High Definition Compatible Digital
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| Media type | Optical disc |
|---|---|
| Capacity | Typically up to 700 MB |
| Read mechanism | 780 nm wavelength semiconductor laser |
| Developed by | Pacific Microsonics Inc. |
| Usage | Audio storage |
| Extended from | Redbook |
High Definition Compatible Digital, or HDCD is a patented encode-decode process, now owned by Microsoft, that improves the audio quality of standard Redbook audio CDs, while retaining backward compatibility with existing Compact disc players.
At over 4000 titles, HDCD-encoded releases constitute a fraction of the total CD commercial music catalog, but many popular artists insist on using HDCD for their new releases in favour of technologies that don't need additional decoding hardware, e.g. Sony's SBM Direct(DSD). A web site has been devoted to listing HDCD recordings.
A number of universal CD and DVD players include HDCD decoding, and version 9 and above of the Windows Media Player software (on personal computers with a 24-bit sound card) are capable of decoding HDCD.
An HDCD-encoded CD usually, but not always, has the HDCD logo printed on the back cover. An HDCD logo may also be displayed in Windows Media Player 9 or above when an HDCD encoded disc is played.
New HDCD-encoded CDs are still being mastered and being added to various catalogs, and there is no additional cost for these HDCD recordings, unlike the higher prices charged for newer digital audio formats based on higher bit-rate media such as Super Audio CD (SACD) and DVD-Audio. However, as the technology still needs additional playback hardware support, and also as the industry has seen the rise of alternative technologies which do not require additional hardware, a reduction in HDCD releases has been seen, but a great number of new albums is still HDCD-encoded as well.
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HDCD encodes the equivalent of 20 to 24 bits worth of data in a 16-bit digital audio signal by using custom dithering, audio filters, and some reversible amplitude and gain encoding; Peak Extend, which is a reversible soft limiter and Low Level Range Extend, which is a reversible gain on low-level signals. There is thus a benefit at the expense of increase in noise. Many audiophiles like the end result.[1][2][3][4]
HDCD encoding places a control signal in the least significant bit of a small subset of the 16-bit Red Book audio samples (a technique known as in-band signaling). The HDCD decoder in the consumer's CD or DVD player, if present, responds to the signal. If no decoder is present, the disc will be played as a regular CD.
In itself, the use of the first bit in the dithered least significant bit stream does not degrade the sound quality on a non-HDCD player; it only decreases the signal-to-noise ratio by a minuscule amount. HDCD Peak Extension, if chosen in HDCD mastering, will apply compression to the peaks which will be audible in playback on a non-HDCD system which does not apply the approriate expansion curve.
HDCD provides several digital features, which the audio mastering engineer controls at his/her own discretion. They include:
- Dynamic range compression and expansion, with which virtually 4 more bits of dynamic range can be added to the musical signal.[citation needed]
- Precision digital interpolation filtering with multiple modes of operation, which can reduce alias distortion and temporal smearing, resulting in a more natural, open, and accurate sound reproduction.[citation needed]
HDCD technology was developed between 1986 and 1991 by "Professor" Keith O. Johnson and Michael "Pflash" Pflaumer of Pacific Microsonics Inc. It was made publicly available as HDCD-enabled audio CDs in 1995.
In 2000, Microsoft acquired the company and all of its intellectual property assets.
There have been a number of players and processors over the years that were capable of properly decoding the information from HDCDs. Included were those from California Audio Labs (USA), Mark Levinson/Madrigal (USA), Burmester (Germany), Cary (USA), Naim (UK), Linn (UK), Classe (Canada), A&R Cambridge Ltd (ARCAM) (UK), Rotel (Japan) and Cayin-Spark (China). Outboard DACs (digital to analog converters) were produced by Classe, Mark Levinson and others.
In 1998 Burr-Brown (now part of Texas Instruments) and Sanyo Electronics of Japan introduced low cost D to A converters with HDCD decoding included, allowing HDCD to be used in CD and DVD players in the $100 range. HDCD algorithms were included in DVD chips from many IC makers including Motorola and C-Cubed, allowing HDCD to be offered by mass-market DVD player makers such as Panasonic. As of 2007, a number of players continue to feature HDCD capability, including Harman Kardon, Denon, Marantz, Cary, Rotel, Mark Levinson, Shanling, and NAD (all higher-end manufacturers it should be noted).
