308 lines
15 KiB
HTML
308 lines
15 KiB
HTML
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<!doctype HTML public "-//W3C//DTD HTML 4.0 Frameset//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
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<meta name="generator" content="Adobe RoboHelp 9">
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<title>Automixer</title>
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<link rel="StyleSheet" href="HtmlHelp.css" type="text/css">
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<style title="hcp" type="text/css">
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<!--
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span.hcp1 { font-weight:bold; }
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p.hcp2 { font-weight:bold; }
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span.hcp3 { font-weight:normal; }
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p.hcp4 { margin-bottom:0; }
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-->
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</style>
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</head>
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<body class="ns-0 ltr">
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<div id="globalWrapper">
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<div id="column-content">
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<div id="content">
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<p><a name="top" id="top"></a></p>
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<h1 class="firstHeading">Automixer Gain Sharing</h1>
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<div id="bodyContent">
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<p id="siteSub"> <br>
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<img src="Automixer.jpg" alt="" border="0"></p>
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<p>In addition to the features of a conventional mixer
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'Automixers' allow 'hands-free' multi-microphone mixing
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without the need for 'manual gain riding' to keep background
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noise and feedback under control.</p>
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<p>These objects use an Adaptive Threshold Gain Sharing
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technique to control the attenuation in each input channel.
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Note that due to this automation, automatic mixers can
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use many DSP resources.</p>
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<p>All inputs share the available gain; i.e. an 'open'
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microphone will attract the most gain. If more than one
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microphone is in use, the gain in the active channels
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is shared to give the same overall system gain. When all
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inputs are idle, the shared gain keeps all channels slightly
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active to avoid 'pumping' of the background noise. Downward
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expansion is however available for further reducing the
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background noise contribution from idle microphones. Options
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are provided to allow the mixer to be expanded not only
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within a given device, but also across the network. Aux.
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buses can be created and direct channel outputs may be
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made available for final mixing elsewhere, or for adding
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equalisation or other processing.</p>
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<br>
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<div class="editsection" style="float: right; margin-left: 5px;">
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<p> </p>
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</div>
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<p><a name="Inputs_and_Outputs" id="Inputs_and_Outputs"></a></p>
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<h2>Inputs and Outputs</h2>
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<p>The number of inputs can be set from 2 to 48.</p>
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<p>The output is either mono or stereo.</p>
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<p>There is optionally one output for each aux. bus.</p>
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<p>There is optionally one output for each group bus.</p>
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<p>The direct out property produces an output per channel.</p>
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<p>The master option adds a further Mix Input, Chain Input
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and Threshold Output.</p>
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<p>The slave option adds a further Mix Input, Chain Input,
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Threshold Input and Chain Output.</p>
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<div class="editsection" style="float: right; margin-left: 5px;">
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<p> </p>
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</div>
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<p><a name="Properties" id="Properties"></a></p>
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<h2>Properties</h2>
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<div class="editsection" style="float: right; margin-left: 5px;">
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<p> </p>
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</div>
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<p><a name="Number_of_Channels:" id="Number_of_Channels:"></a></p>
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<h4>Number of Channels:</h4>
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<p>The number of input channels can be selected between
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2 and 48.</p>
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<div class="editsection" style="float: right; margin-left: 5px;">
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<p> </p>
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</div>
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<p><a name="Stereo:" id="Stereo:"></a></p>
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<h4>Stereo:</h4>
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<p>Set to "Yes" the automixer will have a stereo
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pair of outputs, L and R. In Master or Slave mode there
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will also be a Left and Right Mix Input</p>
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<div class="editsection" style="float: right; margin-left: 5px;">
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<p> </p>
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</div>
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<p><a name="Number_of_Groups:" id="Number_of_Groups:"></a></p>
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<h4>Number of Groups:</h4>
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<p>Up to 4 group output buses can be selected.</p>
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<div class="editsection" style="float: right; margin-left: 5px;">
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<p> </p>
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</div>
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<p><a name="Number_of_Auxes:" id="Number_of_Auxes:"></a></p>
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<h4>Number of Auxes:</h4>
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<p>Up to 4 aux. output buses can be selected.</p>
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<div class="editsection" style="float: right; margin-left: 5px;">
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<p> </p>
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</div>
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<p><a name="Pan_Law:" id="Pan_Law:"></a></p>
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<h4>Pan Law:</h4>
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<p>The law of the pan controls may be set to either -3.0dB,
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-4.5dB or -6.0dB. These figures relate to the attenuation
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applied to each channel at the central pan position.</p>
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<div class="editsection" style="float: right; margin-left: 5px;">
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<p> </p>
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</div>
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<p><a name="Master.2FSlave_Status:" id="Master.2FSlave_Status:"></a></p>
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<h4>Master/Slave Status:</h4>
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<p>For expanding the mixer, either for making a larger
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mixer within a device, or for splitting a mixer across
