[FFmpeg-user] Problem with using pipe:1 when creating webm audio

[Mike Speciner]

I'm attempting to create a webm audio on the fly within my website, with 
a command like

ffmpeg -i one2twenty.wav -aq 6 -dash 1 -f webm pipe:1 > foo.d1p

although the piped output is actually being sent out over the web; I 
just redirected it to file in the above so I could investigate it. If 
instead I do

ffmpeg -i one2twenty.wav -aq 6 -dash 1 -f webm foo.d1f

I get a similar file, but slightly shorter. The problem is that the 
piped version (foo.d1p) doesn't work properly in firefox--apparently 
there is something wrong with the cues and firefox (using the <audio> 
element) claims the audio is not seekable and won't seek into it, 
although it will play it from the beginning. There is no such problem 
with the directly written version (foo.d1f).

Do I have to do something special to get the piping to work, or do I 
have to fall back to writing the file and then reading it back in to 
serve it? I discovered this problem using ffmpeg 2.7.2, but I've now 
tried it with ffmpeg 3.1, and it still fails the same way.

By the way, I tried to submit a bug report (assuming this problem is 
actually an ffmpeg bug), but when I attempted to register, the system 
claimed my registration was spam without giving me any clue as to why.

Thanks.

--ms