[FFmpeg-user] Converting MPEG 2 issues

Moritz Barsnick barsnick at gmx.net
Wed Apr 4 00:07:40 EEST 2018

On Tue, Apr 03, 2018 at 17:43:03 +0200, rava77 at gmx.de wrote:
> > $ [...] -map 0:v -map 0:a:0 -map 0:a:1
> That also fails:

Because, unlike mpv, ffmpeg fails to recognize the audio streams which
appear later:

> # ffmpeg -hide_banner -y -ss 1:15.500 -i capture_V0.mpg -t 30 capture_V1_30s.mkv
> [mpeg @ 0x15b27c0] New audio stream 0:4 at pos:76978190 and DTS:75.3496s
> [mpeg @ 0x15b27c0] New audio stream 0:5 at pos:76980238 and DTS:75.3496s
> [mpeg @ 0x15b27c0] New audio stream 0:6 at pos:76982286 and DTS:75.3496s
> [mpeg @ 0x15b27c0] New audio stream 0:7 at pos:77015054 and DTS:75.4456s

Using just
$ ffmpeg -i capture_V0.mpg
you will see that ffmpeg doesn't see the audio streams initially.

In order to access these, ffmpeg requires the option(s) "-probesize"
and/or "-analyzeduration".

Please try whether
$ ffmpeg -probesize 100000000 -analyzeduration 100000000 -i capture_V0.mpg
shows info about significantly more streams (i.e. including the
expected audio streams 0:4 .. 0:8). Try with larger values as well. If
so, add those options to your conversion command line. You can then try
my suggested maps again, or "-map 0:v -map 0:4 -map 0:5" or the likes.


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