ITU-RBS.642-1 High-
Quality Variable-Emphasis
Limiter
by M.B. International S.r.l.

Software Overview

The software limits the dynamic of input audio signal to a preset value, taking in account the 
effects of a pre-emphasis distorion as found in transmission circuits.
The algorithm reduces the level of audio signal by varying the frequency response and/or the total 
level, according to ITU-R BS.642-1.
Emphasis can be set to 50 ms, 75 ms, or to custom values. Attack and release time can be changed 
according to different standard.
Input and output audio signals are stereo and coded according to AES/EBU.

Features and Benefits

•	Lower cost than analog
•	Very efficient assembly-optimized language code
•	Absolute stability—no periodical recalibration
•	Program is downloaded to internal RAM for fast execution
•	First class THD, noise level, and spurious response
•	Absolute precision—guarantees absence of illegal codes due to values outside preset range

Processor and System Requirements

•	Supported on `C3x ~ 50 or 60 MHz
•	Audio input and output via serial port
•	Input sampling rate: 32, 44.1, 48 and 192 k samples ~ 16 to 24 bits
•	Output sampling rate same as input or 192 k samples @ 16 to 24 bits

Usage Limitations or Performance Considerations

•	External program memory (ROM): 1k words
•	External optional parameters memory (RAM): 1 word
•	Internal data memory: 256 words
•	Internal program memory: 256 words
•	External delay line (RAM): 128 to 256 kwords
•	Processor loading: requires exclusive use of processor

Algorithm Verification

•	15-tone THD test signal supplied
•	Single-tone suprious test signal supplied
•	Pulse for frequency and group delay measurement supplied
•	25 seconds audio file for testing supplied
•	Conforms to ITU-R BS. 642-1

Availability

Available now

Company Background and Contact Information

M.B. International is a research and design company serving mainly broadcasting equipment 
manufacturers. Our lab has 20 years of experience and has contributed to the big development of the 
Italian broadcasting industry. We are now an international company, serving customers worldwide. 
Several patents certify our involvement in new technologies.
Contact:	Mike Bargauan
		M.B. International srl
		Via Beolchi 1
		20151, Milano
		Italy
		+39 2 4091 0570
		Fax: +39 2 4091 0582
		e-mail: 100522.2272@compuserve.com