Audible.com QC standards

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Audible.com QC standards

Permanent link to this post Posted by c.craig58 » Tue May 07, 2013 2:48 pm

I am a new audiobook producer, using the ACX.com site, which sets the recording standards for posting audiobooks to Audible.com The standards page is at https://www.acx.com/help/rules-for-audi ... /200485520

I get good recording quality on my recording gear, and Audacity is very good for editing and exporting in the formatting required here.

My concern is: is Audacity capable of allowing me to meet the QC mastering (quality control) standards that this page states? And if not, what kind of mastering software would this forum recommend to me?

THANKS VERY MUCH -
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Re: Audible.com QC standards

Permanent link to this post Posted by kozikowski » Tue May 07, 2013 4:26 pm

Pretty much what we have been recommending people do forever -- except for punch-in. Audacity doesn't do that. One alternative method not mentioned is to set a label with hot keys when you make a fluff and start the sentence over again right then. The label will tell you where to go back later to patch the work. Surgically remove the fluff. Much faster than copy/paste editing.

They even got the editing time down. Three or four times the show length to get the editing done. That burns people all the time.

They hit all the high points except room echo. Generally, sounding like you were recording in a kitchen is to be avoided as are neighborhood noises like dogs barking and running the TV. We can't fix those in post production. You have to have a quiet room at the start. They even got the WAV/MP3 thing down. Never record directly to MP3.

I'm saving that link. I've only seen that list one other place and that was to set up the dual-header broadcast I shot -- people interviewing each other from different cities without Skype. We didn't have to worry about a lot of it because we had a semi-studio in LA, but I can imagine they get a lot of recording newbees.

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Re: Audible.com QC standards

Permanent link to this post Posted by kozikowski » Tue May 07, 2013 4:33 pm

Audacity can do everything in that list short of Punch-In. Amplify, Normalize, Compressor, the lot -- but in post production. Audacity does not apply effects and filters in real time. You really do have to get the recording right without a lot of digital help.

It may be harder than you think. We're on chapter three of a poster who wants to do a simple interview recording.

viewtopic.php?f=27&t=72353

The longest posting on the forum, ever, was someone who wanted to simply record his acoustic guitar.

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Re: Audible.com QC standards

Permanent link to this post Posted by c.craig58 » Tue May 07, 2013 4:48 pm

Thanks very much for the feedback - I'm a very good narrator, but new at audio mastering standards & terminology. So - once the editing work is done, (this is not difficult for me at all, since I reread phrases one after the other in the first recording, then select the one I like best) - I will Normalize at -3dB, right? But after that is done, how do I check the files to see that these other standards are met?

Here are the specific standards that my question relates to: "Your submitted files should measure between -23dB and -18dB RMS, with peaks hovering around -3dB. Your noise floor should fall between -60dB and -50dB"

I realize that the spoken word is FAR less challenging than multi track music recordings -- I very much appreciate your taking the time to respond on this... :-)
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Re: Audible.com QC standards

Permanent link to this post Posted by steve » Tue May 07, 2013 4:59 pm

c.craig58 wrote:is Audacity capable of allowing me to meet the QC mastering (quality control) standards that this page states?

Yes it is, though as Koz notes, their description of "good" recording is detailed and fairly comprehensive, but not "complete". They mention "room tone" several times, and it is important, but the "type" of room tone is also important - if it sounds like a bathroom or corridor, then (unless that is appropriate for the book, which usually it is not) you will need to do something about the recording location, such as putting up sound absorbing materials around the space or using a "vocal shield" or "vocal booth". This is a common problem with home recording.

Some of the technical detail is a little bit "out", for example:
"There should be exactly 500ms (0.5 seconds) at the head of each file"
The start time of an MP3 file is not "exact" due to limitations of the format - what they mean here is "There should be very close to 500ms (0.5 seconds) at the head of each file".
Also:
"Your submitted files should measure between -23dB and -18dB RMS"
This specification is incomplete as they do not state the RMS "weighting" or "window size". In practice the exact definition probably does not matter too much - I assume that they are just trying to give an indication that the recording should be "reasonably" loud without pushing the loudness too much - the compression / limiting steps that they describe are likely to be close enough to the right ball park figure. Comparing your recording with some of their published recordings will immediately show you if your recordings are too loud or too quiet. There are also some plug-ins that can give you an RMS and peak amplitude figure for your recording such as the "Stats" plug-in available here: viewtopic.php?p=99454#p99454
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)
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Re: Audible.com QC standards

Permanent link to this post Posted by kozikowski » Tue May 07, 2013 5:19 pm

Do you suppose their "noise floor" is taken with the microphone turned off? Room Tone rarely gets to -60 even in some studios.

