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User16840867725783411178 (Mind The Gap) asked a question.

September 14, 2023 at 9:31 PM
Different Integrated Level Readings When Recording v Playback in the Dolby Renderer
Hi Gentlemen
Back again! When I record an Atmos Master in the Dolby Renderer, the integrated level readings differ between recording and playback. An Atmos Master I recently recorded was showing an integrated reading at -18.1. But on playback it was showing -18.5. Why is there a difference?
Also, I'm using Logic Pro to produce Dolby Atmos mixes. But their native Limiters are not responsive to your low threshold of -18 db to control the peaks. Is there a plugin to Logic or a 3rd party plugin which can effectively manage these peaks?
Let me know and as always, many thanks!
Marc
  • 12 answers

  • AdamP (Dolby Labs)

    HI Marc,

    If you are using the Dolby Audio Bridge and Dolby Atmos Music Panner to route audio to the Dolby Atmos Renderer application you can use VCAs or a Master fader. However no audio is going through the master so dynamics processing on the master has no impact. If you are using the integrated Dolby Atmos Renderer in Logic than dynamics processing inserted on the master fader ahead of the Dolby Atmos Renderer plug-in affects the Bed audio only as the Obect audio is routed to the plug-in directly.

    The binaural renderer runs hot compare to the Atmos measurement based on the 5.1. They will generally never be the same. The Atmos measurement should be used when trying to hit the loudness levels in a delivery specification, not the binuaral measurement.

    Best,
    Adam
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    Selected as Best

  • AdamP (Dolby Labs)

    Hi Marc,

    Thanks for posting. The realtime measurement starts when the Renderer transport starts chasing so silence in the pre-roll/post-roll can affect the integrated value depending on how much pre-roll/post-roll is used and the overall length of the song/program. You can try to hit reset to coincide with the start. The offline loudness analysis should be the definitive source of truth.

    Re: Logic I'm confused by the -18dB threshold you refer to. Most delivery specs allow peaks up to -1dBTP or higher so there is no reason for a limiter threshold to be set at -18 which should be the integrated measurement. Let me know if I've misunderstood.

    Thanks,
    Adam
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    • User16840867725783411178 (Mind The Gap)

      Thanks Adam for your prompt reply! I understand now how the integrated measurement works.

      Regarding the limiter issue, should I use it like I do on a stereo mix? That is, I have a limiter on the master bus in Logic and prevents the mix signal from exceeding +6. I normally set it so the limit is in the range of 2 to 4 db of reduction. Now, the Renderer doesn't want the integrated level to exceed -18. Should I use the master fader in Logic to adjust the level?

      I hope to understand here the relationship between the levels in Logic Pro and the levels in the Renderer.

      Thanks again for your help!

      Marc
      Expand Post

  • AdamP (Dolby Labs)

    Hi Marc,

    Integrated measurements in Atmos are based on a 5.1 render.

    Integrated loudness and peak measurements are related but independent depending on the dynamic range of the content and panning. Limiting will need to be applied to the bed and to objects alike to to keep True Peak levels below -1dBTP on the 5.1 render that is used for loudness measurement.

    Managing integrated levels should be done with overall gain. The best way to do this will be with VCA's in Logic if you are using the Dolby Audio Bridge and Dolby Atmos Music Panner. Channels can be assigned to VCAs is the mixer view of Logic by selecting channel strips and either creating VCA or assigning strips to existing VCAs.

    Managing True Peaks levels in the 5.1 render used for loudness measurement can be tricky as rendering involves summing and the True Peak levels can vary widely depending on program content and who much bed audio and object audio is panned in a similar way at any point in time. To avoid True Peaks exceeding -1dBTP while keeping integrated loudness at -18LKFS or lower, you may want to put limiters on bed and objects starting with a threshold of -3dB and see if that prevents any overages and adjust the threshold lower on each channel as needed.

    Obviously lowering overall levels with VCAs in Logic will also lower peak levels but again, there isn't a direct correlation. Also keep in mind that while music deliverables shouldn't exceed -18LKFS, they can be more quiet if you feel that limiting to avoid exceeding -1 dBTP is altering your mix too much.

    I hope this helps.

    Best,
    Adam
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    • User16840867725783411178 (Mind The Gap)

      Very helpful, Adam! Thank you.

      I'd like to clarify two points.

      Should I still put a Limiter on the Master fader or is it optional? I understand the use of VCAs and using the limiters on beds and objects but I'm curious if you would recommend a final Limiter on the Master fader.

      Finally, after analyzing the loudness reports of this mix, I noticed the Atmos report had a reading of -19.9 LKFS but the Binaural report had a reading of -18.1. Does that suggest I should create a separate Atmos mix to get it closer to -18 LKFS?

      I've attached the two reports for your perusal below.

      Thanks again,
      Marc
      Expand Post
      • Catch My Vibe Atmos Report

      • AdamP (Dolby Labs)

        HI Marc,

        If you are using the Dolby Audio Bridge and Dolby Atmos Music Panner to route audio to the Dolby Atmos Renderer application you can use VCAs or a Master fader. However no audio is going through the master so dynamics processing on the master has no impact. If you are using the integrated Dolby Atmos Renderer in Logic than dynamics processing inserted on the master fader ahead of the Dolby Atmos Renderer plug-in affects the Bed audio only as the Obect audio is routed to the plug-in directly.

        The binaural renderer runs hot compare to the Atmos measurement based on the 5.1. They will generally never be the same. The Atmos measurement should be used when trying to hit the loudness levels in a delivery specification, not the binuaral measurement.

        Best,
        Adam
        Expand Post
        Selected as Best

      • User16840867725783411178 (Mind The Gap)

        Hi Adam

        Thanks for clarifying this issue. It's extremely helpful!

        Last question: So if my Atmos loudness measurement reads -18.1 but my binaural measurement reads hotter at -16.5, that's still considered within the delivery specs? Or does it require separate mixes to to keep them at or below -18?

        Thanks again,
        Marc
        Expand Post

      • AdamP (Dolby Labs)

        Hi Marc,

        Cool. Glad I could help. If the Atmos loudness measurment reads -18.1LKFS you are within delivery specs even if the binaural reads hotter. No need for a separate mix.

        Best,
        Adam

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