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