The Dolby LM100 broadcast loudness meter is a tool for measuring the subjective loudness of dialogue within broadcast programming. The LM100 has applications ranging from postproduction and quality control to final transmission, program turnaround, and cable head-end facilities.
LM100 measurement results are presented in a numerical format. This eliminates the variations in results multiple operators often find when using traditional VU or PPM meters (neither of which measures subjective loudness).
The LM100 features a new measurement technology, Dialogue Intelligence. Dialogue Intelligence has been developed to analyze the input signal and only measure the program loudness during the presence of dialogue.
LM100 measurement results are presented in a numerical format. This eliminates the variations in results multiple operators often find when using traditional VU or PPM meters (neither of which measures subjective loudness).
The LM100 can also determine the unweighted peak and a range of other information about the signal. A set of user-definable alarms and monitoring functions can be used to inform an operator of input loss, signal clipping, overmodulation (LM100-NTSC version), high or low signal levels, silence, and incorrectly set dialogue level (dialnorm) values. A dedicated GPI/O port provides a tally of these alarm conditions, with more extensive monitoring available through the serial ports and an internal event log.
The single-rack space LM100 incorporates a large display that can indicate two measured values. The unit can simultaneously display the incoming dialnorm value of a Dolby Digital program (or any program within a Dolby E bitstream) for direct comparison to the actual measured value. The front panel also includes LEDs for indication of fault, error, and audio alarm conditions, and a headphone jack with volume control.
The rear panel provides a pair of RCA connectors for two-channel confidence and signal presence monitoring of the selected source, an AES3 digital input with loop-through, and two balanced analog inputs on combination XLR/¼-inch TRS connectors. Front- and rear-panel serial interfaces provide a means for remote control, status logging, and software updates.
The unit is available in two configurations. The LM100-LTC includes a timecode input, which allows the alarm and other signal conditions to be logged either to an internal time-of-day clock or external timecode. The LM100-NTSC includes an RF input specifically for NTSC CATV and "off-air" television measurement applications. The RF tuner replaces the linear timecode input in this version of the unit. Logging, in this version, is therefore referenced to the internal time-of-day clock.
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