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more than one device. The control signals are shared using
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two special versions of the automixer - Master and Slave.</p>
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<div class="editsection" style="float: right; margin-left: 5px;">
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<p> </p>
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</div>
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<p><a name="Voice_Band_filters:" id="Voice_Band_filters:"></a></p>
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<h4>Voice Band filters:</h4>
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<p>Filtering may be included so that the automixing action
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favours frequencies in the human vocal range. This helps
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the mixer to distinguish between speech and noise, giving
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a voice signal a better chance of 'winning' against a
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noise signal on another channel.</p>
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<div class="editsection" style="float: right; margin-left: 5px;">
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<p> </p>
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</div>
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<p><a name="Direct_Outs:" id="Direct_Outs:"></a></p>
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<h4>Direct Outs:</h4>
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<p>In addition to a single mixed output, the individual
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automixed channels may be output for further processing
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or mixing elsewhere.  These individual outputs are
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taken from before the mix but after any processing such
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as gain and so on are applied.  Set to Yes if Direct
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outputs are required. .</p>
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<div class="editsection" style="float: right; margin-left: 5px;">
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<p> </p>
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</div>
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<p><a name="Control_Panel" id="Control_Panel"></a></p>
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<h2>Control Panel</h2>
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<p> <br>
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<img src="Automix_control_panel.jpg" alt="Image:Automix control panel.jpg" title="Image:Automix control panel.jpg" style="border-width: 2px;
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border-style: solid; margin-top: 0px; margin-bottom: 0px;
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margin-left: 0px; margin-right: 0px;" width="605" height="637" border="2"></p>
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<p> <span class="hcp1"><br>
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Fader</span> for each input. This controls the level of
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the channel's input before the automix logic is applied.</p>
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<p><span class="hcp1">Pan control</span>
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control (stereo objects only)</p>
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<p><span class="hcp1">Mute</span> button
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for each input.</p>
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<p><span class="hcp1">Polarity</span> button
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for each input (for signal inversion)</p>
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<p><span class="hcp1">Gain</span> control
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for each output</p>
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<p><span class="hcp1">Solo</span> control
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for each input channel for quick identification of signals
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and level setting: Allows only 'soloed' channels to be
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heard. NOTE: This feature is disabled in any 'master'
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or 'slave' automixer.</p>
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<p>! This is a 'solo-in-place' which impacts the main output.</p>
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<p><span class="hcp1">Override</span> button
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for each input: Forces this channel to be heard above
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all the others. Useful for a chairperson to interrupt
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a conference speaker for example. NOTE: Use of this feature
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modifies the behavior of the 'On Indicator.'</p>
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<p><span class="hcp1">Auto/Manual button</span>
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assigns each channel to operate as either a conventional
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mixer channel (Manual) or an automated channel (Auto).
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 It should be noted that when a channel is set to
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manual it will still contribute to the overall gain attenuation
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for the channels which are set to Auto.</p>
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<p><span class="hcp1">Off Gain</span> determines
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what maximum attenuation will be applied by the downward
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expander to an idle channel. The Off Gain provides some
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downward expansion per input, which allows the relative
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difference between 'winning' inputs and 'losing' inputs
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to be accentuated. This is useful for suppressing low
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level 'idle' inputs (i.e. background noise), giving a
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larger offset between the louder winning signal (which
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we want to hear) and suppressing low level signals (which
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we don't want to hear). When this control is set to 0dB,
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no downward expansion is applied. The setting of this
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control has some effect on the point at which the On indicators
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illuminate.</p>
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<p><span class="hcp1">Gain</span> control
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for the Main output(s)</p>
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<p><span class="hcp1">Master Mute</span>
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button for the Main output(s)</p>
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<p><span class="hcp1">Slope</span> control
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determines how aggressive the gain sharing is. Low slope
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settings cause the object to behave just like a conventional
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mixer. High slope settings cause the inputs to attenuate
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more deeply for 'closed' microphones. The fully clockwise
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2:1 setting will be appropriate for most applications,
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but if you find the action to be too aggressive and do
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not want idle microphones to be 'dimmed' as much, then
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back this control off slightly.</p>
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<p><span class="hcp1">Speed</span> control
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determines how quickly a channel recovers from being open.
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Fast (anti-clockwise) settings will be needed if different
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speakers are speaking in quick succession since slow settings
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would prevent a newly active channel from fading up quickly
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enough. If the setting is too fast however, the gain sharing
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could 'pump' the gain up and down between spoken words.
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A setting somewhere near the centre of the travel will
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be found suitable in most cases.</p>
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<p><span class="hcp1">On Indicator</span>
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for each input shows when a channel is active. The 'on'
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level is related to the setting of the 'off gain' control.
