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     40 >Video for Linux Two API Specification: Revision 0.24</TH
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     71 ><H1
     72 ><A
     73 NAME="VIDIOC-ENUMAUDIOOUT"
     74 ></A
     75 >ioctl VIDIOC_ENUMAUDOUT</H1
     76 ><DIV
     77 CLASS="REFNAMEDIV"
     78 ><A
     79 NAME="AEN8308"
     80 ></A
     81 ><H2
     82 >Name</H2
     83 >VIDIOC_ENUMAUDOUT&nbsp;--&nbsp;Enumerate audio outputs</DIV
     84 ><DIV
     85 CLASS="REFSYNOPSISDIV"
     86 ><A
     87 NAME="AEN8311"
     88 ></A
     89 ><H2
     90 >Synopsis</H2
     91 ><DIV
     92 CLASS="FUNCSYNOPSIS"
     93 ><P
     94 ></P
     95 ><A
     96 NAME="AEN8312"
     97 ></A
     98 ><P
     99 ><CODE
    100 ><CODE
    101 CLASS="FUNCDEF"
    102 >int ioctl</CODE
    103 >(int fd, int request, struct v4l2_audioout *argp);</CODE
    104 ></P
    105 ><P
    106 ></P
    107 ></DIV
    108 ></DIV
    109 ><DIV
    110 CLASS="REFSECT1"
    111 ><A
    112 NAME="AEN8322"
    113 ></A
    114 ><H2
    115 >Arguments</H2
    116 ><P
    117 ></P
    118 ><DIV
    119 CLASS="VARIABLELIST"
    120 ><DL
    121 ><DT
    122 ><CODE
    123 CLASS="PARAMETER"
    124 >fd</CODE
    125 ></DT
    126 ><DD
    127 ><P
    128 >File descriptor returned by <A
    129 HREF="r14090.htm"
    130 ><CODE
    131 CLASS="FUNCTION"
    132 >open()</CODE
    133 ></A
    134 >.</P
    135 ></DD
    136 ><DT
    137 ><CODE
    138 CLASS="PARAMETER"
    139 >request</CODE
    140 ></DT
    141 ><DD
    142 ><P
    143 >VIDIOC_ENUMAUDOUT</P
    144 ></DD
    145 ><DT
    146 ><CODE
    147 CLASS="PARAMETER"
    148 >argp</CODE
    149 ></DT
    150 ><DD
    151 ><P
    152 ></P
    153 ></DD
    154 ></DL
    155 ></DIV
    156 ></DIV
    157 ><DIV
    158 CLASS="REFSECT1"
    159 ><A
    160 NAME="AEN8342"
    161 ></A
    162 ><H2
    163 >Description</H2
    164 ><P
    165 >To query the attributes of an audio output applications
    166 initialize the <CODE
    167 CLASS="STRUCTFIELD"
    168 >index</CODE
    169 > field and zero out the
    170 <CODE
    171 CLASS="STRUCTFIELD"
    172 >reserved</CODE
    173 > array of a struct&nbsp;<A
    174 HREF="r9688.htm#V4L2-AUDIOOUT"
    175 >v4l2_audioout</A
    176 > and
    177 call the <CODE
    178 CLASS="CONSTANT"
    179 >VIDIOC_G_AUDOUT</CODE
    180 > ioctl with a pointer
    181 to this structure. Drivers fill the rest of the structure or return an
    182 <SPAN
    183 CLASS="ERRORCODE"
    184 >EINVAL</SPAN
    185 > error code when the index is out of bounds. To enumerate all audio
    186 outputs applications shall begin at index zero, incrementing by one
    187 until the driver returns <SPAN
    188 CLASS="ERRORCODE"
    189 >EINVAL</SPAN
    190 >.</P
    191 ><P
    192 >Note connectors on a TV card to loop back the received audio
    193 signal to a sound card are not audio outputs in this sense.</P
    194 ><P
    195 >See <A
    196 HREF="r9688.htm"
    197 >ioctl VIDIOC_G_AUDOUT, VIDIOC_S_AUDOUT(2)</A
    198 > for a description of
    199 struct&nbsp;<A
    200 HREF="r9688.htm#V4L2-AUDIOOUT"
    201 >v4l2_audioout</A
    202 >.</P
    203 ></DIV
    204 ><DIV
    205 CLASS="REFSECT1"
    206 ><A
    207 NAME="AEN8355"
    208 ></A
    209 ><H2
    210 >Return Value</H2
    211 ><P
    212 >On success <SPAN
    213 CLASS="RETURNVALUE"
    214 >0</SPAN
    215 > is returned, on error <SPAN
    216 CLASS="RETURNVALUE"
    217 >-1</SPAN
    218 > and the <CODE
    219 CLASS="VARNAME"
    220 >errno</CODE
    221 > variable is set appropriately:</P
    222 ><P
    223 ></P
    224 ><DIV
    225 CLASS="VARIABLELIST"
    226 ><DL
    227 ><DT
    228 ><SPAN
    229 CLASS="ERRORCODE"
    230 >EINVAL</SPAN
    231 ></DT
    232 ><DD
    233 ><P
    234 >The number of the audio output is out of bounds, or
    235 there are no audio outputs at all and this ioctl is not
    236 supported.</P
    237 ></DD
    238 ></DL
    239 ></DIV
    240 ></DIV
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