05-11-2018, 04:56 PM
13 bit PCM was good enough for audio with well controlled levels which was going to be utilised by FM transmitters. If correctly dithered to avoid unpleasant effects 13 bits gives you about 80dB s/n ratio which is better than an FM transmission. It was also a lot better than the analogue circuits previously used from the studios to the transmitters. Getting stereo beyond London and Wrotham was a horrible business before PCM. I can remember Angus McKenzie writing in Hifi News about the BBC's failure to get decent stereo even as far as Birmingham.
Required number of bits is always an interesting debate. Assuming you use dithering correctly, it'ssimply a matter of what signal to noise ratio you want to achieve. Roughly 6dB per bit. If audio levels are not accurately controlled then you need more bits. My understanding is that 16 bits is fine for controlled levels (think CD) while in the studio you want at least 20. In practice I suspect that a lot of modern audiio kit uses 32 bt arithmetic simply because it costs nothing. Audio ADCs can get to 20 bit accuracy with some certainty. Any more than that is probably wishful thinking.
Required number of bits is always an interesting debate. Assuming you use dithering correctly, it'ssimply a matter of what signal to noise ratio you want to achieve. Roughly 6dB per bit. If audio levels are not accurately controlled then you need more bits. My understanding is that 16 bits is fine for controlled levels (think CD) while in the studio you want at least 20. In practice I suspect that a lot of modern audiio kit uses 32 bt arithmetic simply because it costs nothing. Audio ADCs can get to 20 bit accuracy with some certainty. Any more than that is probably wishful thinking.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