There are no labels that record and release only HDCDs. Reference Recordings has produced many classical CDs in the HDCD format, which include new releases and have won numerous awards. Linn Recordings has a number of hybrid HDCD / SACDs, and also seem to enjoy a good reputation amongst music enthusiasts.
As for "mainstream" popular artists, Tool, The Grateful Dead, Jerry Garcia, Madonna, Mark Knopfler, King Crimson, Roxy Music (also Bryan Ferry), Van Halen, Joni Mitchell, Neil Young, Mannheim Steamroller, Dixie Chicks, The B-52s, NOFX and Mike Oldfield have released quite a few of their albums on HDCD. As of January 2007, there are roughly the same number of titles released on SACD as there are on HDCD CD's.
Windows Media Player 9, 10 or 11 running on Windows XP and Windows Media Player 11 running on Windows Vista are all capable of decoding and playing HDCDs on personal computers with a 24-bit sound card installed.[5][6] Media Player 9 indicates the presence of an HDCD by flashing the logo in the control bar at the bottom of the application window. This was removed from versions 10 and 11; if an HDCD is inserted into a burner with WMP 10/11 running the HDCD logo no longer appears.
This feature must be enabled by changing a WMP speakers setting involving 24-bit audio. The path to this setting is found in the Player's Options control panel which can be accessed from the Tools menu: Tools/Options/Devices/Speakers/Properties/Performance.[7]
Due to player design, the HDCD decoding is placed within the CD read chain. Thus, HDCD decoding can only be achieved whilst directly playing back HDCD formatted disks. The MS Windows Media Player software is not currently able to decode HDCD information present from ripped images of disks.[citations needed] However, Media Player 9 is able to recognize copies of HDCDs.[8]
Windows Media Player does not decode HDCD audio streams during ripping and the decoded encoded extra HDCD information is lost. By using a WAV output recorded plugin, it is possible to grab a perfect digital copy of a decoded HDCD stream, which can then be used for encoding into other formats.[citations needed]
Illustrate's dBpoweramp CDGrabber has a DSP effect which allows tracks from HDCDs to be ripped to 24-bit WAV files. The files have a bit rate of 2116.8 kbps and are 1.5 times as large as 16-bit WAV files. For example, King Sunny Ade's "Jigi Jigi Isapa" (from the odú~ album) has a 16-bit WAV size of 58.5MB, while the "24-bit" WAV file is 87.8MB. While the files will be listed as 24-bit, only 20 bits per sample contain actual data.[9]
A 24-bit capable sound card is required in order to play the files. Format conversion programs can also use these files to create 24-bit lossy and lossless files. The format, of course, must support 24-bit samples. ALAC, Apple's lossless codec, can only convert to 16-bit mode.
Many software players can play these files including foobar 2000, iTunes Player (iPod players, however, cannot play the files), Windows Media Player and Winamp.
- ^ "What is HDCD?". Retrieved on 2007-05-29.
- ^ "HDCD Encoder System". Retrieved on 2007-05-29.
- ^ "Process Overview". Retrieved on 2007-05-29.
- ^ "AES Paper". Retrieved on 2007-05-29.
- ^ Features of Windows Media Player 9 Series
- ^ Smart Jukebox Features
- ^ This information used to be available on the Microsoft website and the XP Help files. Extensive searches of both WMP 11 and Microsoft.com were unable to locate the directions.
- ^ The "HDCD" indicator comes on when a copy of a disc is placed into the burner.
- ^ dBPoweramp's DSP Effects page [1]; Local Help file for DSP Effects, CDGrabber Help files
- A list of HDCD CD's
- Growing user-compiled HDCD list
- Patent 5,479,168
- Patent 5,872,531
- Reference Recordings - Home of "Prof" Johnson's HDCD recordings
- Brochure of Model Two HDCD Processor (Encoder)
- Doom9 discussion thread about a command line HDCD decoder
