CD ripper

History

In the early days of computer CD-ROM drives and audio compression mechanisms (such as MP2), CD ripping was considered undesirable by copyright holders, with some attempting to retrofit copy protection into the ISO 9660 standard. As time progressed, most music publishers became more open to the idea that since individuals had bought the music, they should be able to create a copy for their own personal use on their own computer.

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Design

Summarize

Perspective

As an intermediate step, some ripping programs save the extracted audio in a lossless format such as WAV, FLAC, or even raw PCM audio. The extracted audio can then be encoded with a lossy codec like MP3, Opus, Vorbis, WMA or AAC. The encoded files are more compact and are suitable for playback on digital audio players. They may also be played back in a media player program on a computer.

Most ripping programs will assist in tagging the encoded files with metadata. The MP3 file format, for example, allows tags with title, artist, album and track number information. Some will try to identify the disc being ripped by looking up network services like AMG's LASSO, FreeDB, Gracenote's CDDB, GD3 or MusicBrainz, or attempt text extraction if CD-Text has been stored.

Some all-in-one ripping programs can simplify the entire process by ripping and burning the audio to disc in one step, possibly re-encoding the audio on-the-fly in the process.

Not all CD rippers read or copy Compact Disc subcodes, a fact exploited by several types of digital rights management (DRM) to prevent successful copying of discs or to prevent effective use of software copied from discs. CloneCD is able to copy subcode data to bypass certain types of DRM.

Difficulties in obtaining accurate reproductions

Summarize

Perspective

Ripping a CD to audio files that will faithfully reproduce the same CD if burnt again is not trivial. Such a rip (along with a cue sheet file and other metadata describing the layout of the files on the disc) is sometimes referred to as an "accurate", "perfect" or "secure" rip.^[2] Some CD ripping software is specifically intended to provide accurate rips, including CloneCD, Exact Audio Copy, cdda2wav, CDex, cdparanoia and whipper. There is also a reference database with hash values of known good rips that can be used to confirm a successful rip and in some cases calibrate parameters for a CD drive.^[3]

In the context of digital audio extraction from compact discs, seek jitter causes extracted audio samples to be doubled-up or skipped entirely if the Compact Disc drive re-seeks. The problem occurs because the Red Book standard does not require block-accurate addressing during seeking.^[a] As a result, the extraction process may restart a few samples early or late, resulting in doubled or omitted samples. These glitches often sound like tiny repeating clicks during playback. A successful approach to correction in software involves performing overlapping reads and fitting the data to find overlaps at the edges. Most extraction programs perform seek jitter correction. CD manufacturers avoid seek jitter by extracting the entire disc in one continuous read operation, using special CD drive models at slower speeds so the drive does not re-seek.

Properties of an optical drive helping in achieving a perfect rip are a small sample offset (at best zero), no jitter, no or deactivatable caching, and a correct implementation and feed-back of the C1 and C2 error states. There are databases listing these features for multiple brands and versions of optical drives. Also, EAC has the ability to autodetect some of these features by a test-rip of a known reference CD.^[4]

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Examples

Notes

Due to additional sector level addressing added in the Yellow Book, CD-ROM data discs are not subject to seek jitter.

History

Etymology

Design

Difficulties in obtaining accurate reproductions

Examples

See also

Notes

References

External links

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