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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 exact sampling rate of 44.1 kHz was inherited from PCM adaptors which was the most affordable way to transfer data from the recording studio ...
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.
Sampling rate used by the Mitsubishi X-80 digital audio recorder. 64,000 Hz Uncommonly used, but supported by some hardware [18] [19] and software. [20] [21] 88,200 Hz Sampling rate used by some professional recording equipment when the destination is CD (multiples of 44,100 Hz).
The DVD format uses the 48 kHz sampling rate, and its doublings. In digital audio, 48,000 Hz (also represented as 48 kHz or DVD Quality) is a common sampling rate. It has become the standard for professional audio and video. 48 kHz is evenly divisible by 24, a common frame rate for media, such as film, unlike 44.1 kHz. [i]
Both modulations require neighboring samples to reconstruct the original waveform; the more neighboring samples, the lower the frequency that can be encoded. DSD is 1-bit, has a sampling rate of 2.8224 MHz, and makes use of noise shaping quantization techniques in order to push 1-bit quantization noise up to inaudible ultrasonic frequencies.
ALAC supports up to 8 channels of audio at 16, 20, 24 and 32 bit depth with a maximum sample rate of 384 kHz. ALAC data is frequently stored within an MP4 container with the filename extension.m4a. This extension is also used by Apple for lossy AAC audio data in an MP4 container (same container, different audio encoding).
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.
Method 2 will work in more general cases, e.g. where the ratio of sample rates is not rational, or two real-time streams must be accommodated, or the sample rates are time-varying. See decimation and upsampling for further information on sample-rate conversion filter design/implementation.