MPEG Audio Encoder
by Atlanta Signal Processors, Inc.

Software Overview

The MPEG (Moving Picture Experts Group) audio algorithm provides high-quality audio coding for mono 
and stereo signals. The compression ratio is adjustable over a wide range, delivering sound quality 
ranging from high fidelity CD-level down to approximately "toll" telephone quality. It is well 
suited for a variety of consumer and professional audio applications in digital broadcasting, home 
entertainment, multimedia, and telephony. The MPEG audio algorithm is standardized by the 
International Standards Organization.
The highest standard of signal quality is referred to as transparent quality, meaning that any 
coding artifacts in the reproduced sound are imperceptible to a trained listener. This algorithm 
can achieve transparent quality at a compression ratio of 6:1 using layer 2 coding and 4:1 using 
layer 1.

Features and Benefits

•	Mono, stereo, joint-stereo, and dual-channel modes 
•	Generates MPEG error-protection information
•	32 kHz, 44.1 kHz, 48 kHz-input sample rates
•	Compatible with the Texas Instruments TMS320AV110 MPEG audio decoder chip
•	Uses `C3x floating-point internally for high precision 

•	CPU loading (static memory):

Sample Rate (Hz)
Max %
60-ns
Mono
Max %
60-ns
Stereo
Max %
50-ns
Mono
Max %
50-ns
Stereo
32,000
35
70
35
60
44,100
50
45
85
48,000
55
45
90
These figures represent the encoder procedure percentage processor loading without I/O overhead, 
which was excluded as it varies widely between systems.
•	Memory requirements:
External: 17,288 words
Internal: 1,652 words
These figures do not include system-level code and additional input and output buffers.
•	Minimum analog requirement: 16-bit A/D, D/A

Usage Limitations or Performance Considerations

•	The free-format bit-rate mode of operation of the MPEG Audio layer 1 and layer 2 specification is 
not implemented at this time.
•	Note that a 50-ns (40-MHz) `C3x device, such as the ASPI Elf Coprocessor Board, is needed to 
perform stereo encoding at 44.1-kHz and 48-kHz sampling rates.

Algorithm Verification

•	Fully compliant with the ISO MPEG audio standard layers 1 and 2. Extensively test by several 
major multinational consumer electronics manufacturers.

Availability

•	Written by Texas Instruments and available now through Atlanta Signal Processors.

Company Background and Contact Information

Atlanta Signal Processors was founded in 1981 by Ronald W. Schafer, Thomas P. Barnwell III, and 
Russell M. Mersereau, three Professors of Electrical Engineering at the Georgia Institute of 
Technology with over 80 years of experience in the field. The company has focused its efforts on 
developing tools for professional signal-processing design engineers and now offers digital 
signal-processing hardware and software products to DSP designers worldwide.

Contact:	Atlanta Signal Processors, Inc.
		1375 Peachtree St. NE, Suite 690
		Atlanta, Georgia  30309-3115
		(404) 892-7265
		Fax: (404) 892-2512
		e-mail: aspi@aspi.com