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<concept id="GUID-ACA48BEE-FE73-5C47-B022-E50728CEDBEE" xml:lang="en"><title>Architecture</title><shortdesc>Describes the architecture of the Sound Driver.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>There are three main parts: </p>
<ul>
<li id="GUID-6EEE9FF2-FA3A-5B50-9CD9-D098C66D5331"><p>the user side interface
to the <xref href="GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6.dita#GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6/GUID-4D6A01FE-47E7-5A6F-9DFE-F612B880165B">Driver
channel</xref>. This is an instance of a class derived from <xref href="GUID-B0118EDD-2B08-353E-BE92-2DC75E5622B3.dita"><apiname>RSoundSc</apiname></xref>. </p> <p>The
class <xref href="GUID-B0118EDD-2B08-353E-BE92-2DC75E5622B3.dita"><apiname>RSoundSc</apiname></xref> provides the user side interface to the
driver. This class is defined in <filepath>\e32\include\d32soundsc.h</filepath>.
An instance of <xref href="GUID-B0118EDD-2B08-353E-BE92-2DC75E5622B3.dita"><apiname>RSoundSc</apiname></xref> is required for each <xref href="GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6.dita#GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6/GUID-4D6A01FE-47E7-5A6F-9DFE-F612B880165B">driver channel</xref> opened by the client. When opening a <xref href="GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6.dita#GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6/GUID-4D6A01FE-47E7-5A6F-9DFE-F612B880165B">driver channel</xref>, the client specifies a channel number for the <xref href="GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6.dita#GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6/GUID-74B14664-8D9D-57D2-B090-709136FEB5E3">audio
channel</xref>. Channel numbers 0 to 3 are allocated for output/playback channels
and channels 4 to 7 are allocated for input/record channels. </p> </li>
<li id="GUID-FA62DA0C-F56E-51B4-84B2-EF8316CACC1B"><p>the <xref href="GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6.dita#GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6/GUID-4D6A01FE-47E7-5A6F-9DFE-F612B880165B">driver channel</xref>, also known as the logical channel or LDD. </p> <p>The
class <xref href="GUID-5807543D-A30F-3EB9-8F28-91A623B0D484.dita"><apiname>DSoundScLdd</apiname></xref> is the <xref href="GUID-0956CE5E-C02B-5EEE-890A-5E8E84A8D9A1.dita">logical
channel</xref> object for either audio playback or record. This class is defined
in <filepath>\e32\include\drivers\soundsc.h</filepath>. An instance of <xref href="GUID-5807543D-A30F-3EB9-8F28-91A623B0D484.dita"><apiname>DSoundScLdd</apiname></xref> is
created for each <xref href="GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6.dita#GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6/GUID-4D6A01FE-47E7-5A6F-9DFE-F612B880165B">driver
channel</xref> opened. The driver implements play and record operation over
a single audio hardware device as two separate <xref href="GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6.dita#GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6/GUID-7C8FF32F-2E84-57B1-8962-9EDB4D51FEE6">units</xref>. Therefore, a client that needs to issue both record and playback requests
has to open two separate <xref href="GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6.dita#GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6/GUID-4D6A01FE-47E7-5A6F-9DFE-F612B880165B">driver
channels</xref>. </p> <p> <codeph>DSOundScLdd</codeph> is derived from <xref href="GUID-A3CC1D95-4681-3349-A67C-F113A614041D.dita"><apiname>DLogicalChannel</apiname></xref>. <xref href="GUID-A3CC1D95-4681-3349-A67C-F113A614041D.dita"><apiname>DLogicalChannel</apiname></xref> is
the base class for a logical channel and provides the framework in which user
side client requests are normally executed in the context of a kernel side
thread. However, for this particular driver, not every request is executed
in the context of a kernel thread. Requests that do not require access to
hardware are handled in the context of the calling thread. </p> </li>
<li id="GUID-861F1E3E-9087-530A-938D-DDD934D4EB67"><p>the <xref href="GUID-461A9DAD-1C1D-537D-A7A7-9E1AF33ABBA2.dita">physical
channel</xref>, also known as the PDD, manages access to the audio hardware
device for all instances of the <xref href="GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6.dita#GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6/GUID-4D6A01FE-47E7-5A6F-9DFE-F612B880165B">driver
channel</xref>. </p> <p>The class <xref href="GUID-61CC68CB-A01D-3CA0-93D9-F3717ABD6424.dita"><apiname>DSoundScPdd</apiname></xref> is the base
class for the Sound Driver PDD object. This class is used for either playback
or record, it implements the platform specific layer of the driver and an
instance of this class is created for each <xref href="GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6.dita#GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6/GUID-4D6A01FE-47E7-5A6F-9DFE-F612B880165B">driver
channel</xref> opened. This is created by the Sound Driver physical device
class <xref href="GUID-AA9C0AAC-C718-3DE7-BF4B-D10C277AED6D.dita"><apiname>DSoundScPddFactory</apiname></xref> when a channel is opened. The
class <xref href="GUID-61CC68CB-A01D-3CA0-93D9-F3717ABD6424.dita"><apiname>DSoundScPdd</apiname></xref> is defined in <filepath>\e32\include\drivers\soundsc.h</filepath>. </p> <p>The
following diagram illustrates the Sound Driver architecture. The interactions
between the user side and kernel side classes are shown. </p> </li>
</ul>
<fig id="GUID-257F5F90-AC86-5029-81EB-5CBB16B8A1F9">
<title>           The main classes involved in Sound Driver implementation.
         </title>
<image href="GUID-8C9F26BC-2579-545C-9A86-9C45E06679F0_d0e32265_href.png" placement="inline"/>
</fig>
</conbody></concept>