ITU G.726
ADPCM Waveform Coder
for TMS320C3x/'C4x
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 
TMS320C3x. 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

•	User-selectable processing frame size
•	ITU G.721 and G.723 compatible
•	Object-based interface
•	Independent, C-callable functions
•	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: TMS320C3x, TMS320C4x
•	Algorithm category: Vocoder
•	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, and a processing frame size of 10 
samples. All measurements were made using an executable demonstration built for a third-party PC 
plug-in board.
Function
Avg MIPS*
Chip RAM
Data
Program
Encoder (half duplex)
3.9
0.7 k
4 k
0.9 k
Decoder (half duplex)
4.6
0.7 k
4 k
1 k
Full Duplex*
8.5
0.8 k
8 k
1.8 k
*   Significant portions of read-only program and data are shared by the encoder and decoder.

User Functions

The G.726 implementation consists of two independent, C-callable functions that perform encoding 
and decoding operations. It also includes functions that reflect the implementation's object-based 
interface. The encoder and decoder interface with arrays of 13- or 14-bit linear or 8-bit 
logarithmic PCM samples and 2-, 3-, 4-, or 5-bit code words.
G.726 Encoder
APE_create (...)
Dynamically allocates and initializes data memory for encoder
APE_delete (...)
Frees encoder's usage of dynamically-allocated data memory
APE_encode (...)
Encodes a frame of PCM samples into a frame of code words
G.726 Decoder
APD_create (...)
Dynamically allocates and initializes data memory for decoder
APD_delete (...)
Frees decoder's usage of dynamically-allocated data memory
APD_decode (...)
Decodes a frame of code words into a frame of PCM samples

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. 

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