<refentry id="vidioc-enumstd">
  <refmeta>
    <refentrytitle>ioctl VIDIOC_ENUMSTD</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>VIDIOC_ENUMSTD</refname>
    <refpurpose>Enumerate supported video standards</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcprototype>
	<funcdef>int <function>ioctl</function></funcdef>
	<paramdef>int <parameter>fd</parameter></paramdef>
	<paramdef>int <parameter>request</parameter></paramdef>
	<paramdef>struct v4l2_standard *<parameter>argp</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Arguments</title>

    <variablelist>
      <varlistentry>
	<term><parameter>fd</parameter></term>
	<listitem>
	  <para>&fd;</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>request</parameter></term>
	<listitem>
	  <para>VIDIOC_ENUMSTD</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	  <para></para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para>To query the attributes of a video standard,
especially a custom (driver defined) one, applications initialize the
<structfield>index</structfield> field of &v4l2-standard; and call the
<constant>VIDIOC_ENUMSTD</constant> ioctl with a pointer to this
structure. Drivers fill the rest of the structure or return an
&EINVAL; when the index is out of bounds. To enumerate all standards
applications shall begin  at index zero, incrementing by one until the
driver returns <errorcode>EINVAL</errorcode>. Drivers may enumerate a
different set of standards after switching the video input or
output.<footnote>
	<para>The supported standards may overlap and we need an
unambiguous set to find the current standard returned by
<constant>VIDIOC_G_STD</constant>.</para>
      </footnote></para>

    <table pgwide="1" frame="none" id="v4l2-standard">
      <title>struct <structname>v4l2_standard</structname></title>
      <tgroup cols="3">
	&cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>index</structfield></entry>
	    <entry>Number of the video standard, set by the
application.</entry>
	  </row>
	  <row>
	    <entry>&v4l2-std-id;</entry>
	    <entry><structfield>id</structfield></entry>
	    <entry>The bits in this field identify the standard as
one of the common standards listed in <xref linkend="v4l2-std-id" />,
or if bits 32 to 63 are set as custom standards. Multiple bits can be
set if the hardware does not distinguish between these standards,
however separate indices do not indicate the opposite. The
<structfield>id</structfield> must be unique. No other enumerated
<structname>v4l2_standard</structname> structure, for this input or
output anyway, can contain the same set of bits.</entry>
	  </row>
	  <row>
	    <entry>__u8</entry>
	    <entry><structfield>name</structfield>[24]</entry>
	    <entry>Name of the standard, a NUL-terminated ASCII
string, for example: "PAL-B/G", "NTSC Japan". This information is
intended for the user.</entry>
	  </row>
	  <row>
	    <entry>&v4l2-fract;</entry>
	    <entry><structfield>frameperiod</structfield></entry>
	    <entry>The frame period (not field period) is numerator
/ denominator. For example M/NTSC has a frame period of 1001 /
30000 seconds.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>framelines</structfield></entry>
	    <entry>Total lines per frame including blanking,
e.&nbsp;g. 625 for B/PAL.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>reserved</structfield>[4]</entry>
	    <entry>Reserved for future extensions. Drivers must set
the array to zero.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table pgwide="1" frame="none" id="v4l2-fract">
      <title>struct <structname>v4l2_fract</structname></title>
      <tgroup cols="3">
	&cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>numerator</structfield></entry>
	    <entry></entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>denominator</structfield></entry>
	    <entry></entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table pgwide="1" frame="none" id="v4l2-std-id">
      <title>typedef <structname>v4l2_std_id</structname></title>
      <tgroup cols="3">
	&cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u64</entry>
	    <entry><structfield>v4l2_std_id</structfield></entry>
	    <entry>This type is a set, each bit representing another
video standard as listed below and in <xref
linkend="video-standards" />. The 32 most significant bits are reserved
for custom (driver defined) video standards.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <para><programlisting>
#define V4L2_STD_PAL_B          ((v4l2_std_id)0x00000001)
#define V4L2_STD_PAL_B1         ((v4l2_std_id)0x00000002)
#define V4L2_STD_PAL_G          ((v4l2_std_id)0x00000004)
#define V4L2_STD_PAL_H          ((v4l2_std_id)0x00000008)
#define V4L2_STD_PAL_I          ((v4l2_std_id)0x00000010)
#define V4L2_STD_PAL_D          ((v4l2_std_id)0x00000020)
#define V4L2_STD_PAL_D1         ((v4l2_std_id)0x00000040)
#define V4L2_STD_PAL_K          ((v4l2_std_id)0x00000080)

