[gst-devel] Controlling the queue behaviour

[Sameer Naik]

Thanks Wim, 

i was hoping to get a response from you.
I will make the said changes in code and get back on the status

Thanks again
Regards
~Sameer


On Monday 29 December 2008 4:32:45 pm Wim Taymans wrote:
> On Sun, 2008-12-28 at 11:18 +0530, Sameer Naik wrote:
> > Hi,
> > I have written a  gstreamer plugin that does video decoding on
> > specialized hardware, and also written a videosink plugin that opens the
> > framebuffer device,etc . For optimizing the entire pipeline the videosink
> > plugin has the _pad_alloc functionality, that directly makes available
> > the framebuffer memory to the decoder plugin, so that the output images
> > can directly be written to the video memory. I would also mention, that
> > the videosink can make available 3 such buffers (triple buffering) to the
> > decoder, so effectively the decoder should not request for more than
> > three buffers at the same time, in which case if it does the _pad_alloc
> > function will not return any buffer.
> > Now, if i construct my pipeline as such
> >
> > gst-launch filesrc location=file.mpeg ! demultiplexer name=demux !
> > videodecoder ! queue ! videosink  demux. ! audiodecoder ! audioconvert !
> > queue ! audiosink
> >
> > what happens is, due to the queue element (after the videodecoder), the
> > part of the bin goes into its own thread. as a result, the videodecoder
> > ends up making a lot more buffer requests to the videosink, than the
> > videosink can really allocate.
> > Due to this, in gstreamer version 0.10.9 i would add the queue before the
> > videodecoder. like so
> >
> > gst-launch filesrc location=file.mpeg ! demultiplexer name=demux ! queue
> > ! videodecoder ! videosink  demux. ! audiodecoder ! audioconvert ! queue
> > ! audiosink
> >
> > and everything works fine.
> >
> > But the current version 0.10.21 does not allow me to do this, as in the
> > pipeline does not PREROLL.
> >
> > I would like to know, whether it is possible to control how the queue
> > functions so that it does not store more than 3 buffers. i tried
> > specifying max-size-buffers=3 on the queue, but it did not help.
> > I would also be interested in knowing any other ways this can be taken
> > care ç of.
>
> For this, the sink should block in the buffer_alloc function until an
> old buffer is rendered and there is a buffer available again for
> rendering into. When shutting down you should of course unblock and
> return WRONG_STATE from the buffer_alloc function.
>
> Wim
>
> > Reagrds
> > ~Sameer
> >
> >
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