First phase of CD:
"Each audio sample is a
signed 16-bit
two's complement integer, with sample values ranging from −32768 to +32767. The source audio data is divided into frames, containing twelve
samples each (six left and right samples, alternating), for a total of 192 bits (24 bytes) of audio data per frame
2nd stage:
"
This stream of audio frames, as a whole, is then subjected to
CIRC encoding, which segments and rearranges the data and expands it with
parity bits
in a way that allows occasional read errors to be detected and
corrected. CIRC encoding also interleaves the audio frames throughout
the disc over several consecutive frames so that the information will be
more resistant to
burst errors.
Therefore, a physical frame on the disc will actually contain
information from multiple logical audio frames. This process adds 64
bits of
error correction data to each frame. After this, 8 bits of
subcode or subchannel data are added to each of these encoded frames, which is used for control and addressing when playing the CD.
3rd stage:
"
CIRC encoding plus the subcode byte generate 33-bytes long frames,
called "channel-data" frames. These frames are then modulated through
eight-to-fourteen modulation
(EFM), where each 8-bit word is replaced with a corresponding 14-bit
word designed to reduce the number of transitions between 0 and 1. This
reduces the density of
physical pits
on the disc and provides an additional degree of error tolerance. Three
"merging" bits are added before each 14-bit word for disambiguation and
synchronization. In total there are 33 × (14 + 3) = 561 bits. A 27-bit
word (a 24-bit pattern plus 3 merging bits) is added to the beginning of
each frame to assist with synchronization, so the reading device can
locate frames easily. With this, a frame ends up containing 588 bits of
"channel data" (which are decoded to only 192 bits music).
And if that is not enough:
"The smallest entity in a CD is a channel-data
frame, which
consists of 33 bytes and contains six complete 16-bit stereo samples: 24
bytes for the audio (two bytes × two channels × six samples = 24
bytes), eight CIRC error-correction bytes, and one
subcode byte. As described in the "Data encoding" section, after the EFM modulation the number of bits in a frame totals 588.
On a Red Book audio CD, data is addressed using the MSF scheme, with timecodes expressed in minutes, seconds and another type of frames
(mm:ss:ff), where one frame corresponds to 1/75th of a second of audio:
588 pairs of left and right samples. This timecode frame is distinct
from the 33-byte channel-data frame described above, and is used for
time display and positioning the reading laser. When editing and
extracting CD audio, this timecode frame is the smallest addressable
time interval for an audio CD; thus, track boundaries only occur on
these frame boundaries. Each of these structures contains 98
channel-data frames, totaling 98 × 24 = 2,352 bytes of music. The CD is
played at a speed of 75 frames (or sectors) per second, thus 44,100
samples or 176,400 bytes per second.
And lots more even more complicated data stuff.
Naturally I am not making the stuff up, I stole it from a Wiki entry.
I remember back in the late 1980's reading a book which was all about the complexity of the CD. It had all that info about how CDs are encoded, and decoded.
So CDs are not just some reading simple zeros and ones...
They read really really complicated zeros and ones!
(since yes indeed the transition (All transitions!) is a one, and all the others are zeros.
And not pits are one and lands are the other. LOL.
