[gst-devel] Plugin creation

cammille at polytech.unice.fr cammille at polytech.unice.fr
Fri Mar 6 14:10:46 CET 2009 

If I try this :
v4l2src ! "video/x-raw-rgb,bpp=16,depth=16" ! testfilter ! videoscale !
ffmpegcolorspace ! xvimagesink

I obtain that :
(gst-launch-0.10:3704): GStreamer-WARNING **: pad v4l2src0:src returned
caps which are not a real subset of its template caps
ERROR: Pipeline doesn't want to pause.
ERROR: from element /GstPipeline:pipeline0/GstV4l2Src:v4l2src0: Could not
negotiate format



> You have to force rgb16 format in the filter src, and I'd also use the
> videoscale and ffmpegcolorspace elements after the filtering has taken
> place. Try this:
>
> v4l2src ! "video/x-raw-rgb,bpp=16,depth=16" ! testfilter ! videoscale !
> ffmpegcolorspace ! xvimagesink
>
>
> El vie, 06-03-2009 a las 11:59 +0100, cammille at polytech.unice.fr
> escribió:
>> I resolve the problem !
>>
>> But there still is the problem I had at the beginning : Could not
>> negotiate format...
>>
>>
>> I remember you my pipeline :
>> v4l2src  !  videoscale !  ffmpegcolorspace ! testfilter ! xvimagesink
>>
>> Where testfilter should apply a red mask.
>>
>> > Thanks for your help !
>> >
>> > I have another problem when I compile my project :  error:
>> > gst/video/video.h: No such file or directory
>> >
>> > So I can't test your code. I searched on google but it seems that
>> nobody
>> > have the problem.
>> >
>> > Do you know how to resolve the problem ?
>> >
>> >> (I sent another email with an implementation of a silly video filter
>> >> that applies different color masks to an rgb stream, but for some
>> reason
>> >> it did not hit the list, guess it does not like attachments so I
>> removed
>> >> it, hopefully this one will make it. If you want the code, say so and
>> >> I'll send it to you directly).
>> >>
>> >> In summary, you just need to get the red_mask from the caps:
>> >>
>> >> gst_filter_set_caps (GstPad * pad, GstCaps * caps)
>> >> {
>> >>   Gstmyvideo *filter;
>> >>   GstPad *otherpad;
>> >>
>> >>   filter = GST_MYVIDEO (gst_pad_get_parent (pad));
>> >>   otherpad = (pad == filter->srcpad) ? filter->sinkpad :
>> filter->srcpad;
>> >>   gst_object_unref (filter);
>> >>
>> >>   GstStructure *structure = gst_caps_get_structure (caps, 0);
>> >>   ...
>> >>   gst_structure_get_int (structure, "red_mask", &filter->red_mask);
>> >>   ...
>> >> }
>> >>
>> >> Then, in your process function, apply the mask to the samples,
>> something
>> >> like this does the trick:
>> >>
>> >> ...
>> >> guint samples = GST_BUFFER_SIZE (buf) / 2;
>> >> guint16 *data = (guint16 *) GST_BUFFER_DATA (buf);
>> >> gint i;
>> >>
>> >> for (i=0; i<samples; i++) {
>> >>     data[i] = data[i] & filter->red_mask;
>> >>  }
>> >> ...
>> >>
>> >> Iago
>> >>
>> >> El vie, 06-03-2009 a las 09:05 +0100, cammille at polytech.unice.fr
>> >> escribió:
>> >>> Nobody knows how to filter the red color ?
>> >>>
>> >>> If someone can explain me how to manipulate the buffer just to keep
>> the
>> >>> red color it would be great.
>> >>>
>> >>> Thank you.
>> >>>
>> >>> > Thanks everybody !
>> >>> >
>> >>> > I'm ok with you Albert, I think the simplest is RGB.. but there
>> still
>> >>> is a
>> >>> > problem.
>> >>> > If I define a cap I have an error which is :
>> >>> > ERROR: from element /GstPipeline:pipeline0/GstV4l2Src:v4l2src0:
>> Could
>> >>> not
>> >>> > negotiate format
>> >>> >
>> >>> > So I tried to force the format in the pipeline and I have the same
>> >>> error !
