[Theora] trying to encode from dvd using mplayer

[Tim Olsen]

Hello.  I'm trying to encode an Ogg Theora file from an unencrypted
dvd using mplayer and encoder_example.

I set up named pipes stream.wav and stream.yuv. 

I then run:

mplayer -ao pcm -aofile stream.wav -vo null /dev/dvd &
mplayer -vo yuv4mpeg -ao null -nosound /dev/dvd &
encoder_example -v1 -a 1 stream.wav stream.yuv > lec1.ogg

but I get the following error:

File stream.wav is 16 bit 2 channel 48000 Hz RIFF WAV audio.
File stream.yuv is 720x480 29.97 fps YUV12 video.
Compressing....
-Loss of framing in YUV input data


Encoding works if I give mplayer an MPEG-1 file on disk as input.  

Anybody know what I can do to get around this?  I was thinking I could
try copying the VOB files to disk and then encoding each one but then
I would have two ogg files that I would have to join.

thanks for your help

-Tim