[gst-devel] Transcoding and otherwise dealing with streams.

[Marco Ballesio]

Hi,

sorry for the late reply. I hope it will help.

On Fri, Sep 10, 2010 at 7:52 PM, Baldur Gislason <baldur at medizza.com> wrote:

> I am trying to construct a C application that can either pick up
> audio/video from a file (mpeg transport stream) or receive mpeg  transport
> stream on a UDP socket.
> Input format is MPEG2 A/V and output is H.264 with MPEG audio or AAC,
> transport stream multiplexing on output.
> So far I have managed to transcode video from network but am getting buffer
> underruns on the queue. If I add audio everything just stops, the pipeline
> does nothing and I can't quite figure out why.
>

I don't have many details about how your pipelines ar4e built, but in 90% of
the cases the behaviour you're observing is due to a missing queue at the
right point. The audio thread should be straightforward from source to sink,
while one queue element should be separating the video thread before the
muxer.


> If I read the data from a file, I get buffer overruns. So clearly this is a
> clocking thing. I have searched for documentation regarding clocking in
> gstreamer but found nothing useful.


You can find something here:

http://cgit.freedesktop.org/gstreamer/gstreamer/tree/docs/design/part-clocks.txt

and here:

http://cgit.freedesktop.org/gstreamer/gstreamer/tree/docs/design/part-scheduling.txt
http://cgit.freedesktop.org/gstreamer/gstreamer/tree/docs/design/part-synchronisation.txt


> The app developers manual mentions clocking but nothing about how it
> applies to code, and gst-inspect says none of the elements I have looked at
> have any clocking capabilities?!f
>
> Anyway, I was wondering if anyone had an example for building an MPEG
> transcoding pipeline in C, for working with a live stream and not file
> input, file output. File input, network output would be the other
> scenario.
>

See here the excellent guide (should be from Mark Nauwelaerts):

http://gentrans.sourceforge.net/docs/head/manual/html/howto.html

Regards


>
> Baldur Gislason
>
>
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