1<html><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 V1.78.1"><link rel="home" href="index.html" title="LINUX MEDIA INFRASTRUCTURE API"><link rel="up" href="user-func.html" title="Appendix A. Function Reference"><link rel="prev" href="vidioc-g-jpegcomp.html" title="ioctl VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP"><link rel="next" href="vidioc-g-output.html" title="ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><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="vidioc-g-jpegcomp.html">Prev</a> </td><th width="60%" align="center">Appendix A. Function Reference</th><td width="20%" align="right"> <a accesskey="n" href="vidioc-g-output.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="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"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><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 2*<var class="pdparam">argp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><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 3*<var class="pdparam">argp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idp1114773868"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>fd</code></em></span></dt><dd><p>File descriptor returned by <a class="link" href="func-open.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"><a name="idp1114777980"></a><h2>Description</h2><p>To query the attributes of a modulator applications initialize 4the <em class="structfield"><code>index</code></em> field and zero out the 5<em class="structfield"><code>reserved</code></em> array of a struct <a class="link" href="vidioc-g-modulator.html#v4l2-modulator" title="Table A.76. struct v4l2_modulator">v4l2_modulator</a> and 6call the <code class="constant">VIDIOC_G_MODULATOR</code> ioctl with a pointer 7to this structure. Drivers fill the rest of the structure or return an 8<span class="errorcode">EINVAL</span> error code when the index is out of bounds. To enumerate all modulators 9applications shall begin at index zero, incrementing by one until the 10driver returns <span class="errorcode">EINVAL</span>.</p><p>Modulators have two writable properties, an audio 11modulation set and the radio frequency. To change the modulated audio 12subprograms, applications initialize the <em class="structfield"><code>index 13</code></em> and <em class="structfield"><code>txsubchans</code></em> fields and the 14<em class="structfield"><code>reserved</code></em> array and call the 15<code class="constant">VIDIOC_S_MODULATOR</code> ioctl. Drivers may choose a 16different audio modulation if the request cannot be satisfied. However 17this is a write-only ioctl, it does not return the actual audio 18modulation selected.</p><p>To change the radio frequency 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 19is available.</p><div class="table"><a name="v4l2-modulator"></a><p class="title"><b>Table A.76. struct <span class="structname">v4l2_modulator</span></b></p><div class="table-contents"><table summary="struct v4l2_modulator" width="100%" border="0"><colgroup><col class="c1"><col class="c2"><col class="c3"></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 20application.</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 21string. 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 22for this field, the tuner flags in struct <a class="link" href="vidioc-g-tuner.html#v4l2-tuner" title="Table A.87. struct v4l2_tuner">v4l2_tuner</a> 23are used accordingly. The audio flags indicate the ability 24to encode audio subprograms. They will <span class="emphasis"><em>not</em></span> 25change 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 26KHz, or if the <em class="structfield"><code>capability</code></em> flag 27<code class="constant">V4L2_TUNER_CAP_LOW</code> is set, in units of 62.5 28Hz, or if the <em class="structfield"><code>capability</code></em> flag 29<code class="constant">V4L2_TUNER_CAP_1HZ</code> is set, in units of 1 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 30KHz, or if the <em class="structfield"><code>capability</code></em> flag 31<code class="constant">V4L2_TUNER_CAP_LOW</code> is set, in units of 62.5 32Hz, or if the <em class="structfield"><code>capability</code></em> flag 33<code class="constant">V4L2_TUNER_CAP_1HZ</code> is set, in units of 1 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 34audio sub-carriers shall be modulated. It contains a set of flags as 35defined in <a class="xref" href="vidioc-g-modulator.html#modulator-txsubchans" title="Table A.77. Modulator Audio Transmission Flags">Table A.77, “Modulator Audio Transmission Flags”</a>. Note the tuner 36<em class="structfield"><code>rxsubchans</code></em> flags are reused, but the 37semantics are different. Video output devices are assumed to have an 38analog or PCM audio input with 1-3 channels. The 39<em class="structfield"><code>txsubchans</code></em> flags select one or more 40channels for modulation, together with some audio subprogram 41indicator, 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 42applications must set the array to zero.</td></tr></tbody></table></div></div><br class="table-break"><div class="table"><a name="modulator-txsubchans"></a><p class="title"><b>Table A.77. Modulator Audio Transmission Flags</b></p><div class="table-contents"><table summary="Modulator Audio Transmission Flags" width="100%" border="0"><colgroup><col class="c1"><col class="c2"><col class="c3"></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 43has more channels, a down-mix of channel 1 and 2. This flag does not 44combine with <code class="constant">V4L2_TUNER_SUB_STEREO</code> or 45<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 46channel of a stereo audio signal. When the input has only one channel 47or two channels and <code class="constant">V4L2_TUNER_SUB_SAP</code> is also 48set, channel 1 is encoded as left and right channel. This flag does 49not combine with <code class="constant">V4L2_TUNER_SUB_MONO</code> or 50<code class="constant">V4L2_TUNER_SUB_LANG1</code>. When the driver does not 51support 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 52language of a bilingual audio signal. When the input has only one 53channel it is used for both languages. It is not possible to encode 54the primary or secondary language only. This flag does not combine 55with <code class="constant">V4L2_TUNER_SUB_MONO</code>, 56<code class="constant">V4L2_TUNER_SUB_STEREO</code> or 57<code class="constant">V4L2_TUNER_SUB_SAP</code>. If the hardware does not 58support the respective audio matrix, or the current video standard 59does not permit bilingual audio the 60<code class="constant">VIDIOC_S_MODULATOR</code> ioctl shall return an <span class="errorcode">EINVAL</span> error code 61and 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 62<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 63</code> the first channel is encoded as mono audio, the last 64channel as Second Audio Program. When the input has only one channel 65it is used for both audio tracks. When the input has three channels 66the mono track is a down-mix of channel 1 and 2. When combined with 67<code class="constant">V4L2_TUNER_SUB_STEREO</code> channel 1 and 2 are 68encoded as left and right stereo audio, channel 3 as Second Audio 69Program. When the input has only two channels, the first is encoded as 70left and right channel and the second as SAP. When the input has only 71one channel it is used for all audio tracks. It is not possible to 72encode a Second Audio Program only. This flag must combine with 73<code class="constant">V4L2_TUNER_SUB_MONO</code> or 74<code class="constant">V4L2_TUNER_SUB_STEREO</code>. If the hardware does not 75support the respective audio matrix, or the current video standard 76does not permit SAP the <code class="constant">VIDIOC_S_MODULATOR</code> ioctl 77shall return an <span class="errorcode">EINVAL</span> error code and driver shall fall back to mono or stereo 78mode.</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"><a name="idp1114810988"></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. The generic error codes are described at the <a class="link" href="gen_errors.html#gen-errors" title="Table 19.1. Generic error codes">Generic Error Codes</a> chapter.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="errorcode">EINVAL</span></span></dt><dd><p>The struct <a class="link" href="vidioc-g-modulator.html#v4l2-modulator" title="Table A.76. struct v4l2_modulator">v4l2_modulator</a> 79<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="vidioc-g-jpegcomp.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="user-func.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="vidioc-g-output.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> 80