Basic Operation within Protools

We advice to use the AAX version in PT 10 to ensure the correct initialisation of the plugin for each file that is measured.

LevelNorm is an AudioSuite plugin and therefore only operates on a selected file or part of a file and not in real time on a channel of your virtual mixing desk. Consequence is it will ignore the fader positions of your mixing desk. This means that if you like to use LevelNorm for making your final mix comply to the EBU or ATSC recommendation, first you need to print your mix to a separate mono, stereo or surround track. Operation then is as usual with Audio Suite plugins: select the audio file and open LevelNorm from the AudioSuite menu (it can be found in the ‘Grimm Audio’ section). The LevelNorm User Interface window now opens, as seen below.

LevelNorm automatically sets the amount of channels to mono, stereo or surround, dependent on the source. In case your source is surround, please make sure that the ‘format’ is set to the right channel order. You can change this setting by clicking the window next to the text ‘format’. A drop down menu will open with a choice between SMPTE, Film and DTS channel order.

AudioSuite processing in Protools has relatively large freedom in selecting files and part of files. For instance for stereo either a true stereo track or two mono tracks can be selected. It is also possible to select part of a file or even more than one file on the timeline and analyse or process the total amount of selected audio.

After the track count format, set the target level. With LevelNorm-EBU, 0 LU equals -23 LUFS. For LevelNorm-ATSC, 0 LU is -24 LKFS. Normally your target will be 0 LU. When using LevelNorm in the course of your mix process however, it can be convenient to normalize for instance background music to your favorite level below 0 LU. This may speed up your production time considerably. To use this function, just select the preferred target level with the slider before clicking ‘Process’.

Next step is to either only ‘Find LU’ of the file, or directly ‘Process’ it to the loudness target level set with the slider. A progress bar will be shown during the calculation and the normalized file will replace the original file on the timeline. If the average loudness of the file was so low that normalizing it to 0 LU would cause a clip, LevelNorm will show a warning and amplify the file to a maximum peak level of 0 dBTP. Mark that to maintain the correct 0 LU level of a normalized track during a second print, the channel fader and master fader should be set to 0 dB.

Normally your target level will be 0 LU. When using LevelNorm in the course of a mix process however, it can be convenient to normalize for instance background music to your favorite level below 0 LU. This may speed up your production time considerably. To use this function, just select the preferred target level with the slider before clicking ‘Process’.

The AAX version of LevelNorm-ATSC has an extra option: “Dialog Gate”. This enables ‘Dialog Intelligence’ (by Dolby), a process that automatically detects speech and only enables the loudness measurement for audio fragments in which speech is present. Automatic speech detection is a difficult task and therefore an algorithm like this can not replace manual detection perfectly. But if your aim is to use speech as an anchor element, you may use LevelNorm-ATSC for this.

Working with LevelNorm

The best way to mix audio files for broadcasting in the new paradigm may at first seem quite dangerous. Basically you just lower your modulation levels, ignore your meters and focus on the sound. Once in a while you take a glimpse at the digital peak meter to make sure you are not clipping. Don’t be afraid that you will loose resolution by modulating low, with current 24 bit high resolution equipment this is no threat anymore.

If you feel insecure working without visual feedback, please consider using a realtime EBU mode loudness meter. Alternatively use your VU’s or PPM’s but align them correctly. A proper alignment for your VU meter would be 0 VU to equal -18 dBFS. For analog PPM’s, keep the 0 PPM = -9 dBFS level. During production, avoid modulating hot all the time. But at the same time do not hesitate to use all that headroom. If you are using a digital peak meter next to the other ones, ATSC and EBU allow peaks to reach almost 0 dBFS, so don’t worry about short peaks above -9 dBFS.

The key to almost automatically achieve consistent results without using meters, is to adopt the film postproduction practice of aligning the monitor gain to a fixed acoustic level. In the broadcast case, the EBU tech 3276 document prescribes to align a -18 dBFS (rms measured) pink noise track to a sound pressure level of 82 dBA per speaker for stereo or 78 dBA per speaker for 5 channel surround. If you prefer to have your monitor SPL a little lower, just note the deviation from the calibrated level for later reference. The alternative is to simply normalize a well known file to -23 LUFS, play it back and set the volume control to your preferred listening level. The main concept is to now mark the monitor control position and work at this reference level position 90% of the time or more. Your ears will tell you how loud you should mix, you don’t need a meter for that anymore.

When you are satisfied with your mix and overall sound, just print the result to a seperate stereo or surround track, let LevelNorm analyze and process the file on this track and your audio is finished for release. After some practice you will note the necessary adjustment by LevelNorm will be minimal.

Broadcast and post production engineers in the US know that according to the ATSC recommendation A/85 they need to adjust the volume of their program based upon analysis of the dialog track(s) only. LevelNorm can be a big time safer here because it allows to very quickly measure the loudness of (part of) the dialog track. The 2009 edition of ATSC A/85 has no ‘relative gate’ in the measurement and a target of -24 LKFS (= LUFS) in stead of -23 LUFS like in EBU R128. The LevelNorm-ATSC plugin complies to that standard. Since the ITU has adopted the EBU R128 relative gate in 2011, it is now unclear if ATSC A/85 advices to measure ‘all with gating’ or dialog only. Grimm Audio will closely follow the developments.

Loudness References

  • provides all kinds of information about the EBU R128 broadcast loudness recommendation. The official R128 documents and guidelines can be found, as well as introduction papers and videos.
  • At the ATSC A/85 recommendation is available for download.

Technical specifications

EBU and ATSC standards

LevelNorm-EBU uses the official EBU R128 settings:

  • ITU BS.1770-3 measurement, including -10 LU ‘background sound’ gate
  • 0 LU = -23 LUFS
  • Adjustment of the target level to 0 LU +/- 6 LU

LevelNorm-ATSC uses the 2009 version of the ATSC A/85 recommendation:

  • ITU BS.1770-1 measurement, without relative gate
  • 0 LU = -24 LKFS
  • Adjustment of the target level to 0 LU +/- 6 LU

Surround channel order

The LUFS measurement has a different weighting for the surround speakers. Therefore LevelNorm must know the channel order of multichannel files in your facility. There are three options:

  • SMPTE/ITU (L-R-C-Lfe-Ls-Rs)
  • Film (L-C-R-Ls-Rs-Lfe)
  • DTS (L-R-Ls-Rs-C-Lfe)


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