forked from auracaster/pyalsaaudio
8fa9d27a88
r1585 | casper | 2005-07-09 23:26:15 +0200 (Sat, 09 Jul 2005) | 3 lines Last checkin before version 0.2 git-svn-id: svn://svn.code.sf.net/p/pyalsaaudio/code/trunk@12 ec2f30ec-7544-0410-870e-f70ca00c83f0
328 lines
14 KiB
HTML
328 lines
14 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<title>4.3 Mixer Objects</title>
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<H2><A NAME="SECTION002430000000000000000"></A>
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<A NAME="mixer-objects"></A>
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<BR>
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4.3 Mixer Objects
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</H2>
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<P>
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Mixer objects provides access to the ALSA mixer API.
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<P>
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<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
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<td><nobr><b><span class="typelabel">class</span> <tt id='l2h-16' xml:id='l2h-16' class="class">Mixer</tt></b>(</nobr></td>
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<td><var></var><big>[</big><var>control</var><big>]</big><var>, </var><big>[</big><var>id</var><big>]</big><var>, </var><big>[</big><var>cardname</var><big>]</big><var></var>)</td></tr></table></dt>
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<dd>
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<var>control</var> - specifies which control to manipulate using this mixer object. The list
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of available controls can be found with the <tt class="module">alsaaudio</tt>.<tt class="function">mixers</tt> function.
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The default value is 'Master' - other common controls include 'Master Mono', 'PCM', 'Line', etc.
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<P>
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<var>id</var> - the id of the mixer control. Default is 0
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<P>
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<var>cardname</var> - specifies which card should be used (this is only relevant
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if you have more than one sound card). Omit to use the default sound card
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</dl>
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<P>
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Mixer objects have the following methods:
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<P>
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<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
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<td><nobr><b><tt id='l2h-17' xml:id='l2h-17' class="method">cardname</tt></b>(</nobr></td>
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<td><var></var>)</td></tr></table></dt>
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<dd>
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Return the name of the sound card used by this Mixer object
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</dl>
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<P>
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<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
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<td><nobr><b><tt id='l2h-18' xml:id='l2h-18' class="method">mixer</tt></b>(</nobr></td>
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<td><var></var>)</td></tr></table></dt>
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<dd>
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Return the name of the specific mixer controlled by this object, For example 'Master'
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or 'PCM'
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</dl>
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<P>
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<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
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<td><nobr><b><tt id='l2h-19' xml:id='l2h-19' class="method">mixerid</tt></b>(</nobr></td>
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<td><var></var>)</td></tr></table></dt>
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<dd>
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Return the ID of the ALSA mixer controlled by this object.
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</dl>
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<P>
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<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
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<td><nobr><b><tt id='l2h-20' xml:id='l2h-20' class="method">switchcap</tt></b>(</nobr></td>
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<td><var></var>)</td></tr></table></dt>
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<dd>
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Returns a list of the switches which are defined by this specific mixer. Possible values in
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this list are:
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<P>
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<div class="center"><table class="realtable">
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<thead>
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<tr>
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<th class="left" >Switch</th>
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<th class="left" >Description</th>
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</tr>
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</thead>
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<tbody>
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<tr><td class="left" valign="baseline"><Volume Capabilities>'Mute'</Volume></td>
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<td class="left" >This mixer can be muted</td></tr>
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<tr><td class="left" valign="baseline"><Volume Capabilities>'Joined Mute'</Volume></td>
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<td class="left" >This mixer can mute all channels at the same time</td></tr>
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<tr><td class="left" valign="baseline"><Volume Capabilities>'Playback Mute'</Volume></td>
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<td class="left" >This mixer can mute the playback output</td></tr>
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<tr><td class="left" valign="baseline"><Volume Capabilities>'Joined Playback Mute'</Volume></td>
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<td class="left" >Mute playback for all channels at the same time</td></tr>
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<tr><td class="left" valign="baseline"><Volume Capabilities>'Capture Mute'</Volume></td>
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<td class="left" >Mute sound capture</td></tr>
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<tr><td class="left" valign="baseline"><Volume Capabilities>'Joined Capture Mute'</Volume></td>
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<td class="left" >Mute sound capture for all channels at a time</td></tr>
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<tr><td class="left" valign="baseline"><Volume Capabilities>'Capture Exclusive'</Volume></td>
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<td class="left" >Not quite sure what this is</td></tr></tbody>
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</table></div>
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<P>
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To manipulate these swithes use the <tt class="method">setrec</tt> or <tt class="method">setmute</tt> methods
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</dl>
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<P>
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<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
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<td><nobr><b><tt id='l2h-21' xml:id='l2h-21' class="method">volumecap</tt></b>(</nobr></td>
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<td><var></var>)</td></tr></table></dt>
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<dd>
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Returns a list of the volume control capabilities of this mixer. Possible values in
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the list are:
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<P>
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<div class="center"><table class="realtable">
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<thead>
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<tr>
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<th class="left" >Capability</th>
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<th class="left" >Description</th>
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</tr>
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</thead>
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<tbody>
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<tr><td class="left" valign="baseline"><Volume Capabilities>'Volume'</Volume></td>
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<td class="left" >This mixer can control volume</td></tr>
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<tr><td class="left" valign="baseline"><Volume Capabilities>'Joined Volume'</Volume></td>
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<td class="left" >This mixer can control volume for all channels at the same time</td></tr>
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<tr><td class="left" valign="baseline"><Volume Capabilities>'Playback Volume'</Volume></td>
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<td class="left" >This mixer can manipulate the playback volume</td></tr>
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<tr><td class="left" valign="baseline"><Volume Capabilities>'Joined Playback Volume'</Volume></td>
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<td class="left" >Manipulate playback volumne for all channels at the same time</td></tr>
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<tr><td class="left" valign="baseline"><Volume Capabilities>'Capture Volume'</Volume></td>
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<td class="left" >Manipulate sound capture volume</td></tr>
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<tr><td class="left" valign="baseline"><Volume Capabilities>'Joined Capture Volume'</Volume></td>
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<td class="left" >Manipulate sound capture volume for all channels at a time</td></tr></tbody>
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</table></div>
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<P>
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</dl>
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<P>
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<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
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<td><nobr><b><tt id='l2h-22' xml:id='l2h-22' class="method">getvolume</tt></b>(</nobr></td>
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<td><var></var><big>[</big><var>direction</var><big>]</big><var></var>)</td></tr></table></dt>
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<dd>
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Returns a list with the current volume settings for each channel. The list elements
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are integer percentages.
