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The number of possible values that an integer bit depth can represent can be calculated by using 2 n, where n is the bit depth. [1] Thus, a 16-bit system has a resolution of 65,536 (2 16) possible values. Integer PCM audio data is typically stored as signed numbers in two's complement format. [2]
The selection of the sample rate was based primarily on the need to reproduce the audible frequency range of 20–20,000 Hz (20 kHz). The Nyquist–Shannon sampling theorem states that a sampling rate of more than twice the maximum frequency of the signal to be recorded is needed, resulting in a required rate of greater than 40 kHz.
The audio bit rate for a Red Book audio CD is 1,411,200 bits per second (1,411 kbit/s) or 176,400 bytes per second; 2 channels × 44,100 samples per second per channel × 16 bits per sample. Audio data coming in from a CD is contained in sectors, each sector being 2,352 bytes, and with 75 sectors containing 1 second of audio.
A PCM stream has two basic properties that determine the stream's fidelity to the original analog signal: the sampling rate, which is the number of times per second that samples are taken; and the bit depth, which determines the number of possible digital values that can be used to represent each sample.
Using this technique, the audio data is stored as a sequence of fixed amplitude (i.e. 1-bit) values at a sample rate of 2.884 MHz, which is 64 times the 44.1 kHz sample rate used by CD. At any point in time, the amplitude of the original analog signal is represented by the density of 1's or 0's in the data stream.
The Signal-to-quantization-noise ratio is a multiple of the bit depth. Audio CDs use a bit depth of 16-bits, while DVD-Video and Blu-ray discs can use 24-bit audio. The maximum dynamic range of a 16-bit system is about 96 dB, [10] while for 24 bit it is about 144 dB.
High-resolution audio (high-definition audio or HD audio) is a term for audio files with greater than 44.1 kHz sample rate or higher than 16-bit audio bit depth. It commonly refers to 96 or 192 kHz sample rates. However, 44.1 kHz/24-bit, 48 kHz/24-bit and 88.2 kHz/24-bit recordings also exist that are labeled HD audio.
For example, CD audio uses 16 bits per sample, and therefore it will have quantization noise approximately 96 dB below the maximum possible sound pressure level (when summed over the full bandwidth) The amount of space required to store PCM depends on the number of bits per sample, the number of samples per second, and the number of channels ...