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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE chapter>
<!-- Copyright (C) 2005-2018 Jo\u00EBl Kr\u00E4hemann -->
<!-- Permission is granted to copy, distribute and/or modify this document -->
<!-- under the terms of the GNU Free Documentation License, Version 1.3 -->
<!-- or any later version published by the Free Software Foundation; -->
<!-- with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. -->
<!-- A copy of the license is included in the section entitled "GNU -->
<!-- Free Documentation License". -->
<chapter xmlns="http://docbook.org/ns/docbook"
xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0">
<title>The soundcard and sequencer interface</title>
<para>
With AgsSoundcard and AgsSequencer interface you can obtain information about
output or input devices. Getting the next buffer for playback something can be
achieved, too. As well reading MIDI data from current buffer is supported.
Note these operations are performed all delayed in order to avoid concurrent
memory access.
</para>
<para>
Latency is at most one buffer time. Operations on buffers might be performed
non-blocking so the thread returns earlier than expected. This has the advantage
of controlling timings and let the thread continue to do more synchronization
runs. Real-time behaviour is indicated as all pending sync operations were fulfilled
as the next buffer is needed.
</para>
<para>
The Advanced Gtk+ Sequencer framework implements following
soundcard objects. Note to register soundcards by a sound server make
use of AgsSoundServer interface. This applies to JACK, Pulseaudio and CoreAudio
backend.
</para>
<itemizedlist mark="bullet">
<listitem>
<para>
AgsDevout ALSA and OSSv4 soundcard output.
</para>
</listitem>
<listitem>
<para>
AgsDevin ALSA and OSSv4 soundcard input.
</para>
</listitem>
<listitem>
<para>
AgsPulseDevout Pulseaudio output.
</para>
</listitem>
<listitem>
<para>
AgsJackDevout JACK Audio Connection Kit output.
</para>
</listitem>
<listitem>
<para>
AgsJackDevin JACK Audio Connection Kit input.
</para>
</listitem>
<listitem>
<para>
AgsWasapiDevout Windows soundcard output.
</para>
</listitem>
<listitem>
<para>
AgsWasapiDevin Windows soundcard input.
</para>
</listitem>
<listitem>
<para>
AgsCoreAudioDevout macos soundcard output.
</para>
</listitem>
<listitem>
<para>
AgsCoreAudioDevin macos soundcard input.
</para>
</listitem>
</itemizedlist>
<para>
The Advanced Gtk+ Sequencer framework implements following
sequencer objects.
</para>
<itemizedlist mark="bullet">
<listitem>
<para>
AgsMidiin ALSA and OSSv4 MIDI input.
</para>
</listitem>
<listitem>
<para>
AgsJackMidiin JACK Audio Connection Kit MIDI input.
</para>
</listitem>
<listitem>
<para>
AgsCoreAudioMidiin macos MIDI input.
</para>
</listitem>
</itemizedlist>
<sect1>
<title>Gathering PCM information of soundcard</title>
<para>
In this short example we just get some information out of AgsSoundcard by using
<code language="C">void ags_soundcard_pcm_info(AgsSoundcard*, gchar*, guint*, guint*, guint*, guint*, guint*, guint*, GError*)</code>.
It tells us the card identifier, minimum and maximum supported audio channels, samplerate and buffer size.
</para>
<example>
<title>PCM information from AgsSoundcard</title>
<programlisting language="C">
<xi:include href="../listings/pcm_info.c" parse="text" />
</programlisting>
</example>
</sect1>
<sect1>
<title>Obtain audio buffer</title>
<para>
Here we get audio buffer from AgsSoundcard and write some sine synth tone at
440 Hz. First we get presets from soundcard, then we fill the AgsSynthUtil struct
and finally compute the sine sound using utility function.
</para>
<example>
<title>Get AgsSoundcard buffer</title>
<programlisting language="C">
<xi:include href="../listings/soundcard_buffer.c" parse="text" />
</programlisting>
</example>
</sect1>
<sect1>
<title>Read from MIDI device</title>
<para>
</para>
<example>
<title>Get AgsSequencer buffer</title>
<programlisting language="C">
<xi:include href="../listings/sequencer_buffer.c" parse="text" />
</programlisting>
</example>
</sect1>
</chapter>
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