CCRMA Music 252b [Winter 1997]:
Topic in Computer Music: Perceptual Audio Coding

* Course Description

The need for a significant reduction in bit-rate for wide-band digital audio signal transmission and storage has led to the development of psychoacoustics-based data compression techniques. In this approach the limitations of human hearing are exploited to remove inaudible components of audio signals. The degree of bit rate reduction achievable without sacrificing perceived quality using these methods greatly exceeds that possible using lossless techniques alone. Perceptual audio codecs are currently used in many applications including Digital Radio and Television, Digital Movie Sound, and Multimedia/Internet Audio. In this course, the basic principles of perceptual audio coding will be reviewed. Current and future applications (e.g. AC-3, MPEG) will be presented. In-class demonstrations will allow students to hear the quality of state-of-the-art implementations at varying bit-rates and they will be required to program their own simple perceptual audio codec during the course.

* Administrative Information

The course on Perceptual Audio Coding (Music 252) is offered during the 96-97 Winter quarter. The class will meet Friday afternoons from 4:15 pm to 6:00 pm in the CCRMA Ballroom (on the main floor at The Knoll).

Basic knowledge of signal processing and C programming.

You may sign up for one or three units. The one unit course does not involve the completion of a final project. You will be responsible only for completing the homework assignments. Signing up for three unit implies that at least three hours per week will be devoted to a project.

The final project consists of an independent study or programming project. The independent study project consists of research in psychoacoustics (e.g. temporal masking vs. simultaneous masking, pitch and critical bands excitations, binaural hearing), digital audio processing (e.g. analysis and comparison of different time to frequency mapping implementations), audio quality measurements (e. g. subjective vs. objective audio quality measurements), or application of audio codecs (analysis of different coding technologies and their applications). The programming project consists of the design and implementation of a simple audio codec. Groups of up to three students are recommended for the programming projects.

Requirements for the final project include a written proposal (one page) by the fourth week of the quarter, a written report by the ninth week of the quarter, and a presentation of the report by the end of the quarter. The aim of the report should be to fully document your study, project methodology and results. The written report is due by 5pm on Friday March 7, 1997. The final project presentations will take place on Friday March 14th, 1997.

The grade is based on attendance, homework, and final project.

Office hours:
Marina Bosi's office hours are by appointment on Friday afternoons from 6:00 pm to 7:00pm. It is best to make an appointment with Marina by e-mail (

Computer Usage:
You may use the computer of your choice. ANSI C is the preferred programming language for programming projects. Any student taking a course for credit has access to campus computing facilities - if you wish to use CCRMA computer facilities, please contact Fernando Lopez Lezcano (

* Tentative Lectures Outline, Winter 1996-97

* Recommended Reading

©1996 CCRMA, Stanford University. All Rights Reserved.
Created and mantained by Fernando Lopez-Lezcano,