[gst-devel] Plugin creation

cammille at polytech.unice.fr cammille at polytech.unice.fr
Fri Mar 6 11:59:39 CET 2009 

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
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>>> >>>>>
>>> >>>>
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>>> >>> Francisco,
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>>> >>> -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
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>>> >>
>>> >>
>>> >>
>>> >> ------------------------------------------------------------------------------
>>> >> 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
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>>> >> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
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>>> >>
>>> >>
>>> >>       ------------------------------------------------------------------------------
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>>> >> 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_______________________________________________
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>>> >
>>> >
>>> >
>>> > ------------------------------------------------------------------------------
>>> > 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
>>> > _______________________________________________
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>>>
>>>
>>>
>>> ------------------------------------------------------------------------------
>>> 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
>

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