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Loudness Metering

mastermonloudnessandlraThe introduction of loudness metering as an addition to traditional peak measurement has been a hotly debated topic in TV broadcast circles for some time. Background to the discussion is abrupt changes in level on the same channel: Trailers and commercial breaks are typically so much louder, making spectators adjust the volume repeatedly. This is also an issue when switching back and forth between channels. The move to audio measurement requirements based on loudness is intended to result in higher dynamic range and more consistent loudness levels.

truepeakmeterThe SALZBRENNER STAGETEC MEDIAGROUP is actively engaged in the development of loudness metering. The XCPU09, the latest generation CPU board for NEXUS, incorporates a loudness meter in the master-monitoring path. With the new XCPU09, STAGETEC proves once again that their systems always adopt the latest technical standards and therefore represent future-proof investments. Furthermore, the new functionality of the XCPU09 demonstrates a development trend of all STAGETEC product lines, i.e. making as many peripherals as possible obsolete by integrating their functionality directly into the audio network.

Loudness metering implemented on NEXUS networks complies with the ITU-R BS.1770-2, ITU-R BS.1771, ATSC A/85, and EBU R128
standards.
Users can choose from different types of loudness metering available simultaneously:

  • Momentary loudness with an integration time of 400 ms.
  • Short-term loudness with an integration time of 3 s.
  • Integrated loudness with custom integration time, using a gating function.

mastermonrtaThe results of the integrated measurement can be used directly as metadata in a Dolby E®-encoder stream. Various configuration dialogues provide numerous settings. Loudness is measured using a new unit, LUFS, which stands for Loudness Units Full-Scale. The EBU R128 loudness reference is –23 LUFS absolute or 0 LU relative.

Loudness range (LRA) — The calculated value provides information on the loudness level distribution within a programme. LRA is measured using a long-term integration with LU (loudness units) as the unit of measurement.

mastermonmodeconfigA NEXUS XCPU can compute up to three loudness-meter instances each with up to eight channels simultaneously and independently. A total of 256 configurations can be created for each loudness-meter instance which can be managed using NEXUS Logic Control functions. Start, stop and pausing of the long-term measurements can also be controlled by NEXUS Logic functions.

The level metering stage is implemented as an ITU-R BS.1770-2-compliant true-peak meter. Using oversampling, peak levels are detected between samples, thus ensuring precise metering.

mastermonsetupSpectral analysis is another new function which could be realised directly in NEXUS thanks to the XCPU 09’s high-power processing. The spectrum analyser displays the frequency distribution of any channel or sum on the NEXUS as 31 or 61 frequency bands. This flexibility makes the spectrum analyser a practical tool for monitoring the master and replaces external analysers.

mastermonlayerconfigVarious settings including the reference level, the metering range and ballistics, etc. can be accessed in the configuration screens. Curves can be »frozen« and then saved and reloaded.

The master monitoring software featuring loudness metering, loudness range, true-peak meter, and spectral analysis is an option that can be purchased separately for the XCPU 09 board.

The XCPU 09 can be installed in a NEXUS network which includes Base Devices that still employ the predecessor XCPU 08 board. In addition, Base Devices incorporating the new board integrate seamlessly into existing NEXUS STAR networks.