Old 08-13-2019, 03:11 PM   #1
kenTheriot
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Default Compliance With Amazon ACX?

I couldn't find this in a Forum search. But is there a recommended method for recording/editing spoken work audio so that it meets the Amazon ACX requirements? They require that audio complyh with these standards:

Peak Level: -3dB max
RMS: less than -23dB min (needs to be between -18dB -23 dB)
noise floor is -60 dB

The noise floor is easy enough - just use ReaFIR to reduce background noise. The challenge is to balance the average volume with the maximum peak level. Often I find myself editing such that the peak volume is lower than -3dB, only to find that the average volume is now too low. When I adjust (usually by some sort of compression) for average volume, I might then get a peak over -3dB and it becomes this "push-me/pull-you" kind of see-saw back and forth until you pass their "ACX Check."

Thoughts? Thanks!
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Old 08-13-2019, 04:57 PM   #2
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That's a strange requirement, -3db peak? Weird.

Are you not using a limiter to keep yourself under that value...and help tame some dynamics a little more?
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Old 08-13-2019, 05:12 PM   #3
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I can wrangle things into shape OK with normalization, compression/limiting. What I'm really after is how best to use Reaper tools to do this. For example, you can analyze your track with SWS: Analyze and display item peak and RMS (entire item) so you know what needs adjusting. I need to play with it, but there is also a tool that can adjust your audio to a target average value, which is AWESOME - if it works like it sounds like it does - SWS: Set RMS analysis/normalize options. So theoretically, I could apply that last action to get the average volume in the target zone, and then like you say, use a limiter on the master track keep the top peak below -3.

Will test tomorrow and report what I find as to how well this can be done in Reaper.
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Old 08-13-2019, 06:33 PM   #4
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Given those requirements, I would just use Sound Forge and reach for the RMS and/or Peak Normalization functions. It just seems like the right tool for the job but I'm sure it can be done in Reaper as well with enough effort.
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Old 08-13-2019, 07:00 PM   #5
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Quote:
Originally Posted by kenTheriot View Post
Will test tomorrow and report what I find as to how well this can be done in Reaper.
I await your thoughts...


I am not familiar with Amazon ACX but I do something similar when creating my ambient stuff.

I always aim for -1dB True Peak with an integrated -16dB LUFS. I do this manually, at the moment, within REAPER. And, as you say, it can be a lengthy "push me/pull you" process.

I know I could use compressor/limiter tools but I specifically stay away from squashing the dynamics.

I currently use Pro-L on the master buss, which might sound laughable, but I really like it as a monitoring tool, and it can be set up to measure in LUFS. I set the output to -1dB.

Once I am happy with the mix I will play the project from start to finish and then make a note of the LUFS level. At this point it can be as low as -8dB LUFS.

So, assuming that is the case, I need to boost the input by around +8dB in order to get close to my target. Generally this take a couple of iterations.

I then make note of where the peaks are, using Pro-L. Basically, I want to manually ride the levels so that my limiter doesn't have to do any work. And when I say "ride the levels," I don't mean the master fader... That stays at zero. Instead I alter individual track levels in order to lower the peaks and sometimes raise levels in sections that are a little bit too quiet, which also raises the overall LUFS level.

And that is where the push me/pull you thing becomes a labour of love, I guess. For one thing, by the time project is "finished," if I am still liking it myself then it's good to go haha!

Does that sound mad? I am guessing that it does. I have developed this particular technique in isolation, using the tools in front of me and in line with general discussions elsewhere about streaming level requirements of various websites.


cheers

andy
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Old 08-13-2019, 07:03 PM   #6
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Targeting -20 LUFS with -3dB peaks should get you close... also... LUFS = loudness units full scale so it's 'kinda' not really -20 LUFS; if the peaks are -3 dBFS, it would be -23 LUFS. I wonder if they are aware of that.
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Old 08-14-2019, 09:06 AM   #7
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Quote:
Originally Posted by karbomusic View Post
Targeting -20 LUFS with -3dB peaks should get you close... also... LUFS = loudness units full scale so it's 'kinda' not really -20 LUFS; if the peaks are -3 dBFS, it would be -23 LUFS. I wonder if they are aware of that.
Good point but the original post stated "RMS" and not LUFS. Similar since the intent is the same of targeting an average loudness but I believe that would explain the difference you noted.
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Old 08-14-2019, 09:44 AM   #8
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The Audacity website has a good wiki entry about audiobook mastering and there is a very handy ACX Check plug-in for Audacity.


If you have a good recording to start with it's a straightforward process.


Quote:
The noise floor is easy enough - just use ReaFIR to reduce background noise.
You have to be a little careful because they can reject you if "artificial" noise reduction makes the noise floor too low or if the noise reduction causes artifacts, even if it passes the automated tests. The want to hear some "room tone".


Quote:
The challenge is to balance the average volume with the maximum peak level. Often I find myself editing such that the peak volume is lower than -3dB, only to find that the average volume is now too low.
Regular-linear volume adjustment changes the peak and average by the same amount (in dB). Compression and/or limiting bring the peak & average closer together. (The Audacity-recommended process uses limiting after setting the RMS level.)

Quote:
That's a strange requirement, -3db peak? Weird.
Weird yes! But, the ACX Requirements clearly say "no higher than -3dB".

Last edited by DVDdoug; 08-14-2019 at 09:54 AM.
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Old 08-14-2019, 09:47 AM   #9
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Quote:
Originally Posted by Rednroll View Post
Good point but the original post stated "RMS" and not LUFS. Similar since the intent is the same of targeting an average loudness but I believe that would explain the difference you noted.
Yes, that would explain it... I totally missed that it didn't say LUFS LOL.
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