#define V4L2_STD_PAL_M          ((v4l2_std_id)0x00000100)
#define V4L2_STD_PAL_N          ((v4l2_std_id)0x00000200)
#define V4L2_STD_PAL_Nc         ((v4l2_std_id)0x00000400)
#define V4L2_STD_PAL_60         ((v4l2_std_id)0x00000800)
</programlisting></para><para><constant>V4L2_STD_PAL_60</constant> is
a hybrid standard with 525 lines, 60 Hz refresh rate, and PAL color
modulation with a 4.43 MHz color subcarrier. Some PAL video recorders
can play back NTSC tapes in this mode for display on a 50/60 Hz agnostic
PAL TV.</para><para><programlisting>
#define V4L2_STD_NTSC_M         ((v4l2_std_id)0x00001000)
#define V4L2_STD_NTSC_M_JP      ((v4l2_std_id)0x00002000)
#define V4L2_STD_NTSC_443       ((v4l2_std_id)0x00004000)
</programlisting></para><para><constant>V4L2_STD_NTSC_443</constant>
is a hybrid standard with 525 lines, 60 Hz refresh rate, and NTSC
color modulation with a 4.43 MHz color
subcarrier.</para><para><programlisting>
#define V4L2_STD_NTSC_M_KR      ((v4l2_std_id)0x00008000)

#define V4L2_STD_SECAM_B        ((v4l2_std_id)0x00010000)
#define V4L2_STD_SECAM_D        ((v4l2_std_id)0x00020000)
#define V4L2_STD_SECAM_G        ((v4l2_std_id)0x00040000)
#define V4L2_STD_SECAM_H        ((v4l2_std_id)0x00080000)
#define V4L2_STD_SECAM_K        ((v4l2_std_id)0x00100000)
#define V4L2_STD_SECAM_K1       ((v4l2_std_id)0x00200000)
#define V4L2_STD_SECAM_L        ((v4l2_std_id)0x00400000)
#define V4L2_STD_SECAM_LC       ((v4l2_std_id)0x00800000)

/* ATSC/HDTV */
#define V4L2_STD_ATSC_8_VSB     ((v4l2_std_id)0x01000000)
#define V4L2_STD_ATSC_16_VSB    ((v4l2_std_id)0x02000000)
</programlisting></para><para><!-- ATSC proposal by Mark McClelland,
video4linux-list@redhat.com on 17 Oct 2002
--><constant>V4L2_STD_ATSC_8_VSB</constant> and
<constant>V4L2_STD_ATSC_16_VSB</constant> are U.S. terrestrial digital
TV standards. Presently the V4L2 API does not support digital TV. See
also the Linux DVB API at <ulink
url="https://linuxtv.org">https://linuxtv.org</ulink>.</para>
<para><programlisting>
#define V4L2_STD_PAL_BG         (V4L2_STD_PAL_B         |\
				 V4L2_STD_PAL_B1        |\
				 V4L2_STD_PAL_G)
#define V4L2_STD_B              (V4L2_STD_PAL_B         |\
				 V4L2_STD_PAL_B1        |\
				 V4L2_STD_SECAM_B)
#define V4L2_STD_GH             (V4L2_STD_PAL_G         |\
				 V4L2_STD_PAL_H         |\
				 V4L2_STD_SECAM_G       |\
				 V4L2_STD_SECAM_H)
#define V4L2_STD_PAL_DK         (V4L2_STD_PAL_D         |\
				 V4L2_STD_PAL_D1        |\
				 V4L2_STD_PAL_K)
#define V4L2_STD_PAL            (V4L2_STD_PAL_BG        |\
				 V4L2_STD_PAL_DK        |\
				 V4L2_STD_PAL_H         |\
				 V4L2_STD_PAL_I)
#define V4L2_STD_NTSC           (V4L2_STD_NTSC_M        |\
				 V4L2_STD_NTSC_M_JP     |\
				 V4L2_STD_NTSC_M_KR)
#define V4L2_STD_MN             (V4L2_STD_PAL_M         |\
				 V4L2_STD_PAL_N         |\
				 V4L2_STD_PAL_Nc        |\
				 V4L2_STD_NTSC)
#define V4L2_STD_SECAM_DK       (V4L2_STD_SECAM_D       |\
				 V4L2_STD_SECAM_K       |\
				 V4L2_STD_SECAM_K1)
#define V4L2_STD_DK             (V4L2_STD_PAL_DK        |\
				 V4L2_STD_SECAM_DK)

