Journal of the AES, vol. 46

It is my view that digital audio was made possible at that point, and between 1970 and 1980 numerous meetings were held between Philips and Sony. In order to understand the technical choices concerning sample resolution and such at that time one must look to what was happening with studio equipment and with digital audio in broadcasting. The BBC in the UK was one of the first to adopt digital sound, and they were working with a 13-bit distribution system for the transmitter network, sampled at 32 kHz. Stockham's experiments in 1972-3 with the Soundstream system involved sample rates averaging around 40 kHz, and he used computer tape as the means of storage, which made it practical to store data at 16 bit resolution because of the byte-orientated nature of computer data storage. 8 bits would have been too few, and 14 bits would have meant inefficient use of the storage space, so 16 bits seemed logical. Computer tape was really the only way of storing perhaps one hour of sound at the time. Towards the end of the 70s, (PCM) adapters were developed which used ordinary analogue video recorders as a means of storing digital audio data, since these were the only widely available devices with sufficient bandwidth. This helps to explain the choice of sampling frequency for the CD, because the number of video lines, frame rate and bits per line end up dictating the sampling frequency one can achieve if wanting to store 2 channels of audio. The sampling frequencies of 44.1 and 44.056 kHz were thus the result of a need for compatibility with the NTSC and PAL video formats used for audio storage at the time.