Multi-Rate VQ Voice Coder
by D2 Technologies, Inc.

Software Overview

D2's Multi-Rate Vector Quantization (MRVQ) voice coder algorithm module compresses either linear or 
codec voice data to bit rates of 5.2 kbps to 9.6 kbps at significantly lower complexity than any 
voice coders at comparable bit rates and speech quality. The quality of the MRVQ voice coder is 
"sub-toll," but meets the requirements of almost all speech applications. The speech is highly 
intelligible and the quality is very natural, preserving all of the characteristics of the 
speaker's voice. It is also robust for multi-speaker, music, etc.
Designed to the VP Open interface, the MRVQ 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, the MRVQ voice coder consists of 
robust software that is rigorously tested.

Features and Benefits

•	Compresses the voice data to rates between 5.2 kbps and 9.6 kbps
•	Lower complexity at higher bit rates
•	Natural and intelligible quality
•	Robust for different voices, multi-talker and music input

Processor and System Specifications

•	Devices supported: TMS320C2xx, TMS320C5x
•	Algorithm category: Vocoder
•	Processor resource required:
TMS320C2xx (Est.)
TMS320C5x (Est.)
Program memory
6 kwords for encoder,
2 kwords for decoder
5–6 kwords for encoder,
1.5–2 kwords for decoder
Data memory/port
500 words
500 words
Processor loading
(worst case)
9.6 kbps: 8 MIPS (encoder), 2.2 MIPS (decoder)
7 kbps: 10 MIPS (encoder), 2.2 MIPS (decoder)
5.2 kbps: 10 MIPS (encoder), 
2.2 MIPS (decoder)
9.6 kbps: 7.5 MIPS (encoder), 
2 MIPS (decoder)
7 kbps: 9 MIPS (encoder),
2 MIPS (decoder)
5.2 kbps: 9 MIPS (encoder), 2 MIPS (decoder)

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 MRVQ voice coder algorithm module is validated through the following suite of tests:
•	Voice-input quality tests with different telephone band voice samples, and background noise 
conditions, music, etc.
•	Mean Opinion Score test as per ITU-T P.80 specification for 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 MRVQ module is integrated with other VP Open modules and 
tested in real-time on the D2 VDS50 system 

Availability

Scheduled for release 1Q 1996 for the TMS320C5x and 2Q 1996 for the TMS3202xx. A demonstration 
cassette tape is available.

Company Background and Contact Informatio

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