#define V4L2_STD_SECAM          (V4L2_STD_SECAM_B       |\
				 V4L2_STD_SECAM_G       |\
				 V4L2_STD_SECAM_H       |\
				 V4L2_STD_SECAM_DK      |\
				 V4L2_STD_SECAM_L       |\
				 V4L2_STD_SECAM_LC)

#define V4L2_STD_525_60         (V4L2_STD_PAL_M         |\
				 V4L2_STD_PAL_60        |\
				 V4L2_STD_NTSC          |\
				 V4L2_STD_NTSC_443)
#define V4L2_STD_625_50         (V4L2_STD_PAL           |\
				 V4L2_STD_PAL_N         |\
				 V4L2_STD_PAL_Nc        |\
				 V4L2_STD_SECAM)

#define V4L2_STD_UNKNOWN        0
#define V4L2_STD_ALL            (V4L2_STD_525_60        |\
				 V4L2_STD_625_50)
</programlisting></para>

    <table pgwide="1" id="video-standards" orient="land">
      <title>Video Standards (based on [<xref linkend="itu470" />])</title>
      <tgroup cols="12" colsep="1" rowsep="1" align="center">
	<colspec colname="c1" align="left" />
	<colspec colname="c2" />
	<colspec colname="c3" />
	<colspec colname="c4" />
	<colspec colname="c5" />
	<colspec colnum="7" colname="c7" />
	<colspec colnum="9" colname="c9" />
	<colspec colnum="12" colname="c12" />
	<spanspec namest="c2" nameend="c3" spanname="m" align="center" />
	<spanspec namest="c4" nameend="c12" spanname="x" align="center" />
	<spanspec namest="c5" nameend="c7" spanname="b" align="center" />
	<spanspec namest="c9" nameend="c12" spanname="s" align="center" />
	<thead>
	  <row>
	    <entry>Characteristics</entry>
	    <entry><para>M/NTSC<footnote><para>Japan uses a standard
similar to M/NTSC
(V4L2_STD_NTSC_M_JP).</para></footnote></para></entry>
	    <entry>M/PAL</entry>
	    <entry><para>N/PAL<footnote><para> The values in
brackets apply to the combination N/PAL a.k.a.
N<subscript>C</subscript> used in Argentina
(V4L2_STD_PAL_Nc).</para></footnote></para></entry>
	    <entry align="center">B, B1, G/PAL</entry>
	    <entry align="center">D, D1, K/PAL</entry>
	    <entry align="center">H/PAL</entry>
	    <entry align="center">I/PAL</entry>
	    <entry align="center">B, G/SECAM</entry>
	    <entry align="center">D, K/SECAM</entry>
	    <entry align="center">K1/SECAM</entry>
	    <entry align="center">L/SECAM</entry>
	  </row>
	</thead>
	<tbody valign="top">
	  <row>
	    <entry>Frame lines</entry>
	    <entry spanname="m">525</entry>
	    <entry spanname="x">625</entry>
	  </row>
	  <row>
	    <entry>Frame period (s)</entry>
	    <entry spanname="m">1001/30000</entry>
	    <entry spanname="x">1/25</entry>
	  </row>
	  <row>
	    <entry>Chrominance sub-carrier frequency (Hz)</entry>
	    <entry>3579545 &plusmn;&nbsp;10</entry>
	    <entry>3579611.49 &plusmn;&nbsp;10</entry>
	    <entry>4433618.75 &plusmn;&nbsp;5 (3582056.25
&plusmn;&nbsp;5)</entry>
	    <entry spanname="b">4433618.75 &plusmn;&nbsp;5</entry>
	    <entry>4433618.75 &plusmn;&nbsp;1</entry>
	    <entry spanname="s">f<subscript>OR</subscript>&nbsp;=