>> >>> >
>> >>> > here is my command : gst-launch
>> >>> > --gst-plugin-path=$HOME/gst-template/gst-plugin/src/.libs/ v4l2src
>>  !
>> >>> > videoscale !  ffmpegcolorspace ! testfilter ! xvimagesink
>> >>> >
>> >>> > I have searched in vain other examples...
>> >>> >
>> >>> > It's strange, because in my code, if I change my buffer like that
>> :
>> >>> > int i;
>> >>> > int size = GST_BUFFER_CAST(buf)->size;
>> >>> >
>> >>> > for(i=1; i < size; i++) {
>> >>> >   (buf->data)[i] = 0;
>> >>> > }
>> >>> >
>> >>> > The images become all green... I really don't understand why.
>> >>> >
>> >>> > I think there is a simple way to just keep the red color.. but I
>> >>> don't
>> >>> > find it.
>> >>> >
>> >>> >
>> >>> >
>> >>> >> Hi,
>> >>> >> the plugin name and description can (must...) be changed in the
>> >>> >> plugin_init function and GST_PLUGIN_DEFINE macro definition in
>> the
>> >>> code
>> >>> >> that must be present in your code.
>> >>> >> Concerning the filtering itself, you must check that you have RGB
>> (I
>> >>> >> guess
>> >>> >> that's the simplest) image buffers coming to your plugin in order
>> to
>> >>> >> make
>> >>> >> your processing in the chain function. Best way would be to set
>> the
>> >>> caps
>> >>> >> of your sink pad to video/x-rgb flow. Check other exisitng
>> plugins
>> >>> to
>> >>> >> see
>> >>> >> how to do this. You'll need a ffmpegcolorspace element before
>> your
>> >>> >> plugin
>> >>> >> to let the flow be in the good format.
>> >>> >> The example plugin is just a skeleton, you need now to specialize
>> it
>> >>> >> with
>> >>> >> your own code... Read the gstreamer plugin writer's guide, it
>> will
>> >>> give
>> >>> >> you information.
>> >>> >> Regards,
>> >>> >> Al
>> >>> >>
>> >>> >>
>> >>> >>
>> >>> >> ________________________________
>> >>> >> De : "cammille at polytech.unice.fr" <cammille at polytech.unice.fr>
>> >>> >> À : Discussion of the development of GStreamer
>> >>> >> <gstreamer-devel at lists.sourceforge.net>
>> >>> >> Envoyé le : Jeudi, 5 Mars 2009, 12h15mn 55s
>> >>> >> Objet : Re: [gst-devel] Plugin creation
>> >>> >>
>> >>> >> I found the problem ! The fact is that my plugin is not named
>> >>> >> "testfilter".. It's named "plugin". How can I change this name ?
>> >>> >> beacause
>> >>> >> I have never specified that my plugin is named "plugin".
>> >>> >>
>> >>> >> Another question, : now, I would like to create a simple plugin :
>> >>> >> I would like to filter the video taken by my webcam and filter
>> the
>> >>> red
>> >>> >> color (i would like to apply an effect like the effectv plugin).
>> >>> >> I know the algorithm, but I'm not sure how to do that.
>> >>> >>
>> >>> >> Do you think I should create this plugin by using the example
>> plugin
>> >>> ?
>> >>> >>
>> >>> >>
>> >>> >>> assuming that the shared library name is libgsttestfilters.so
>> >>> >>>
>> >>> >>> On Thu, Mar 5, 2009 at 4:28 PM, ved kpl <ved.kpl at gmail.com>
>> wrote:
>> >>> >>>> Try gst-inspect on your plugin
>> >>> >>>>
>> >>> >>>> Assuming that the plugin is installed in
>> >>> >>>> "$HOME/gst-template/gst-plugin/src/.libs/"
>> >>> >>>> do the following and see what you get
>> >>> >>>>
>> >>> >>>>  gst-inspect
>> >>> >>>> $HOME/gst-template/gst-plugin/src/.libs/libgsttestfilters.so
>> >>> >>>>
>> >>> >>>> On Thu, Mar 5, 2009 at 4:15 PM,  <cammille at polytech.unice.fr>
>> >>> wrote:
>> >>> >>>>> Hello !
>> >>> >>>>> I would like to create a simple plugin such as effectv..
>> >>> >>>>>
>> >>> >>>>> But, first of all, I would like to create a "test plugin".
