[gst-devel] getting data format info

[thiagoss]

On Mon, Sep 1, 2008 at 12:59 PM, Hendrik Schober <spamtrap at gmx.de> wrote:

> thiagoss wrote:
> >
> >
> > On Mon, Sep 1, 2008 at 11:56 AM, Hendrik Schober <spamtrap at gmx.de
> > <mailto:spamtrap at gmx.de>> wrote:
> >
> >     thiagoss wrote:
> >      >
> >      > On Mon, Sep 1, 2008 at 11:18 AM, Hendrik Schober <spamtrap at gmx.de
> >     <mailto:spamtrap at gmx.de>
> >      > <mailto:spamtrap at gmx.de <mailto:spamtrap at gmx.de>>> wrote:
> >      >
> >      >     Hi,
> >      >
> >      >     we are using (or is that abusing?) gstreamer in order to
> capture
> >      >     video data from an USB camera. For this we have setup a v4lsrc
> >      >     and a fake sink and grab the data in the handoff hook of the
> >      >     latter. So far, so good. However, despite several hours of
> >      >     tinkering we haven't found out how to determine what format
> >      >     (width, height, encoding) the data comes in.
> >      >     What do we need to do to get these values?
> >      >
> >      >
> >      > Check the 'caps' in the source pad of the v4lsrc element.
> >
> >      Thanks for your answer.
> >      In fact, we already did that -- and got back a rather long
> >      list of caps. But that doesn't tell us which one's currently
> >      used. (Also, they specify a range for width and height, while
> >      we need the ones that actually are negotiated.)
> >
> >
> > You should check the caps in the buffers you get from the handoff
> > buffers instead.
>
>   Thanks, we hadn't even found those yet.
>  However, this now leads to another question:
>  Since these are rather suboptimal for us, we need to change
>  them. We could use the ffmpegcolorspace conversion plugin,
>  but IIUC we need to make this and the fakesink use the right
>  pad.
>  Where and how would we do this? When we setup the pipeline?
>  By forcing some caps/pad onto the fakesink's source?
>

You can do like this:

v4lsrc ! ffmpegcolorspace ! capsfilter caps="yourdesiredcaps" ! fakesink

If you need scaling put a videoscale between ffmpegcolorspace and
capsfilter.


>
>  Schobi
>
>
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-- 
Thiago Sousa Santos

Embedded Systems and Pervasive Computing Lab (Embedded)
Center of Electrical Engineering and Informatics (CEEI)
Federal University of Campina Grande (UFCG)
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