4406250 &plusmn;&nbsp;2000, f<subscript>OB</subscript>&nbsp;= 4250000
&plusmn;&nbsp;2000</entry>
	  </row>
	  <row>
	    <entry>Nominal radio-frequency channel bandwidth
(MHz)</entry>
	    <entry>6</entry>
	    <entry>6</entry>
	    <entry>6</entry>
	    <entry>B: 7; B1, G: 8</entry>
	    <entry>8</entry>
	    <entry>8</entry>
	    <entry>8</entry>
	    <entry>8</entry>
	    <entry>8</entry>
	    <entry>8</entry>
	    <entry>8</entry>
	  </row>
	  <row>
	    <entry>Sound carrier relative to vision carrier
(MHz)</entry>
	    <entry>+&nbsp;4.5</entry>
	    <entry>+&nbsp;4.5</entry>
	    <entry>+&nbsp;4.5</entry>
	    <entry><para>+&nbsp;5.5 &plusmn;&nbsp;0.001
<footnote><para>In the Federal Republic of Germany, Austria, Italy,
the Netherlands, Slovakia and Switzerland a system of two sound
carriers is used, the frequency of the second carrier being
242.1875&nbsp;kHz above the frequency of the first sound carrier. For
stereophonic sound transmissions a similar system is used in
Australia.</para></footnote> <footnote><para>New Zealand uses a sound
carrier displaced 5.4996 &plusmn;&nbsp;0.0005 MHz from the vision
carrier.</para></footnote> <footnote><para>In Denmark, Finland, New
Zealand, Sweden and Spain a system of two sound carriers is used. In
Iceland, Norway and Poland the same system is being introduced. The
second carrier is 5.85&nbsp;MHz above the vision carrier and is DQPSK
modulated with 728&nbsp;kbit/s sound and data multiplex. (NICAM
system)</para></footnote> <footnote><para>In the United Kingdom, a
system of two sound carriers is used. The second sound carrier is
6.552&nbsp;MHz above the vision carrier and is DQPSK modulated with a
728&nbsp;kbit/s sound and data multiplex able to carry two sound
channels. (NICAM system)</para></footnote></para></entry>
	    <entry>+&nbsp;6.5 &plusmn;&nbsp;0.001</entry>
	    <entry>+&nbsp;5.5</entry>
	    <entry>+&nbsp;5.9996 &plusmn;&nbsp;0.0005</entry>
	    <entry>+&nbsp;5.5 &plusmn;&nbsp;0.001</entry>
	    <entry>+&nbsp;6.5 &plusmn;&nbsp;0.001</entry>
	    <entry>+&nbsp;6.5</entry>
	    <entry><para>+&nbsp;6.5 <footnote><para>In France, a
digital carrier 5.85 MHz away from the vision carrier may be used in
addition to the main sound carrier. It is modulated in differentially
encoded QPSK with a 728 kbit/s sound and data multiplexer capable of
carrying two sound channels. (NICAM
system)</para></footnote></para></entry>
	  </row>
	</tbody>
      </tgroup>
    </table>
  </refsect1>

  <refsect1>
    &return-value;

    <variablelist>
      <varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	  <para>The &v4l2-standard; <structfield>index</structfield>
is out of bounds.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><errorcode>ENODATA</errorcode></term>
	<listitem>
	  <para>Standard video timings are not supported for this input or output.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>