This page discusses the technical details of a variety of production audio codecs.

• Simple Time Domain Audio Coding [HTML], [LyX]: This document covers a range of simple time domain (as opposed to frequency domain) coding formats including PCM, DPCM, and ADPCM.
• MPEG Audio: Here are links to Masters theses that deal with decoding MPEG I Layer III (MP3) audio. Both explain the underlying concepts and principles of the algorithm and include well-commented reference implementations.
  • MP3 Decoder Masters Thesis by Krister Lagerstrom
  • Whitney Thesis Project by Björn Wesén
  • MP3 Extensions: This document describes various third party extensions used to encode extra information in MP3 files
• GSM 06.10:
  • Toast GSM 06.10: This is a link to a free, open source software distribution that encodes and decodes GSM 06.10 data.
  • Digital Speech Compression: Putting the GSM 06.10 RPE-LTP algorithm to work This is a link to a Dr. Dobb's Journal GSM 06.10 article written by the authors of the aforementioned GSM 06.10 package.
• A/52 / AC-3 (PDF File): This document describes the official A/52 algorithm, a.k.a. AC-3.
• Vorbis Audio: This is a link to a detailed technical explanation of the open sourcec Vorbis audio coding method.
  • Vorbis spec errata sheet: Because there are, however, some mistakes in the Vorbis spec.
• Free Lossless Audio Compression (FLAC): This site describes the format of the FLAC, which, as the name implies, is a compression system that losslessly encodes audio, and is also free (and open source).
• Meridian Lossless Packing (PDF File): This is a paper that discusses the principles behind Meridian Lossless Packing (MLP) used on DVD-audio discs.
• Overview of Advanced Audio Coding (AAC): This Wiki page details the basic concepts and capabilites of the AAC standard.
• QDesign Analysis (QDMC/QDM2) (PDF file): This is a link to a PDF file that investigates the inner workings of the QDesign music codec used in many Apple Quicktime files.
• ATRAC3 High-Quality Audio Encoding Technology (PDF file): Brief whitepaper describing the inner workings of Sony's Adaptive Transform Acoustic Coding 3 format.

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