[gst-devel] getting data format info

[Hendrik Schober]

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

  That did the trick! We got it working now.

  Thank you for your support.

  Schobi