Orban Loudness Meter for Windows    README

 

2008 April 30 (version 1.0.2; public beta)

This free software is the first of a family of Orban meters. Future paid versions will offer upgraded features, including logging, surround monitoring, and oversampled peak measurements that accurately indicate the peak level of the audio after D/A conversion.

                                                                                                              

 

Revision History

 

Version 1.0.0 was the original public beta release.

 

Version 1.0.1:

  • Reduces CPU load caused by refreshing the meter’s display. This allows slower computers to operate at the meter’s maximum 100 Hz refresh rate, minimizing flicker.
  • Changes the color scheme to improve appearance and to make the meters easier to read.
  • Changes the graphic design of the single-bar meter display elements like peak hold to make them easier to read and to prevent them from being obscured.
  • On startup, checks whether the computer’s CPU supports the SSE2 instruction set and exits gracefully if it does not.
  • Increase the gain of the VU meter by 10 dB for a given setting of the VU Meter Gain control. When the control is set to 0 dB and the meter is fed by a sinewave, the VU meter will now display the same level as the absolute peak meter.
  • Clarifies the readme (this document) to better explain how the meter interacts with your computer’s sound device(s).
  • Moves the Audio Input selector to the Settings page.

Version 1.0.2:

  • Causes the meters to be reset when disabled.
  • In computers running Windows 2000, the software now gives the correct result when testing whether the computer’s CPU supports the SSE2 instruction set.
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Hardware and Operating System Requirements

  • Microsoft Windows® XP (SP2 or greater) or Vista (SP1 or greater)
  • 1.5 GHz or faster Intel Pentium 4 or Intel-compatible processor that implements the SSE2 instruction set. Note that this is a function of the processor, not the operating system.           

    http://en.wikipedia.org/wiki/SSE2

    (Because of efficient use of SSE2 instruction to implement the DSP, video refresh is the main contributor to CPU load. To deal with slower computers, the application has a control that allows the user to trade off CPU usage against video refresh rate.)
  • 1024x768 or larger display
  • 20 megabytes of free RAM in which to run the application
  • Sound device supporting Windows Wave I/O.

The Orban meter response to audio signals received by one of the audio input devices on your computer. Some audio hardware supports capturing the audio output. If your hardware supports this, you can play audio out of your computer using an application such as Windows Media Player and configure the meter to listen to the audio output capture.

If your sound card or motherboard integrated sound system does not support capturing the audio output, the Orban meter will only respond to audio applied to the sound device’s hardware audio input.

One work-around is to use Ntonyx’s Virtual Audio Cable software in conjunction with its Repeater Application.

http://www.ntonyx.com/vac.htm

 

                                                                                                             

 

Installation

To install the Loudness Meter, run

setup_Free_Orban_Loudness_Meter_1.0.1.exe

Follow the installer’s prompts.

Please note that although Orban offers this executable version of the Loudness Meter software free of charge to end users, this software is not in the public domain and Orban retains all rights and indemnities to maximum extent permitted by law. To complete the installation, you must agree to the License Agreement that the installer presents to you. If you do not agree, the installer will allow you to cancel the installation.

 

                                                                                                              

 

Operation

Launch the Loudness Meter via the icon on the desktop or in the Quick Launch bar. Click the Settings tab. This allows you to set several operating parameters for the meters.

  • In the Audio Input drop-down, choose which Windows installed sound device the Loudness Meter should monitor. As noted in the Hardware and Operating System Requirements above, if you wish to use the meter to monitor the output of playout function like Windows Media player, the chosen sound device must support capturing the audio output.
  • The Meter Refresh Rate lets you trade off the solidity of the display against CPU usage. If the application uses too much CPU (as indicated in the Windows Task Manager Performance tab), reduce the meter’s Refresh Rate as needed. Best display quality occurs at 100 Hz.
  • The CBS Loudness Gain sets the reference level of the CBS meter with respect to digital full scale. We prefer to set this at +10 dB to match the CBS long-term indication (cyan bar) most closely to the BS.1770 meter and to +7 dB to match the CBS peak short-term indication most closely to the ITU BS.1770 meter.
  • The CBS Peak Averaging Time allows you to set the time window over which the CBS long-term averaging algorithm works. We prefer 3 to 4 seconds. Longer times will smooth out the indication but will also look further into the past history of the program material, which may be undesirable if you are trying to use the meter for real-time program monitoring.
  • The ITU BS.1770 Time sets the integration time of the BS.1770 meter. Note that this algorithm gives equal weight to all samples within the time window; it does not weight more recent samples higher than older samples. The algorithm’s designer prefers three seconds for real-time program monitoring.
  • The VU Meter Gain control sets the reference level of the VU meter with respect to digital full scale. Because this meter’s scale is different from that of a standard VU meter, you will have to decide what indication you want to correspond to the customary “0 VU.”               

