The compact disc launched
the digital audio revolution in 1982. CD fabrication
begins with the voltage produced by a microphone and
captured/recorded by a magnetic tape, hard drive, or
The amplitude of the microphone's voltage is sampled, looked at and measured, 44,100 times per second by an analog to digital converter, a sampling rate of 44.1KHz. The sampled voltage is compared to and assigned a value from a predetermined table of 65,536 values. The assigned-value is a close approximation of the originally sampled-voltage.
Each value is a 16-bit binary word from a numeric alphabet of two numbers, 0 & 1, defined as bits. The binary word is simply a string of 16 zeros or ones with a total of 65,536 possible permutations. Each bit location in the string represents a fixed percentage of the total possible voltage. Each bit in the string has its particular voltage turned on or off per its instructions: 0 = Off & 1 = On.
All 16 bits in the ON
position = total possible voltage.
The 1st bit in the string = half of the total possible voltage.
The 2nd bit = half of the 1st bit.
The 3rd bit = half of the 2nd bit.
The 4th bit = half of the 3rd bit.
This pattern continues to the 16th bit.
1111111111111111 = the total possible voltage.
00000000000 = 0 volts.
10000000000 = 1/2 of the total voltage.
01000000000 = 1/4 of the total voltage.
11000000000 = 3/4 of the total voltage.
A micron or micrometer = one millionth of a meter.
16-bit CD data embeds as a microscopic 0.5-micron wide
spiral track of injected pits onto the poly-carbonate molded
compact disc surface that begins near the center of the
disc. The injected-pits, covered in a reflective
aluminum layer, are protected by a top acrylic layer.
A laser targets the spiral track during playback as the disc
spins. The CD-pits and the area between the pits alter the
reflecting laser light. An optoelectric pickup
converts the reflected light into an electric current.
CD is a 16-bit code sampled at 44.1 thousand times per second.
DVD is a 24-bit code sampled at 96 thousand time per second.
DVD-A is 24-bit code sampled at 192 thousand times per second.
Blu-Ray is a 24-bit code sampled at 192 thousand times/second with up to 6 audio channels, or 92 thousand time/second with up to 8 audio channels.
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