Tutorial - How to import CDs
A Compact Disc (also known as a CD) is an optical disc used to store digital data. It was originally developed to store sound recordings exclusively, but later it also allowed the preservation of other types of data. Audio CDs have been commercially available since October 1982. They remain the standard physical storage medium for audio. although sales of commercial CDs have been falling for some years while digital downloads (for storage on hard drives or flash-based music players) have been increasing.
Standard CDs have a diameter of 120 mm and can hold up to 80 minutes of uncompressed audio (700 MB of data). The Mini CD has various diameters ranging from 60 to 80 mm. Mini CDs are sometimes used for CD singles or device drivers, storing up to 24 minutes of audio.
The vast majority of audio CDs are encoded according to the Red Book Standard. The Red Book standard is a 16-bit, 44,100 Hz PCM stereo stream of audio. This is very similar to (though not directly comparable with) stereo WAV and AIFF files encoded at 16-bit, 44,100 Hz. Audio CD quality sounds identical to those formats. However, because the data is a stream with a TOC (Table of Contents), rather than a set of self-contained files, most operating systems cannot open the audio for editing in the same way that a WAV or AIFF file can be opened.
The basic Red Book specifications state that:
- Maximum playing time is 79.8 minutes.
- Minimum duration for a track is 4 seconds (including 2-second pause).
- Maximum number of tracks is 99.
- Maximum number of index points (subdivisions of a track) is 99 with no maximum time limit.
Importing data from CDs
Users new to audio editing are often surprised to find that they cannot import the audio from CDs into Audacity with the bits on the disc. That is why when you look at an audio CD in a file manager like Windows Explorer, each CD track will appear only as a small .cda "file" 44 bytes in size, which is merely header information for the stream.command. In fact, most operating systems do not actually allow the import of data from the CD tracks into applications, because audio CDs do not have files or a file system like computer media, but consist essentially of a stream of
In order to import tracks from an audio CD, you must first usually extract (or "rip") the tracks to a WAV or AIFF audio file using CD extraction software; then you can import those WAV or AIFF files into Audacity with the usualcommand.
|Do not extract the CD to smaller-sized MP3 format if you want to edit the audio in Audacity, because every time you export an MP3 file, some of the quality is lost. Extract to WAV or AIFF which are lossless. You can always export to MP3 from Audacity after editing, but do that only once for the finished audio.|
Audio CDs may be ripped to WAV with Windows Media Player 11 or 12 (clickand choose "WAV (Lossless)" in the Format dropdown in "Rip Settings"). Earlier versions of Windows Media Player are not appropriate for extracting CD audio for editing in Audacity, because they are unable to extract to WAV.
Alternatively the Windows version of iTunes (which is free to download) may be used to extract audio CDs to WAV or AIFF.
Mac users have a quick way to import CDs, because when a CD is put in the drive, the CDA tracks are mounted as AIFF files in the Finder. It's thus possible to either drag the AIFF files from the Finder into Audacity, or use thecommand, instead of extracting the audio.