Hi,
I wrote libtimer and libwebcam (along with mstute) for Classic. The
timer idea was ok and working great in most cases, but it highly
depended on the timer implementation we chose for each operating system.
On win32 there's timeSetEvent() which i believe uses kernel timers. On
Linux and others we used a thread that sleeped itself the right time.
While it worked apparently great it's hard to say if it was really doing
the right thing.
One thing i'm sure though, is that you're right when you say the new
approach causes problems; on all operating systems, you can't expect
sleep() to sleep the right amount of time.
I believe tanguy & philippe are responsible for the rewrite of libwebcam
in NG, maybe they'll tell you more.
Matthias Schneider wrote:
Hi all,
comparing the V4L implementation of Wengophone classic
(libs/webcam/src/v4l-driver/WebcamV4l.cpp)
and NG (libs/webcam/src/v4l/V4LWebcamDriver.cpp) I noticed a completely
different architecture.
While classic makes use of a timer in order to trigger the capturing of a
frame, the NG driver
consists of a loop that sleep for 1/fps seconds and then captures a frame. This
rather simple
approach raises problems when trying to use higher frame rates (e.g. desired
framerate = 25 fps,
resulting in a sleep of 40ms - however an additional execution time of 20 ms of
the rest of the
loop results in a loop interval of 60ms on my machine, lowering the framerate
to a jittery 15
fps).
I would like to ask about the motivation of leaving the more sophisticated
(classic) approach in
favor of the new implementation which is not really usable for high bitrates
and quite
undeterministic.
Thanks in advance
Matthias Schneider
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