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User16501428677062515740 (Hijack) asked a question.

August 10, 2023 at 9:00 AM
Sync HD and Atmos Renderer - Sync Issues
Hi all,

I have spoken with AVID technical support and then Dolby directly to try and get an answer to this. They suggested to ask the forum as they did not know what to suggest.

My issue is that we are using Dolby Atmos Renderer 5.0.0 on the same machine as Pro Tools for Dolby Atmos HE Mixing.

We have a Sync HD and Rosendahl Nanosync as our clocking system. In order to select the Sync HD in the Pro Tools "Session Setup" window I need to select HD Native as the Playback Engine. When HD Native is the Playback Engine the only way I can route to the Dolby Atmos Renderer is via AUX/IO

As you know the AUX/IO roundtrip (from PT> Dolby Atmos Renderer> PT) introduces a significant delay. Although I can compensate for this effectively with "Video Sync Offset" within Pro Tools, it can make editing laborious as there is a delay between the waveform being at the playback head and hearing the actual sound.

Alternatively I can set the Playback Engine to the Dolby Audio Bridge and work without an external clock. This would obviously introduce its own sync issues.

Is there any way, while using Avid hardware, for me to use the Sync HD clock without introducing delay? If not what is the most cost effective solution to achieve this on a single machine?

Failing this can anyone recommend the best workflow for being able to edit and Mix in an Atmos template on a single machine without sync issues?

Any and all help would be much appreciated.

Thanks,

Rich
  • 17 answers

  • AdamP (Dolby Labs)

    Hi Rich,

    Thanks for the question. Are you using external video playback with the Pro Tools chasing LTC or is video in Pro Tools on a video track? Running the Dolby Audio Bridge as the playback engine with a video track should be stable. An offset maybe required but it shouldn't drift. A separate Renderer workstation is preferable for this scenario with longform work but I realize that is not what you are asking. If Pro Tools is chasing LTC from an external video source than you clocking the HD Sync and addressing the offset induced by the Aux I/O is the only solution on a single workstation.

    Any further details would be helpful and I will confer internally re: any other suggestions.

    Best,
    Adam
    Expand Post

    • User16501428677062515740 (Hijack)

      Thanks very much, Adam.
      The video file is playing on a Pro Tools video track via a Black Magic Ultrastudio 4K. Historically when we set the Playback Engine to HD Native and had no external clock source there would be slight variations in sync playback that makes it impossible to cut SFX in sync while using the Black Magic card.

      However it sounds as though you are suggesting that the Dolby Audio Bridge as the Playback Engine should also get around that issue even when using the Ultrastudio 4k to output video?

      My plan is to mix everything in Atmos from now on regardless of final deliverables.
      Expand Post

  • AdamP (Dolby Labs)

    Hi Rich,

    When using the Dolby Audio Bridge at the Playback Engine, Pro Tool will clock to the Dolby Audio Bridge which in turn will clock to the core audio output device. If the output device can clock to the Rosendahl this should be a stable scenario. Exporting and bringing a re-render back into Pro Toolsl should validate this. There may still be offset in the video playback as noted but it should be a constant.

    Best,
    Adam
    Expand Post

  • AdamP (Dolby Labs)

    Hi Rich,

    What is the core audio device connected to the Renderer? Can the core audio device and the Ultrastudio both clock to the Rosendahl?

    Thanks,
    Adam

    • User16501428677062515740 (Hijack)

      Thanks Adam, so the question is can the Rosendahl send a video ref signal to the Ultrastudio 4K?

      I am not sure of the answer to this, but without this would the Ultrastudio 4K likely drift slightly? I have only ever connected the Rosendahl to the Sync HD to provide the Video Ref sync.

      I am a bit confused as to the flow of the clock signal in this scenario :)

      • User16501428677062515740 (Hijack)

        The playback device connected to the renderer is the HD Native, which is connected to the Sync HD. However I'm not aware of any clock settings in the renderer - unless I'm wrong?

      • AdamP (Dolby Labs)

        Got it so if the SyncHD and Blackmagic are both clocked to the Rosendahl that should be the most stable scenario. The Renderer doesn't have any clock settings but will clock to the output device.

  • AdamP (Dolby Labs)

    My mistake. You mentioned the HD Native which doesn't have a clock input. Were a different Core Audio device with a clock input available for the speaker outputs from the Renderer the Rosendahl could simultaneously provide WC to the audio interface and Ref to the Ultrastudio.

    • User16501428677062515740 (Hijack)

      Yes were I not using another non-Avid interface I don't think this would be an issue.

      So given the kit I am using the likelihood is that the Ultrastudio 4k will drift as the PT/ Renderer system is stable but not following the same clock source?

      Or... if I am able to send a video ref signal from Rosendahl to the Ultrastudio then frame accurate sync should be possible?

  • AdamP (Dolby Labs)

    I think it should be stable regardless if the Ultrastudio is connected via Thunderbolt to the same mac but I'd want to test the Audio and Video interfaces clocked to the Rosendahl should this be an issue. I need to configure some tests and will also have a look into some of the test plans to see what has been tested.

    Best,
    Adam
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