--- /dev/null
+
+<h2>Introduction</h2>
+<p>
+ An engineer reading and using audio level meters compares to a musician
+ reading or writing sheet-music. Just like there are virtuoso musicians
+ who can't read a single note, there are great sound-engineers who just
+ go by their ears and produce great mixes and masters without ever looking
+ at a single meter.
+</p>
+<p>
+ Yet, if you want to work in or with the broadcast industry, it is
+ usually unavoidable to use meters.
+</p>
+<p>
+ Audio level meters are very powerful tools that are useful in every
+ part of the entire production chain:
+</p>
+<ul>
+ <li>When tracking, meters are used to ensure that the input
+ signal does not <dfn>overload</dfn> and maintains reasonable
+ <dfn>headroom</dfn>.</li>
+ <li>Meters offer a <dfn>quick visual indication</dfn> of a
+ activity when working with a large number of tracks.</li>
+ <li>During mixing, meters provide an rough estimate of the
+ <dfn>loudness</dfn> of each track.</li>
+ <li>At the mastering stage, meters are used to check
+ compliance with upstream <dfn>level</dfn> and <dfn>loudness
+ standards</dfn> and to optimize the <dfn>loudness range</dfn>
+ for a given medium.</li>
+</ul>
+
+<h2>Meter Types</h2>
+<p>
+ A general treatise on metering is beyond the scope of this
+ manual. It is a complex subject with a history...
+ For background information and further reading we recommend:
+</p>
+<ul>
+ <li><a href="http://www.digido.com/how-to-make-better-recordings-part-2.html">How To Make Better Recordings in the 21st Century - An Integrated Approach to Metering, Monitoring, and Leveling Practices</a> by Bob Katz. Has a good historic overview of meters and motivates the K-meter</li>
+ <li><a href="https://en.wikipedia.org/wiki/Peak_programme_meter#Table_of_characteristics">Wikipedia: Peak programme meter</a> - overview of meter types.</li>
+ <li>"Audio Metering: Measurements, Standards and Practice: Measurements, Standards and Practics", by Eddy Brixen. ISBN: 0240814673</li>
+ <li>"Art of Digital Audio", by John Watkinson. ISBN: 0240515870</li>
+</ul>
+
+<p>
+ There are different metering standards, most of which are available in Ardour. In short:
+</p>
+
+<dl>
+ <dt>Digital peak-meter</dt>
+ <dd>A <dfn>Digital Peak Meter</dfn> displays the absolute maximum signal
+ of the raw audio PCM signal (for a given time). It is commonly used when
+ tracking to make sure the recorded audio never clips. To that end, DPMs
+ are always calibrated to 0 <abbr title="DeciBel Full
+ Scale">dBFS</abbr>, or the maximum level that can be represented digitally
+ in a given system. This value has no musical reason whatsoever and depends
+ only on the properties of the signal chain or target medium. There are
+ conventions for <dfn>fall-off-time</dfn> and <dfn>peak-hold</dfn>, but no
+ exact specifications.
+ <p>
+ Various conventions for DPM fall-off times and dBFS line-up level can be
+ chosen in <kbd class="menu">Edit > Preferences > GUI</kbd>.
+ </p>
+ </dd>
+
+ <dt>RMS meters</dt>
+ <dd>An <dfn><abbr title="Root Mean Square">RMS</abbr>-type meter</dfn>
+ is an averaging meter that looks at the energy in the signal. It
+ provides a general indication of loudness as perceived by humans. Ardour
+ features three RMS meters, all of which offer additonal peak indication.
+ <ul>
+ <li><dfn>K20</dfn>: A meter according to the K-system introduced by Bob
+ Katz, scale aligned to -20 dBFS, rise/fall times and color schema
+ according to spec.</li>
+ <li><dfn>K14</dfn>: Same as K20 with scale aligned to -14 dBFS.</li>
+ <li><dfn>K12</dfn>: Same as K20 with scale aligned to -12 dBFS (since 3.5.143).</li>
+ <li><dfn>Peak + RMS</dfn>: standard RMS, customizable via
+ <kbd class="menu">Edit > Preferences > GUI > Metering</kbd></li>
+ </ul>
+ </dd>
+
+ <dt>IEC PPMs</dt>
+ <dd><dfn><abbr title="International Electrontechnical Commission">IEC</abbr>-type
+ <abbr title="Peak Programme Meters">PPM</abbr>s</dfn> are a mix between DPMs and
+ RMS meters, created mainly for the purpose of
+ interoperability. Many national and institutional varieties exist (<abbr
+ title="European Broadcasting Union">EBU</abbr>, <abbr title="British Broadcasting
+ Corporation">BBC</abbr>, <abbr title="Deutsche Industrie-Norm">DIN</abbr>).
