[theora] Encoding from fifo's

[emaillist+ot at dogphilosophy.net]

On Sunday 02 February 2003 06:57 pm, Cameron Kerr wrote:
> Hello, I'm new to the list, so if this is an FAQ, please point me to the
> relevant docs.
>
> I'm playing with Theora, to see what kind of quality I can expect (I
> realise its not for production use yet). I've download the source from
> CVS, and got it to build, with the example encoder and player.
[...]
> cd /tmp
> mkfifo stream.yuv
> mkfifo audiodump.wav
> mplayer -dvd 2 -vo yuv4mpeg -ao pcm
>
> That part works fine.
>
> I then set up encoder_example as follows
>
> cd /tmp
> encoder_example -a 3 -v 7 stream.yuv audiodump.wav
>
> It correctly identifies the input streams (and therefore can read
> correctly), however, when it gets to its compression loop, it blocks.
[...]

I ran into the same problem initially.  It seems (I'm guessing) that the
4-month-old example encoder needs to get the packets from video and audio
initially in a particular order, and mplayer is starting with them in
a different order (i.e. encoder_example may want the first video packet
and then the first audio packet, but mplayer is sending the first audio
packet and then the first video packet, perhaps?) and you end up with
encoder_example waiting for a packet from mplayer before it can take the
next packet off of the fifo, and mplayer is waiting for a packet to be
taken off of the fifo before sending any more...

The work-around for me was to use TWO mplayer instances - one exporting only
the audio and another exporting only the video.  That seemed to get it going.

You can find a slightly rambling but maybe-helpful "HOWTO" file for the Alpha
1 release at:

http://www.dogphilosophy.net/SECTION-Technical_Stuff/ogg-theora-microhowto.html

Let me know if it's helpful...

I SUSPECT a lot of the issues in the Alpha 1 release will be nicely handled
when the next release finally comes out.  Right now it's scheduled to be Beta
1 sometime in March, though I don't know if it's on track to be out by then or
not.
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