[media] DocBook: Software Defined Radio Interface
Document V4L2 SDR interface. Cc: Hans Verkuil <hverkuil@xs4all.nl> Signed-off-by: Antti Palosaari <crope@iki.fi> Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
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Antti Palosaari
Mauro Carvalho Chehab
Родитель
70b5efb8b7
Коммит
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@ -2535,6 +2535,16 @@ fields changed from _s32 to _u32.
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</orderedlist>
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</section>
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<section>
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<title>V4L2 in Linux 3.15</title>
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<orderedlist>
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<listitem>
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<para>Added Software Defined Radio (SDR) Interface.
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</para>
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</listitem>
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</orderedlist>
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</section>
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<section id="other">
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<title>Relation of V4L2 to other Linux multimedia APIs</title>
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@ -0,0 +1,104 @@
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<title>Software Defined Radio Interface (SDR)</title>
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<para>
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SDR is an abbreviation of Software Defined Radio, the radio device
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which uses application software for modulation or demodulation. This interface
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is intended for controlling and data streaming of such devices.
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</para>
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<para>
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SDR devices are accessed through character device special files named
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<filename>/dev/swradio0</filename> to <filename>/dev/swradio255</filename>
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with major number 81 and dynamically allocated minor numbers 0 to 255.
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</para>
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<section>
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<title>Querying Capabilities</title>
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<para>
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Devices supporting the SDR receiver interface set the
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<constant>V4L2_CAP_SDR_CAPTURE</constant> and
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<constant>V4L2_CAP_TUNER</constant> flag in the
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<structfield>capabilities</structfield> field of &v4l2-capability;
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returned by the &VIDIOC-QUERYCAP; ioctl. That flag means the device has an
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Analog to Digital Converter (ADC), which is a mandatory element for the SDR receiver.
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At least one of the read/write, streaming or asynchronous I/O methods must
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be supported.
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</para>
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</section>
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<section>
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<title>Supplemental Functions</title>
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<para>
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SDR devices can support <link linkend="control">controls</link>, and must
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support the <link linkend="tuner">tuner</link> ioctls. Tuner ioctls are used
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for setting the ADC sampling rate (sampling frequency) and the possible RF tuner
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frequency.
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</para>
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<para>
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The <constant>V4L2_TUNER_ADC</constant> tuner type is used for ADC tuners, and
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the <constant>V4L2_TUNER_RF</constant> tuner type is used for RF tuners. The
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tuner index of the RF tuner (if any) must always follow the ADC tuner index.
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Normally the ADC tuner is #0 and the RF tuner is #1.
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</para>
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<para>
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The &VIDIOC-S-HW-FREQ-SEEK; ioctl is not supported.
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</para>
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</section>
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<section>
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<title>Data Format Negotiation</title>
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<para>
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The SDR capture device uses the <link linkend="format">format</link> ioctls to
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select the capture format. Both the sampling resolution and the data streaming
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format are bound to that selectable format. In addition to the basic
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<link linkend="format">format</link> ioctls, the &VIDIOC-ENUM-FMT; ioctl
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must be supported as well.
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</para>
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<para>
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To use the <link linkend="format">format</link> ioctls applications set the
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<structfield>type</structfield> field of a &v4l2-format; to
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<constant>V4L2_BUF_TYPE_SDR_CAPTURE</constant> and use the &v4l2-format-sdr;
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<structfield>sdr</structfield> member of the <structfield>fmt</structfield>
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union as needed per the desired operation.
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Currently only the <structfield>pixelformat</structfield> field of
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&v4l2-format-sdr; is used. The content of that field is the V4L2 fourcc code
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of the data format.
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</para>
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<table pgwide="1" frame="none" id="v4l2-format-sdr">
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<title>struct <structname>v4l2_format_sdr</structname></title>
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<tgroup cols="3">
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&cs-str;
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<tbody valign="top">
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<row>
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<entry>__u32</entry>
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<entry><structfield>pixelformat</structfield></entry>
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<entry>
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The data format or type of compression, set by the application. This is a
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little endian <link linkend="v4l2-fourcc">four character code</link>.
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V4L2 defines SDR formats in <xref linkend="sdr-formats" />.
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</entry>
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</row>
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<row>
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<entry>__u8</entry>
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<entry><structfield>reserved[28]</structfield></entry>
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<entry>This array is reserved for future extensions.
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Drivers and applications must set it to zero.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>
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An SDR device may support <link linkend="rw">read/write</link>
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and/or streaming (<link linkend="mmap">memory mapping</link>
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or <link linkend="userp">user pointer</link>) I/O.
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</para>
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</section>
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@ -1005,6 +1005,12 @@ should set this to 0.</entry>
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<entry>Buffer for video output overlay (OSD), see <xref
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linkend="osd" />.</entry>
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</row>
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<row>
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<entry><constant>V4L2_BUF_TYPE_SDR_CAPTURE</constant></entry>
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<entry>11</entry>
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<entry>Buffer for Software Defined Radio (SDR), see <xref
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linkend="sdr" />.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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@ -811,6 +811,14 @@ extended control <constant>V4L2_CID_MPEG_STREAM_TYPE</constant>, see
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</table>
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</section>
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<section id="sdr-formats">
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<title>SDR Formats</title>
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<para>These formats are used for <link linkend="sdr">SDR Capture</link>
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interface only.</para>
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</section>
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<section id="pixfmt-reserved">
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<title>Reserved Format Identifiers</title>
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@ -548,6 +548,7 @@ and discussions on the V4L mailing list.</revremark>
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<section id="ttx"> &sub-dev-teletext; </section>
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<section id="radio"> &sub-dev-radio; </section>
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<section id="rds"> &sub-dev-rds; </section>
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<section id="sdr"> &sub-dev-sdr; </section>
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<section id="event"> &sub-dev-event; </section>
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<section id="subdev"> &sub-dev-subdev; </section>
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</chapter>
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@ -169,6 +169,13 @@ capture and output devices.</entry>
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<entry>Sliced VBI capture or output parameters. See
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<xref linkend="sliced" /> for details. Used by sliced VBI
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capture and output devices.</entry>
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</row>
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<row>
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<entry></entry>
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<entry>&v4l2-format-sdr;</entry>
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<entry><structfield>sdr</structfield></entry>
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<entry>Definition of a data format, see
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<xref linkend="pixfmt" />, used by SDR capture devices.</entry>
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</row>
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<row>
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<entry></entry>
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@ -294,6 +294,12 @@ interface. For more information on audio inputs and outputs see <xref
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emit RF-modulated video/audio signals. For more information about
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modulator programming see
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<xref linkend="tuner" />.</entry>
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</row>
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<row>
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<entry><constant>V4L2_CAP_SDR_CAPTURE</constant></entry>
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<entry>0x00100000</entry>
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<entry>The device supports the
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<link linkend="sdr">SDR Capture</link> interface.</entry>
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</row>
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<row>
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<entry><constant>V4L2_CAP_READWRITE</constant></entry>
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