Create an Account
username: password:
 
  MemeStreams Logo

44100 Explained

search

Hijexx
Picture of Hijexx
My Blog
My Profile
My Audience
My Sources
Send Me a Message

sponsored links

Hijexx's topics
Arts
  Movies
   Documentary
  Electronic Music
Business
  Finance & Accounting
  Telecom Industry
Games
Health and Wellness
Home and Garden
Miscellaneous
  Humor
Current Events
Recreation
Local Information
Science
  Biology
Society
  Politics and Law
   Civil Liberties
    Internet Civil Liberties
  Media
Sports
Technology
  Computer Security
  Linux
  High Tech Developments

support us

Get MemeStreams Stuff!


 
44100 Explained
Topic: Miscellaneous 4:09 pm EST, Dec 27, 2002

From John Watkinson, The Art of Digital Audio, 2nd edition, pg. 104:

In the early days of digital audio research, the necessary bandwidth of about 1 Mbps per audio channel was difficult to store. Disk drives had the bandwidth but not the capacity for long recording time, so attention turned to video recorders. These were adapted to store audio samples by creating a pseudo-video waveform which would convey binary as black and white levels. The sampling rate of such a system is constrained to relate simply to the field rate and field structure of the television standard used, so that an integer number of samples can be stored on each usable TV line in the field. Such a recording can be made on a monochrome recorder, and these recording are made in two standards, 525 lines at 60 Hz and 625 lines at 50 Hz. Thus it is possible to find a frequency which is a common multiple of the two and is also suitable for use as a sampling rate.

The allowable sampling rates in a pseudo-video system can be deduced by multiplying the field rate by the number of active lines in a field (blanking lines cannot be used) and again by the number of samples in a line. By careful choice of parameters it is possible to use either 525/60 or 625/50 video with a sampling rate of 44.1KHz.

In 60 Hz video, there are 35 blanked lines, leaving 490 lines per frame or 245 lines per field, so the sampling rate is given by :

60 X 245 X 3 = 44.1 KHz

In 50 Hz video, there are 37 lines of blanking, leaving 588 active lines per frame, or 294 per field, so the same sampling rate is given by

50 X 294 X3 = 44.1 Khz.

The sampling rate of 44.1 KHz came to be that of the Compact Disc. Even though CD has no video circuitry, the equipment used to make CD masters is video based and determines the sampling rate.



 
 
Powered By Industrial Memetics
RSS2.0