The Nebula tip of the month (#40 - September 2012)

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The Nebula tip of the month (#40 - September 2012)

Post by enriquesilveti » Wed Aug 15, 2012 2:36 pm

Using the new audio meters

. The K-meter
K-meter supports one of the latest industry standard tools for subjective loudness measurements, LUFS/LKFS measurements and fully compatible with EBU r-128 and ITU-R BS.1771-2 momentary and short-term measurements. Note that K-Meter does not support a gated, integrated measurement and true peak measurement.
The three K-System meter scales are named K-20, K-14, and K-12. The K-20 meter is intended for wide dynamic range material, like large theater mixes, audiophile music, classical symphonic music, audiophile pop music mixed in 5.1 surround, and so on. The K-14 meter is for the vast majority of moderately compressed high fidelity productions intended for home listening, like folk or rock music. The K-12 meter is for productions to be dedicated for broadcast.
The peak and average scales are calibrated as per AES-17, so that peak and average sections are referenced to the same decibel value with a pure sine wave signal. In other words, 20 dBFS RMS with sine wave reads the same as 20 dBFS peak, and this parity will be true only with a sine wave. Analog voltage level is not specified in the K-system, only SPL and digital values and there is no conflict with -18 dBFS or -20 dBFS analog reference points commonly used in Europe and America.
The K-System will probably not be needed for multitracking a simple peak meter or true peak meter is sufficient but for highest sound quality, use K-20 while mixing and save K-14 for the calibrated mastering suite. K-Meter doesn't prevent the mix engineer from using compressors during mixing, but hopes that engineers will return towards using compression as an aesthetic device rather than a loudness maker tool.
K-Meter v2 add a new scale K-16 and is similar to -16 LUFS/LKFS measurements, this value is the recommended for digital music distribution and delivery.

. The EBU r-128 and ITU-R BS.1771-2 meter
Like K-meter both r-128 and ITU-R BS.1771-2 meters supports subjective loudness measurements plus integrated measurements that is a long term measurement over the entire length of the audio program and a true peak metering with 4 times oversampling. In addition r-128 and ITU-R BS.1771-2 meter provide us a loudness range value (LU).
For loudness measurements, momentary term, short term and integrated, all channels are processed with a K-filter (high pass filter plus a high shelf filter) then applied AES-17 measurements like in K-meter and then summed all together go find an average value. For integrated measurement level gate is added plus a start/stop function. Like k-meter EBU r-128 and ITU-R BS.1771-2 meter has three scales: +9, +18, +27. Like in the old EBU r-68 and SMPTE rp-155 there is a programme level value and a permitted maximum level level value by default.

In conclusion EBU r-128 and ITU-R BS.1771-2 meters provide us all values what need for work. True peak value replaces peak meter program or quasi peak program meter. Momentary value replaces VU meter and short term value can replaces K-meter. Plus we have an integrated meter with the measurement of the entire length of the audio program.
EBU r-128 and ITU-R BS.1771-2 will meter also provide loudness range value, integrated value and true peak value in metadata so audio material can be process with dynamic range compressor, if is needed, for a non theatrical playback device like portable players.

As you can see the idea behind EBU r-128 and ITU-R BS.1771-2 is to change the way that broadcast stations normalize the levels from peak values normalization to integrated average normalization values in order to avoid the loudness war and avoid the level jumps between audio programs, but also add a true peak meter that is useful to avoid inter sample peaks with values above 0.00 dBFS in the customers D/A converters.