Hi!
On Thu, 1 Nov 2001, Ronald Bultje wrote:
> I'm currently still facing one problem with capturing video using either
> lavrec or gstreamer, sometimes (completely random, it seems), VIDIOCSYNC
> will return with an EIOERR ("input/output error"). I'm not able to find out
> why.
In case of bttv look at the syslog files. There should be additional
messages giving a hint about what caused the premature returns.
> One last thing, do I need to do ioctl(fd, VIDIOCMCAPTURE, &1); to capture,
> or is VIDIOCMCAPTURE only useful for enabling/disabling the video overlay
> display? Supposing that it's not necessary to do ioctl(fd,VIDIOCMCAPTURE,
VIDIOCMCAPTURE(i) requests the next available TV frame to be captured to
buffer[i]. You must call VIDIOCMCAPTURE for every frame you want. As
VIDIOCMCAPTURE returns immediately a queue of several requested frames may
be built. (And subsequently a VIDIOCSYNC(i) for every exposed
VIDIOCMCAPTURE(i) should follow. VIDIOCCSYNC cannot be queued because it
returns not before the respective frame/buffer has finished its capture.)
VIDIOCCAPTURE(0|1) controls overlay mode.
> &1), how do I de-queue the buffers after being done capturing? Or can I
> just leave them and requeue the same buffers when I want to continue
> capturing at a later time (without having unmap()'ed/mmap()'ed the memory
> or in any other way restarted the process)?
After VIDIOCSYNC(i) has returned, apart from processing its content, no
further action to the corresponding buffer is needed. So, just leave them.
Or do you mean by "de-queue" to delete already accepted frame requests
that have not begun or finished their capture? That's not possible.
Bye,
Rolf
