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Sample rate Bit rate Bits per sample Latency CBR VBR Stereo Multichannel G.711: companding A-law or μ-law, PCM: 8 kHz 64 kbit/s 8 bit 125 μs (typical) Yes No No No G.711.0: Lossless compression of G.711: 8 kHz 0.2–65.6 kbit/s 8 bit 5–40 ms No Yes No No G.711.1: MDCT, A-law, μ-law: 8, 16 kHz 64, 80, 96 kbit/s 16 bit 11.875 ms Yes Yes No No
The sampling frequency or sampling rate, , is the average number of samples obtained in one second, thus = /, with the unit samples per second, sometimes referred to as hertz, for example 48 kHz is 48,000 samples per second.
An analog signal (in red) encoded to 4-bit PCM digital samples (in blue); the bit depth is four, so each sample's amplitude is one of 16 possible values (16 = 2 4). In digital audio using pulse-code modulation (PCM), bit depth is the number of bits of information in each sample, and it directly corresponds to the resolution of each sample
Max sample depth (bits) Max sample rate (Hz) Applications Notes Ref; Analog Devices: AD1848 1992 Multiple stereo channels, unlimited 16 48,000 Original Windows Sound System card by Microsoft, Ensoniq Soundscape S-2000 and Elite cards Digital-to-analog codec chip, 2-channel stereo input/output [93] ARM Ltd. VIDC20: 1994 8 16 44,100 Risc PC ...
Each companded sample is quantized as 8 bits, resulting in a 64 kbit/s bit rate. G.711 is a required standard in many technologies, such as in the H.320 and H.323 standards. [ 1 ] It can also be used for fax communication over IP networks (as defined in T.38 specification).
Different bit depth/sampling rate/channel combinations can be used on a single disc. For instance, a DVD-Audio disc may contain a 96 kHz/24-bit 5.1-channel audio track as well as a 192 kHz/24-bit stereo audio track. Also, the channels of a track can be split into two groups stored at different resolutions.
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.
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.