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My video playout is out of sync, what could cause this? - Knowledgebase / just:live/play - ToolsOnAir-Support

My video playout is out of sync, what could cause this?

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Everything was fine now for weeks and months, but suddenly my video playout is out of sync, what could cause this?


1. AV volume: Usually this happens because the storage used to deliver the video data has problems to deliver the data to process the frames. In such a case the buffer status in just:play/live (and in the diagnostic window of just:out) is empty, and the master timecode is far behind of the current time or even moving back and forward. Make sure the data rate of the  storage device used for video playout is sufficient all the time.

2. Unsupported/broken file: A broken file can also harm the playout. Usually such a file would not start at all or would play until the last playable frame has reached and shows this frame for the rest of the clip length.

3. Video output device selected as the sound output device: Like mentioned in the user manual and covered by the system check, you should NEVER select the video device you are using for playout as your sound output device in the Sound system preference pane. Doing so will not only make the playout unsync, but (depending on the setup), will also the system sounds will be played out mixed to the audio of the real play out.


In each of the above cases, the video playout should be ok as soon as the next video clip starts. In case the data rate of your disk drive allows realtime playback again (point 1) a technology of our engine called catchUp is used to synchronize the playout also for the clip which is playing out right now

4. Unstable video input: Make sure, that the incoming video signal is stable and continuous with no video sync interruption while using the build-in switch to live method. Failing to provide a continuously stable signal will cause  the video device, used to do the playout, to loose its internal reference, resulting in any kind of errors like black frames, unstable video or unsync video playout in your final output. In order to stabilise the signal in advance, i.e. before it's sent to the video card input, you can use a frame synchronizer like the FS1/FS2 from AJA or a BMD ATEM Video Switch. In case of an unstable input signal, the output will be affected doe snot matter if a movie or a live signal is on air, and only a restart of just:out (or even the mac) will solve the problem.