I Submit! I Submit!

We’ve recently revamped our Audio Submission Requirements for ACX (formerly known as the Rules For Audiobook Production), and we’re highlighting some of the changes. Rest assured that most of the requirements remain the same – we’ve just made them easier to understand!

The importance of the Audio Submission Requirements

You’re in competition with the best!Audible has over 150,000 audio programs for sale, with recordings from both the biggest studios in the business and ACX users’ home studios. Both recording environments can sound great with the right settings, and our submission requirements help ensure that your titles meet the same specifications as all of Audible’s providers.

You want to get your title on sale as quickly as possible! – Books created through ACX are distributed to Audible, Amazon and iTunes, and the sooner they’re available for sale, the sooner you can start racking up positive reviews and generating sales. Our Quality Assurance process is streamlined to get your titles to Audible’s audio processing teams efficiently, and your title may be held up if it doesn’t meet our audio specs.

As ACX Audio Production Coordinator Andrew Grathwohl, puts it

Familiarizing yourself with our Audio Submission requirements will help ensure that your title passes our QA screening without a hitch. In doing so, you can be confident that your audiobook will stand shoulder-to-shoulder with all the other titles in the Audible catalog.

What’s New About These Revamped Requirements?

Glad you asked! Each aspect of production is now headed by the requirement and explained with a straightforward description. Requirements are broken up between broad, title-level items, and specific file-level details, and they are given to you in bite-sized, easily digestible prose that everyone from audiobook experts to brand-newbies can understand.

We’ve also simplified a few key points in the production process. We’ve eliminated grouping of chapters once and for all (so don’t even try it!), and we’ve given you a bit more leeway in the spacing at the top and tail of each file.

A Few Quick Examples

You can find the new Audio Submission Requirements page over on ACX, but here are a few sections of note that you might find helpful:

Your submitted audiobook must:

Be consistent in overall sound and formatting.

Why? – Consistency in audio levels, tone, noise level, spacing, and pronunciation helps give the listener a great experience. Drastic changes can be jarring and are not in keeping with a professional production. Extreme fluctuations in volume means the listener will have to keep a hand on the volume control of their listening device. This detracts from the listening experience and may lead to poor reviews and reduced sales.

Include a retail audio sample that is between one and five minutes long.

Why? – The retail audio sample used on Audible and Amazon is a preview of your audiobook. A great sample will show off your material and attract paying customers! (Note: iTunes automatically uses the first five minutes of the book as their sample.)

Each uploaded file must:

Contain only one chapter or section.

Why? – This ensures listeners can easily navigate between sections, and that skipping forwards or backwards moves them forward or back one section. Combining multiple sections in one file creates a confusing navigation experience. If the audiobook is not in a traditional chapterized format and you’re unsure how best to separate your files, please contact audio@acx.com for guidance.

Be 192kbps or higher MP3, Constant Bit Rate (CBR)

Why? – Before going on sale in the Audible store, titles are encoded in a variety of formats that customers have the option of downloading. 192kbps (or higher), Constant Bit Rate MP3 files are required so this encoding process works without error. You may upload 256kbps or 320kbps files if you’d like, but the difference in quality heard by listeners will be negligible.

Have our submission requirements made it easier for you to produce and upload high quality audiobooks to ACX?

23 responses to “I Submit! I Submit!

  1. I had the understanding that you wanted tails to run 3.5 seconds. I see now that anything between 1 and 5 seconds is OK. Is this a change?

    • Hi Jack,

      We’re attempting to make things easier on ACX producers by being a little more lenient on this point. Hope it helps!

  2. For me, I think requiring files “Contain only one chapter or section” is especially welcome, thank you 😉

    I do think this will make the listener’s experience much easier and, more importantly, more enjoyable.

  3. Earlier we were told to combine short chapters. Can we re-edit books that are already on sale and resubmit them? I much prefer separating chapters.

  4. Weren’t these already requirements? Not exactly sure what has changed except the head and tail spacing. Good to go over the requirements as a refresher. Thanks

  5. Reblogged this on Concordia Tree Media and commented:
    Thanks for the update! Very handy information.

  6. Where the requirement says “interleaved stereo,” I’m not sure what you mean. MP3 provides for mono, stereo, and joint stereo. Joint stereo can be implemented as mid+side encoding or intensity encoding.

