Dolby Laboratories DP570 - Manual (Page 43)

Using the DP570 Features Measuring and Setting the Dialogue Level
Dolby ® DP570 Multichannel Audio Tool User’s Manual 31
characters with different vocal qualities. In programs without dialogue, such as a music
concert, sections of average level need to be identified.
With representative audio clips identified, you can use the DP570 to set the dialogue level
parameter. You can use either the software interface or the front‐panel buttons; for this
operation we describe using the software interface first.
4.7.2 Measuring the Average Loudness of Identified Clips
The measurement feature complies fully with IEC 60804 (2000‐10): Integrating‐Averaging
Sound Level Meters (Leq(A)) and includes the addition of two distinct measurement modes
relating to the measurement period itself: infinite and short‐term. This section describes the
behavior of both modes.
IMPORTANT NOTE REGARDING MEASUREMENT ACCURACY:
Leq(A)‐based measurements are most accurate when they cover signals with similar
spectra, such as dialogue; the more similar the spectra, the more accurate the measurement.
This is why we recommend the use of Leq(A) measurements to provision the dialogue level
value within Dolby E and Dolby Digital bitstreams. The DP570 measurement feature will
yield best results when the operator measures portions of the program that contain only
minimal nondialogue material.
Using Infinite Measurements
Infinite measurement mode conforms to the specifications of IEC 60804 (2000‐10). In this
mode, the calculated value is the long‐term A‐weighted level, Leq(A), integrated over the
entire period since the measurement was last reset.
Infinite mode is typically used to measure the entire duration of the program, or several
long sections of a program, to find the long‐term A‐weighted level. Since Dialogue
Intelligence is available only in the Dolby LM100 Broadcast Loudness Meter, we suggest
using the following steps to obtain an estimated Leq(A) value for the entire program:
1. Review the program, noting the locations of several representative sections where
dialogue is present.
2. Cue the beginning of the first selected segment.
3. Click Reset to clear past measurements.
4. Measure the first segment, then click Pause to pause measurement.
5. Cue the second segment.
6. Click Pause again to resume measurement.
7. Continue in this fashion, pausing measurement between selected segments until the
program is completed.
Note: These changes harmonize both the core measurement algorithm and the
measurement modes between the DP570 and the Dolby LM100 Broadcast
Loudness Meter. Dialogue Intelligence™, however, is available only in the LM100.