ITU-T G.728 CELP
Speech Coder
by SYNTECH

Software Overview

The ITU G.728 standard is a 16-kbps algorithm for coding telephone bandwidth speech using low-delay 
code-excited linear prediction (CELP). The G.728 standard was designed to provide speech-quality 
equivalent to the G.721 32-kbps ADPCM. It is based on a standard analysis by synthesis CELP-coding 
technique with several modifications (short-excitation vectors and backward-adaptive predictions in 
order to reach a low coding delay, 2.5 ms).
The SYNTECH G.728  encoder/decoder is composed of two C-callable functions and runs full duplex on 
40+ MHz `C3x (including `C32).

Features and Benefits

•	Low-delay (2.5 ms) code-excited linear prediction
•	Compatible with Eonic VIRTUOSO©  operating system
•	Provides toll-quality speech at 16 kbps
•	Complies fully with every aspect of ITU G.728
•	Callable in TI TMS320 floating-point C

Processor and System Specifications

•	External memory: < 10 kword
•	Processor requirement:	40+ MHz
•	Internal memory:
		Coder: 94+105 words (stack)
		Decoder: 67+105 words (stack)
		Postfilter: 36 words
•	Minimum analog requirement: 14-bit linear A/D D/A 8 kHz

Usage Limitations or Performance Considerations

•	Performance data available on request

Algorithm Verification

•	The implementation is fully compliant with the ITU-T G.728 recommendation.

Availability

•	Available directly from SYNTECH SA
•	Compatible with Eonic VIRTUOSO -operating system
•	SYNTECH also offers real-time hardware for product integration

Company Background and Contact Information

SYNTECH, based at Sophia Antipolis, has developed high-quality DSP hardware and software products 
for applications in the following areas: multimedia, medical imagery, ultrasound, pursuit radar, 
filtering, geological radar, optical character recognition, meteorological image processing, 
security, robotics, instrumentation, process control, scientific calculations, signal recognition, 
and synthesis. The founders of SYNTECH are Mr. Simon Elkrief (President), a specialist in 
industrial data processing and automatization and Mr. Serge Serafini (General Director), a 
specialist in radar technology also the President of ANATECH, France, which conceives high 
technology DSP military acquisition and scientific products.

Contact:	SYNTECH
		Mr. R. Gauguey
		AREP Center
		Traverse des Brucs
		Sophia Antipolis
		06560 Valbonne
		France
		+ (33) 93 65 28 66
		Fax: + (33) 93 65 22 93
		e-mail: syntech@slnet.mc