<?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>ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="LINUX MEDIA INFRASTRUCTURE API" /><link rel="up" href="apa.html" title="Appendix A. Function Reference" /><link rel="prev" href="re44.html" title="ioctl VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP" /><link rel="next" href="re46.html" title="ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re44.html">Prev</a> </td><th width="60%" align="center">Appendix A. Function Reference</th><td width="20%" align="right"> <a accesskey="n" href="re46.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR"><a id="vidioc-g-modulator"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR — Get or set modulator attributes</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">ioctl</b>(</code></td><td>int <var class="pdparam">fd</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">request</var>, </td></tr><tr><td> </td><td>struct v4l2_modulator *<var class="pdparam">argp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">ioctl</b>(</code></td><td>int <var class="pdparam">fd</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">request</var>, </td></tr><tr><td> </td><td>const struct v4l2_modulator *<var class="pdparam">argp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2717123"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>fd</code></em></span></dt><dd><p>File descriptor returned by <a class="link" href="re64.html" title="V4L2 open()"><code class="function">open()</code></a>.</p></dd><dt><span class="term"><em class="parameter"><code>request</code></em></span></dt><dd><p>VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR</p></dd><dt><span class="term"><em class="parameter"><code>argp</code></em></span></dt><dd><p></p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2717192"></a><h2>Description</h2><p>To query the attributes of a modulator applications initialize the <em class="structfield"><code>index</code></em> field and zero out the <em class="structfield"><code>reserved</code></em> array of a struct <a class="link" href="re45.html#v4l2-modulator" title="Table A.50. struct v4l2_modulator">v4l2_modulator</a> and call the <code class="constant">VIDIOC_G_MODULATOR</code> ioctl with a pointer to this structure. Drivers fill the rest of the structure or return an <span class="errorcode">EINVAL</span> error code when the index is out of bounds. To enumerate all modulators applications shall begin at index zero, incrementing by one until the driver returns <span class="errorcode">EINVAL</span>.</p><p>Modulators have two writable properties, an audio modulation set and the radio frequency. To change the modulated audio subprograms, applications initialize the <em class="structfield"><code>index </code></em> and <em class="structfield"><code>txsubchans</code></em> fields and the <em class="structfield"><code>reserved</code></em> array and call the <code class="constant">VIDIOC_S_MODULATOR</code> ioctl. Drivers may choose a different audio modulation if the request cannot be satisfied. However this is a write-only ioctl, it does not return the actual audio modulation selected.</p><p>To change the radio frequency the <a class="link" href="re42.html" title="ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY"><code class="constant">VIDIOC_S_FREQUENCY</code></a> ioctl is available.</p><div class="table"><a id="v4l2-modulator"></a><p class="title"><b>Table A.50. struct <span class="structname">v4l2_modulator</span></b></p><div class="table-contents"><table summary="struct v4l2_modulator" width="100%" border="0"><colgroup><col /><col /><col /></colgroup><tbody valign="top"><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>index</code></em></td><td valign="top">Identifies the modulator, set by the application.</td></tr><tr><td valign="top">__u8</td><td valign="top"><em class="structfield"><code>name</code></em>[32]</td><td valign="top">Name of the modulator, a NUL-terminated ASCII string. This information is intended for the user.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>capability</code></em></td><td valign="top">Modulator capability flags. No flags are defined for this field, the tuner flags in struct <a class="link" href="re51.html#v4l2-tuner" title="Table A.60. struct v4l2_tuner">v4l2_tuner</a> are used accordingly. The audio flags indicate the ability to encode audio subprograms. They will <span class="emphasis"><em>not</em></span> change for example with the current video standard.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>rangelow</code></em></td><td valign="top">The lowest tunable frequency in units of 62.5 KHz, or if the <em class="structfield"><code>capability</code></em> flag <code class="constant">V4L2_TUNER_CAP_LOW</code> is set, in units of 62.5 Hz.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>rangehigh</code></em></td><td valign="top">The highest tunable frequency in units of 62.5 KHz, or if the <em class="structfield"><code>capability</code></em> flag <code class="constant">V4L2_TUNER_CAP_LOW</code> is set, in units of 62.5 Hz.