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pilluli · 2009-03-15, 17:32

Hi,

I was just curious on how XMBC does the video 23.976 framerate conversion to 24Hz - 50Hz - 60Hz TVs refresh rates (or even 30fps -> 50Hz for that matter) . I know there are initiatives (smoothvideo brach) to kind of solve this but I couldn't find anything in the docs about how it is currently implemented. Any ideas?

regards,

**alanwww1** · 2009-03-16, 10:28

I think xbmc-smoothvideo simply matches the framerate of playback to your refresh rate if it is within a certain x% speed difference. It changes the pitch of the sound to match it with the video framerate.

So eg. if you have an 50hz refresh rate than it will play your 24 (or 23.97)fps material a little bit faster (25fps). This way it is really smooth.

If you have a 60Hz TV. It makes the material to 24 fps, than makes a 3:2 pulldown i think. But i am not certain about that. Bobo1on1 migh know better.

pilluli · 2009-03-17, 22:39

Thanks for the reply alan,

alanwww1 Wrote:I think xbmc-smoothvideo simply matches the framerate of playback to your refresh rate if it is within a certain x% speed difference. It changes the pitch of the sound to match it with the video framerate.

Yeah, that's what I thought so I wonder if the smoothvideo branch is trying to do that what is currently XBMC doing? I've got my TV refresh rate now at 50Hz and I play 23.976fps, 25fps and 30fps. I do note judder in some camera pans so how is it matching the refresh rate? is it dropping frames? duplicating some? :confused2:

regards,

**bobo1on1** · 2009-03-19, 03:58

Every videoframe has a timestamp, xbmc waits until that time and then presents the videoframe.

It doesn't do any speed changes (smoothvideo does though).

pilluli · 2009-03-20, 23:34

bobo1on1 Wrote:Every videoframe has a timestamp, xbmc waits until that time and then presents the videoframe.

It doesn't do any speed changes (smoothvideo does though).

Hi bobo1on1,

Thank you for stoping in this thread. If I understand correctly then, in order to match the videoframe timestamp to the refreshrate of the screen, I guess at each screen refresh the last decoded video frame (last timestamp) is selected. So for instance in a 24fps to 50Hz conversion frames are duplicated except each ~1/2 sec which are triplicated...

Seeing that, I'm going to give the smoothvideo branch a try... Smile