[gst-devel] Plugin creation

Fri Mar 6 09:05:04 CET 2009

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.
>>>>>
>>>>>
>>>>>
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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
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> SFAD
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