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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_d0e398281_href.png" placement="inline"/>

</fig>

</conbody></concept>