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>txsubchans</code></em></td><td valign="top">With this field applications can determine how audio sub-carriers shall be modulated. It contains a set of flags as defined in <a class="xref" href="re45.html#modulator-txsubchans" title="Table A.51. Modulator Audio Transmission Flags">Table A.51, “Modulator Audio Transmission Flags”</a>. Note the tuner <em class="structfield"><code>rxsubchans</code></em> flags are reused, but the semantics are different. Video output devices are assumed to have an analog or PCM audio input with 1-3 channels. The <em class="structfield"><code>txsubchans</code></em> flags select one or more channels for modulation, together with some audio subprogram indicator, for example a stereo pilot tone.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>reserved</code></em>[4]</td><td valign="top">Reserved for future extensions. Drivers and applications must set the array to zero.</td></tr></tbody></table></div></div><br class="table-break" /><div class="table"><a id="modulator-txsubchans"></a><p class="title"><b>Table A.51. Modulator Audio Transmission Flags</b></p><div class="table-contents"><table summary="Modulator Audio Transmission Flags" width="100%" border="0"><colgroup><col /><col /><col /></colgroup><tbody valign="top"><tr><td valign="top"><code class="constant">V4L2_TUNER_SUB_MONO</code></td><td valign="top">0x0001</td><td valign="top">Modulate channel 1 as mono audio, when the input has more channels, a down-mix of channel 1 and 2. This flag does not combine with <code class="constant">V4L2_TUNER_SUB_STEREO</code> or <code class="constant">V4L2_TUNER_SUB_LANG1</code>.</td></tr><tr><td valign="top"><code class="constant">V4L2_TUNER_SUB_STEREO</code></td><td valign="top">0x0002</td><td valign="top">Modulate channel 1 and 2 as left and right channel of a stereo audio signal. When the input has only one channel or two channels and <code class="constant">V4L2_TUNER_SUB_SAP</code> is also set, channel 1 is encoded as left and right channel. This flag does not combine with <code class="constant">V4L2_TUNER_SUB_MONO</code> or <code class="constant">V4L2_TUNER_SUB_LANG1</code>. When the driver does not support stereo audio it shall fall back to mono.</td></tr><tr><td valign="top"><code class="constant">V4L2_TUNER_SUB_LANG1</code></td><td valign="top">0x0008</td><td valign="top">Modulate channel 1 and 2 as primary and secondary language of a bilingual audio signal. When the input has only one channel it is used for both languages. It is not possible to encode the primary or secondary language only. This flag does not combine with <code class="constant">V4L2_TUNER_SUB_MONO</code>, <code class="constant">V4L2_TUNER_SUB_STEREO</code> or <code class="constant">V4L2_TUNER_SUB_SAP</code>. If the hardware does not support the respective audio matrix, or the current video standard does not permit bilingual audio the <code class="constant">VIDIOC_S_MODULATOR</code> ioctl shall return an <span class="errorcode">EINVAL</span> error code and the driver shall fall back to mono or stereo mode.</td></tr><tr><td valign="top"><code class="constant">V4L2_TUNER_SUB_LANG2</code></td><td valign="top">0x0004</td><td valign="top">Same effect as <code class="constant">V4L2_TUNER_SUB_SAP</code>.</td></tr><tr><td valign="top"><code class="constant">V4L2_TUNER_SUB_SAP</code></td><td valign="top">0x0004</td><td valign="top">When combined with <code class="constant">V4L2_TUNER_SUB_MONO </code> the first channel is encoded as mono audio, the last channel as Second Audio Program. When the input has only one channel it is used for both audio tracks. When the input has three channels the mono track is a down-mix of channel 1 and 2. When combined with <code class="constant">V4L2_TUNER_SUB_STEREO</code> channel 1 and 2 are encoded as left and right stereo audio, channel 3 as Second Audio Program. When the input has only two channels, the first is encoded as left and right channel and the second as SAP. When the input has only one channel it is used for all audio tracks. It is not possible to encode a Second Audio Program only. This flag must combine with <code class="constant">V4L2_TUNER_SUB_MONO</code> or <code class="constant">V4L2_TUNER_SUB_STEREO</code>. If the hardware does not support the respective audio matrix, or the current video standard does not permit SAP the <code class="constant">VIDIOC_S_MODULATOR</code> ioctl shall return an <span class="errorcode">EINVAL</span> error code and driver shall fall back to mono or stereo mode.</td></tr><tr><td valign="top"><code class="constant">V4L2_TUNER_SUB_RDS</code></td><td valign="top">0x0010</td><td valign="top">Enable the RDS encoder for a radio FM transmitter.</td></tr></tbody></table></div></div><br class="table-break" /></div><div class="refsect1" title="Return Value"><a id="id2717738"></a><h2>Return Value</h2><p>On success <span class="returnvalue">0</span> is returned, on error <span class="returnvalue">-1</span> and the <code class="varname">errno</code> variable is set appropriately:</p><div class="variablelist"><dl><dt><span class="term"><span class="errorcode">EINVAL</span></span></dt><dd><p>The struct <a class="link" href="re45.html#v4l2-modulator" title="Table A.50. struct v4l2_modulator">v4l2_modulator</a> <em class="structfield"><code>index</code></em> is out of bounds.</p></dd></dl></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re44.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="apa.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re46.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">ioctl VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT</td></tr></table></div></body></html>