>> >>> >>>>> So, I tried to make the example described in the GStreamer
>> Plugin
>> >>> >>>>> Writer's
>> >>> >>>>> Guide.
>> >>> >>>>>
>> >>> >>>>> I compiled the "test plugin" with the makefile, and now I'm
>> >>> trying
>> >>> to
>> >>> >>>>> launch this plugin, but I have an error..
>> >>> >>>>>
>> >>> >>>>> What's wrong with :
>> >>> >>>>>
>> >>> >>>>> $ gst-launch
>> >>> >>>>> --gst-plugin-path=$HOME/gst-template/gst-plugin/src/.libs/
>> >>> >>>>> fakesrc ! testfilters ! fakesink silent=TRUE
>> >>> >>>>>  > WARNING: erroneous pipeline: no element "testfilters"
>> >>> >>>>>
>> >>> >>>>> Maybe I have forgotten something ?
>> >>> >>>>>
>> >>> >>>>>
>> >>> >>>>> Thank you.
>> >>> >>>>>
>> >>> >>>>>
>> >>> >>>>>
>> >>> >>>>> ------------------------------------------------------------------------------
>> >>> >>>>> Open Source Business Conference (OSBC), March 24-25, 2009, San
>> >>> >>>>> Francisco, CA
>> >>> >>>>> -OSBC tackles the biggest issue in open source: Open Sourcing
>> the
>> >>> >>>>> Enterprise
>> >>> >>>>> -Strategies to boost innovation and cut costs with open source
>> >>> >>>>> participation
>> >>> >>>>> -Receive a $600 discount off the registration fee with the
>> source
>> >>> >>>>> code:
>> >>> >>>>> SFAD
>> >>> >>>>> http://p.sf.net/sfu/XcvMzF8H
>> >>> >>>>> _______________________________________________
>> >>> >>>>> gstreamer-devel mailing list
>> >>> >>>>> gstreamer-devel at lists.sourceforge.net
>> >>> >>>>> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>> >>> >>>>>
>> >>> >>>>
>> >>> >>>
>> >>> >>> ------------------------------------------------------------------------------
>> >>> >>> Open Source Business Conference (OSBC), March 24-25, 2009, San
>> >>> >>> Francisco,
>> >>> >>> CA
>> >>> >>> -OSBC tackles the biggest issue in open source: Open Sourcing
>> the
>> >>> >>> Enterprise
>> >>> >>> -Strategies to boost innovation and cut costs with open source
>> >>> >>> participation
>> >>> >>> -Receive a $600 discount off the registration fee with the
>> source
>> >>> code:
>> >>> >>> SFAD
>> >>> >>> http://p.sf.net/sfu/XcvMzF8H
>> >>> >>> _______________________________________________
>> >>> >>> gstreamer-devel mailing list
>> >>> >>> gstreamer-devel at lists.sourceforge.net
>> >>> >>> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>> >>> >>>
>> >>> >>
>> >>> >>
>> >>> >>
>> >>> >> ------------------------------------------------------------------------------
>> >>> >> Open Source Business Conference (OSBC), March 24-25, 2009, San
>> >>> >> Francisco,
>> >>> >> CA
>> >>> >> -OSBC tackles the biggest issue in open source: Open Sourcing the
>> >>> >> Enterprise
>> >>> >> -Strategies to boost innovation and cut costs with open source
>> >>> >> participation
>> >>> >> -Receive a $600 discount off the registration fee with the source
>> >>> code:
>> >>> >> SFAD
>> >>> >> http://p.sf.net/sfu/XcvMzF8H
>> >>> >> _______________________________________________
>> >>> >> gstreamer-devel mailing list
>> >>> >> gstreamer-devel at lists.sourceforge.net
>> >>> >> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>> >>> >>
>> >>> >>
>> >>> >>
>> >>> >>       ------------------------------------------------------------------------------
>> >>> >> Open Source Business Conference (OSBC), March 24-25, 2009, San
>> >>> >> Francisco,
>> >>> >> CA
>> >>> >> -OSBC tackles the biggest issue in open source: Open Sourcing the
>> >>> >> Enterprise
>> >>> >> -Strategies to boost innovation and cut costs with open source
>> >>> >> participation
>> >>> >> -Receive a $600 discount off the registration fee with the source
>> >>> code:
>> >>> >> SFAD
>> >>> >> http://p.sf.net/sfu/XcvMzF8H_______________________________________________
>> >>> >> gstreamer-devel mailing list
>> >>> >> gstreamer-devel at lists.sourceforge.net
>> >>> >> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>> >>> >>
>> >>> >
>> >>> >
>> >>> >
>> >>> > ------------------------------------------------------------------------------
