Orban Loudness Meter

€˘ Is available for Macs running OS X10.6 and higher.

€˘ Supports both the ITU BS.1770-1 and BS.1770-2 standards, user selectable. BS.1770-2 adds gating to the previous BS.1770-1 standard so that the meter ignores silence and is weighted toward louder program material, which contributes most to a listener’s perception of loudness. BS.1770-2 indicates only sounds that fall within a floating window that extends from the loudest sounds within the preset integration period to sounds that are 10 dB quieter than the loudest sounds.

€˘ Supports EBU R 128 measurements. R 128 calls for three meters: an ungated “momentary” meter having a time integration window of 400 ms, an ungated “short-term” meter having a time integration window of 3 seconds, and an “integrated” meter, having a user-selectable time integration window and gating as specified in BS.1770-2.

The Orban application provides a dedicated meter for the “momentary” indication while indicating the “short-term” and “integrated” loudness on a second meter, where a yellow bar displays the short-term loudness and a single cyan segment indicates the integrated loudness. A numerical display of the integrated loudness appears to the right of the meter.

The Orban meter implements the “loudness range” measurement per EBU – TECH 3342, which is incorporated into R 128 by reference. The “loudness range” measurement is most commonly used in Manual Mode to assess the dynamic range of entire program segments. EBU – TECH 3341 calls for two selectable meter scales and two selectable ranges. The scales are either absolute (in units of LUFS or LKFS, which are the same) or are relative with respect to a user- selectable reference level (which usually corresponds to the program’s Dolby Digital® dialnorm metadata value [in dB] and whose units of measure are LU or LK, which are the same). ATSC A/85, Annex K (“Requirements for Establishing and Maintaining Audio Loudness of Commercial Advertising in Digital Television When Using Non-AC-3 Audio Codecs”) and EBU – TECH 3344 (“Practical guidelines for distribution systems in accordance with EBU R 128”) provide instructions on how to choose the reference level in systems that do not use Dolby Digital to convey the program to the consumer.

The ATSC A/85 2011, ITU-R BS.1770-2, and various EBU R 128- related documents are available as free downloads and can easily be located with a search engine.

€˘ Allows manual start/stop operation of the meter per BS.1770-2.

€˘ Extends the maximum integration period to three hours for both program monitoring and manual modes. This allows the meter to measure the integrated loudness and LRA of most long-form program material such as feature films.

€˘ Changes the scale of the CBS Loudness Meter to match the scale of the EBU meters. This allows the readings of the BS.1770 and CBS meters to be compared easily. In addition, it changes the scaling of the “CBS Loudness Gain” control so that +10 dB on the V1 meter is equivalent to “0 dB” on the V2 meter.

€˘ Supports Annex 2 of ITU-R Rec. BS.1770-2 (“Considerations for accurate peak metering of digital audio signals”) by adding a peak- reading meter with a sample rate of 384 kHz and a recovery characteristic that is the same as a PPM, which we chose arbitrarily to make the meter easy to read.

This “Reconstructed Peak” meter indicates the peak value of the signal following D/A conversion (including the reconstruction filter) with an accuracy of better than 0.2 dB, assuming that this signal path has constant group delay and a low frequency cutoff low enough to avoid introducing tilt into the waveform. This meter indicates “intra- sample peaks,” which can cause clipping in the analog section of a playback device even if the magnitude of the digital samples is constrained to 0 dBFS. This is a serious problem with many popular playback devices.

Assuming that the D/A converter and reconstruction filter in a playback device have constant group delay and that response in the analog signal path is flat to DC, the worst-case overshoot is +3 dBFS, as exemplified by a sinewave whose frequency is 25% of the sampling frequency and where the samples are taken 45 degrees before and after the zero-crossings of the sinewave. If the “Reconstructed Peak” meter indicates higher than 0 dBFS, this indicates that clipping will occur in many playback devices.

The Orban meter does not implement the optional “HF pre-emphasis” and “DC block” blocks in the block diagram in Section 2 of Annex 2 of the BS.1770-2 standard. This is because the choice of pre-emphasis and DC blocking frequency characteristics is completely arbitrary, attempting to compensate for non-constant group delay and DC blocking that may or may not exist in the analog signal path of a given target playback device and which may or may not cause analog clipping from low frequency tilt even if they do exist.

€˘ Oversamples the PPM attack time processing to 384 kHz. This allows the meter to match the attack characteristics of EBU Tech. 3205-E more closely because this standard was originally developed for analog meters that are measuring analog signals.

€˘ Permits the important meter readings to be logged into a comma- delimited text file that can be imported into any spreadsheet or graphing program for further analysis and display. The sample period of the log file is user adjustable via the “Logging Interval” control.

€˘ Adds support for the Microsoft WASAPI Loopback Interface (Windows Vista and 7/8 only). WASAPI Loopback eliminates the requirement for a sound device to support Wave I/O or what is traditionally called “Stereo Mix” to play and record/monitor files played through Windows Audio.

€˘ Fixes a bug that caused the sample peak meter to indicate the values of positive-going peaks incorrectly.

€˘ Extends the VU Gain control range to +20 dB. This allows the VU meter to be aligned to SMPTE (–20 dBFS) or EBU (–18 dBFS) line-up level.