I see a very weird problem when reading from an analog capture card with MPEG
encoder using libevent 1.4 and an EV_READ callback function (persistent mode).
Actually so far I used the same code for reading from a dvb dvr device, which
always worked very well. Now with the /dev/video I loose parts of the data, it
seems as if the dvr_read function is not always called when data comes in. Or
it's called too late, so that the device driver might have to drop data due to
buffer underruns.
I inspected the polling behaviour of the device and figured that it works well
to read from the device with a polling loop like this:
while(running) {
if(poll(&poll, 1, 500) > 0) {
do {
len = read(fd, &buf[0], 188);
if(len < 188 && len > 0)
printf("read err\n");
write(fdo, &buf[0], len);
} while (len==188);
} else
usleep(100000);
}
To see a similiar behaviour as I have with libevent I have to remove the else
and do the sleep whenever read returned len != 188.
Has anyone any ideas what my be the cause of this?
-Julian
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