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The standard audio sampling rate used by professional digital video equipment such as tape recorders, video servers, vision mixers and so on. This rate was chosen because it could reconstruct frequencies up to 22 kHz and work with 29.97 frames per second NTSC video – as well as 25 frame/s, 30 frame/s and 24 frame/s systems.
For example, Compact Disc Digital Audio and Digital Audio Tape systems use different sampling rates, and American television, European television, and movies all use different frame rates. Sample-rate conversion prevents changes in speed and pitch that would otherwise occur when transferring recorded material between such systems.
Analog audio is often recorded by sampling it 44,100 times per second, and then these samples are used to reconstruct the audio signal when playing it back. The 44.1 kHz audio sampling rate is widely used due to the compact disc (CD) format, dating back to its use by Sony from 1979.
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.
The details of media encoding, such as signal sampling rate, ... audio 2 – 6 (equal to sampling rate) 4000 ÷ sample rate 4 [note 4] aptX audio RFC 7310 dynamic
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.
It can also be corrected in the digital domain using a drift correction algorithm. Such an algorithm compares the relative rates of two or more devices and drops or adds samples from the streams of any devices that drift too far from the master device. Sample rate will also vary slightly over time, as crystals change in temperature, etc.
For audio, this type of encoding reduces the number of bits required per sample by about 25% compared to PCM. Adaptive differential pulse-code modulation (ADPCM) is a variant of DPCM that varies the size of the quantization step, to allow further reduction of the required bandwidth for a given signal-to-noise ratio .