[FFmpeg-user] Confusion over stream specifier on -map, -codec, and -filter_complex

[gqqnb2005]

Dear Mark,

Thank you for your reply. But I'm looking at the syntax of Stream
specifiers. It clearly specifies 7 forms.


   1. stream_index
   2. stream_type[:additional_stream_specifier]
   3. g:group_specifier[:additional_stream_specifier]
   4. p:program_id[:additional_stream_specifier]
   5. #stream_id or i:stream_id
   6. m:key[:value]
   7. u


0:1 fits none of the 7 forms.
[LOW]  fits none of the 7 forms.

I wonder is it a documentation bug that it misses other forms of
specifiers, or do I misunderstand something?



Mark Filipak <markfilipak.imdb at gmail.com> 於 2024年7月25日 週四 下午2:46寫道：

> On 25/07/2024 00.56, gqqnb2005 wrote:
> > Basically, I want to figure out how to specify streams for the option
> -map,
> > -codec,  and -filter_complex.
> >
> > ffmpeg -i INPUT -map 0:1 out.wav
> >
> > Is 0:1 a stream specifier (
> > https://ffmpeg.org//ffmpeg.html#Stream-specifiers-1)? Which form is it?
>
> Yes. Input 0, stream 1 (i.e., the 2nd stream, of any type). 'map' wires
> things to the output. No
> 'map', no output.
> > ffmpeg -i INPUT -map 0 -c copy -c:v:1 libx264 -c:a:137 libvorbis OUTPUT
> >
> > v:1 and a:137 seem to follow the syntax of stream specifier because a
> and v
> > are stream_type.
>
> Yes, the 2nd video stream. There can't be 138 audio streams, so that has
> to be wrong.
>
> > ffmpeg -i in.flac -filter_complex 'acrossover=split=1500[LOW][HIGH]' -map
> > '[LOW]' low.wav -map '[HIGH]' high.wav
> >
> > Is '[LOW]' in the syntax of stream specifier?
>
> In a sense, yes. It's a 'plug'. You connect plugs within a filter complex
> and to the output 'map'
> like they are physical equipment.
>
> --Mark.
>
>
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