Hmm, firstly, please forgive me if I'm send this to the improper place. I'm working on a fork of xcompmgr called compton. Some users complain about screen tearing when playing videos with compton running. Most of the reports come from Intel integrated graphic chip users, but one from a nVidia card user. (I don't know why the "Sync to VBlank" support in the binary blob isn't working for him.) And they demand VSync support on compton, but I don't see X Render supporting it. I could not reproduce this issue on my nVidia GTX 670 + binary blob regardless of how I change the settings, so effectively I'm working on this "blindly". I've tried 3 ways:
1. Let compton paint with the pace of the refresh rate, using 3 different methods: software method (sleep using nanosleep()), DRM_IOCTL_WAIT_VBLANK, and OpenGL SGI_video_sync. According to the debugging output they supplied, I'm pretty sure that compton is painting with the correct interval. And they are reporting a tearing line that either stays at fixed place in the screen or moves very slowly, instead of going away. If the tearing line is moving, they says, it moves in one direction to the bottom, then starts from the top. So looks like, regardless of when compton starts painting, the tearing does not go away. 2. Let compton paint to a backbuffer provided by X DBE extension. This has no effect according to their reports. 3. Let compton paint to the X composite overlay window (what XCompositeGetOverlayWindow() returns). No effect, even combined with the double buffering above, they says. So, despite all my efforts, the best result I got is a tearing line that sticks in a particular place on the screen. And despite all my efforts, I got no further information from them about how this problem is happening. I did recommend them to try the unaccelerated x11 video output, and test if VSync features of other compositing window managers (mostly, cairo-compmgr) works, but I'm afraid they either didn't follow my advice or did not report the result to me. This is the original issue report, in case I missed any information: https://github.com/chjj/compton/issues/7 So I wonder what is the correct cure to the tearing issue in video playback, for a compositing window manager using X Render as backend? What could I have missed? And if possible, I hope somebody could provide a hint about why all my 3 approaches are failing, and why the software VSync (sleep using nanosleep(), calculated from the initial paint time and refresh rate) causes the tearing line to constantly move in one direction. (I expect it to move back and forth.) Thanks in advance. Regards, Richard Grenville _______________________________________________ xorg@lists.x.org: X.Org support Archives: http://lists.freedesktop.org/archives/xorg Info: http://lists.x.org/mailman/listinfo/xorg Your subscription address: arch...@mail-archive.com
