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v4l open/read/close "atomic" speed and S910/S510/bayer help




Hi,

I have begin to work about a video mixer that use a Hercules Dj Console Rmx for
composing multiples v4l devices outputs into one X11 window (for video mixing /
composing between an Hauppauge WinTV-HVR1110 and one or two USB webcams for
example).

I have make a very basic YUYV to RGB[A] conversion routine that seem to work
with the WinTV (but only on B&W for the instant, but this isn't a problem
because I can read directely RGB values from my /dev/video2 and so, haven't to
deal with top/bottom frames entrelacement and lines inversions with the RGB
format as it's the case with the YUYV format ... and I have already a B&W video
flux with the YUYV format, so I think the color support on YUYV is really near)

This work "good" with the WinTV because I have only to make a conversion from
RGB24 (my WinTV card output) to RGB (my video card input), but when I have make
some timings, I found that the read to the /dev/video spend something like 80ms
per frame and I have only something like 12 fps on the end :(

Something like 50ms isn't normally a minimum for to have something decent ???

Is really the Hauppauge WinTV-HVR1110 driver as "slow" with open/read/close
on /dev/video ???

In first, I have think that is my RGB24 to RGB32 conversion and/or the X11
display via XImage that can spend the most of time ... but this isn't the case
(only somes very littles milliseconds, a little fraction of the total time,
something like 5%/10% at maximum)

But my problem isn't really here because I think that I use until now a very bad
v4l programming model with my open(s)/read(s)/close(s) on multiples /dev/video*
and project to use a multibuffered schema in a very near future (V4L docs say
that this can be really more speed)

But my real problem is that I don't know (and have really a lot of difficulty to
find) how to decompress the S910 or S510 video format that a lot of various
webcams that I have tested can output :(

=> where can I find simple/basic C/C++ tutorials for to make S510/S910 to RGB[A]
or YUYV conversions ???


@+
Yannoo

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