[gst-devel] data-sink in rsvgoverlay

[Sebastian Dröge]

On Thu, 2010-09-09 at 15:05 +0200, Olivier Aubert wrote:
> On Thu, 2010-09-09 at 14:37 +0200, Sebastian Dröge wrote:
> > On Thu, 2010-09-09 at 14:12 +0200, Olivier Aubert wrote:
> > > Hello
> > > 
> > > I have implemented a data-sink to feed SVG data to the proposed new
> > > rsvgoverlay element. However, I still have one issue: the following
> > > pipeline:
> > > 
> > > pygst-launch videotestsrc ! ffmpegcolorspace ! rsvgoverlay name=overlay ! ffmpegcolorspace ! xvimagesink filesrc blocksize=102400 location=/tmp/a.svg ! image/svg ! overlay.data_sink
> > > 
> > > works only if I specify the blocksize= parameter to filesrc, so that the
> > > SVG file is sent as one chunk. It greatly simplifies the rsvgoverlay
> > > code to make this assumption (else I would have to gather chunks in the
> > > overlay code to build the whole data). However, the blocksize hack is
> > > not satisfactory. Is there any way to specify this (whole files wanted)
> > > in the pad definition? I am attaching the code to also get some feedback
> > > about problems that could still be there.
> > 
> > You can simply wait and concatenate buffers until you get the EOS event
> > and only then start the real processing.
> Hello Sebastian. Thanks for the answer. Yes, it is not that complicated,
> but I would have hoped that the gstreamer infrastructure provided some
> infrastructure to do this, optimizing memory allocation and freeing,
> since it looks like a common thing in gstreamer elements. Is there no
> such thing?

GstAdapter could help here. You push buffers into it and after EOS can
get a single, large buffer from it

http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer-libs/html/GstAdapter.html
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