[gst-devel] dataflow synchronization

[Benoit Fouet]

please forget my last question, sorry :-)

Ben


Benoit Fouet wrote:

>Thank you !
>
>I don't really think I would need a queue before the video renderer,
>unless it is mandatory, so that I can have as less threads as possible
>to avoid context switch as much as I can.
>I wonder one thing (again :-) ): tee elements can have two different
>frame rates on their source pads ? i guess so, but it's to be sure...
>
>Thanks again,
>Ben
>
>
>Edgard Lima wrote:
>
>  
>
>>If you want something like:
>>
>>videosrc ! tee tee0. ! queue ! videorendersink tee0. ! queue !
>>videoencsink
>>
>>we could make
>>
>>videosrc ! tee ! queue ! videorendersink tee0. ! queue ! videoreate ! 
>>video/x-raw-yuv, framerate=\(fraction\)15/1   !  videoencsink
>>
>>Or else
>>
>>if your "videoencsink" has a rate property
>>
>>
>>BR,
>>Edgard Lima - alima
>>edgard.lima at indt.org.br
>>
>>
>>
>>ext Benoit Fouet wrote:
>>
>>    
>>
>>>Wim Taymans wrote:
>>>
>>>      
>>>
>>>>On Thu, 2006-04-27 at 18:39 +0200, Benoit Fouet wrote:
>>>> 
>>>>
>>>>        
>>>>
>>>>>Hi,
>>>>>
>>>>>I've read Gstreamer documentation (i.e. Application Development Manual
>>>>>and Plugin Writer's Guide) and one point remains obscure to me.
>>>>>I can't figure out how data is synchronized over the pipeline.
>>>>>
>>>>>e.g. when having a pipeline as simple as an audio file source, a
>>>>>decoder
>>>>>and an audio plugin, the source is able to provide data much more
>>>>>quickly than the decoder can work, itself more quickly than the audio
>>>>>sink is able to flush data on driver.
>>>>>
>>>>>though, my question is: what is the event that allows an element to
>>>>>provide data over its source pad ?
>>>>>is it that gst_pad_push is called in the same thread, and is by the
>>>>>way
>>>>>blocking the upstream element, or are there other synchronization
>>>>>methods ?
>>>>>  
>>>>>          
>>>>>
>>>>Yep, pad_push() eventually blocks somewhere downstream, either in a
>>>>sink
>>>>that does
>>>>synchronisation or another element that rate controls in one way or
>>>>another (queue, based on buffer size, some network element).
>>>>All elements in a pipeline share the same clock normally, a typical
>>>>sink
>>>>waits for the clock to reach the propor time corresponding to the
>>>>buffer
>>>>timestamps before rendering a buffer. As soon as the buffer is rendered
>>>>(or scheduled for rendering in the case of audio) pad_push() returns
>>>>and
>>>>upstream elements can produce new data.
>>>>
>>>>Hope that explains,
>>>>Wim
>>>>
>>>> 
>>>>
>>>>        
>>>>
>>>It does explain, thanks :)
>>>I have a related second question: in case an element has multiple
>>>source pads (let's say 2 for instance), is there a way to have one of
>>>them blocked and the other one allowed to produce new data ?
>>>e.g. if a video source element provides data to both a
>>>renderer/display (rather quick) and an encoder (slower), is it
>>>possible that the display element have access to more frames than the
>>>encoder ?
>>>in other words, let's say you can produce 30 frames per second and
>>>you encode at 15 but you want to display 30.
>>>do the downstream elements have to manage themselves to drop frames
>>>they don't need ?
>>>
>>>Regards,
>>>Ben
>>>
>>>      
>>>
>>>> 
>>>>
>>>>        
>>>>
>>>>>Thanks,
>>>>>Ben
>>>>>
>>>>>
>>>>>
>>>>>-------------------------------------------------------
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>>>>>
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>>>>>  
>>>>>          
>>>>>
>>
>>-------------------------------------------------------
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>>easier
>>Download IBM WebSphere Application Server v.1.0.1 based on Apache
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>>    
>>
>
>
>
>-------------------------------------------------------
>Using Tomcat but need to do more? Need to support web services, security?
>Get stuff done quickly with pre-integrated technology to make your job easier
>Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
>http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
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