Re: GStreamer access to raw audio data

[Zach Morgan <zpmorgan gmail com>]

Hi, Torsten.

I took your advice and cannibalized GStreamer::Interfaces to create
bindings for Appsink and Appsrc. I'm not clear on how you would make
it nice and perlish, so any criticism is welcome. Also, I've never
used xs or created bindings before. I didn't touch the set_callbacks
methods, and the GstAppStreamType enum, which isn't even tested,
probably could have been handled better.

$appsink->pull_buffer() seems to work though; It's what I'm mainly
interested in.

And a question: Will GStreamer buffers leak every bit of data that
they're set with? I don't see what this comment is referring to.
http://git.gnome.org/browse/perl-GStreamer/tree/xs/GstBuffer.xs#n100

My GStreamer::App repo is at https://github.com/zpmorgan/GStreamer-App

Thanks,
Zach Morgan

On 1/17/12, Torsten Schoenfeld <kaffeetisch gmx de> wrote:
> On 16.01.2012 17:06, Zach Morgan wrote:
> > First of all, Gtk2, Glib, Gstreamer are all phenomenal bindings. They
> > have truly turned a spaghetti nightmare into a gizmo paradise. Thank
> > you.
>
> Thanks for the feedback!
>
> > It doesn't look like it will be that easy for audio. 'convert-frame'
> > doesn't handle audio caps, and #gstreamer on freenode insists that an
> > appsink is the way to capture audio. I have a significant problem with
> > appsink, which is that it appsink methods don't appear to work. My
> > appsink object is instantiated by the GStreamer::ElementFactory, but
> > calling, for example, $appsink->pull_preroll() produces this error:
> >
> > Can't locate object method "gst_app_sink_pull_preroll" via package
> > "Glib::Object::_Unregistered::GstAppSink" at lib/PDL/GStreamer.pm line
> > 54.
>
> I cannot comment on whether GstAppSink is the best way to achieve this.
>   But assuming it is, the problem at hand is that we have no bindings
> for it.  GstAppSink seems to be part of the libgstapp library, which in
> turn is part of gst-plugins-base, i.e. not of gstreamer itself.  So I
> think the best way to wrap GstAppSink would be to create a separate Perl
> module GStreamer::App along the lines of the existing module
> GStreamer::Interfaces.  I cannot promise to tackle this soon myself, but
> I would definitely try to provide all the necessary help if someone else
> wanted to give it a shot.
>
> The code in your github repository looks fine to me.  Looking at
> capture_image, though, I'm reminded of how awkward the
> GStreamer::Structure stuff is.  The current bindings are basically a
> one-to-one mapping of the C API.  But in this case I think a more
> natural Perl wrapper would be handy.
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