[mythtv-users] Bob deinterlacing drops frames, but not high CPU

Matt Doran matt.doran at papercut.biz
Fri May 25 03:08:53 UTC 2007

Phill Edwards wrote:
>> I finally got a chance to update my modeline.  I used xvidtune.  For
>> some reason I need to set my rate to slighlty above 50Hz in the modeline
>> to make it really 50Hz.  It seems to drop 0.1Hz for some reason??
> Would you mind sharing your modeline as I have a Panasonic plasma as
> well with HDMI input. On a different thread I've been hacking my
> modeline to get BOB working and come up with this but I think it may
> not be 50Hz which is probably not a good thing:
> "1280x720"     74.25   1280 1720 1760 1984    720  725  730  750 +hsync +vsync
> I have to admit I don't actually understand where the Hz is specified.
Will do, when I get home.   If I forget, give me a yell or email direct.

It's all very confusing ... and I'm a techie/software developer.   I 
ended up getting lots of help on the list and looking at the code to 
figure out what was going on.  It would be impossible for a mere mortal 
to get this working without help from the list.

I used xvidtune and hit the "narrower"?? button a once or twice.  It 
shows what the vsync rate is.    You then press the Show (display??) 
button which outputs the new modeline to stdout.

The problem for me was that even though xvidtune shows 50Hz, when 
running it was actually set to 49.9.  So I had to go to 50.1 or 50.2 in 
xvidtune to get a true 50Hz.

Once I got that working I enabled bob and opengl vsync, and the result 
is much smoother playback.

-- Matt

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