Originally Posted by jamiedonnelly
...why for TV/Film the sample rate is 48 kHz....
Reverse chronological basis for 48kHz digital audio standard: *1981
: AES adopts 48kHz as professional digital audio sampling rate standard. 48kHz was proposed by Alastair Heaslett of Ampex
. Heaslett's rationale was based on the following considerations:
1) Data "block" (integral samples) boundaries should coincide with frame boundaries of NTSC/PAL/SECAM/Film sound track (for ease of editing).
2) System clock frequency should be multiple of NTSC/PAL/SECAM/Film horizontal frequency (for lock).
3) System clock frequency should be multiple of sampling frequency.
4) Sampling frequency should be twice that (Nyquist theorem) of 22.5kHz (20kHz human hearing range + 2.5kHz, so anti-aliasing filter has required attenuation to prevent aliasing components from appearing in audio passband, ie > 45kHz). *1977
(Snowbird, Utah): AES Standards Committee Meeting
Ampex want 48kHz
SMPTE want 60kHz
3M want 50kHz
Soundstream want 50kHz
BBC/EBU want 32kHz (broadcast Sat uplink; Euro telecom at 8kHz)
Matsushita want 44.1kHz
Philips/Sony want 44.1kHz
Technics want 49kHz
Denon want 47.25kHz
Mitsubishi/Teac want 47.5kHz
Toshiba want 50kHz
Hitachi want 35kHz *1954
RCA convinces FCC (NTSC) to adopt frame-drop system so that sound sub-carrier frequency did not produce visible beat in color sub-carrier frequency. FCC refused to change sound sub-carrier, but agreed to change color sub-carrier. *1941:
FCC (NTSC) adopts field refresh rate exactly matching 60Hz AC power in U.S., to avoid beating intermodulation (rolling bars on screen).