Hi,
On 06/03/2010 09:03 AM, Bjørn Mork wrote:
Mauro Carvalho Chehab<mchehab@xxxxxxxxxxxxx> writes:
Em 02-06-2010 18:09, Andrew Morton escreveu:
On Sun, 30 May 2010 14:29:55 GMT
bugzilla-daemon@xxxxxxxxxxxxxxxxxxx wrote:
https://bugzilla.kernel.org/show_bug.cgi?id=16077
2.6.33 -> 2.6.34 performance regression in dvb webcam frame rates.
I don't think this is a regression. Probably, the new code is allowing a higher
resolution. As the maximum bandwidth from the sensor to the USB bridge doesn't
change, and a change from QVGA to VGA implies on 4x more pixels per frame, as
consequence, the number of frames per second will likely reduce by a factor of 4x.
I've asked the reporter to confirm what resolutions he is setting on 2.6.33
and on 2.6.34, just to double check if my thesis is correct.
Well, the two video clips attached to the bug shows the same resolution
but a much, much lower video (and overall) bitrate in 2.6.34. Output
from mediainfo:
I notice in the original bug report that you claim that the lower framerate
clip with 2.6.34 has "much better quality", could you define this a bit better.
I think that what is happening is the code for the new (correct) sensor is
setting a higher exposure value (and thus a lighter / less dark image), but
setting a higher exposure value comes at the cost of framerate. As the framerate
can never be higher then 1 / exposure_time_for_1_frame.
2 things:
1) Go the preferences in cheese, and see which resolutions you can select, and
make sure you are using the same resolution in 2.6.34 and 2.6.33
2) Start a v4l2 control panel applet, like v4l2ucp or gtk-v4l, and try playing
around with the controls (note the controls inside cheese are software not
hardware controls so don't use those).
Regards,
Hans
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