    • I’m thinking I’ll stick with mono (see last sentence of the paragraph in question):
      “Submitted audiobooks may not contain both mono and stereo files. Stereo files must be ‘stereo interleaved.’ Mono files are strongly recommended.”

  7. Interleaving is something that’s done in .wav files. In MP3 one could have mono, dual channel (such as english on one channel and Spanish on the other), stereo (2 channels), or joint stereo. Joint stereo is more efficient at encoding stereo audio than 2 channel stereo since it takes advantage of the redundancy in the stereo signal. We produce full cast dramatic audiobooks so stereo is important to the listening experience.

  8. I am struggling to get the volume levels on my files right. Can someone share a short file that meets the requirements, so I can compare? TIA

    • If you use Twisted Wave, run the File/Analyze after you’re done. Your Peak Amplitude should be around -3 and Average RMS between -18 and -23. That’s far more accurate than “listening.” Adjust the gain (volume) on your microphone to get where you need to be by the time you master the audio.

    • The average RMS level depends on the narrator’s pacing – so I don’t think this is really a good measure. The peak level is much more meaningful. My suggestion is that you get hold of some audiobooks from the major publishers and pull those files into your editing system – if you pull them from CDs, then they probably are very well mastered. Soundcloud is another good source of clips from audiobooks. It’s also a great way to promote your projects. Here is my company’s soundcloud page:

  9. Darby Croasdale

    This new stereo interleaved thing is really jarring since my program doesn’t make such a file, nor does it make Mono 192 Kbps. What am I going to do?

    • Darby: you have a choice for your files, either all mono or all interleaved stereo. I keep it simple: all mono. As for your mono rate, it’s time for a new program. TwistedWave is great if you have a Mac.

    • “Interleaved” is an option when you are making wav files which you are not. It’s not an option in mp3 files which is what you will upload. Audible takes your mp3 file and processes it into four different encoding schemes, with four bitrates, and the lower bit rate codec (ACLEP) doesn’t support stereo. You will get significantly better audio quality at the higher bit rates with mono, but stereo is sometimes important in the listenting experience. The entire book needs to be in stereo or mono, and also you need to have identical settings for all mp3 files in the book. Another thing that I suggest you be careful of is to utilize ID3 tags in your MP3 files. These are just metadata describing the files, but some (non-Audible) players, like the Sansa Clip, use the ID3 tags to know what mp3 files are audiobook files vs. music files.

      • Hi Bruce,

        Thanks for the helpful info! One thing we’d caution: please do not include any embedded metadata (id3 tags or cover art) in your ACX files. You may find that you are unable to upload to ACX if you’ve embedded metadata in your mp3s.

  10. The audiobook I have been working on has now been in the ‘headed for retail’ stage for 3 weeks. This is my first narration project and I’m wondering how long this phase usually takes.

  11. In my experience, 3 weeks is the usual review time. I did have a book take over 8 weeks recently, but that was a fluke: it didn’t get handed from one review team to the next correctly.

  12. I’m confused by the requirements saying use 192 Kbps mono, but Sound Forge has a max Kbps of 128 Kbps in Mono (higher in stereo). I’m using Windows.

  13. JackWestCoast

    You can always open your audio files with another program that does give you the 192 setting.

  14. I use SoundForge. Just use the 256K stereo option. If your source file is mono you’ll end up with L and R channels that are the same and in high quality. When you select “save as”, select 256Kbps stereo from the templates list, then click “custom…” and then unclick the option for “joint stereo” and select the button for “stero” (which will give you two identical mono L and R tracks), slide the quality bar all the way to “highest quality” and make sure that the “VBR quality” checkbox is NOT checked. To prevent ID3 tags from being added to the file (per ACX above in this thread), go to the ID3 tab and uncheck the box that says “save both ID3 Version 1 and Version 2 tags.” You’ll notice that it takes quite a while for Sony’s mp3 encoder to convert on the high quality setting but that is because it does a much better job than a lot of the encoders (codecs) on the market.

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