[gst-devel] How to Set Buffer Size Within Plugin

[Marco Ballesio]

Hi,

as usual, late reply, but hopefully it still helps..

On Mon, Oct 18, 2010 at 2:40 PM, Greg Wunder <gwunder at eoir.com> wrote:

>  Tracing the pipeline debug messages (noted below) showed that during the
> first fixate_caps() call, the input/output video sizes have been fixated
> already.
> Before that in the transform_caps() calls, the video sizes range [1,
> 32767], until the output video size is fixated into the input video size
> 320x240 & then fixate_caps() is called.
> I couldn't know the input video size, before the output video size has been
> set by the pipeline application.
>
> Using GstBaseTransform, the two functions called before setcap() are:
>
> 1) trans_class->transform_caps = GST_DEBUG_FUNCPTR
> (gst_mosaick_transform_caps);
> 2) trans_class->fixate_caps = GST_DEBUG_FUNCPTR (gst_mosaick_fixate_caps);
>
> If I understand well, here you need a caps renegotiation once the proper
output size is known by the transformation element. More info here:

http://www.gstreamer.net/data/doc/gstreamer/head/pwg/html/section-nego-upstream.html

This doc appears also to be quite handy:

http://cgit.freedesktop.org/gstreamer/gstreamer/tree/docs/pwg/advanced-negotiation.xml

But I'd suggest, if you cloned the gstreamer core, to build the
corresponding manual and read it instead of this xml file.

Regards
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