[mythtv] Time Stretch with PVR-350 (Possible solution to adjustaudio pitch)

Nick Rosier nick.rosier at gmail.com
Sun May 1 12:01:23 UTC 2005


I have to agree with John on this one. My first idea was also to do
something like this but the problem would be keeping audio and video
in sync. That's why I wanted to see if realtime pitch adjust is
possible. I know the soundtouch libraries are already in place but I
wouldn't know how to begin modifying the MythTv-code.  A simple
"test-case" using sox to modify the pitch of line-in would show me if
this solution is able to keep audio and video in sync.

N.

On 4/30/05, John Harvey <john.p.harvey at btinternet.com> wrote:
> My understanding of the checkbox is that it allows you to control the volume
> of the tv if you feed the output of the 350 to the line in of your audio
> card. This requires the code to open the audio device though even though it
> isn't actually used for audio playback. By ticking this box you say that you
> aren't using the audio card for tv playback so it won't try to open it (and
> possibly fail) but this means you can't control the volume.
> 
> As for keeping the audio and video in sync I suspect it will be a complete
> nightmare. The delay in ivtv's mpeg playback is quite large and I suspect
> not very well defined.
> 
> You would probably need to grab the information from the vsync and number of
> frames played etc. and use that to keep it all in sync.
> 
> John


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