Synchronizing Multiple Pipelines

[sasikiran G]

Hi, my name sasikiran,
Synchronize the start times of multiple GStreamer pipelines to ensure that
the output videos from each pipeline are exactly the same, even though they
are processed at different sizes. Achieving this level of synchronization
can be a bit tricky once you've mentioned that the pipelines start at
different times and you want precise synchronization, you might need to use
more advanced synchronization techniques. One approach could involve using
the sync property of elements within each pipeline. For example, setting
the sync property of the video sinks to true might help synchronize the
playback of videos. You could also experiment with the clock-rate property
and other synchronization properties to fine-tune the synchronization
behavior.Another approach would be to use the clockoverlay element to
overlay a clock timestamp onto each video frame. This way, you can visually
inspect the videos and determine the exact offset between them. Once you
identify the offset, you might need to introduce delays in the pipelines
that are ahead of others to align their start times.However, please note
that achieving frame-level synchronization across multiple pipelines might
be challenging due to the inherent nature of how GStreamer's data flow and
buffering work. It's possible that slight variations in processing time
could cause frames to get out of sync over time.If achieving perfect
synchronization is critical, you might need to consider more specialized
solutions or tools designed for high-precision video synchronization.
Regards,
Sasikiran G. Transcoding Engineer

On Fri, 11 Aug, 2023, 11:13 pm Dwight Kulkarni via gstreamer-devel, <
gstreamer-devel at lists.freedesktop.org> wrote:

> Hi all,
>
> I have 4 pipelines.
>
> Pipeline 1 :   video src -> app sink1
> Pipeline 2 :   app src2   ->  video 1
> Pipeline 3 :   app src3   ->  downsampled  video 2
> Pipeline 4 :   app src4   ->   downsampled  video 3
>
> In app sink 1, I connect a new-sample callback
>
> I then take the sample, make a copy and push it to each of the app sources.
>
> The problem I have is that each pipeline (pipeline 2 to 4) will start at
> different times.
>
> If I take a video of a stop watch, I notice that pipeline 2 is 8 seconds
> offset from the other 2 pipelines.
>
> The behaviour I am going for is that from one video source I want to end
> up with 3 different videos at different sizes. Eg. 1080p, 720p, etc.
> However, each video should be exactly the same.
>
> I tried to avoid using a Tee and making a single pipeline because Tees
> take away control over how the frames are going into each element and they
> might get out of synch.
>
> With the app source I was hoping to push exactly a certain number of
> frames into each pipeline and then call the "spit now"  function with
> splitmux sink.
>
> However, this depends on all pipelines starting at the same time and being
> in synch.
>
> Can you advise how to achieve this ?   Thanks !
>
> --
> Sincerely,
>
> Dwight Kulkarni
> B.ASC, M.ASC, PMP
>
> Realize Potential
>
>
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