[Telepathy] best frame rate for video chat

[Sjoerd Simons]

On Sun, 2010-08-22 at 16:57 +0200, Alexey Fisher wrote:
> Hallo all,
> i currently working on performance problem by cheese and looks like
> empathy has same issue only with other encoder. It looks like empathy
> encode with same frame rate, what webcam said it can provide. For
> example, my both cams tell they can 30fps. With all respect even for dvd
> used 25fps. Any way, most webcams say they do 30fps but provide less
> than 15fps.
> 
> you can test it with fpsdisplaysink: 
> gst-launch v4l2src ! video/x-raw-yuv,width=320,height=240 !
> ffmpegcolorspace ! fpsdisplaysink
> 
> With kernel "rmmod uvcvideo && modprobe uvcvideo trace=15" i got this
> log:
> camera init by skype:
> [34467.478549] uvcvideo: Trying format 0x56595559 (YUYV): 320x240
> [34467.478551] uvcvideo: Using default frame interval 66666.6 us (15.0
> fps).
> [34467.503945] uvcvideo: Setting frame interval to 1/15 (666666).
> 
> 
> camera init by empathy:
> [36203.506493] uvcvideo: Control 0x00980924 not found.
> [36203.506495] uvcvideo: Control 0x08000000 not found.
> [36203.517378] uvcvideo: Trying format 0x47504a4d (MJPG): 320x240.
> [36203.517381] uvcvideo: Using default frame interval 66666.6 us (15.0
> fps).
> [36203.544280] uvcvideo: Setting frame interval to 1/30 (333333).
> 
> 
> you can see, skype use YUYV and set stream to 15 fps. empathy use mjpg
> stream and set it back to 30fps. Probably MJPG is cheaper to transcode
> than YUYV :D

No, it's not cheaper at all, it's a lot more expensive. This bug has
been fixed in gstreamer recently:
http://cgit.freedesktop.org/gstreamer/gst-plugins-good/commit/?id=dcea1b2dfcdad92c381281aafd09786a7abe8a83


-- 
Sjoerd Simons <sjoerd.simons at collabora.co.uk>
Collabora Ltd.