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Introduction...................................................................................2 Features........................................................................................2 System requirements.....................................................................2 Basic Use......................................................................................5 Radar Page...................................................................................5 Loudness History: Radar............
INTRODUCTION LM5D Radar Loudness Meter LM5D represents a quantum leap away from simply measuring audio level to measuring perceived loudness. The old level method is responsible for unacceptable level jumps in television, for music CDs getting increasingly distorted, and for different audio formats and program genres becoming incompatible: Pristine music tracks from the past don’t co-exist with new recordings, TV commercials don’t fit drama, classical music or film and broadcast doesn’t match.
Since 1998, TC has performed listening tests and evaluation of loudness models; and therefore holds an extensive, Universal Database of loudness, based on ten thousands of assessments. The database covers all sorts of broadcast material, music, commercials, feature film and experimental sounds, and is verified against other independent studies. The Universal Database is authoritative from an academic as well as a practical point of view.
ever decreasing dynamic range. By now, the pop music industry is “right of” In Flight Entertainment in the illustration. LM5D offers a standardized option: The visualization of loudness history and DRT in combination with long-term descriptors from production onwards, is a transparent and well sounding alternative to our current peak level obsession. Not only for music, but also in production for broadcast or film.
BASIC USE LM5D makes use of a unique way of visualizing short-term loudness, loudness history, and long-term statistical descriptor. It may be used with mono, stereo and 5.1 material for any type of program material. Press the “Radar” key to bring up the Radar page. This page will probably be used most of the time. The basic functionality of the Radar page is shown in Fig 3. RADAR PAGE Fig.
Current Loudness: Outer Ring The outer ring of the Radar page displays current loudness. The 0 LU point (i.e. Target Loudness) is at 12 o’clock, and marked by the border between green and yellow, while the Low Level point is marked by the border between green and blue. The “0 LU Equals” and “Low Level Below” parameters are found on Prefs page. Keep the outer ring in the green area, and around 12 o’clock on the average.
LOUDNESS HISTORY: RADAR The Loudness Radar shows a history of loudness over time. The loudness “landscape” may be used to judge if loudness emphasis is put where you want it to be: If dialog segments are balanced against action parts, if the chorus of a song has a lift against the verse, if the audience is too loud in a gameshow, or maybe as a target to aim for during a live transition etc. Fig. 5, Different types of program shown on the Radar. Left: 5.
Universal Descriptors and Dolby LM100 Unlike methods that measure dialog only, LM5D may be used with any type of audio – which includes dialog, of course. If you wish to measure dialog, it’s recommended to do a manual spot check of a program or a film. Find 10-30 secs of regular dialog and measure it with LM5D . Where dialog may be soft, regular or loud, and shift by more than 15 dB inside a film, regular dialog tends to be less ambiguous and more consistent across a program.
THE RADAR METER IN USE The meter displays momentary loudness and Loudness History in a single, unique Radar View, see Fig. 3. The circular, color-coded display makes it easy to balance audio visually and to see when level falls below or exceeds the end-listener’s loudness range tolerance. Fig. 3 shows a scene from Desperate Housewives which is generally too soft. It’s a tremendous help for a mixing engineer or a video editor to know which radar area to stay inside as shown in Fig.
PPM PAGE Press the “PPM” key to bring up the PPM display, Fig. 7. The PPM page is used to inspect balance between channels, headroom, overload of channels etc. ENGLISH Fig. 7, PPM True-peak meter features. Bargraph PPM meters are shown next to the round Current Loudness display, which is identical to the Outer Ring of the Radar page. The True-peak meters operate regardless of the status of the Run/Stop/Pause controls. Click on the bargraphs to reset the peak history.
The peak meters of LM5D display true-peak as specified in ITU-R BS.1770-2. True-peak meters give a better indication of headroom and risk of distortion in downstream equipment such as sample rate converters, data reduction systems and consumer electronics than digital sample meters used e.g. in CD mastering. Fig. 8, PPM True-peak meter example showing film in 5.1. ENGLISH True-peak meters in LM5D are fully synchronous and inlcude internal headroom.
