Synchronization precision

[RiccardoCagnasso]

At gstreamer conference 2017, doctor Raghavan gave a presentation about his
library that allowed to create simple synchronized. During his conference he
did highlight something that I had encountered before: the synchronized
playback is not really perfectly accurate.

There's usually, an random error that is maximum less than a frame. This
means that "sometimes", usually once in several seconds, a frame is rendered
slight after or before its counterpart. This seems to happen with the same
extent whether the two videos are played on the same computer or on two
distinct connected via ethernet (which makes sense, since the delay of
ethernet is sub-1ms).

In practical scenarios, the error is unnoticeable if any kind of bezel is
involved, e.g. any kind of video wall, but it becomes apparent on a
continuous screen, e.g. a ledwall. It's also quite easy to spot using the
"slow motion" feature (120 fps) of any smartphone.

https://youtu.be/-1EhKn8E5zY here is an example taken from a very big
videowall.

Is there any kind of active development trying to isolate/fix/mitigate this
issue? With the availability of sub 1mm pitch ledwall, there's definitely a
market for synchronized playback. It's not immediately obvious how to play a
16k video on a number of smaller, contiguous screens.

We don't have the resources nor the expertise to work on this, but we might
be able to provide some (very, very limited. small company with a different
core business) financial incentive to someone tackling this.



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