[mythtv] bttv recordings run fast

bobnvic at everestkc.net bobnvic at everestkc.net
Fri Mar 5 13:44:41 EST 2004

Joseph A. Caputo wrote:
> On Friday 05 March 2004 09:58, bobnvic at everestkc.net wrote:
> > I upgraded to cvs on 3/2/04 from cvs from early March and every
> > recording on bttv card since then plays very fast.  The recording
> > starts out playing normally for the first few seconds and then
> > everything speeds up by a significant amount making it 
> impossible to follow.
> Are you using btaudio?  You might need to make sure your audio 
> sample 
> rate for capture is 32000Hz.  Most bttv cards only support this 
> sample 
> rate.  If you're recording your audio at a sample rate that's 
> higher 
> than the actual, your entire playback will be sped up.  So if 
> you're 
> recording with a 48000Hz sample rate, your playback (in Myth) will 
> likely be 48/32 = 1.5 times faster than it should.  Remember 
> that's 
> "sample rate", not "bit rate".
> You might also play around with the "use video as timebase" option 
> in 
> Setup->TV->Playback, but if you're recording at the wrong sample 
> rate 
> then that will also probably give you weird results (perhaps slow 
> or 
> stuttering audio?).

I'm not using btaudio and everything was fine until upgrading cvs,
so something changed in February to cause it.  bttv has always seemed
somewhat flakey on my system, however.  I often have the problem of
fast forwarding causing the video to loop back to a previous point
in the recording, but only for the bttv recordings, not the pvr-250
recordings or pvr transcoded recordings.  I've considered upgrading
to bttv 0.9.x, but I don't see how this particular problem with the
speed could be a bttv problem since it works fine in windows.

I'll try the "use video as timebase" option and see what happens.
Are there any other ideas?


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