Encoding for ACX

I just tried to upload a chapter of a book to ACX and I got the following message:

"File is encoded below 192 Kbps. Re-encode the
original source audio of this file using a bit rate of 192 Kbps or higher.

File is not encoded in Constant Bit Rate (CBR). "

I’ve never encoded anything before. How do I do that?

Sara Moser Bartlett

Read the replies to this post: ACX AudioLab recording feedback - bit rate criteria

That was the answer I needed.

Thank you so much,
Sara Moser Bartlett

That was the answer I needed.

Post back if they accept it. They may not depending on how you got there.

First note is a clarification of the requirement. They want at least 192 quality. That’s a minimum specification, you don’t have to hit it on the nose, you can go over. And, as you found, you can’t go under.

You can’t open your low quality MP3 and “convert it” to 192. The compression distortion and damage in your original submission is permanent.

Ideally, you prepare your Chapter Edit Masters as perfect quality WAV (Microsoft) 16-bit files. That’s where you make your safety backups. You can convert those to anything. Open a copy of your WAV edit master chapter and export it as MP3, 192 quality (or higher), Constant Bitrate. Submit that.

You can also use perfect quality Audacity Projects as edit masters, but those can have problems depending on your computer system. They’re not as stable as WAV.

I can make this worse. The bitrate value is part of an early, semi-automated ACX testing. They also have Human Quality Control which comes later. That’s where they judge voice quality and sound distortions. That’s where I failed. They didn’t like my lip smacks.


Yes, they did accept it. Thanks so much!
Sara Bartlett