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Since the gain sharing algorithm is a linear process,
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there is actually no concept of absolute 'on' or 'off'.
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Note that only one On indicator is allowed to be 'on'
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at a time so that the indicators may be applied to logic
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outputs to identify the speaker in automated camera applications.
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NOTE: When any channel is placed into 'Override' mode,
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the on indicator for that channel will be on as long as
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override mode is engaged. The on indicators for non-override
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channels will be off.</p>
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<p><span class="hcp1">Aux Masters</span>
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level and mute control for each aux bus output (Auxes
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are post-fader and post processing)</p>
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<p><span class="hcp1">Group level</span>
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level and mute control for each group bus output</p>
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<p><span class="hcp1">Signal Name</span>
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shows the name of the input signal</p>
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<h2> <br>
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Automixer Expansion</h2>
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<p class="hcp2"><span class="hcp3">It
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is possible to combine several Automixers together so
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that they act as one large Automixer. This makes use of
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the Master/Slave Status setting in the Properties Pane
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and also makes use of the Threshold and Chain control
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signals. These control signals can be passed across devices
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using Cobraet, Digital Audio Bus or Digital cards, if
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required. Note: these control signals cannot be across
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devices using the analogue inputs and outputs.</span></p>
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<p class="hcp2"> </p>
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<p class="hcp2">Connecting two Automixers</p>
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<p class="hcp2"><span class="hcp3">Connect
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the Threshold Out of the master to the Threshold In of
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the slave, and the Chain Out of the slave to the Chain
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In of the master. If you require the outputs of the two
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mixers to be combined, connect the Mix Out of the slave
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to the Mix In of the master, then use the Mix Out of the
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master.</span></p>
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<p> <img src="Automixers_two.png" alt="Image:Automixers_two.png</p> <p style=" font-weight:="" title="Image:Automixers_two.png</p> <p style=" width="666" height="276" border="0"></p>
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<p class="hcp2">Connecting more than two
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Automixers</p>
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<p>Create one master and several slaves and connect the
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Threshold Out on the master to all the Threshold Ins of
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the slaves and 'daisy chain ' the Chain Out of one slave
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to the Chain In of the next slave, and so on (in any order)
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to the Chain In of the master. If you require the outputs
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of all the mixers to be combined, 'daisy chain' the Mix
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Out of one slave to the Mix In of the next slave and so
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on (in any order) to the Mix In of the master, then use
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the Mix Out of the master.</p>
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<p> <img src="Automixers_four.png" alt="Image:Automixers_four.png</p> <p> <span style=" margin-bottom:="" font-weight:="" title="Image:Automixers_four.png</p> <p> <span style=" width="830" height="521" border="0"><br>
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 </p>
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<p><span style="margin-bottom: 0; font-weight: bold;">N</span><span class="hcp1">otes on connecting several
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Automixers</span></p>
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<p class="hcp4"><EFBFBD> The Speed and Slope controls
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should be set the same on all linked Automixers for correct
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operation.</p>
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<p class="hcp4"><EFBFBD> If you require the Aux or
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Group outputs of two or more Automixers you will need
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to combine them manually using a Summer or Mixer.</p>
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<p style="margin-bottom: 0; font-weight: bold;">Threshold
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Bus and Chain control signals</p>
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<p class="hcp4">Combining Automixers is made
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possible by distributing a Threshold bus control signal.
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This control signal represents the RMS sum of all the
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Automixers<72> input signals. This control signal is required
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by every individual Automixer to allow all the Automixers
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to act as a composite Automixer.</p>
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<p class="hcp4">Each slave Automixer contributes
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to the Threshold bus by summing its local control signal
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to the signal received at its Chain In input, and passing
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the resultant signal via its Chain Out output to the next
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slave Automixer<65>s Chain In input. These are connected
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in a daisy chain fashion until the last slave Automixer<65>s
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Chain Out is connected to the Chain In of the master Automixer.</p>
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<p class="hcp4">The master Automixer then
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sums this signal with its local control signal, creating
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the resultant Threshold bus. This resultant Threshold
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bus is then sent from the master to every one of the slave
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Automixers, so that every Automixer receives the same
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resultant Threshold bus. This is achieved by connecting
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the Threshold Out of the master Automixer to the Threshold
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Input of every slave Automixer.</p>
|
|||
|
|
<p class="hcp4"><span class="hcp1">Notes</span>:
|
|||
|
|
! This object is capable of raising signal levels beyond
|
|||
|
|
the clipping point, so care should be exercised when using
|
|||
|
|
positive gain values.</p>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
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|
|
</div>
|
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|
|
</body>
|
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</html>
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