[gst-devel] dynamic change element's parameter

[Stefan Kost]

On 14.09.2010 10:48, Chandler Li wrote:
> I have read the mail Nicola and Stefan given, and that really inspired
> me a lot.
> Thank you!
> In the first, I try to replace some elements and encounter some
> problem, the following I will show my target first.
> Because I want to stream webcam frame on the internet,
> and dynamically change the frame size without stopping the pipeline.
>
> According to my experience, if the v4l2src element opens webcam
> device, it only captures one size at one time.
> if I want to change the size of webcam, I need to restart it.
>   

v4l2src does not support changing the resolution on the fly. This is a
v4l2 interface limitation right now - one needs to stop streaming, set
new format and restart streaming. So your observation is correct.

> So I try another architecture of gstreamer,
>
>     v4l2src  ->  capsfilter1  ->  videoscale -> capsfilter2  ->
> ffmpegcolorspace ->   .... (to internet)
>
> videoscale links two filters, the first filter (capsfilter1)
> negotiates with v4l2src in a static frame size,
> I want to change the size I assigned in the second filter (capsfilter2) ,
>
> BUT I get an error message after I change the capsfilter2 to the new filter,
>
>     videoscale can't link to new capsfilter,
>   

that should work. Can you paste a few lines of the code here. You should
create new caps and just set the new format on capsfilter2.

Stefan
> I don't know what's happened? does anyone know that?
> Thank you!
>
> Best regards,
> Chandler Lee.
>
> 2010/9/14 Stefan Kost <ensonic at hora-obscura.de>:
>   
>> Am 12.09.2010 09:01, schrieb Chandler Li:
>>     
>>> Hi all,
>>>     I'm new to use gstreamer,
>>>     and I have a problem don't know how to solve for a long time,
>>>
>>>     Is there possible to dynamic change the parameter in elements or pads?
>>>       
>> gobject parameters -> g_object_set or use GstController
>>
>>
>>     
>>>     For example,
>>>     In a playing state streaming,
>>>     could I dynamic change the size of video without stop the streaming?
>>>       
>> yes you can. if you resize the video window for xvimagesink the video adjusts if
>> it can. So if you run gst-launch videotestsrc ! xvimagesink, the videotest is
>> sending videoframes in the native resolution instead of xvimagesink scaling them.
>>
>> Stefan
>>
>>     
>>>     hopes that's not a stupid question,
>>>     and very hopefully for your reply,
>>>     Thank you
>>>
>>>     Chandler Lee
>>>
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>>
>>