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    12 <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>

    13 <p>There are three main parts: </p>

    14 <ul>

    15 <li id="GUID-6EEE9FF2-FA3A-5B50-9CD9-D098C66D5331"><p>the user side interface

    16 to the <xref href="GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6.dita#GUID-E2641957-8163-5EF4-B282-FC3FD9CA75A6/GUID-4D6A01FE-47E7-5A6F-9DFE-F612B880165B">Driver

    17 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

    18 class <xref href="GUID-B0118EDD-2B08-353E-BE92-2DC75E5622B3.dita"><apiname>RSoundSc</apiname></xref> provides the user side interface to the

    19 driver. This class is defined in <filepath>\e32\include\d32soundsc.h</filepath>.

    20 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

    21 channel</xref>. Channel numbers 0 to 3 are allocated for output/playback channels

    22 and channels 4 to 7 are allocated for input/record channels. </p> </li>

    23 <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

    24 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

    25 channel</xref> object for either audio playback or record. This class is defined

    26 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

    27 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

    28 channel</xref> opened. The driver implements play and record operation over

    29 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

    30 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

    31 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

    32 the base class for a logical channel and provides the framework in which user

    33 side client requests are normally executed in the context of a kernel side

    34 thread. However, for this particular driver, not every request is executed

    35 in the context of a kernel thread. Requests that do not require access to

    36 hardware are handled in the context of the calling thread. </p> </li>

    37 <li id="GUID-861F1E3E-9087-530A-938D-DDD934D4EB67"><p>the <xref href="GUID-461A9DAD-1C1D-537D-A7A7-9E1AF33ABBA2.dita">physical

    38 channel</xref>, also known as the PDD, manages access to the audio hardware

    39 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

    40 channel</xref>. </p> <p>The class <xref href="GUID-61CC68CB-A01D-3CA0-93D9-F3717ABD6424.dita"><apiname>DSoundScPdd</apiname></xref> is the base

    41 class for the Sound Driver PDD object. This class is used for either playback

    42 or record, it implements the platform specific layer of the driver and an

    43 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

    44 channel</xref> opened. This is created by the Sound Driver physical device

    45 class <xref href="GUID-AA9C0AAC-C718-3DE7-BF4B-D10C277AED6D.dita"><apiname>DSoundScPddFactory</apiname></xref> when a channel is opened. The

    46 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

    47 following diagram illustrates the Sound Driver architecture. The interactions

    48 between the user side and kernel side classes are shown. </p> </li>

    49 </ul>

    50 <fig id="GUID-257F5F90-AC86-5029-81EB-5CBB16B8A1F9">

    51 <title>           The main classes involved in Sound Driver implementation.

    52          </title>

    53 <image href="GUID-8C9F26BC-2579-545C-9A86-9C45E06679F0_d0e32265_href.png" placement="inline"/>

    54 </fig>

    55 </conbody></concept>