ITU G.726
ADPCM Waveform Coder
for TMS320C5x
by DSP Software Engineering, Inc.

Software Overview

The G.726 ADPCM waveform coder software is an implementation of ITU (formerly CCITT) G.726 for the 
TMS320C5x. G.726 is an international standard for encoding 8-kHz sampled-audio signals for 
transmission over 16-, 24-, 32-, and 40-kbps channels. G.726 is a superset of ITU recommendations 
G.721 and G.723. G.726 provides 4 kHz of audio bandwidth with a processing delay equal to the 
processing frame size.
G.726 encodes 13- or 14-bit linear-PCM samples, or 8-bit G.711 m-law/A-law encoded data, into 2-, 
3-, 4-, or 5-bit code words. G.726 has numerous applications in products that require high-quality, 
robust audio. These applications include videoconferencing, multimedia, ISDN communications, and 
flight recording.

Features and Benefits

•	C-callable functions
•	ITU G.721 and G.723 compatible
•	In-band synchronization capable
•	SPOX compatible
•	User-selectable input and output formats: 8-bit m-law or A-law, 13-bit or 14-bit linear PCM

Processor and System Requirements

•	Devices supported: TMS320C5x
•	Algorithm category: Vocoder
•	Requirements:
All memory requirements are in units of 16-bit words. The MIPs ratings presented require the listed 
amounts of dual-access RAM, zero-wait-state program and data memory, and sample by sample 
processing. All measurements were made using an executable demonstration built for a third-party PC 
plug-in board.
Function
MIPS
DARAM
Data
Program
Encoder (half duplex)
11
0.13 k
0
2.2 k
Decoder (half duplex)
12
0.13 k
0
2.2 k
Full Duplex*
23
0.25 k
0
2.2 k
* Read-only program memory is shared by the encoder and decoder.

User Functions

The G.726 implementation consists of two independent, C-callable functions. One that performs  
encoding or decoding operations, and one that creates the G.726 object. The encoder and decoder 
interface with 13- or 14-bit linear- or 8-bit logarithmic-PCM samples and 2-, 3-, 4-, or 5-bit code 
words.
G.726 Encoder/Decoder
create_g726 (...)
Creates and initializes a G.726 object for either encode or decode operations.
g726 (...)
Performs G.726 encoding or decoding using the created object.

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