[FFmpeg-user] concat + pipe protocols

[Nicolas George]

Le decadi 10 prairial, an CCXXII, Mark Bogdanoff a écrit :
> I'm attempting to run the command without intermediates or named pipes
> utilizing additional file descriptors. For now, I'm attempting this simple
> test:
> 
> ffmpeg -i input.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts pipe:1 |
> ffmpeg -f mpegts -i concat:pipe:0 -c copy -bsf:a aac_adtstoasc concat.mp4 
> 
> When I run this, I get this error: concat:pipe:0: Function not implemented
> 
> Looking at the source
> (http://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavformat/concat.c;h=3bbc83dfef16b629264c975dad4c28a37cee002d;hb=refs/heads/master#l101),
> it appears that ffmpeg is failing because it cannot get the size of the
> incoming pipe. Since this works with named pipes, I'm assuming there's an
> interaction here that isn't working with ffmpeg's pipes? Is this expected
> behavior or is there another way of specifying concat with pipes?

Yes, the concat protocol requires seekable streams. I do not think it ever
worked with named pipes. What work with named pipes is concatenation at the
OS level, using the cat command or similar. You can do without, for example
using the following command (or, depending on your shell, with command
substitution, as explained by somebody else):

{ cmd1; cmd2 } | cmd3

I suggest you get familiar with that syntax with something simpler than
ffmpeg.

Regards,

-- 
  Nicolas George
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