If you're an experienced presenter then you know all about soundproof studios, etc. It's not impossible to do at home. I know people who crawl into their closet with quilts on the wall to avoid reflections and echoes.

A few furniture moving pads might be in order.

http://www.kozco.com/pictures/boothFini ... op-mic.jpg

The microphone on the right has a reflection suppressor behind it that may be of help.

http://www.kozco.com/tech/audacity/pix/ ... dShoot.jpg

We were speaking with one presenter who admitted he got his very good environment suppression and clarity by waiting for trucks and buses to pass his house completely before recording.

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Re: Audible.com QC standards

Permanent link to this post Posted by kozikowski » Tue May 07, 2013 6:11 pm

You might also consider Chris' Compressor.

http://theaudacitytopodcast.com/chriss- ... -audacity/

Chris designed this all-in-one compressor so he could listen to opera in the car without constantly turning the volume up and down. It evens out volume variations remarkably well during speaking performances. I download a voice radio show and since it doesn't go through the radio station compressors, is all but unlistenable in the car. "Hi, Today______ ___ ____HA! HA! HA!! ____ ___ mumble____ -__ ."

As I like to put it, Christ started out with cadenzas and arpeggios and not millisecond attack and release times. His work is very pleasing and musical even if it may not be statistically perfectly accurate.

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Re: Audible.com QC standards

Permanent link to this post Posted by c.craig58 » Tue May 07, 2013 7:29 pm

HAHAHAHA!! Your post about the fellow listening to opera is awesome - I was a vocal major at Univ. of Houston years ago, and totally get what your saying here! :-)

EXTREMELY helpful responses to my post - thank you very much.
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Re: Audible.com QC standards

Permanent link to this post Posted by Robert J. H. » Tue May 07, 2013 8:32 pm

There are some tutorials on the web site that deal especially with the gear and room Setup.
They did not Forget this part.
To have an Impression about the noise floor, you can generate some pink noise with an Amplitude of about 0.007 and see the rms values with this snippet for the nyquist prompt (press debug):
Code: Select all
(snd-display (linear-to-db (rms s)))

Although the RMS matches perfectly between -50 and -60 dB, the noise is rather loud, so I think that the Peak value is meant.
An Amplitude of 0.003 for the pink noise should be nearer the truth.
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Re: Audible.com QC standards

Permanent link to this post Posted by khanley » Sun Jul 21, 2013 5:37 pm

I'm getting ready to record my first audiobook and I must admit I am still flummoxed by this topic.

To review, here is the ACX guideline for mastering:

Mastering:

Your submitted files should measure between -23dB and -18dB RMS, with peaks hovering around -3dB. Your noise floor should fall between -60dB and -50dB.
To make the audiobook levels louder and more-even throughout is vital. Typically, this process is achieved by RMS normalization around -20db, or compression/limiting. Compression should be applied with a fast attack and release, around a ratio of 3:1. A hard limiter may also be used, and audiobooks are EQ’d during this time, to sweeten the sound and make it more pleasing to the ear. Often, muddled low end and mid-range is cut to make the audiobook sound more clear and smooth.

When I got to Audacity > Effect > Compressor, I see the following slider bars:

Threshold
Noise Floor
Ratio
Attack Time
Decay Time

Plus there are two check boxes:

Make-up gain for 0dB after compressing
Compress based on Peaks

Can anyone help me determine what the sliders should be set at and which boxes should be ticked in order to meet the ACX Mastering Guidelines above? I've tried contacting ACX at their general email address but have received no response as of yet.

I greatly appreciate any help offered. I can't believe I'm the only person baffled by this.

Thanks in advance,

Kirk
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