A sox pipe mystery

[Martin Guy <martinwguy@gmail.com>]

Hi all

    I'm looking at launching external programs to decode a million other 
formats automatically and have run into a mystery I cannot fathom.


     sox "|ffmpeg -loglevel quiet -i 'Candy Toy.wma' -f ircam -" 'Candy 
Toy.wav'

works but

     sox "|ffmpeg -loglevel quiet -i 'Candy Toy.wma' -f sox -" 'Candy 
Toy.wav'

fails saying

    sox FAIL formats: can't open input  `-': can't find sox file format 
identifier

as do

     -f wav   sox FAIL formats: can't open input  `-': WAVE: RIFF header 
not found
     -f aiff  sox FAIL formats: can't open input  `-': AIFF header does 
not begin with magic word `FORM'

though

     ffmpeg -loglevel quiet -i 'Candy Toy.wma' -f sox -" > 'Candy Toy.sox'

     sox 'Candy Toy.sox' 'Candy Toy.wav'

works.


Is it because ffmpeg is seeking back in the file and rewriting the 
header once it's decoded? Nope:

     ffmpeg -loglevel quiet -i 'Candy Toy.wma' -f sox - | cat > 'Candy 
Toy.sox'

     cat 'Candy Toy.sox' | sox - 'Candy Toy.wav'

works too.


What's the difference for sox between that last command pair that works and

     ffmpeg -loglevel quiet -i 'Candy Toy.wma' -f sox - | sox - 'Candy 
Toy.wav'

or

     ffmpeg -loglevel quiet -i 'Candy Toy.wma' -f sox - | cat | sox - 
'Candy Toy.wav'

that don't?


And how come -f ircam works in the simple pipeline invocations but -t 
{wav,aiff,sox} don't?

(Not that I'm complaining - at least one intermediate format works. 
Finally, a use for ircam format!)


     M



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