Dolby E Sync and Offset

Updated 2 weeks ago by Nick Horowitz

Hardware encoders have a 1 frame latency and the decoders have a 1 frame latency as well. Offset is often a puzzling setting, so recall that hardware encoders and decoders each have 1 frame of latency. Each piece of hardware retards by one frame, which is to the right on your timeline.

In SurCode for Dolby E, use a negative Frame Offset setting of "+1 frame" to emulate hardware. To compensate for "hardware" latency, you would use negative Frame Offset values. Negative to advance, positive to retard. When in doubt about a complete workflow, always send a test file or lay back to your downstream production partner to make sure everyone is in agreement.

 The Dolby E product you create is self-contained and should not require any second guessing or compensation downstream in the post process. That is the purpose of the Offset adjustment; to make things simply work in a world where some stakeholders have Dolby E hardware and others have Dolby E software. The compensation you specify in the Encoder allows the Decoder to lock and decode in sync with picture. The downstream folks should not have to second guess anything. They should be able to simply drop the asset onto their timeline, set their deck in Data Mode, do the layback and have it all work. In workflows where no Dolby E hardware is present, no offset is needed because, unlike hardware, software does not impose any delay.  

We suggest you ask the folks downstream if they're using Dolby E hardware or not. If not, no offset/compensation should be needed. Either way, you may want to create a short duration test file, send it to them and verify that everything works as planned. Once you all have the workflow nailed down, you can deliver your show without incident.


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