On a similar subject, you may have noticed that the two most common sampling frequencies for digital audio are 44.1 kHz and 48 kHz (along with their multiples,

On a similar subject, you may have noticed that the two most common sampling frequencies for digital audio are 44.1 kHz and 48 kHz (along with their multiples, such as 88.2 kHz and 96 kHz). Why is that? Specifically, where did 44.1 kHz come from? It's because early digital audio, before compact discs existed, was done by recording data onto video cassettes by the use of an adapter that converted analog audio to digital, then generated a signal that looked (to the videotape recorder) like a video signal. In non-interlaced NTSC video, there are 30 frames per second, and 525 scan lines. But not all 525 are usable because of the vertical blanking interval. (Essentially that interval is just the time it takes for the CRT to move the electron beam back up to the top of the display.) So these adapters just encoded 3 samples' worth of data into a single row of video, and used 490 out of 525 lines because of the vertical blanking interval. And 3 * 490 * 30 == 44100, so 44100 samples per second. NTSC also has an interlaced mode, which is 60 fields per second (two interlaced fields equal one frame), but each field is half as many lines, so the math works out the same. PAL video is similar except that it is 25 frames per second instead of 60, so to compensate, when encoding audio into PAL video, there are 6/5 as many lines used, and 3 * 588 * 25 = 44100 as well. More info: https://en.wikipedia.org/wiki/44,100_Hz#Recording_on_video_equipment https://en.wikipedia.org/wiki/44,100_Hz#Recording_on_video_e...