audio packets, total
> 1,    1517696,    1517696,      512,     1084, 0xe54d2b6f
> -cut-           +---------+
> 0,    2846573,  ¦ 2854080 ¦    3753,   640654, 0xb9811068
> 1,    1518208,  +---------+     512,     1084, 0xe54d2b6f
> 1,    1518720,    1518720,      512,     1084, 0xe54d2b6f
> 1,    1519232,    1519232,      512,     1084, 0xe54d2b6f
> 1,    1519744,  +---------+     512,     1084, 0xe54d2b6f
> 0,    2850327,  ¦ 2850327 ¦    3753,   640652, 0xbf9ad2d1 <= NOT CUT
> 1,    1520256,  +---------+     512,     1084, 0xe54d2b6f
> 1,    1520768,    1520768,      512,     1084, 0xe54d2b6f
> 1,    1521280,    1521280,      512,     1084, 0xe54d2b6f
> 1,    1521792,    1521792,      512,     1084, 0xe54d2b6f
> 0,    2854080,    2861588,     3753,   640652, 0x8f98895e
> :
>
> Q1: How can I force the mp4 muxer to use the existing PTSs?
> Q2: Why are there 50 audio packets ahead of the -cut-?
> Q3: How can I force the mp4 audio time_base to 1/90000?
>

https://git.ffmpeg.org/gitweb/ffmpeg.git/blob/HEAD:/libavformat/movenc.c

(oh, it grow to 300 kb?) there are options

"movie_timescale", "set movie timescale"
and
video_track_timescale", "set timescale of all video tracks"

AND

"pts", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = MOV_PRFT_SRC_PTS}, 0, 0,
AV_OPT_FLAG_ENCODING_PARAM, "prft"},

but you probably need to consult documentation on how exactly they used

https://ffmpeg.org/ffmpeg-formats.html#Options-4

but if you have some time it will be interesting to hear if script I found
on videohelp forums for testing open-gop/closed gop situations shows
something interesting for your source file?

Somewhere at second level someone said that blurays specifically not
mandate closed-gop video streams, and only  demand full decoder refres (IDR
frame) at chapter marks.

I wonder if your m2ts stream encoded like this ?

How exactly you determinated keyframe to cut at, initially?


Q4: Why wasn't INPUT PTS=2850360 cut off?
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