Question about serialized events

Ikaheimonen, JP jp_ikaheimonen at
Tue Feb 25 06:09:13 PST 2014

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?


JP Ikaheimonen | SW Development Engineer
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