<?xml version="1.0" encoding="ANSI_X3.4-1968" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>Tuners and Modulators</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1" /><link rel="home" href="index.html" title="LINUX MEDIA INFRASTRUCTURE API" /><link rel="up" href="common.html" title="Chapter 1. Common API Elements" /><link rel="prev" href="audio.html" title="Audio Inputs and Outputs" /><link rel="next" href="standard.html" title="Video Standards" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Tuners and Modulators</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="audio.html">Prev</a> </td><th width="60%" align="center">Chapter 1. Common API Elements</th><td width="20%" align="right"> <a accesskey="n" href="standard.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="tuner"></a>Tuners and Modulators</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="section"><a href="tuner.html#idm140470036151056">Tuners</a></span></dt><dt><span class="section"><a href="tuner.html#idm140470036138880">Modulators</a></span></dt><dt><span class="section"><a href="tuner.html#idm140470036127568">Radio Frequency</a></span></dt></dl></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="idm140470036151056"></a>Tuners</h3></div></div></div><p>Video input devices can have one or more tuners demodulating a RF signal. Each tuner is associated with one or more video inputs, depending on the number of RF connectors on the tuner. The <em class="structfield"><code>type</code></em> field of the respective struct <a class="link" href="vidioc-enuminput.html#v4l2-input" title="Table A.35. struct v4l2_input">v4l2_input</a> returned by the <a class="link" href="vidioc-enuminput.html" title="ioctl VIDIOC_ENUMINPUT"><code class="constant">VIDIOC_ENUMINPUT</code></a> ioctl is set to <code class="constant">V4L2_INPUT_TYPE_TUNER</code> and its <em class="structfield"><code>tuner</code></em> field contains the index number of the tuner.</p><p>Radio input devices have exactly one tuner with index zero, no video inputs.</p><p>To query and change tuner properties applications use the <a class="link" href="vidioc-g-tuner.html" title="ioctl VIDIOC_G_TUNER, VIDIOC_S_TUNER"><code class="constant">VIDIOC_G_TUNER</code></a> and <a class="link" href="vidioc-g-tuner.html" title="ioctl VIDIOC_G_TUNER, VIDIOC_S_TUNER"><code class="constant">VIDIOC_S_TUNER</code></a> ioctl, respectively. The struct <a class="link" href="vidioc-g-tuner.html#v4l2-tuner" title="Table A.82. struct v4l2_tuner">v4l2_tuner</a> returned by <code class="constant">VIDIOC_G_TUNER</code> also contains signal status information applicable when the tuner of the current video or radio input is queried. Note that <code class="constant">VIDIOC_S_TUNER</code> does not switch the current tuner, when there is more than one at all. The tuner is solely determined by the current video input. Drivers must support both ioctls and set the <code class="constant">V4L2_CAP_TUNER</code> flag in the struct <a class="link" href="vidioc-querycap.html#v4l2-capability" title="Table A.88. struct v4l2_capability">v4l2_capability</a> returned by the <a class="link" href="vidioc-querycap.html" title="ioctl VIDIOC_QUERYCAP"><code class="constant">VIDIOC_QUERYCAP</code></a> ioctl when the device has one or more tuners.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="idm140470036138880"></a>Modulators</h3></div></div></div><p>Video output devices can have one or more modulators, uh, modulating a video signal for radiation or connection to the antenna input of a TV set or video recorder. Each modulator is associated with one or more video outputs, depending on the number of RF connectors on the modulator. The <em class="structfield"><code>type</code></em> field of the respective struct <a class="link" href="vidioc-enumoutput.html#v4l2-output" title="Table A.39. struct v4l2_output">v4l2_output</a> returned by the <a class="link" href="vidioc-enumoutput.html" title="ioctl VIDIOC_ENUMOUTPUT"><code class="constant">VIDIOC_ENUMOUTPUT</code></a> ioctl is set to <code class="constant">V4L2_OUTPUT_TYPE_MODULATOR</code> and its <em class="structfield"><code>modulator</code></em> field contains the index number of the modulator.</p><p>Radio output devices have exactly one modulator with index zero, no video outputs.</p><p>A video or radio device cannot support both a tuner and a modulator. Two separate device nodes will have to be used for such hardware, one that supports the tuner functionality and one that supports the modulator functionality. The reason is a limitation with the <a class="link" href="vidioc-g-frequency.html" title="ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY"><code class="constant">VIDIOC_S_FREQUENCY</code></a> ioctl where you cannot specify whether the frequency is for a tuner or a modulator.</p><p>To query and change modulator properties applications use the <a class="link" href="vidioc-g-modulator.html" title="ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR"><code class="constant">VIDIOC_G_MODULATOR</code></a> and <a class="link" href="vidioc-g-modulator.html" title="ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR"><code class="constant">VIDIOC_S_MODULATOR</code></a> ioctl. Note that <code class="constant">VIDIOC_S_MODULATOR</code> does not switch the current modulator, when there is more than one at all. The modulator is solely determined by the current video output. Drivers must support both ioctls and set the <code class="constant">V4L2_CAP_MODULATOR</code> flag in the struct <a class="link" href="vidioc-querycap.html#v4l2-capability" title="Table A.88. struct v4l2_capability">v4l2_capability</a> returned by the <a class="link" href="vidioc-querycap.html" title="ioctl VIDIOC_QUERYCAP"><code class="constant">VIDIOC_QUERYCAP</code></a> ioctl when the device has one or more modulators.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="idm140470036127568"></a>Radio Frequency</h3></div></div></div><p>To get and set the tuner or modulator radio frequency applications use the <a class="link" href="vidioc-g-frequency.html" title="ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY"><code class="constant">VIDIOC_G_FREQUENCY</code></a> and <a class="link" href="vidioc-g-frequency.html" title="ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY"><code class="constant">VIDIOC_S_FREQUENCY</code></a> ioctl which both take a pointer to a struct <a class="link" href="vidioc-g-frequency.html#v4l2-frequency" title="Table A.68. struct v4l2_frequency">v4l2_frequency</a>. These ioctls are used for TV and radio devices alike. Drivers must support both ioctls when the tuner or modulator ioctls are supported, or when the device is a radio device.</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="audio.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="common.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="standard.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Audio Inputs and Outputs </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Video Standards</td></tr></table></div></body></html>
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