<refentry id="vidioc-g-enc-index"> <refmeta> <refentrytitle>ioctl VIDIOC_G_ENC_INDEX</refentrytitle> &manvol; </refmeta> <refnamediv> <refname>VIDIOC_G_ENC_INDEX</refname> <refpurpose>Get meta data about a compressed video stream</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_enc_idx *<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_G_ENC_INDEX</para> </listitem> </varlistentry> <varlistentry> <term><parameter>argp</parameter></term> <listitem> <para></para> </listitem> </varlistentry> </variablelist> </refsect1> <refsect1> <title>Description</title> <note> <title>Experimental</title> <para>This is an <link linkend="experimental">experimental</link> interface and may change in the future.</para> </note> <para>The <constant>VIDIOC_G_ENC_INDEX</constant> ioctl provides meta data about a compressed video stream the same or another application currently reads from the driver, which is useful for random access into the stream without decoding it.</para> <para>To read the data applications must call <constant>VIDIOC_G_ENC_INDEX</constant> with a pointer to a &v4l2-enc-idx;. On success the driver fills the <structfield>entry</structfield> array, stores the number of elements written in the <structfield>entries</structfield> field, and initializes the <structfield>entries_cap</structfield> field.</para> <para>Each element of the <structfield>entry</structfield> array contains meta data about one picture. A <constant>VIDIOC_G_ENC_INDEX</constant> call reads up to <constant>V4L2_ENC_IDX_ENTRIES</constant> entries from a driver buffer, which can hold up to <structfield>entries_cap</structfield> entries. This number can be lower or higher than <constant>V4L2_ENC_IDX_ENTRIES</constant>, but not zero. When the application fails to read the meta data in time the oldest entries will be lost. When the buffer is empty or no capturing/encoding is in progress, <structfield>entries</structfield> will be zero.</para> <para>Currently this ioctl is only defined for MPEG-2 program streams and video elementary streams.</para> <table pgwide="1" frame="none" id="v4l2-enc-idx"> <title>struct <structname>v4l2_enc_idx</structname></title> <tgroup cols="3"> &cs-str; <tbody valign="top"> <row> <entry>__u32</entry> <entry><structfield>entries</structfield></entry> <entry>The number of entries the driver stored in the <structfield>entry</structfield> array.</entry> </row> <row> <entry>__u32</entry> <entry><structfield>entries_cap</structfield></entry> <entry>The number of entries the driver can buffer. Must be greater than zero.</entry> </row> <row> <entry>__u32</entry> <entry><structfield>reserved</structfield>[4]</entry> <entry spanname="hspan">Reserved for future extensions. Drivers must set the array to zero.</entry> </row> <row> <entry>&v4l2-enc-idx-entry;</entry> <entry><structfield>entry</structfield>[<constant>V4L2_ENC_IDX_ENTRIES</constant>]</entry> <entry>Meta data about a compressed video stream. Each element of the array corresponds to one picture, sorted in ascending order by their <structfield>offset</structfield>.</entry> </row> </tbody> </tgroup> </table> <table pgwide="1" frame="none" id="v4l2-enc-idx-entry"> <title>struct <structname>v4l2_enc_idx_entry</structname></title> <tgroup cols="3"> &cs-str; <tbody valign="top"> <row> <entry>__u64</entry> <entry><structfield>offset</structfield></entry> <entry>The offset in bytes from the beginning of the compressed video stream to the beginning of this picture, that is a <wordasword>PES packet header</wordasword> as defined in <xref linkend="mpeg2part1" /> or a <wordasword>picture header</wordasword> as defined in <xref linkend="mpeg2part2" />. When the encoder is stopped, the driver resets the offset to zero.</entry> </row> <row> <entry>__u64</entry> <entry><structfield>pts</structfield></entry> <entry>The 33 bit <wordasword>Presentation Time Stamp</wordasword> of this picture as defined in <xref linkend="mpeg2part1" />.</entry> </row> <row> <entry>__u32</entry> <entry><structfield>length</structfield></entry> <entry>The length of this picture in bytes.</entry> </row> <row> <entry>__u32</entry> <entry><structfield>flags</structfield></entry> <entry>Flags containing the coding type of this picture, see <xref linkend="enc-idx-flags" />.</entry> </row> <row> <entry>__u32</entry> <entry><structfield>reserved</structfield>[2]</entry> <entry>Reserved for future extensions. Drivers must set the array to zero.</entry> </row> </tbody> </tgroup> </table> <table pgwide="1" frame="none" id="enc-idx-flags"> <title>Index Entry Flags</title> <tgroup cols="3"> &cs-def; <tbody valign="top"> <row> <entry><constant>V4L2_ENC_IDX_FRAME_I</constant></entry> <entry>0x00</entry> <entry>This is an Intra-coded picture.</entry> </row> <row> <entry><constant>V4L2_ENC_IDX_FRAME_P</constant></entry> <entry>0x01</entry> <entry>This is a Predictive-coded picture.</entry> </row> <row> <entry><constant>V4L2_ENC_IDX_FRAME_B</constant></entry> <entry>0x02</entry> <entry>This is a Bidirectionally predictive-coded picture.</entry> </row> <row> <entry><constant>V4L2_ENC_IDX_FRAME_MASK</constant></entry> <entry>0x0F</entry> <entry><wordasword>AND</wordasword> the flags field with this mask to obtain the picture coding type.</entry> </row> </tbody> </tgroup> </table> </refsect1> <refsect1> &return-value; <variablelist> <varlistentry> <term><errorcode>EINVAL</errorcode></term> <listitem> <para>The driver does not support this ioctl.</para> </listitem> </varlistentry> </variablelist> </refsect1> </refentry> <!-- Local Variables: mode: sgml sgml-parent-document: "v4l2.sgml" indent-tabs-mode: nil End: -->