    Note that the VU meter is defined as an averaging meter, which the Orban VU meter is. The average value of a sinewave is 3.9224 dB below its peak value. By design, when the Orban meter’s VU Meter Gain is set to 0 dB, the VU meter indicates what might be called “equivalent sinewave peak” with respect to digital full-scale. In other words, a VU Meter Gain setting of 0 dB makes a 0 dBfs sinewave indicate 0 on the VU meter, not –3.994.
  • The PPM Attack Time control determines whether the PPM’s attack time is 10 ms or 5 ms, allowing the meter to emulate several different variants of the PPM standard.

You can start and stop the meter by clicking the Start/Stop button at the bottom of the screen. Some settings can only be adjusted when the meter is stopped.

You can click the small button to the left of each meter to activate or defeat it. If you defeat a meter while it is operating, its indication will reset so that the meter indicates nothing.

If the meters do not respond to audio: Open the Windows Volume Control panel. It is usually possible to do this by clicking on the small “loudspeaker” icon in the extreme right side of the Windows task bar. If this icon is not present:

  • Navigate to Start>Settings>Control Panel>Sounds and Audio Devices.
  • Click the “Volume” tab.                       

    (You may wish to check “Place volume icon in the taskbar” so that the shortcut to the Volume Control Panel is available in the future.)
  • Click the Device Volume’s “Advanced” button. The Master Volume control panel will open.

·      Navigate to Options>Properties in the Volume window.         



·      Click the “Adjust Volume for Recording” button and check the boxes to the left the sources you wish to monitor with the meter. To monitor the output of an application like Windows Media Player, you must check “Wave” or its equivalent. These functions may have different names in your computer so you may have to experiment. For example, “Wave” may be called “Stereo Mix,” as it is in the screenshot above.                

·         Click OK. The Recording Control panel should open.       

·      Check the “Select” Box for the “Wave” or “Stereo Mix” fader and adjust the fader so that the absolute peak indication on the Orban meter agrees with the peak level of a source being played. For example, to calibrate the Orban meter you could play out a sinewave file of known peak amplitude that you created in an application like Adobe Audition.

 

 

                                                                                                             

 

About the Meter and Its Implemented Algorithms

 

Loudness is subjective: it is the intensity of sound as perceived by the ear/brain system. No simple meter, whether peak program meter (PPM) or VU, provides a reading that correlates well to perceived loudness. A meter that purports to measure loudness must agree with a panel of human lis­teners.

The Orban Loudness Meter receives a two-channel stereo signal from any Windows sound device and measures its loudness and level. It can simultaneously display instantaneous peaks, VU, PPM, CBS Technology Center loudness, and ITU BS.1770 loudness. The meter includes peak-hold functionality that makes the peak indications of the meters easy to see.

 

Jones & Torick (CBS Technology Center) Meter

The CBS meter is a “short-term” loudness meter intended to display the details of moment-to-moment loudness with dynamics similar to a VU meter. It uses the Jones & Torick algorithm [Bronwyn L. Jones and Emil L. Torick, “A New Loudness Indicator for Use in Broadcasting,” J. SMPTE September 1981, pp. 772-777]. Our DSP implementation of this algorithm typically matches the original meter within 0.5 dB on sinewaves, tone bursts and noise. (The original meter uses analog circuitry and an LED bar graph display with 0.5 dB resolution.) Many researchers have been curious about the Jones & Torick meter but been unable to evaluate it and compare it with other loudness meters. We developed this software because we believed it would be useful to practicing sound engineers and researchers and because we are using the CBS meter in our Optimod 8585 Surround Audio Processor.

The Jones & Torick algorithm improves upon the original loudness measurement algorithm developed by CBS researchers in the late 1960s. Its foundation is psychoacoustic studies done at CBS Laboratories over a two year period by Torick and the late Benjamin Bauer. After surveying existing equal-loudness contour curves and finding them inapplicable to measuring the loudness of broadcasts, Torick and Bauer organized listening tests that resulted in a new set of equal-loudness curves based on octave-wide noise reproduced by calibrated loudspeakers in a semireverberant 16 x 14 x 8 room, which is representative of a room in which broadcasts are normally heard. They published this work in “Researches in Loudness Measurement,” IEEE Transactions on Audio and Electroacoustics, Volume AU-14, Number 3, September 1966, pp. 141-151. This paper also presented results from other tests whose goal was to model the loudness integration time constants of human hearing.

