[gst-devel] handling x-raw-gray/Y16 (16bits) signal

Daniel Fischer dan at f3c.com
Wed Jun 4 15:23:06 CEST 2008

quoting Brandon Lewis <brandon_lewis at berkeley.edu>:
> Albert Costa wrote:
> > Hi,
> > 
> > I'm trying to use a dc1394 camera that supports 16 bits depth gray 
> > images. However, whatever I try, I find no way to set the caps of my 
> > dc1394 plugin to this format.
> > 
> > For example,
> > 
> > "gst-launch dc1394src ! video/x-raw-gray,depth=16 ! fakesink" returns 
> > with not negociated caps error (I have tried many combinations of 
> > pipelines, none succeeded)...
> I think that's an invalid pipeline for a number of reasons:
> 1) dc1394src -- did you mean dv1394src?

Brandon: no, he means dc1394src. It uses libdc1394 (based on the "digital camera" specs) to adress various "scientific/industrial" cameras that deliver an uncompressed video signal in various formats.

> 2) video/x-raw-gray,depth=16 ... this isn't an element. it's a 
> capability...using ! doesn't make sense. try using a capsfilter -- i.e.
> .... ! capsfilter caps=video/x-raw-gray ! ...

of course it makes sense ;) there's no need to explicitly instantiate "capsfilter" in a gst-launch pipeline, just stating the caps between two !s connects the elements "filtered". try:
  gst-launch-0.10 videotestsrc ! video/x-raw-yuv, width=100, height=100 ! xvimagesink

> 3) if you use fakesink, nothing is going to show up anyways

right, but Alberts problem is not that nothing shows up, but that the 16bit caps don't want to play at all. It's quite valid to test that with fakesink.

> 4) you'll want to use ffmpegcolorspace between your source and sink.

True, usually. But ffmpegcolorspace also wouldn't understand depth/bpp=16

Now, Albert: the dc1394src plugin is in gst-plugins-bad for a reason: the format handling especially needs. I dont think that getting the dc1394 formats in line with gstreamer caps is an all to easy task.. It would also be nice to have the camera's adjustable parameters be reflected by either gobject properties, or gstinterfaces.. I currently lack the time to care about this (even though i have interest), so maybe you might want to have a look yourself.

I currently can't get dc1394src to negotiate *any* format...


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