m-law/A-law Detector
for TMS320C3x/'C4x
by DSP Software Engineering, Inc.

Software Overview

The DSPSE m-law/A-law detector differentiates between ITU (formerly CCITT) G.711 m-law encoded data 
and ITU G.711 A-law encoded data. The ITU G.711 m-law standard is predominantly used in North 
America and Japan and the ITU G.711 A-law standard is predominantly used in Europe.
This m-law/A-law Detector implementation works on signals with any SNR and is not dependent on the 
compressed data's underlying signal type. With the detection time configured for 250 ms or more of 
8-kHz samples, the detector can differentiate between m-law and A-law on signals with power as low 
as -80 dB0. With the detection time configured for 5 ms of 8-kHz samples, the detector can 
differentiate on signals with power as low as -40 dB0.

Features and Benefits

•	ITU G.711 m-law and A-law detection
•	Independent C-callable functions
•	Operates on standard 64-kbps and non-standard 56-kbps and 48-kbps coded signals
•	User-selectable processing frame size
•	Independent of coded signal type
•	Object-based interface
•	Requires minimal signal power
•	SPOX compatible

Processor and System Requirements

•	Devices supported: TMS320C3x, TMS320C4x
•	Algorithm category: Telecommunications
•	Requirements:
All memory requirements are in units of 32-bit words. The MIPs ratings presented require the listed 
amounts of on-chip, zero-wait-state program and data memory, a processing frame size of 16 samples, 
and the detect time configured for 384 milliseconds. All measurements were made using an executable 
demonstration built for a third-party PC plug-in board.
Function
MIPS
Chip RAM
Data
Program
m-law/A-law Detector
0.48
0
0.4 k
0.4 k

User Functions

The m-law/A-law detector software consists of a C-callable function that performs G.711 m-law/A-law 
detection. It also includes functions that reflect the implementation's object-based interface. The 
detector interfaces with arrays of ITU G.711 code words and returns a status word.
m-Law/A-Law Detector
UAD_create (...)
Dynamically allocates and initializes data memory for detector
UAD_delete (...)
Frees detector's usage of data memory
UAD_detect (...)
Determine if a frame of samples is m-law or A-law G711 codewords.

Algorithm Verification

•	Call DSPSE for verification details

Availability

•	Source and object code currently available for licensing.

Company Background and Contact Information

DSP Software Engineering, Inc. (DSPSE), founded in 1989, is a leading provider of highly-complex 
digital-signal-processing software used in telecommunications and multimedia applications such as 
computer telephony, digital wireless, PSTN, and satellite communications, and videoconferencing. 
DSPSE sells its products to OEMs and directly to manufacturers of telecommunications products. 
DSPSE provides the complete solution to your DSP needs with DSP solution software packages and 
individual DSP software component algorithms and expert service.

Contact:	DSP Software Engineering, Inc.
		175 Middlesex Turnpike
		Bedford, MA 01730  USA
		(617) 275-3733
		Fax: (617) 275-4323
		e-mail:  info@dspse.com
		www:  http://www.dspnet.com