Post Production

RX Loudness Control

izotope box

iZotope, the maker of a wide range of innovative audio software, has recently released another tool in their line of audio control software devices, the RX Loudness Control plugin. You can try it here.

For those of us delivering mixes and stems in the television broadcast space, the rules of the road regarding loudness standards have changed considerably over the last several years. RX Loudness Control has a number of presets that correspond with the loudness standards in various territories. Some of the major ones included are the EBU R128 for Europe and the ATSC A-85 for the USA. I covered the CALM Act and its specifications, in a prior post here, in it I also discuss loudness measurements in general and LKFS levels specifically.

Avid’s Pro Tools, the workstation I use for mixing, implements the plug as an AudioSuite AAX, an offline, faster than real time process. Currently RX Loudness Control is also available for Avid’s Media Composer 7 & 8, as well as Adobe CC. Check their website for software compatibility.

Using the plug for compliance is a very easy process. Load RX Loudness Control and highlight the audio file of the mix, then choose the loudness standard that you need created. The loudness standard specifications information, specific to the chosen preset, will then be displayed in the Statistics window. Here, in this screenshot, the preset highlighted is the ATSC A/85 on the left. The bottom right of the screenshot shows, in the Statistics window, the reading of the spec, which is a target of -24 LKFS and a true peak reading of -2db levels.


Once the audio is highlighted, click the analyze menu. The window will now display the specific loudness measurements of the selected audio file. A handy additional feature is a History tab, which helps pinpoint specific timings of non-compliance. The analysis can also be exported as a .csv file for record keeping and delivery along with the mix files.

Non Compliance  

The statistics in this screenshot shows that the LKFS integrated reading is out of spec and is indicated by the red number. Its a handy way to easily determine compliance – red for out of spec and green for in spec. A white reading is neutral, meaning it is not being analyzed at the time of the reading. Its a nice touch to an already friendly interface.

To put the final mix into complete compliance, according to the particular preset specification, just click render. The algorithm for this is a newly designed one, specific to RX Loudness Control and built for speed. With one more click it processes the audio to a compliant file, ready for delivery. It is fast too, an hour’s worth of audio media can be processed in a minute or less.


In the case of this example, the LKFS reading is now exactly at the taget level of -24.0, written in green. That was the whole process! Load preset, analyze file, render to specification. It can’t get any easier than that.

The gear wheel next to the preset pull down menu, also reveals a number of other parameters. It offers authorization and updating options and it allows for a choice of surround speaker configurations. There is also a Processing pane, to activate the use of another algorithm of iZotope’s, also for loudness compliance. This algorithm can perform much slower, higher accuracy compliance, specifically for more problematic audio.


Currently, RX Loudness Control works in Pro Tools, Avid Media Composer 7 & 8 as well as Adobe CC, as mentioned. Check iZotope’s website for all of the requirements. They are actively seeking suggestions for other platforms to expand to as well. Be sure to contact them if you want this functionality ported to a system not currently included.

This tool should be of particular interest to video editors, who may have to deliver compliant mixes that are not going to go through a proper audio post workflow. Since it works with Media Composer and Adobe CC, a cross section of picture editors now have an easy to use tool to guarantee loudness compliance. 

For situations where I have to deliver compliant mixes and not just the stems to other territories, a couple of clicks and my USA complaint mix can be used worldwide. As with all of iZotope’s award winning technology, it sounds great and it is easy and intuitive to use. If you are in need of a complete solution for creating compliant mixes you need to check out RX Loudness Control.  

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Woody Woodhall, CAS is Head of Allied Post Audio in Santa Monica, CA and is an award winning supervising sound editor, sound designer and rerecording mixer. He has sound supervised and mixed feature films, documentaries…

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