[FFmpeg-user] Yes or No? About the processing pipeline.

[Carl Zwanzig]

On 6/18/2025 2:41 PM, Mark Filipak wrote:
> Z, how am I or anyone to know what "sost#0:2" means? I don't even know 
> what "sost" means.
(does that specifically matter? I don't think so.)

After that.... RTFM? (I think you've used -map before so probably 
understand the concept of stream specifiers.)


"5.1 Stream specifiers"
stream_type[:additional_stream_specifier]
[...]
     stream_type is one of following: ’v’ or ’V’ for video, ’a’ for 
audio, ’s’ for subtitle, ’d’ for data, and ’t’ for attachments. ’v’ 
matches all video streams, ’V’ only matches video streams which are not 
attached pictures, video thumbnails or cover arts.

and

#stream_id or i:stream_id
     Match the stream by stream id (e.g. PID in MPEG-TS container).


Likewise "4.1.1 Automatic stream selection" tells us-
It will select that stream based upon the following criteria:
[...]
     for subtitles, it is the first subtitle stream found but there’s a 
caveat. The output format’s default subtitle encoder can be either 
text-based or image-based, and only a subtitle stream of the same type 
will be chosen.
(If mp4 only supports text subtitles and dvds have only images, of 
course it'll cough up an error.)


The output -told- you that #0:2 is subtitles, so an error message 
containing that is probably about those subtitles. Seemed obvious to me 
and I don't work much with ffmpeg.

I suggest you reread the basic ffmpeg manual at 
https://www.ffmpeg.org/ffmpeg.html; it's always good to reread the 
basics, sometimes useful things pop out afresh.


z!