What size is the display fifo ?
Remember that if you queue n buffer before starting the display, and you
are able to feed the display driver, then your fifo will always be
full, and you will get a delay :
If you start by doing :
for( i = 0; i < bufcount; i++) {
ioctl(fd,VIDIOC_QBUF, ...);
}
ioctl(fd,VIDIOC_STREAMON);
And then loop :
select();
ioctl(fd, VIDIOC_DQBUF,...); // dequeue buffer from display
... // fill buffer
ioctl(fd, VIDIOC_QBUF..);
this buffer will be displayed after the other buffer
already present in te _driver_ input queue have been displayed.
Reduce the initial buffer count, and you may see improvements, assuming
this description fits the way you are using the V4L2 driver.
Ondrej Pindroch a écrit :
Hi
I have simple loop trought which is proccessing images from CMOS sensor.
Proccessing take sallmost 7ms. In front end I am skipping frames which
are older than 1 frame. Still I have latency from input to outpu 120ms
and some times more. I am sure that I can not spare significant amount
of time in front end. That means that I have more than 2 frames latency
on VPBE (I am useing PAL as output 25fps => 40ms/f) Is there some
special settings to improve this timing on VPBE. I am useing V4L2.
Best regards
*/ Ondrej Pindroch
SoftHard Technology ltd.
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