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

[Carl Eugen Hoyos]

Mike Speciner  alum.mit.edu> writes:

> By the way, I tried to submit a bug report

It's often better to first ask here...

Carl Eugen

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

[Cley Faye]

2016-06-27 19:11 GMT+02:00 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  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.
>

​I don't think it is really a bug in ffmpeg: the output using a pipe can't
obviously move back to update the header when the transcoding operation is
complete​ to create a seek table. Seeking in such a stream should (IMO)
rely on the player's abilities to build such seeking index.

If it's really a header problem, I don't think using a pipe to produce such
file can ever work; if I remember correctly, in a webm the seeking entries
are located before the actual streams and are updated after said streams
are written.
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[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  
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

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