What is chapterpass?
Audible's ACX has established eight technical standards that must be met, with any file that does not satisfy even one of these standards being rejected without exception. Chapterpass takes great care in preparing each chapter file to meet these requirements, ensuring that the RMS loudness falls between -23 and -18 dBFS, peak levels remain below -3 dBFS, the noise floor is kept under -60 dBFS RMS, and room tone is included at both the start and finish, all while producing a 192 kbps CBR MP3 file. Every audio file undergoes a thorough review to verify compliance with all specifications before it becomes available for download, allowing users to view precise measurements for each requirement at all checkpoints. The entire processing occurs in the user's browser through the use of WebAssembly technology, which ensures that audio files are kept on the user's device throughout the operation. Users can utilize the service without the need for an account; the first file is offered free of charge, while subsequent files incur fees of $36 per finished hour, $27 for five hours or more, and $18 for ten hours or more, all billed by the second. Furthermore, a complimentary measurement tool is available at /free-acx-check, enabling users to assess loudness, peak levels, noise floor, and silence padding in relation to the specifications without performing any mastering. Although Chapterpass specializes in mastering the essential technical standards, it does not engage in editing, noise removal, or any corrections to narration, thereby ensuring a smooth and efficient process for creators seeking to meet ACX requirements. This commitment to quality and compliance allows creators to focus on their content while trusting that their audio will meet industry standards.