How to keep record of the current frame when playing video?

[Marcus Nascimento]

Hi  Sebastian,

I think I managed to do that.

That's my solution:

To set the start time, I do this:
GstEvent *ev = gst_event_new_step(GST_FORMAT_TIME, startTimePosition, 1.0,
TRUE, FALSE);








On Tue, Nov 12, 2013 at 11:25 AM, Sebastian Dröge <sebastian at centricular.com
> wrote:

> On Mo, 2013-11-11 at 18:56 -0200, Marcus Nascimento wrote:
> > I'm working on a media platform and I have to implement a wrapper to
> > GStreamer that offers the following interface:
> >
> > - SetStartTime: Set the start position (in time)
> > - SetEndTime: Set the end position (in time)
> > - SetStartFrame: Set the start position (in frames)
> > - SetEndFrame: Set the end position (in frames)
> > - SetStartSample: Set the start position (in samples)
> > - SetEndSample: Set the end position (in samples)
> > - AddTimeAlarm: A listener will be notified when a given time is reached.
> > - AddFrameAlarm: A listener will be notified when a given frame is
> reached.
> > - AddSampleAlarm: A listener will be notified when a given sample is
> > reached.
> >
> > I'll never play streamming media nor remote media, but only local files.
> >
> > The biggest problem up to now cames from the fact it is possible to set
> > Start/End position in time, and add frame alarms, for instance.
> >
> > I'm using STEP events to set the start position. It is just a matter of
> > using gst_event_new_step passing the right parameters for that
> > (GST_FORMAT_TIME for time, GST_FORMAT_DEFAULT for samples and
> > GST_FORMAT_BUFFERS for frames).
> >
> > In any case, I need to know which frame corresponds to the step
> destination.
> > To do that, I'm incrementing the frame counter everytime I receive a QOS
> > message durring the STEP execution. I do that until I receive a STEP_DONE
> > message. By that time, I know what is the current time and current frame.
> > It seems to work fine. Does anyone know if that is not correct?
> >
> > After the STEP is complete, I'm using a pad probe (buffer probe) to keep
> > counting the frames.
> > This way, I can know for sure when a frame alarm has expired.
> >
> > Strange thing is: When I set the StartFrame to 300, the corresponding
> time
> > is a little after 9s.
> > But, when I schedule an alarm to the same frame 300, the corresponding
> time
> > is around 7s.
> > It is very strange for me.
> >
> > Can anyone help me understanding what's going on?
>
> It would be useful to have some test case to explain what exactly you do
> how and to have a way to reproduce it. Also which file formats are you
> using and which GStreamer version on which platform? :)
>
> How do you get "the corresponding time" when you do StartFrame(300)? And
> how for the alarms? The alarms are counting the frames via a pad probe
> and you get the buffer timestamp from there?
>
> --
> Sebastian Dröge <sebastian at centricular.com>
> Centricular Ltd - http://www.centricular.com
> Expertise, Straight from the Source
>
> _______________________________________________
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>
>


-- 
Marcus Nascimento
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