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40>Video for Linux Two API Specification: Revision 0.24</TH
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73><H1
74CLASS="SECTION"
75><A
76NAME="TUNER"
77>1.6. Tuners and Modulators</A
78></H1
79><DIV
80CLASS="SECTION"
81><H2
82CLASS="SECTION"
83><A
84NAME="AEN396"
85>1.6.1. Tuners</A
86></H2
87><P
88>Video input devices can have one or more tuners
89demodulating a RF signal. Each tuner is associated with one or more
90video inputs, depending on the number of RF connectors on the tuner.
91The <CODE
92CLASS="STRUCTFIELD"
93>type</CODE
94> field of the respective
95struct&nbsp;<A
96HREF="r8936.htm#V4L2-INPUT"
97>v4l2_input</A
98> returned by the <A
99HREF="r8936.htm"
100><CODE
101CLASS="CONSTANT"
102>VIDIOC_ENUMINPUT</CODE
103></A
104> ioctl is set to
105<CODE
106CLASS="CONSTANT"
107>V4L2_INPUT_TYPE_TUNER</CODE
108> and its
109<CODE
110CLASS="STRUCTFIELD"
111>tuner</CODE
112> field contains the index number of
113the tuner.</P
114><P
115>Radio devices have exactly one tuner with index zero, no
116video inputs.</P
117><P
118>To query and change tuner properties applications use the
119<A
120HREF="r12342.htm"
121><CODE
122CLASS="CONSTANT"
123>VIDIOC_G_TUNER</CODE
124></A
125> and <A
126HREF="r12342.htm"
127><CODE
128CLASS="CONSTANT"
129>VIDIOC_S_TUNER</CODE
130></A
131> ioctl, respectively. The
132struct&nbsp;<A
133HREF="r12342.htm#V4L2-TUNER"
134>v4l2_tuner</A
135> returned by <CODE
136CLASS="CONSTANT"
137>VIDIOC_G_TUNER</CODE
138> also
139contains signal status information applicable when the tuner of the
140current video input, or a radio tuner is queried. Note that
141<CODE
142CLASS="CONSTANT"
143>VIDIOC_S_TUNER</CODE
144> does not switch the current tuner,
145when there is more than one at all. The tuner is solely determined by
146the current video input. Drivers must support both ioctls and set the
147<CODE
148CLASS="CONSTANT"
149>V4L2_CAP_TUNER</CODE
150> flag in the struct&nbsp;<A
151HREF="r13105.htm#V4L2-CAPABILITY"
152>v4l2_capability</A
153>
154returned by the <A
155HREF="r13105.htm"
156><CODE
157CLASS="CONSTANT"
158>VIDIOC_QUERYCAP</CODE
159></A
160> ioctl when the device has one or
161more tuners.</P
162></DIV
163><DIV
164CLASS="SECTION"
165><H2
166CLASS="SECTION"
167><A
168NAME="AEN418"
169>1.6.2. Modulators</A
170></H2
171><P
172>Video output devices can have one or more modulators, uh,
173modulating a video signal for radiation or connection to the antenna
174input of a TV set or video recorder. Each modulator is associated with
175one or more video outputs, depending on the number of RF connectors on
176the modulator. The <CODE
177CLASS="STRUCTFIELD"
178>type</CODE
179> field of the
180respective struct&nbsp;<A
181HREF="r9149.htm#V4L2-OUTPUT"
182>v4l2_output</A
183> returned by the <A
184HREF="r9149.htm"
185><CODE
186CLASS="CONSTANT"
187>VIDIOC_ENUMOUTPUT</CODE
188></A
189> ioctl is
190set to <CODE
191CLASS="CONSTANT"
192>V4L2_OUTPUT_TYPE_MODULATOR</CODE
193> and its
194<CODE
195CLASS="STRUCTFIELD"
196>modulator</CODE
197> field contains the index number
198of the modulator. This specification does not define radio output
199devices.</P
200><P
201>To query and change modulator properties applications use
202the <A
203HREF="r11430.htm"
204><CODE
205CLASS="CONSTANT"
206>VIDIOC_G_MODULATOR</CODE
207></A
208> and <A
209HREF="r11430.htm"
210><CODE
211CLASS="CONSTANT"
212>VIDIOC_S_MODULATOR</CODE
213></A
214> ioctl. Note that
215<CODE
216CLASS="CONSTANT"
217>VIDIOC_S_MODULATOR</CODE
218> does not switch the current
219modulator, when there is more than one at all. The modulator is solely
220determined by the current video output. Drivers must support both
221ioctls and set the <CODE
222CLASS="CONSTANT"
223>V4L2_CAP_TUNER</CODE
224> (sic) flag in
225the struct&nbsp;<A
226HREF="r13105.htm#V4L2-CAPABILITY"
227>v4l2_capability</A
228> returned by the <A
229HREF="r13105.htm"
230><CODE
231CLASS="CONSTANT"
232>VIDIOC_QUERYCAP</CODE
233></A
234> ioctl when the
235device has one or more modulators.</P
236></DIV
237><DIV
238CLASS="SECTION"
239><H2
240CLASS="SECTION"
241><A
242NAME="AEN437"
243>1.6.3. Radio Frequency</A
244></H2
245><P
246>To get and set the tuner or modulator radio frequency
247applications use the <A
248HREF="r11094.htm"
249><CODE
250CLASS="CONSTANT"
251>VIDIOC_G_FREQUENCY</CODE
252></A
253> and <A
254HREF="r11094.htm"
255><CODE
256CLASS="CONSTANT"
257>VIDIOC_S_FREQUENCY</CODE
258></A
259>
260ioctl which both take a pointer to a struct&nbsp;<A
261HREF="r11094.htm#V4L2-FREQUENCY"
262>v4l2_frequency</A
263>. These ioctls
264are used for TV and radio devices alike. Drivers must support both
265ioctls when the tuner or modulator ioctls are supported, or
266when the device is a radio device.</P
267></DIV
268><DIV
269CLASS="SECTION"
270><H2
271CLASS="SECTION"
272><A
273NAME="AEN445"
274>1.6.4. Satellite Receivers</A
275></H2
276><P
277>To be discussed. See also
278proposals by Peter Schlaf, video4linux-list@redhat.com on 23 Oct 2002,
279subject: "Re: [V4L] Re: v4l2 api".</P
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