G.722
Audio Coder
by Atlanta Signal Processors, Inc.

Software Overview

G.722 is a ITU audio encoding/decoding standard that provides 7-kHz audio bandwidth at 64 kbps and 
has been fully implemented on a single TI TMS320C3x DSP.  The coding system used is sub-band 
adaptive differential pulse-code modulation (SB-ADPCM). The input signal to the coder is digitized 
using a 14-bit or 16-bit A/D sampled at 16 kHz. Output from the encoder is 8 bits at an 8-kHz 
sample rate for 64 kbps, which can be stored to disk for later playback. The decoder operates in 
exactly the opposite fashion. An 8-bit coded input signal is decoded by the SB-ADPCM decoders.  The 
result is a 16-kHz sampled output. The overall compression ratio of the G.722 audio coder is 4 to 
1.
G.722 was designed for high-quality speech applications in the telecommunications market, but may 
be used in a variety of applications, including audio coding for medium-quality audio systems. 
Applications for audio compression include any application where compression and/or transmission of 
voice and audio data is needed, such as voice mail systems, audio-annotated text for multimedia 
systems, T1 multiplexers, and video teleconferencing.

Features and Benefits

•	Code is C callable, relocatable, and SPOX compatible
•	High-quality 64-kbps audio coder offering a 4:1 compression of 16-kHz audio data
•	Fully compliant with ITU G.722 specification
•	Full-duplex real-time capability on a single TMS320C3x DSP

Processor and System Specifications

•	Memory requirement: 
2402 words program, 320 words data
•	Processor loading (33-MHz, TMS320C3x with zero-wait-state SRAM)
58% full duplex, or 30% encoder, 25% decoder, 3% I/O
•	Minimum analog requirement:
TI TLC32046 or similar 16-bit, 16-kHz AIC
•	Ready to run on the Elf DSP Platform from Atlanta Signal Processors
•	Portable to any TMS320C3x target platform

Usage Limitations or Performance Considerations

•	The input signal to the coder is digitized using a 14-bit or 16-bit A/D sampled at 16 kHz. Output 
from the encoder is 8 bits at an 8-kHz sample rate for 64 kbps.

Algorithm Verification

•	Complies with the G.722 standard.

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