What Is CD Extraction?

CD extraction is the controlled process of reading the contents of a compact disc and creating usable digital files or a preservation image. The correct method depends on whether the disc contains CD-DA audio, computer data, video, mixed content or a specialist disc structure.

Why CD extraction is more than copying files

CDs can contain very different structures even though they look almost identical. A commercial audio CD, CD-ROM, recordable data CD and mixed-mode disc require different extraction approaches.

Identifying the type of CD before extraction

Optical discs should be handled carefully and assessed before extraction. Scratches, contamination, disc degradation and ageing recordable media can affect readability. The National Archives notes that optical discs can present long-term preservation challenges.

Audio CD versus data CD

An extraction workflow should begin with identification and condition assessment, followed by the appropriate optical drive and extraction method. Where preservation of the complete disc structure is important, a disc image can be retained alongside extracted files.

Preserving the original disc structure

Audio CDs may be extracted as individual PCM WAV tracks, while data discs may be extracted as files or as a complete image. The output should preserve enough information to support future verification and re-use.

Quality control and verification

Checks should include disc identity, track or file count, durations or sizes, readable sectors, filenames, file integrity and checksums. Problematic discs should be flagged rather than silently producing incomplete output.

Reference guidance: This article is informed by optical-media preservation guidance from the U.S. National Archives and the Library of Congress Recommended Formats Statement. Where appropriate, the article distinguishes preservation guidance from practical extraction procedures.