Xv performance and quality issues at 1920x1080/60 resolution

[Michel Dänzer]

On Tue, 2008-09-16 at 09:14 -0300, Jason Keirstead wrote:
> > It probably only applies to OpenGL rendering, not XVideo. Something like
> > Alex's changes above would be necessary to prevent tearing with textured
> > XVideo.
> 
> No I don't think so... it is not tied to any rendering method. Docs say this:
> 
> There are two mechanisms to sync to VBlank under XOrg.  OpenGL has the
> GLX_SGI_video_sync extension, and DRM has DRM_IOCTL_WAIT_VBLANK .  One
> or both of these works
> on most modern hardware.  Both of these are useable for video output
> -- MythTV, for example,
> will select whichever is available.

The DRM mechanism isn't really suitable for XVideo. The client doesn't
know which CRTC to synchronize to, and even if it happens to pick the
right one, the latency between waiting for vblank and actually
displaying the new video frame (with X11 protocol dispatch etc. in
between) may just be too high to avoid tearing.


-- 
Earthling Michel Dänzer           |          http://tungstengraphics.com
Libre software enthusiast         |          Debian, X and DRI developer