AET 2050 - DAW Production


2. Data Reduction for Audio

Objectives


Why Data Reduction?

As a data coding format, PCM is robust but inefficient. It requires data rate of 1.4 Mbit/s for 2 channels of 16 bits @ 44.1k.

Many contemporary delivery systems (such as those used on the Internet) require much lower data rates - as low as 128kbit/s per channel. This is more than 10 times data reduction needed.

Data Reduction Process

Direct data reduction

Instead of reducing the actual data, a system is needed that can represent the data in an coded form that uses less actual data.

Data Reduction Coding

Perceptual Coding

Perceptual coding is based on psychoacoustic principles which define how some audio is masked by other audio.

Critical Bands

Perceptual Coding Process

Application

Maximum Streaming Rates

Target Audience
Maximum Streaming Rate
Bozo 14.4 Kbps modem 10 Kbps
28.8 Kbps modem 20 Kbps
56 Kbps modem 34 Kbps
64 Kbps ISDN 45 Kbps
112 Kbps dual ISDN 80 Kbps
Corporate LAN 150 Kbps
256 Kbps DSL/cable modem 225 Kbps
384 Kbps DSL/cable modem

350 Kbps

512 Kbps DSL/cable modem 450 Kbps
786 Kbps DSL/cable modem 700 Kbps