[theora] Encoding from fifo's

[Cameron Kerr]

On Mon, Feb 03, 2003 at 10:18:01AM -0700, emaillist+ot at dogphilosophy.net wrote:

> 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.

Alas, the encode plays back terribly on my PIII 800 system, although
there are no artifacts (quality looks damn fine actually), the playback
speed is just not suitable. I got large frequent slowdowns in playback,
a little like someone who suffers from stuttering (but without the
repitition).

I tried encoding the same source (a dvd), in Vorbis+Theora, and again in
MP3+MPEG4. These are the commands I used

cd /tmp/
mkfifo audiodump.wav
mkfifo stream.yuv
mplayer -dvd 2 -vo yuv4mpeg -au null &
mplayer -dvd 2 -vo null -au pcm &
encoder_example -a 2 -v 5 stream.yuv audiodump.wav > test.ogm

It didn't get it all done however, I had errors from mplayer such as the
following:

Too many audio packets in the buffer: (4096 in 8257536 bytes).
Maybe you are playing a non-interleaved stream/file or the codec failed?
For AVI files, try to force non-interleaved mode with the -ni option.

I then repeated the experiment with mencoder

mplayer -dvd 2 -vo yuv4mpeg -au null &
mplayer -dvd 2 -vo null -au pcm &
mencoder -o test.avi -ovc lavc \
        -lavcopts vcodec=mpeg4:vbitrate=1800:vhq \
        -oac mp3lame -lameopts preset=standard \
        -audiofile audiodump.wav stream.yuv

Which plays back fine. I still get the errors from mplayer however.

I also tried extracting the audio first to a seperate file, then reading
the video in a seperate pass straight from the dvd (via mplayer). This
gave the same (unsuitable in Theora) results, but managed to encode the
entire input.

Any ideas why I get these mysterious stalls? Both encoders seem to be
doing about the same fps (~8fps).


-- 
Cameron Kerr
Email:   cameron.kerr at paradise.net.nz
Website: http://nzgeeks.org/cameron/

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