ITU-R BS.645-2
Vu Meter
by M.B. International S.r.l.

Software Overview

The Vu Meter accepts any AES/EBU sampled audio signal and returns the peak or RMS level of left and 
right channel or the level of the sum and difference of the two channels.
Set-up time, decay time, and nominal value can match all ITU-R BS.645-2 parameters or can be set to 
custom values.
Output is in dB and can be linear or logarithmic.
Measurements can be made with pre-emphasis, with de-emphasis or with flat frequency response; 
emphasis time constant can be chosen between 50 ms, 75 ms, and custom values.
The output can be configured to drive LED bars, LED number display, mobile coil ampermeters via a 
D/A converter or other digital hardware, like microprocessors.

Features and Benefits

•	Lower cost than analog Vu meters
•	Program is downloaded to internal RAM for fast execution
•	Absolute stability—no re-tuning or balance adjustment
•	Suitable also for unattended measurement, data logging, and hard copy output
•	Very efficient assembly-optimized language code

Processor and System Requirements

•	Supported on `C2x, `C3x, `C4x, `C5x @ 40, 50, and 60 MHz
•	Audio input via serial port
•	Output on serial port or on bus
•	Suitable to drive LED bar display, LED numbers, voltmeters, and CRTs
•	Input sampling rate 32, 44.1, 48 kHz @ 16 to 24 bits

Usage Limitations or Performance Considerations

•	External program memory (ROM): 1k words
•	External optional selection of operating mode via XF pins
•	Internal data memory: 256 words
•	External delay line (RAM) for RMS measurements: 16k words
•	Internal program memory: 256 words
•	Processor loading 6 to 10 MIPS depending on processor and output type

Algorithm Verification

•	Test tone for checking
•	15 tones with pre-emphasis
•	15 tones with de-emphasis
•	Conforms to ITU R BS.645-2, EBU 3205, OIRT, BBC, and IEC type 1, 2a, and 2b

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