Welcome back to How to Succeed at Audiobook Production. If you’ve been following this series, then you’ve read up on The ACX Mile, which helps you perfect the art of narration recording, perform a complete edit and QC your recorded audio, and learn audio mastering best practices. If you haven’t perused these posts, I recommend doing so before continuing on.
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w that you’re caught up, let’s move on to the fourth and final part of my series: encoding and file delivery.
Rounding The Final Corner
Upon a successful master, your audiobook production is not quite finished. Keeping that in mind, watch the final video in our series, and review the key points I discuss after.
The Home Stretch
I recommend you perform another final QC pass on your audio before moving on to encoding and delivering your audio. After putting so much effort into your production, the last thing we want to do is send an audio review notice to fix missing chapters or out-of-order audio files. The post-mastering QC pass needn’t be as in-depth as what I recommend in the article on editing; it could be as simple as verifying the volume levels are meet our specifications, that the content is complete, and that the audio files are numbered and named in the proper order.
If everything looks ready, then we can begin the encoding process. I cover this in more detail in my post, Encoding Audio with Andrew the Audio Scientist, but I’ll summarize here. That post contains a link to our instructions detailing how to encode your audiobook to ACX specifications using the free and cross-platform fre:ac encoding software.
Keep ACX’s Encoding Requirements in Mind.
All files in your audiobook must:
- Be all mono or all stereo (though we strongly recommend mono).
- Be encoded at a bit rate of at least 192kbps, and contain a sampling frequency of 44.1kHz.
- Not be encoded with VBR or joint stereo options.
Also be cognizant of ACX’s file-level requirements. The encoding options you choose can potentially cause the run-time or the file size to go over our specifications. Each file must contain a single chapter with a length no longer than 120 minutes..
Crossing the Finish Line
Once you verify your audio complies with our MP3 encoding and file-level requirements, you’re ready to upload our audio to the ACX production manager! Here are some last-minute tips that could potentially save you from an audio review notice.
1. Be smart about your sample. The retail sample you provide will likely be a customer’s first glimpse into your work, so make this moment count! I recommend grabbing the audio from an early point in the book, so you don’t give away plot developments. Also, be mindful of the ACX sample requirements, which expressly prohibit erotic/mature content. If your book is on the wilder side, find a section that is appropriate for all audiences.
2. Double-check your book’s chapter order when uploading your files. Files arrive to ACX in the same order as they are uploaded to the Production Manager. Doing this last check will make the QA process simpler and faster, allowing us to get your title on sale more quickly.
3. Ensure your file names are clear and concise. To help ACX best understand your audio, I recommend naming your audio using a template such as:
- 01-BookTitle-OPENING.mp3 <<Your book’s Opening credits.
- 02-BookTitle-PROLOGUE.mp3
- 03-BookTitle-CH1.mp3 <<Chapter one
- 04-BookTitle-CH2-p1.mp3 <<Chapter two, part one
- 05-BookTitle-CH2-p2.mp3 <<Chapter two, part two
Thank You
Since we are at the end of the How to Succeed at Audiobook Production series (but not the end of my regular contributions to the blog), I want to take this opportunity to thank our users, subscribers and readers for your loyal viewership.
But don’t worry, I’ll be back with more audiobook production tips soon. In the meantime, share your own with your fellow readers in the comments below!
Audiobook Creation Exchange Blog (ACX) 
I realy love the topics you’re working on but my city isn’t your program as yet.the moment it is I will sure take advantage of the opprtunity.omar
I have refined so much of what I’m doing just watching/reading this series, Andrew. I had the basics, but realized I was trying too hard…to the point that my “fixes” were actually creating more problems with my audio files, rather than fewer. I went back to basics, reset all my levels, took out a few of the “apps” I was applying during the mastering session, and what a difference!
Thanks. Always learning, always progressing, always looking for ways to improve our audiobook productions.
Thanks again Andrew for all the good information.
Can you please clarify if audio is re-coded to mono before distribution? Does this include distribution to iTunes? You have noted that there are multiple quality settings used for Audible distribution. Are these all mono or is stereo supported?
Related to this, I also wanted to clarify the statement regarding joint stereo encoding, which means either m/s stereo or intensity stereo (or both). The stereo bits are defined in ISO 11172-3 as the “mode” bit field as “00” = stereo, “01” = joint stereo, “10” as dual channel, and “11” as single channel. In joint stereo, either intensity stereo or mid/side stereo, or a combination of both (by sub-band), are allowed, as set by the two bit mode_extension field which can be used to turn off the availability of either m/s or intensity stereo encoding. Joint stereo should provide improved performance relative to the mode bit setting of “stereo” of “dual channel” since there is no way to take advantage of the inherent redundancy in the signal. Can you provide the rationale why joint stereo is to be avoided (meaning no mid/side stereo?)
Is there any plan to change the upload to a lossless format such as FLAC?
Good morning Bruce. Thank you for your question!
It is first important to point out that all Audible formats, other than Audible Enhanced Audio, are mono files. So, any stereo audio that is sent to ACX is likely to be summed to mono when it reaches your listeners. This can lead to higher-than-expected volume levels, audio phase issues, and other undesirable artifacts. We strongly recommend producing your audiobooks in MONO unless your production aesthetic specifically calls for it.
You are correct in pointing out that Joint Stereo permits both intensity coding and m-s processing of stereo information to exist in the same MP3 file. The problem is that these stereo files are more unpredictable, especially when they get processed into other audio formats before they head to retail. Joint Stereo encoding does not reconstruct the stereo image exactly as it came to us, so even if you took much care to center and balance your stereo image when you sent it to us, the resultant MP3 file, and the encoded audio we send to Audible, Amazon, and iTunes, it may not result in that outcome when all is said and done.
At ACX, we do not discount the benefits of Joint Stereo encoding, particularly for bitrates lower than 64kbps per channel, but since ACX’s minimum audio submission requirements state the need for at least a 192kbps MP3, these encoding options often deliver more risk than reward.
I too am curious about the inability to submit stereo. My submission was rejected because it was stereo and not mono. I am now trying to work with garageband to get it to mono even though I am fully compliant with the rest of the requirements. I do believe the sound quality is better in stereo and obviously we want the best product out there possible.
Does ACX check the 15 minute segment we upload to check that it meets requirements Andrew? I was just thinking that this might be a great help for those of us who are getting started so that we don’t do the whole thing wrong.
Pingback: How to Succeed at Audiobook Production: Part 3 | Audiobook Creation Exchange Blog (ACX)
Help please! I had to reload fre:ac and now need to configure for ACX. The link on your page about this now opens masses of blank windows. Could you please check this and post a new link? There does not seem to be any help from fre:ac themselves for this and I couldn’t find our link anywhere else.
Reblogged this on ckylesimmons.