+ <p>
+ These loudness and metering standards provide a common point of
+ reference which is used by broadcasters in particular so that the
+ interchange of material is uniform across their sphere of influence,
+ regardless of the equipment used to play it back.
+ </p>
+ <p>
+ For home recording, there is no real need for this level of
+ interoperability, and these meters are only strictly required when
+ working in or with the broadcast industry. However, IEC-type meters have
+ certain characteristics (rise-time, ballistics) that make them useful
+ outside the context of broadcast.
+ </p>
+ <p>
+ Their specification is very exact, and consquently, there are no
+ customizable parameters.
+ </p>
+ </dd>
+
+ <dt>VU meters</dt>
+ <dd><dfn><abbr title="Volume Unit">VU</abbr> meters</dfn> are the dinosaurs (1939)
+ amongst the meters. They react very slowly, averaging out peaks.
+ Their specification is very strict (300ms rise-time, 1 - 1.5% overshoot,
+ flat frequency response). Ardour's VU meter adheres to that spec, but for
+ visual consistency it is displayed as a bar-graph rather than needle-style
+ (more below).
+ </dd>
+</dl>
+
+<h2>Ardour Specifics</h2>
+
+<img class="right" src="/images/mixer-meter-context-menu.png" alt="mixer strip meter context menu" />
+<p>
+ Meters are available in various places in ardour:
+</p>
+<ul>
+ <li>The mixer window features fixed height meters for each <dfn>channel strip</dfn>.</li>
+ <li>There are small (narrow) meters on each <dfn>track-header</dfn> in the editor window.</li>
+ <li>There are variable height meters in the <dfn>meterbridge window</dfn>.</li>
+ <li>Optionally, a fixed-size <dfn>master meter</dfn> can be displayed in the main toolbar.</li>
+ <li>Various other locations (<dfn>file import</dfn>, <dfn>sends</dfn>) have level-meters.</li>
+</ul>
+<p>
+ They all share the same configuration and color-theme which is available in
+ preferences and the theme-manager. Settings for the Peak and RMS+Peak meters
+ as well as VU meter standards are found in
+ <kbd class="menu">Edit > Preferences > GUI > Metering</kbd>.
+</p>
+<p>
+ The type of meter and the <dfn>metering point</dfn> (the place in the signal chain
+ where the meter taps the signal) are configurable in the context menu of each meter.
+ Depending on the <kbd class="menu">Edit > Preferences > GUI > Mixer
+ Strip</kbd> settings, the metering point is also accessible via a button in
+ each Mixer strip.
+</p>
+<img class="right" src="/images/meter-preferences.png" alt="" />
+<p>
+ Regardless of meter type and standard the meter display will highlight red if
+ the signal on the given channel exceeds the configured peak threshold.
+</p>
+<p>
+ <kbd class="mouse">Left</kbd> on the peak-indicator button resets the
+ <dfn>peak-hold indicator</dfn> of a single channel.<br />
+ <kbd class="mod1 mouse">Left</kbd> resets a whole <dfn>group</dfn>, and<br/>
+ <kbd class="mod13 mouse">Left</kbd> resets all meters.
+</p>
+
+<h2>Overview of meter types</h2>
+
+<p>
+ The figure on the left shows all available meter-types in Ardour 3.4 when fed with a
+ -18 dBFS 1 kHz sine wave.
+</p>
+
+<img class="right" style="max-width:45%;height:400px;" src="/images/needle-meters-18.png"
+alt="Needle-style meters as external LV2 plugins" />
+<img style="max-width:45%; height:400px" src="/images/meter-types-18.png"
+alt="Bar-graph meters in Ardour" />
+
+<p>
+ Due to layout concerns and consistent look&feel all meters available in
+ Ardour itself are bar-graph type meters. Corresponding needle-style meters
+ — which take up more visual screen space — are available as
+ LV2 plugins (see image on the right):
+ <a href="https://github.com/x42/meters.lv2/">meters.lv2</a>.
+</p>
+
projects / ardour-manual / blobdiff