Low-Delay
Vector Quantization
Voice Coder
by D2 Technologies, Inc.

Software Overview

D2's Low-Delay Vector Quantization (LDVQ) voice coder algorithm module compresses either linear or 
codec voice data to 16 kbps at significantly lower complexity than the ITU standard G.728 coder. 
The quality of the LDVQ meets the "toll quality" requirements of speech applications.
Designed to the VP Open interface, the LDVQ voice coder module easily integrates with other VP Open 
modules, runs in real-time concurrently with other VP Open modules, and handles any number of voice 
ports assigned to the DSP. Like all of D2's algorithm modules, LDVQ voice coder consists of robust 
software that is rigorously tested.

Features and Benefits

•	Compresses linear or codec voice data to 16 kbps
•	Low complexity
•	"Toll quality" for speech applications
•	Low delay of under 1.5 msec

Processor and System Specifications

•	Devices supported: TMS320C2xx, TMS320C5x
•	Algorithm category: Vocoder
•	DSP resource required:
TMS320C2xx (Est.)
TMS320C5x (Est.)
Program memory
Encoder: 4.5 kwords
Decoder: 2.2 kwords
Encoder: 4 kwords
Decoder: 2 kwords
Data memory/voice port
300 words
300 words
Processor loading
worst case
Enocder: 11 MIPS
Decoder: 5.5 MIPS
Enocder: 10 MIPS
Decoder: 5 MIPS

Usage Limitations or Performance Considerations

•	The host, voice data input and output, memory allocation, and module to module communication 
interfaces must conform to VP Open as described in the VP Open Software Interface Specification.

Algorithm Verification

D2's LDVQ voice-coder algorithm module is validated through the following suite of tests:
•	Voice input tests with different telephone-band voice samples and background noise conditions
•	Mean Opinion Score (MOS) test per ITU-T P.80 absolute category rating
•	Numerical stability tests with artificial signal such as tones and extreme values
•	Code-error tests for stationary and non-stationary errors
•	VP Open interface validation – the LDVQ module is integrated with other VP Open modules and 
tested in real-time on the D2 VDS50 system

Availability

Will be available for the TMS320C5x and TMS320C2xx 2Q 1996. A demonstration package will be 
available for the TI EVM50 DSP board. A demonstration cassette tape is currently available.

Company Background and Contact Information

D2 Technologies, Inc. was founded by David Y. Wong and David M. Lindsay to help companies innovate 
telecommunications and information products with voice processing technology, which include 
telephony and voice algorithms, real-time system software, and development services.

Contact:	D2 Technologies, Inc.
		Attn:  Product Sales
		104 West Anapamu Street
		Suite J
		Santa Barbara,  CA 93101
		(805) 564-3424
		Fax:  (805) 966-2144
		e-mail:  sales@d2tech.com