 

BS.1770 Loudness Meter

In 2006, the ITU-R published Recommendation ITU-R BS.1770: “Algorithms to measure audio programme loudness and true-peak audio level.” Developed by G.A. Soulodre, the BS.1770 loudness meter uses a frequency-weighted r.m.s. measurement intended to be integrated over several seconds—perhaps as long as an entire program segment. As such, it is considered a “long-term” loudness measurement because it does not take into account the loudness integration time constants of human hearing, as does the CBS meter.

Orban’s BS.1770 loudness meter uses the Leq(RLB2) algorithm as specified in the Recommendation. This applies frequency weighting before the r.m.s. integrator. The frequency weighting is a series connection of pre-filter and RLB weighting curves. The Orban meter precisely implements equations (1) and (2) in this document by using a rolling integrator whose integration time is user-adjustable from one to ten seconds. In an AES convention preprint, Soulodre proposed using a three second integration time when the BS.1770 meter was used to adjust program levels in approximately real time. However, the published BS.1770 standard does not specify a specific integration time.

 

Experimental CBS Long-Term Loudness Measurement

In the Orban meter, we have added an experimental long-term loudness indication by post-processing the CBS algorithm’s output. Displayed by a single cyan bar on the CBS loudness meter, this uses a relatively simple algorithm and we welcome any feedback on its perceived usefulness. This algorithm attempts to mimic a skilled operator’s mental integration of the peak swings of a meter with “VU-like” dynamics. The operator will concentrate most on the highest indications but will tend to ignore a single high peak that is atypical of the others.

The algorithm displays the average of the peak indications of the meter over a user-determined time period. The average is performed before dB conversion All peak indications within the time period are weighted equally with the following exceptions:

  • If the maximum peak in the window is more than 3 dB higher than the second highest peak, it is discarded.
  • All peaks more than 6 dB below the maximum (or second-to-maximum, if the maximum peak was discarded) are also discarded.

 

Meter Scales

In their original publications and standards, each of the meters implemented in the Orban Loudness Meter has a different specified scale and range. To best allow users to compare the indications of the various meters under dynamic program conditions, we chose to present their indications on identical linear-dB scales extending from 0 to –30 dB with respect to digital full-scale. The CBS and VU meters have gain adjustments that allow users to choose their preferred lineup level.

 

Conformance to Published Standards

Our implementation of the PPM can be switched for 5 ms or 10 ms attack times, because there are standards for both variations. The “10 ms attack” mode follows EBU Tech. 3205-E as closely as possible, given the difference in the scale and the limitations introduced by the Orban meter’s 48 kHz internal sample rate. In practice, this means that its indication obeys the dynamic performance specification of the standard within 0.5 dB for tone burst durations of 100, 10, and 5 ms. Because of undersampling, the Orban PPM under-reads a 5 kHz 1.5 ms burst by about 3 dB and a 10 kHz 0.5 ms burst by about 4 dB compared to the standard. In a future version of the meter, we may oversample its detector to comply more closely with the 1.5 ms and 0.5 ms specifications.

Our implementation of the VU meter reaches 99% (–0.09 dB) of steady-state when presented with a 1 kHz tone burst with an “on” duration of 300 ms and an “off” duration of 500 ms or more . In concordance with the standard, the meter has an overshoot of 1%. Because its reading is presented on a dB-linear scale instead of a standard VU “A” or “B” scale, we believe that this is the closest we could come to the spirit of this meter.

Our true peak-reading meter reads the peaks of the 48 kHz digital samples within the meter. It does not attempt to extrapolate the peaks of the signal after D/A conversion, as specified in the BS.1770 standard. This requires oversampling the peak detector, which we may do in a future release. Also, note that the Orban meter may not indicate the true peak sample values of material not originally at 48 kHz sample rate. Windows will sample-rate-convert such material to 48 kHz before the meter and will change the values of the samples when it does so.

 

                                                                                                               

 

Support

Because this software is supplied free of charge, Orban does not provide formal technical support for it. If you find bugs or encounter problems, we encourage you to report them via email to meter@orban.com. We will use your feedback to help improve the meter.

The newest version of the meter can be downloaded from:

www.orban.com/meter

Copyright © 2008 Orban.

All rights reserved. Subject to the provisions of the License Agreement displayed by the software installer.

This software and/or program is protected by copyright law and international treaties. Any reproduction or distribution of this software and/or program, or any portion of it without permission, may result in severe civil and criminal penalties, and will be prosecuted to the maximum extent possible under law.