Although pre-recorded CDs have certainly lost their luster with the convenience of digital music streaming and downloads, it was the CD that started the digital music revolution. Many still love CDs and both buy and play them regularly. Here is what you need to know about Audio CDs, and related disc-based audio formats.
The Audio CD Format
CD stands for Compact Disc. Compact Disc refers to both the disc and the digital audio playback format developed by Philips and Sony in which audio is digitally encoded, similar to the way computer data is encoded (1's and 0's), into pits on a disc, using a process called PCM which is a mathematical representation of the music.
The first CD recordings were manufactured in Germany on August 17, 1982. The title of the first full CD test recording: Richard Strauss' - Alpine Symphony. It was later that year, on October 1st of 1982, that CD players became available in the U.S. and Japan. The first CD sold (first in Japan) was Billy Joel's 52nd Street which had been previously released on vinyl in 1978.
The CD started the digital revolution in audio, PC Gaming, PC storage applications, and also contributed to the development of the DVD. Sony and Philips jointly hold the patents on the development of the CD and CD player technology.
For more info on the history of the CD, check out the report from CNN.com.
Also, check out a photo and a complete review (written in 1983 by Stereophile Magazine) of the first CD Player sold to the public.
HDCD is a variation of the existing CD standard (referred to as "Redbook CD"). By extending the information stored in the CD signal by 4-bits (CDs are based on 16bit audio technology) to 20bits, HDCD can extend the sonic capacity of current CD technology to new standards, but still enabling, HDCD encoded CDs to be played on non-HDCD CD players (non-HDCD players just ignore the extra "bits") without any increase in the price of CD software.
Also, as a by-product of more precise filtering circuitry in HDCD chips, even "regular" CDs will sound fuller and more natural on an HDCD-equipped CD player.
HDCD was originally developed my Pacfic Microsonics, and later became the property of Microsoft. The first HDCD disc was released in 1995, and although it never overtook the Redbook CD format, over 5,000 titles were released.
When buying music CDs, look for the HDCD initials on the back or internal packaging. However, there are many releases that may not include the HDCD label, but, may still be HDCD discs. If you have a CD player that features HDCD decoding, it will automatically detect it and provide the added benefits.
Also Known As: High Definition Compatible Digital, High Definition Compact Digital, High Definition Compact Disc
SACD (Super Audio Compact Disc) is a high resolution audio disc format developed by Sony and Philips (who also developed the CD). Utilizing the Direct Stream Digital (DSD) file format, SACD provides for more accurate sound reproduction than the Pulse Code Modulation (PCM) used in the current CD format.
While the current CD format is tied to 44.1 kHz sampling rate, SACD samples at 2.8224 MHz. Also, with a storage capacity of 4.7 gigabytes per disk (as much as a DVD), SACD can accommodate separate stereo and six-channel mixes of 100 minutes each. The SACD format also has the capability to display photo and text information, such as liner notes, but this feature is not incorporated into most discs.
CD players cannot play SACDS, but SACD players are backward compatible with conventional CDs, and some SACD disks are dual-layer discs with PCM content that can be played on standard CD players.
In other words, the same disk can hold both a CD version and SACD version of recorded content. That means that you can invest in dual-format SACD's to play on your current CD player and then access the SACD content on the same disc later on an SACD-compatible player.
It must be noted that not all SACD discs have a standard CD layer - which means you have to check the disc label to see if a specific SACD disc can also play on a standard CD player.
In addition, there are some higher-end DVD and Blu-ray Disc players can also play SACDs.
SACD's can come in either 2-channel or multi-channel versions.
In cases with an SACD also has a CD version on the disc, the CD will always be 2-channels, but the SACD layer may be either a 2 or multi-channel version.
One additional thing to point out is that the DSD file format coding used in SACDs is also now being used as one of of available formats used for Hi-Res audio downloads. This offers music listeners enhanced quality in a non-physical audio disc format.
Also Known As: Super Audio CD, Super Audio Compact Disc, SA-CD
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