Hi;
I've gotten a little positive and no negative feedback on the changes I
made to PWC (posted a couple weeks ago). I'd like to submit my changes
to the code base. Would this be the forum for doing so?
To recapitulate, my goal was to reduce the latency which occurs when
snapshots are taken. Prior to my modification, the oldest frame in the
buffer list would be returned. I have added an ioctl mode which causes
the youngest frame to be returned instead, and the older frames to be
discarded. I also implemented another ioctl mode which waits until a
frame is finished being captured before returning, allowing one to sync
to the camera's clock, rather than trying to work the other way around.
This is independent of the existing sync ioctl used in mmap operations
and can be used whether actually reading a frame or not.
In the process of implementing these changes, I believe I significantly
improved the frame buffer handling. both by simplifying it and thus
making it possible to run faster on slower hardware. I have tested these
changes on Intel PC's (both AMD and an Intel mini-ITX), and on an ARM-9
sbc. I have only tested them with a Philips 900NC camera, but nothing I
did should affect other devices so far as I can see.
I modified three files: pwc.h, pwc-if.c and pwc-v4l.c. A tarball of the
modified code set can be obtained from:
http://cunningham.homeip.net/code.html
Regards,
--Jeff Cunningham
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