Question about serialized events

[Sebastian Dröge]

On Di, 2014-02-25 at 14:09 +0000, Ikaheimonen, JP wrote:
> Hi all,
> 
> I have an annoying problem.
> 
> 
> 
> I have a pretty much direct pipeline from a camera feed to the screen:
> 
> 
> 
> gst-launch-0.10 v4l2src ! 'video/x-raw-yuv,width=640,height=480,framerate=30/1' ! ffmpegcolorspace ! ximagesink
> 
> 
> 
> This gives me a pipeline v4l2src -> capsfilter -> ffmpegcsp -> ximagesink . No forking paths or threads or queues here.
> 
> 
> 
> I've added some code that sends a custom serialized downstream event in v4l2src, right after it has pushed the buffer downstream.
> 
> I would expect the event be received in ximagesink after the buffer has been received; after all, that's what I think 'serialized' means.
> 
> 
> 
> However, the custom event passes through all the elements in the pipeline without stopping anywhere; the buffers follows through in his own steady pace.
> 
> Why does this happen? Is it because my pipeline is too simple to be serialized? Is it because there's practically no synchronization anywhere in the pipeline (the data never needs to wait for some other buffer to be synchronized) ? Can I solve this problem by adding some synchronizing element in the pipeline?

How do you insert the event into the pipeline, and what type of element
is it?

A serialized event (if sent from the streaming thread), will travel in
the pipeline relative to the other data flow. Buffers (and other
serialized events) before it will stay before it, buffers after it will
stay after it.

-- 
Sebastian Dröge, Centricular Ltd - http://www.centricular.com
Expertise, Straight from the Source
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