[gst-devel] FM radio using v4lsrc

[Stefan Kost]

Alexey Chernov wrote:
> В сообщении от Вторник 16 февраля 2010 18:54:40 вы написали:
>   
>> hi,
>>
>> 4ernov wrote:
>>     
>>> Hello,
>>> we develop an application receiving FM radio based on GStreamer. But I
>>> can't understand how to create a pipeline with v4lsrc or v4l2src only
>>> for radio signal (without video). I tried
>>>
>>> gst-launch -vvv v4l2src device=/dev/radio0 ! decodebin ! pulsesink
>>>       
>> this cannot work. v4l2cards don't capture audio - they simple have an
>> analog connection to your sound card. You can only use the tuner
>> interface on v4l2 to tune the station. And you could capture from
>> alsasrc (need to set the right capture device).
>>     
>
> Stefan, thank you for this suggestion. Could you please help me with the 
> pipeline configuration for this case? I tried today to put v4l2src, alsasrc, 
> audioconvert, audioresample, pulsesink to the pipeline and linked everything 
> except v4l2src. But I couldn't get it work, on setting READY state v4l2src 
> printed an error with message "Device or resource is busy". Should I put audio 
> elements and v4l2src in different pipelines? Or maybe I should operate on 
> v4l2src without any pipeline. I'll continue my experiments tomorrow.
>   

you will probably have to use v4l2 interface directly, or link v4l2src !
fakesink and set v4l2src into locked state at READY. The point is that
there can't be any dataflow between v4l2src and fakesink. The 2nd part
could be e.g. alsasrc ! wavenc ! filesink location="...". You will need
to use the GstMixerInterface on alsasrc to ensure you record from the
right source. I don't have an example for that.

Stefan

>   
>> Stefan
>>
>>     
>>> in command line at first, but it fails:
>>>
>>> (gst-launch-0.10:2489): GLib-WARNING **: g_set_prgname() called
>>> multiple times
>>> Setting pipeline to PAUSED ...
>>> ERROR: Pipeline doesn't want to pause.
>>> ERROR: from element /GstPipeline:pipeline0/GstV4l2Src:v4l2src0: Device
>>> '/dev/radio0' is not a capture device.
>>> Additional debug info:
>>> v4l2_calls.c(504): gst_v4l2_open ():
>>> /GstPipeline:pipeline0/GstV4l2Src:v4l2src0:
>>> Capabilities: 0x50400
>>> Setting pipeline to NULL ...
>>> Freeing pipeline ...
>>>
>>> Could anybody suggest me the right pipeline for FM radio signal
>>> processing or maybe the right parameters for v4lsrc or v4l2src sources?
>>>
>>> Thank you very much in advance,
>>> Alexey Chernov
>>> ------------------------------------------------------------------------
>>>
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>
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