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<P>
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The optional <var>direction</var> argument can be either 'playback' or 'capture', which is relevant
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if the mixer can control both playback and capture volume. The default value is 'playback'
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if the mixer has this capability, otherwise 'capture'
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<P>
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</dl>
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<P>
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<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
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<td><nobr><b><tt id='l2h-23' xml:id='l2h-23' class="method">getmute</tt></b>(</nobr></td>
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<td><var></var>)</td></tr></table></dt>
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<dd>
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Return a list indicating the current mute setting for each channel. 0 means not muted, 1 means muted.
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<P>
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This method will fail if the mixer has no playback switch capabilities.
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</dl>
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<P>
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<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
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<td><nobr><b><tt id='l2h-24' xml:id='l2h-24' class="method">getrec</tt></b>(</nobr></td>
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<td><var></var>)</td></tr></table></dt>
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<dd>
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Return a list indicating the current record mute setting for each channel. 0 means not recording, 1
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means not recording.
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<P>
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This method will fail if the mixer has no capture switch capabilities.
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</dl>
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<P>
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<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
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<td><nobr><b><tt id='l2h-25' xml:id='l2h-25' class="method">setvolume</tt></b>(</nobr></td>
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<td><var>volume,</var><big>[</big><var>channel</var><big>]</big><var>,</var><big>[</big><var>direction</var><big>]</big><var></var>)</td></tr></table></dt>
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<dd>
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Change the current volume settings for this mixer. The <var>volume</var> argument controls
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the new volume setting as an integer percentage.
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<P>
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If the optional argument <var>channel</var> is present, the volume is set only for this channel. This
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assumes that the mixer can control the volume for the channels independently.
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<P>
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The optional <var>direction</var> argument can be either 'playback' or 'capture' is relevant if the mixer
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has independent playback and capture volume capabilities, and controls which of the volumes
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if changed. The default is 'playback' if the mixer has this capability, otherwise 'capture'.
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</dl>
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<P>
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<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
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<td><nobr><b><tt id='l2h-26' xml:id='l2h-26' class="method">setmute</tt></b>(</nobr></td>
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<td><var>mute, </var><big>[</big><var>channel</var><big>]</big><var></var>)</td></tr></table></dt>
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<dd>
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Sets the mute flag to a new value. The <var>mute</var> argument is either 0 for not muted, or 1 for muted.
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<P>
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The optional <var>channel</var> argument controls which channel is muted. The default is to set the mute flag
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for all channels.
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<P>
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This method will fail if the mixer has no playback mute capabilities
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</dl>
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<P>
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<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
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<td><nobr><b><tt id='l2h-27' xml:id='l2h-27' class="method">setrec</tt></b>(</nobr></td>
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<td><var>capture,</var><big>[</big><var>channel</var><big>]</big><var></var>)</td></tr></table></dt>
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<dd>
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Sets the capture mute flag to a new value. The <var>capture</var> argument is either 0 for no capture,
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or 1 for capture.
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<P>
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The optional <var>channel</var> argument controls which channel is changed. The default is to set the capture flag
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for all channels.
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<P>
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This method will fail if the mixer has no capture switch capabilities
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</dl>
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<P>
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<b>A Note on the ALSA Mixer API</b>
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<P>
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The ALSA mixer API is extremely complicated - and hardly documented at all. <tt class="module">alsaaudio</tt> implements
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a much simplified way to access this API. In designing the API I've had to make some choices which
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may limit what can and cannot be controlled through the API. However, If I had chosen to implement the
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full API, I would have reexposed the horrible complexity/documentation ratio of the underlying API.
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At least the <tt class="module">alsaaudio</tt> API is easy to understand and use.
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<P>
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If my design choises prevents you from doing something that the underlying API would have allowed,
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please let me know, so I can incorporate these need into future versions.
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<P>
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If the current state of affairs annoy you, the best you can do is to write a HOWTO on the API and
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make this available on the net. Until somebody does this, the availability of ALSA mixer capable
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devices will stay quite limited.
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<P>
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Unfortunately, I'm not able to create such a HOWTO myself, since I only understand half of the API,
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and that which I do understand has come from a painful trial and error process.
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<P>
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<p></p><hr />
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href="pcm-objects.html"><img src='previous.png'
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border='0' height='32' alt='Previous Page' width='32' /></A></td>
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href="module-alsaaudio.html"><img src='up.png'
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border='0' height='32' alt='Up One Level' width='32' /></A></td>
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href="pcm-example.html"><img src='next.png'
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<td align="center" width="100%">PyAlsaAudio</td>
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<td class='online-navigation'><a rel="contents" title="Table of Contents"
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border='0' height='32' alt='Contents' width='32' /></A></td>
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<span class="release-info">Release 0.2.</span>
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