PREFERENCES PAGE Fig. 9, LM5D Prefs page. Preferences may be stored as Presets, thereby having suitable settings for different conditions easily at hand. Loudness Scale Can be set to either “Loudness Units, LU” or “Loudness Full Scale, LUFS”. Note how LUFS is the same as LKFS. For more info, see paragraph about LKFS, LUFS and LU. When “LU” is selected, the radar and numbers appear as shown in Fig 4 Left.
OBS Indicator Sets the conditions for the OBS indicator to light up. Turn it off, if you don’t want warnings. Time Reference Time Reference can take two values: “Actual Computer Time” or “Program Time”. The first is synchronized to the realtime clock of the computer, the latter to when a new measure was started, i.e. when the “run” key was pressed. Note: The meter history resets when you switch between Time Reference settings. Radar Speed Radar Speed controls how long time each radar revolution takes.
Fig 10, Examples of 5.1 movie left (Matrix) and stereo, classical music right (Bolero). Both examples are shown on a 12 minute per revolution Radar with 10 dB between divisions. Level versus Loudness When level normalization in audio distribution is based on a peak level measure, it favors low dynamic range signatures as shown in Fig 1. This is what has happened to CD. Quasi-peak level meters have this effect.
Unlike electrical level, loudness is subjective, and listeners weigh its most important factors - SPL, Frequency contents and Duration - differently. In search of an “objective” loudness measure, a certain Between Listener Variability (BLV) and Within Listener Variability (WLV) must be accepted, meaning that even loudness assessments by the same person are only consistent to some extent, and depends on the time of day, her mood etc. BLV adds further to the blur, when sex, culture, age etc.
Meter Calibration Because of the frequency and channel weighting, and of the way channels sum, only specific tones and input channels should be used for calibration. The most transparent results are obtained using a 1 kHz sine tone for calibration. Other frequencies or types of signal may be used (square wave, noise etc.), but don’t expect similar results. The beauty of the system lies in its RMS foundation, so this is a feature, not an error.
POST SCRIPT Control of loudness is the only audio issue that has made It to the political agenda. Political regulation is currently being put into effect in Europe to prevent hearing damage and disturbances from PA systems, and to avoid annoying level jumps during commercial breaks in television. In Australia, something similar may happen.
AM6 - TRAILER AND COMMERCIAL METER Radar Leq(M) meter for Cinema Production Pro audio is moving decisively away from the peak level based normalization method that has caused so much havoc with trailers in movie theaters. The new and better mantra is to combine frequency weighting with an energy-integrated measure of sound, or equivalent continuous sound level, abbreviated Leq, and the level regulation of commercials and trailers in movie theaters is based on a measure of annoyance, also known as Leq(M).
When developing AM6, an important, new function was added to complement the integrated Leq(M) number: A proficient way of measuring peak level. Sample-based peak level detection is long past its age of retirement, while true-peak assessment as defined by AES and ITU is trustworthy.
PREFERENCE PAGE Annoyance scale Indicate numbers in the radar and in the Leq(M) readout on a scale related to cinema SPL by selecting “Calibrated”, or on a scale relating to Digital level. Regulation in most countries are based on “Calibrated” numbering. Digital Reference Level When the digital scale is selected, this parameter sets the value shown at 12 o’clock position on the radar outer ring, and at the bold circle of the radar. This would normally be set to the standard operating level.
Low Threshold Low Threshold determines where the shift between green and blue happens in the outer ring. It indicates to the engineer that level is now at risk of being below the noise floor. True Peak Indicator Sets the level at which the Peak indicator lights up. OBS Indicator sets the conditions for the OBS indicator to light up. Turn it off, if you don’t want warnings. ALERT indicator This is where you set the conditions for the ALERT indicator to light up. Turn it off, if you don’t want warnings.