FLAC (Free Lossless Audio Codec)

FLAC (Free Lossless Audio Codec) is an audio compression format that reduces file size while preserving every bit of the original audio data. Unlike lossy formats like MP3, which permanently discard audio information to achieve smaller files, FLAC compression is fully reversible. Decompressing a FLAC file produces a bit-for-bit identical copy of the original audio. FLAC files are typically 50% to 60% the size of equivalent WAV files.

FLAC was created by Josh Coalson and first released in 2001 as a free, open-source alternative to proprietary lossless formats. It became an official project of the Xiph.Org Foundation, the same organization behind the Ogg Vorbis and Opus codecs. Since then it has become the most widely supported lossless audio format, with native playback support across virtually every operating system, media player, and audio editor. Its open nature and zero licensing fees made it a natural choice for archival and professional audio workflows.

For audiobook recording sessions, lossless quality matters because the audio will go through multiple stages of processing before final delivery. Each time a lossy file is decoded and re-encoded, additional quality is lost (generation loss). Recording in a lossless format like FLAC or WAV ensures that the source audio remains pristine through editing, mastering, and final export. The final delivery format may be lossy (ACX requires MP3 at 192 kbps), but starting from a lossless source means that the single lossy encoding step produces the best possible result.

Punch Track records in FLAC format during sessions. This gives narrators the quality benefits of lossless audio with significantly smaller file sizes compared to WAV, which matters when audio is being uploaded to cloud storage and streamed back for playback. When the narrator exports a finished chapter, they can choose their delivery format, but the source material remains lossless throughout the production process.