On Wed, Nov 5, 2014 at 4:05 PM, Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > Hi Rémi, > > On Tuesday 04 November 2014 22:41:44 Rémi Denis-Courmont wrote: >> Le mardi 04 novembre 2014, 15:42:37 Rémi Denis-Courmont a écrit : >> > Le 2014-11-04 14:58, Sakari Ailus a écrit : >> > >> > Have you tried with a different application to see if the problem >> > >> > persists? >> > >> >> > >> Tried mplayer and cheese now, and it seems they are not affected, so >> > >> it's an issue with vlc. I wonder why it doesn't like newer flags.. >> > >> >> > >> Ohwell, sorry for the noise. >> > > >> > > I guess the newer VLC could indeed pay attention to the monotonic >> > > timestamp flag. Remi, any idea? >> > >> > VLC takes the kernel timestamp, if monotonic, since version 2.1. >> > Otherwise, it generates its own inaccurate timestamp. So either that >> > code is wrong, or the kernel timestamps are. >> >> From a quick check with C920, the timestamps from the kernel are quite >> jittery, and but seem to follow a pattern. When requesting a 10 Hz frame >> rate, I actually get a frame interval of about 8/9 (i.e. 89ms) jumping to >> 1/3 every approximately 2 seconds. >> >> From my user-space point of view, this is a kernel issue. The problem >> probably just manifests when both VLC and Linux versions support monotonic >> timestamps. >> >> Whether the root cause is in the kernel, the device driver or the firmware, >> I can´t say. > > Would you be able to capture images from the C920 using yavta, with the > uvcvideo trace parameter set to 4096, and send me both the yavta log and the > kernel log ? Let's start with a capture sequence of 50 to 100 images. I've done 2 captures, if that helps: http://notaz.gp2x.de/tmp/c920_yavta/ The second one was done using low exposure setting, which allows camera to achieve higher frame rate. -- Gražvydas -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
