[mythtv] Ticket #6938: smoother playback

David Engel david at istwok.net
Sun Aug 30 17:03:27 UTC 2009

On Sun, Aug 30, 2009 at 06:31:09AM -0000, MythTV wrote:
> Comment(by markspieth):
>  using opengl vsync with no acceleration, audio controls timing.
>  xvideo, standard and linearblend/kernel deint on one.
>  xvideo, standard and greedyx1/yadifx1 on FE.
>  1080i and 720i dvb source. display is 60Hz in both cases (TV's). original
>  src material is 50Hz (aus DVB). various timestretch speedups between 1.0
>  and 1.85.
>  ive been running this for a couple of years. gave it to a few people for
>  eval. simon kenyon most recently. said it was much better.
>  most noticable in motor racing and news tickers. havent tried without for
>  a long time.
>  effect was 0.5 secs normal and then 0.5 secs hurry up for video out rate
>  adaption.
>  I suspect rtc is why you dont notice it.

Are you using an nvidia card, and if so, do you have Xv sync to VBlank
enabled or disabled?

I used to use opengl vsync with Xv sync to VBlank disabled for SD.  It
was very smooth.  When I switched to HD, this configuration resulted
in tearing and I had to enable XV sync to VBlank to get rid of it.
Using opengl vsync with Xv sync to VBlank resulted in horrible
jerkyness when timestretching.  To get rid of the jerkyness, I
switched to RTC vsync and have running this way for about 2 years now.
It's not ideal in that the timinig MythTV is using isn't exactly in
sync with the display, but it's been close enough.

David Engel
david at istwok.net

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