That's not a particularly accurate explanation. Nothing is scattered across the disk. That would require random reading of the disk and no CDDA works like that. The data is divided into blocks. Each block contains parity bits sufficient to rebuild the blocks before and after it with an extremely high level of reliability. All blocks are read sequentially. The LAST thing you want to make a single storage medium do is perform random read operations. It's only advantageous in RAID 5 arrays where the data really is scattered across the array and can be optimally read non-sequentially and reconstructed by an intelligent controller, and there's no a CD player in the world that complex.
That's not a particularly accurate explanation. Nothing is scattered across the disk. That would require random reading of the disk and no CDDA works like that. The data is divided into blocks. Each block contains parity bits sufficient to rebuild the blocks before and after it with an extremely high level of reliability. All blocks are read sequentially. The LAST thing you want to make a single storage medium do is perform random read operations. It's only advantageous in RAID 5 arrays where the data really is scattered across the array and can be optimally read non-sequentially and reconstructed by an intelligent controller, and there's no a CD player in the world that complex.
vwestlife
Super Member
WAV is Microsoft's file format for storing PCM audio. Originally every software and hardware vendor had their own file format for audio; Apple had AIFF (which they still use today), Sun Microsystems had AU, Creative Labs (Sound Blaster) had VOC, Tandy DeskMate had SND, etc. But as Windows became the dominant operating system, most people and companies standardized on WAV files.
Mystic
We're all born mad
Homemade "CDs" can come in as great a variety of audio codecs (formats) as are available. Playback on CDPs, computers, and other types of "players" might be a challenge re: a few types of audio codecs.
DaveVoorhis
Addicted Member
Yes, but of course those usually aren't audio CD aka "Red Book" format. They're typically one of several CDROM formats which can store anything, or possibly one of various "Enhanced CD" formats for combining audio-only tracks for use on CD players and content for use on computers.
StimpyWan
Addicted Member
This is only correct for CD-Rom data, but not audio. Rom data is repeated in adjacent sectors, so a scratch won't prevent the data for being recovered. Audio does not have any data redundancy. Scratches can be severe enough to prevent audio pits and lands from being properly read, which can render a CD unplayable. CD players do have build in error correction, but even that may not be enough to recover audio data from a radial scratch.
As to a Red Book CD-DA disc, it's only WAV. That's all a stand alone CD player can recognize and play. Anything else is considered a CD-Rom.
Edit - Not trying to pile on Artie. I didn't see ReactiveLoad's excellent response before posting.
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vwestlife
Super Member
There are numerous other official CD formats:
* CD Video, a LaserDisc with some audio-only CD tracks
* Video CD (VCD), which fits an hour of low-resolution video and 224 kbps MPEG-I Layer II (MP2) audio onto a CD.
* Super Video CD (SVCD), same as above with improved resolution
* CD plus Graphics (CD+G), for Karaoke.
* Photo CD, an early digital photo storage format.
* CD Interactive (CD-i), video game system by Philips.
* CDTV, video game system by Commodore.
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StimpyWan
Addicted Member
True. But while players capable of supporting these formats can play CD-DA audio discs, a regular CD player cannot play those. So, those formats are not CD-DA. They're variations of CD-Rom and CD-V formats.
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cpt_paranoia
Addicted Member
That's not quite true. Whilst it's not fully duplicated, as in some RAID schemes, the CIRC (Cross-Interleaved Reed-Solomon) coding includes redundant error coding and interleaving, to provide fairly impressive protection against damage.
https://en.m.wikipedia.org/wiki/Cross-interleaved_Reed–Solomon_coding
StimpyWan
Addicted Member
I should have been clearer in my earlier statement. Audio is cut as a single stream during glass mastering. There is no data redundancy. Then the CIRC process is applied during read and playback, if needed, by processing built into the CD player.
cpt_paranoia
Addicted Member
CIRC is burnt into the 'glass mastering'; the whole point is to error protect the stream of pits as printed into the spiral on the disc. RS error schemes are active encoding of the transmitted (or recorded) data. You cannot correct errors without a redundant encoding of this nature.
JoeESP9
ESL's & tubes since 83
What's on a Red Book CD is not WAV files. WAV is the file type that Microsoft and Windows natively use.
StimpyWan
Addicted Member
This makes me wish that I was still working in CD Replication and pressing. I ran the glass mastering laser beam recorder cutting lathes for 8 years. I used to have these kind of discussions with my boss. He was very familiar with CD encoding. I could have asked him for clarification. Heck, the scientist that designed our lathes worked there too. I could have spoken to him as well.
StimpyWan
Addicted Member
Wav or Aiff. It's uncompressed digital audio. PCM encoded to Red Book CD.
JoeESP9
ESL's & tubes since 83
Sorry what's on a Red Book CD is neither WAV or AIFF. To prove this, take any commercial Red Book CD, insert it into a computer's optical drive and read the directory. You will see a list of zero byte CDA files.
We are in agreement about Red Book CD's not being compressed.
We are in agreement about Red Book CD's not being compressed.
DaveVoorhis
Addicted Member
"Red Book CD", WAV, and AIFF are three different ways of representing PCM (Pulse Code Modulated) digital audio. The latter two are file formats. The first is a physical disk format. All can be equivalent in content, but not the same. An audio CD contains PCM digital audio, it does not contain WAV or AIFF files, or files at all.
However, a computer operating system or software can make an audio CD appear to have files. This is a function of the operating system or software, not the audio CD.
StimpyWan
Addicted Member
You're talking about the file structure of the TOC. The Table Of Contents. The TOC is the first data encoded to a disc. It's contained in the first 150 sectors of the disc, in the lead-in, before the audio. The TOC contains the timecode and the PQ Subcode data. Just like looking at the table of contents of a book, a CD TOC tells the player where each track begins and ends, pause times, track length, and disc length. Info on Emphasis, ISRC Codes, HDCD Encoding, and CD Text is in the TOC as well.
JoeESP9
ESL's & tubes since 83
No! I'm only saying that what's on a Red Book CD is neither WAV, AIFF, MP3 or any of a number of file types that are routinely used with computers.
StimpyWan
Addicted Member
I know that too. A CD-DA disc has no files of any type. Files would make it a Rom disc. I was only saying WAV or AIFF formats are used for creating a CD, since they're uncompressed. Those formats are then PCM encoded for Red Book mastering.
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