On Wednesday 25 October 2006 21:43, Duncan Webb wrote:
> Duncan Webb wrote:
> > Hans Verkuil wrote:
> >> On Wednesday 04 October 2006 23:10, Duncan Webb wrote:
> >>> Is there a way to start and stop mpeg stream. When the mpeg
> >>> stream is opened then we get a GOP, so what would be nice is to
> >>> be able to stop the stream at the end of a group of pictures and
> >>> finish reading the data (with out having to parse a buffer). Or
> >>> even better open the stream in a paused mode and then send a
> >>> start to start the stream running. (A bit like using threads)
> >>
> >> If you call IVTV_IOC_S_GOP_END with arg 1, then the card won't
> >> stop capturing until the end of a GOP is reached.
> >
> > Hope that this is not a silly question.
> >
> > If I do this:
> > cat /dev/video0 >> ~/test.mpeg &
> > ivtvctl --device=/dev/video0 --end-gop=1
> >
> > Would you expect the output to stop?
> >
> > On another xterm running
> > watch ls -l ~/test.mpeg
> > shows the file still growing.
> >
> > TIA
> > Duncan
> >
> > I'm using a PVR-500 and ivtv-0.8.0
>
> I think that I should explain what I'm trying to do a bit more, so
> that I get an answer.
You weren't forgotten, I just didn't have a lot of time.
Now I'm no expert on this and I've never actually tested it, but as far
as I can tell the best way to do what you want is to:
1) call IVTV_IOC_S_GOP_END once during initialization to tell the driver
that you want to wait until the last GOP when the capture stops. It
doesn't actually stop the capture, it just tells the driver HOW to stop
a capture.
2) When you want to stop the capture issue a VIDIOC_STREAMOFF ioctl.
That stops the capture, but allows you to continue reading until no
more data is available. And then you can close the file descriptor
altogether.
Note that this may well change in the future, it's rather ivtv-specific
behavior.
Regards,
Hans
>
> I would like to use the VPS signal to control the start and end of
> the recording. So what is happening is that in the main thread the
> vbi device is being read and the VPS parsed, when a valid time is
> received a second thread is being used to read and write the video
> stream. When the signal changes to another time, then I would like to
> terminate the mpeg worker thread reading until the end of the GOP.
>
> If the IVTV_IOC_S_GOP_END works then there is no problem, if not then
> I may have to parse the MPEG stream in the worker thread, which would
> increase the load on the CPU.
>
> I just want to have confirmation that it is working. And if not in
> all versions, which version does the call work.
>
> TIA
> Duncan
>
>
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