[FFmpeg-trac] #6862(undetermined:closed): SRT conversion failure depends on unrelated other tracks being converted

[FFmpeg]

#6862: SRT conversion failure depends on unrelated other tracks being converted
-------------------------------------+-------------------------------------
             Reporter:  julian       |                    Owner:
                 Type:  defect       |                   Status:  closed
             Priority:  normal       |                Component:
              Version:  git-master   |  undetermined
             Keywords:               |               Resolution:
             Blocking:               |  needs_more_info
Analyzed by developer:  0            |               Blocked By:
                                     |  Reproduced by developer:  0
-------------------------------------+-------------------------------------
Changes (by cehoyos):

 * status:  new => closed
 * resolution:   => needs_more_info


Old description:

> there is something weird going on:
>
> 1.) download the files here ... sorry i couldn't find any other or
> shorter samples exhibiting this issue: http://bit.ly/2gYksPx
> 2.) for simplicity rename the mkv to mmm.mkv and the srt to mmm.srt
> 3.) now start conversion using ffmpeg 3.4 or current git head .. this
> will fail because the SRT has an unknown encoding which can't be guessed
> {{{ffmpeg -fix_sub_duration -i mmm.mkv -i mmm.srt -map 0:0 -map 0:1 -map
> 1:0 -scodec mov_text -vcodec copy -acodec copy  mmm.mp4}}}
> 4.) if do do a completely unrelated change to the command line,
> conversion suddenly succeeds. we tell it to also encode the internal MKV
> subtitle:
> {{{ffmpeg -fix_sub_duration -i mmm.mkv -i mmm.srt -map 0:0 -map 0:1 -map
> 1:0 -map 0:2 -scodec mov_text -vcodec copy -acodec copy  mmm.mp4}}}
> i see no reason why success of the conversion depends on whether the
> internal subtitle is converted, when the problem is with the external SRT
> subtitle. i think this must be a bug. if there is a problem with the SRT,
> ffmpeg should fail (or succeed) regardless of whether other subtitle
> tracks are also specified.
>
> attached are the full outputs of ffmpeg
>
> note that the behaviour is the same whether -sub_charenc is omitted or if
> its added but specifies a wrong encoding

New description:

 there is something weird going on:

 1.) download the files here ... sorry i couldn't find any other or shorter
 samples exhibiting this issue:
 2.) for simplicity rename the mkv to mmm.mkv and the srt to mmm.srt
 3.) now start conversion using ffmpeg 3.4 or current git head .. this will
 fail because the SRT has an unknown encoding which can't be guessed
 {{{ffmpeg -fix_sub_duration -i mmm.mkv -i mmm.srt -map 0:0 -map 0:1 -map
 1:0 -scodec mov_text -vcodec copy -acodec copy  mmm.mp4}}}
 4.) if do do a completely unrelated change to the command line, conversion
 suddenly succeeds. we tell it to also encode the internal MKV subtitle:
 {{{ffmpeg -fix_sub_duration -i mmm.mkv -i mmm.srt -map 0:0 -map 0:1 -map
 1:0 -map 0:2 -scodec mov_text -vcodec copy -acodec copy  mmm.mp4}}}
 i see no reason why success of the conversion depends on whether the
 internal subtitle is converted, when the problem is with the external SRT
 subtitle. i think this must be a bug. if there is a problem with the SRT,
 ffmpeg should fail (or succeed) regardless of whether other subtitle
 tracks are also specified.

 attached are the full outputs of ffmpeg

 note that the behaviour is the same whether -sub_charenc is omitted or if
 its added but specifies a wrong encoding

--

Comment:

 Please provide an input sample.

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Ticket URL: <https://trac.ffmpeg.org/ticket/6862#comment:1>
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