>> >>> > Open Source Business Conference (OSBC), March 24-25, 2009, San
>> >>> Francisco,
>> >>> > CA
>> >>> > -OSBC tackles the biggest issue in open source: Open Sourcing the
>> >>> > Enterprise
>> >>> > -Strategies to boost innovation and cut costs with open source
>> >>> > participation
>> >>> > -Receive a $600 discount off the registration fee with the source
>> >>> code:
>> >>> > SFAD
>> >>> > http://p.sf.net/sfu/XcvMzF8H
>> >>> > _______________________________________________
>> >>> > gstreamer-devel mailing list
>> >>> > gstreamer-devel at lists.sourceforge.net
>> >>> > https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>> >>> >
>> >>>
>> >>>
>> >>>
>> >>> ------------------------------------------------------------------------------
>> >>> Open Source Business Conference (OSBC), March 24-25, 2009, San
>> >>> Francisco, CA
>> >>> -OSBC tackles the biggest issue in open source: Open Sourcing the
>> >>> Enterprise
>> >>> -Strategies to boost innovation and cut costs with open source
>> >>> participation
>> >>> -Receive a $600 discount off the registration fee with the source
>> code:
>> >>> SFAD
>> >>> http://p.sf.net/sfu/XcvMzF8H
>> >>> _______________________________________________
>> >>> gstreamer-devel mailing list
>> >>> gstreamer-devel at lists.sourceforge.net
>> >>> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>> >>>
>> >>
>> >>
>> >> ------------------------------------------------------------------------------
>> >> Open Source Business Conference (OSBC), March 24-25, 2009, San
>> >> Francisco,
>> >> CA
>> >> -OSBC tackles the biggest issue in open source: Open Sourcing the
>> >> Enterprise
>> >> -Strategies to boost innovation and cut costs with open source
>> >> participation
>> >> -Receive a $600 discount off the registration fee with the source
>> code:
>> >> SFAD
>> >> http://p.sf.net/sfu/XcvMzF8H
>> >> _______________________________________________
>> >> gstreamer-devel mailing list
>> >> gstreamer-devel at lists.sourceforge.net
>> >> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>> >>
>> >
>> >
>> >
>> > ------------------------------------------------------------------------------
>> > Open Source Business Conference (OSBC), March 24-25, 2009, San
>> Francisco,
>> > CA
>> > -OSBC tackles the biggest issue in open source: Open Sourcing the
>> > Enterprise
>> > -Strategies to boost innovation and cut costs with open source
>> > participation
>> > -Receive a $600 discount off the registration fee with the source
>> code:
>> > SFAD
>> > http://p.sf.net/sfu/XcvMzF8H
>> > _______________________________________________
>> > gstreamer-devel mailing list
>> > gstreamer-devel at lists.sourceforge.net
>> > https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>> >
>>
>>
>>
>> ------------------------------------------------------------------------------
>> Open Source Business Conference (OSBC), March 24-25, 2009, San
>> Francisco, CA
>> -OSBC tackles the biggest issue in open source: Open Sourcing the
>> Enterprise
>> -Strategies to boost innovation and cut costs with open source
>> participation
>> -Receive a $600 discount off the registration fee with the source code:
>> SFAD
>> http://p.sf.net/sfu/XcvMzF8H
>> _______________________________________________
>> gstreamer-devel mailing list
>> gstreamer-devel at lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>>
>
>
> ------------------------------------------------------------------------------
> Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco,
> CA
> -OSBC tackles the biggest issue in open source: Open Sourcing the
> Enterprise
> -Strategies to boost innovation and cut costs with open source
> participation
> -Receive a $600 discount off the registration fee with the source code:
> SFAD
> http://p.sf.net/sfu/XcvMzF8H
> _______________________________________________
> gstreamer-devel mailing list
> gstreamer-devel at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>

More information about the gstreamer-devel mailing list