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Based on kernel version 3.16. Page generated on 2014-08-06 21:39 EST.

1	<refentry id="vidioc-g-enc-index">
2	  <refmeta>
3	    <refentrytitle>ioctl VIDIOC_G_ENC_INDEX</refentrytitle>
4	    &manvol;
5	  </refmeta>
6	
7	  <refnamediv>
8	    <refname>VIDIOC_G_ENC_INDEX</refname>
9	    <refpurpose>Get meta data about a compressed video stream</refpurpose>
10	  </refnamediv>
11	
12	  <refsynopsisdiv>
13	    <funcsynopsis>
14	      <funcprototype>
15		<funcdef>int <function>ioctl</function></funcdef>
16		<paramdef>int <parameter>fd</parameter></paramdef>
17		<paramdef>int <parameter>request</parameter></paramdef>
18		<paramdef>struct v4l2_enc_idx *<parameter>argp</parameter></paramdef>
19	      </funcprototype>
20	    </funcsynopsis>
21	  </refsynopsisdiv>
22	
23	  <refsect1>
24	    <title>Arguments</title>
25	
26	    <variablelist>
27	      <varlistentry>
28		<term><parameter>fd</parameter></term>
29		<listitem>
30		  <para>&fd;</para>
31		</listitem>
32	      </varlistentry>
33	      <varlistentry>
34		<term><parameter>request</parameter></term>
35		<listitem>
36		  <para>VIDIOC_G_ENC_INDEX</para>
37		</listitem>
38	      </varlistentry>
39	      <varlistentry>
40		<term><parameter>argp</parameter></term>
41		<listitem>
42		  <para></para>
43		</listitem>
44	      </varlistentry>
45	    </variablelist>
46	  </refsect1>
47	
48	  <refsect1>
49	    <title>Description</title>
50	
51	    <para>The <constant>VIDIOC_G_ENC_INDEX</constant> ioctl provides
52	meta data about a compressed video stream the same or another
53	application currently reads from the driver, which is useful for
54	random access into the stream without decoding it.</para>
55	
56	    <para>To read the data applications must call
57	<constant>VIDIOC_G_ENC_INDEX</constant> with a pointer to a
58	&v4l2-enc-idx;. On success the driver fills the
59	<structfield>entry</structfield> array, stores the number of elements
60	written in the <structfield>entries</structfield> field, and
61	initializes the <structfield>entries_cap</structfield> field.</para>
62	
63	    <para>Each element of the <structfield>entry</structfield> array
64	contains meta data about one picture. A
65	<constant>VIDIOC_G_ENC_INDEX</constant> call reads up to
66	<constant>V4L2_ENC_IDX_ENTRIES</constant> entries from a driver
67	buffer, which can hold up to <structfield>entries_cap</structfield>
68	entries. This number can be lower or higher than
69	<constant>V4L2_ENC_IDX_ENTRIES</constant>, but not zero. When the
70	application fails to read the meta data in time the oldest entries
71	will be lost. When the buffer is empty or no capturing/encoding is in
72	progress, <structfield>entries</structfield> will be zero.</para>
73	
74	    <para>Currently this ioctl is only defined for MPEG-2 program
75	streams and video elementary streams.</para>
76	
77	    <table pgwide="1" frame="none" id="v4l2-enc-idx">
78	      <title>struct <structname>v4l2_enc_idx</structname></title>
79	      <tgroup cols="3">
80		&cs-str;
81		<tbody valign="top">
82		  <row>
83		    <entry>__u32</entry>
84		    <entry><structfield>entries</structfield></entry>
85		    <entry>The number of entries the driver stored in the
86	<structfield>entry</structfield> array.</entry>
87		  </row>
88		  <row>
89		    <entry>__u32</entry>
90		    <entry><structfield>entries_cap</structfield></entry>
91		    <entry>The number of entries the driver can
92	buffer. Must be greater than zero.</entry>
93		  </row>
94		  <row>
95		    <entry>__u32</entry>
96		    <entry><structfield>reserved</structfield>[4]</entry>
97		    <entry spanname="hspan">Reserved for future extensions.
98	Drivers must set the array to zero.</entry>
99		  </row>
100		  <row>
101		    <entry>&v4l2-enc-idx-entry;</entry>
102		    <entry><structfield>entry</structfield>[<constant>V4L2_ENC_IDX_ENTRIES</constant>]</entry>
103		    <entry>Meta data about a compressed video stream. Each
104	element of the array corresponds to one picture, sorted in ascending
105	order by their <structfield>offset</structfield>.</entry>
106		  </row>
107		</tbody>
108	      </tgroup>
109	    </table>
110	
111	    <table pgwide="1" frame="none" id="v4l2-enc-idx-entry">
112	      <title>struct <structname>v4l2_enc_idx_entry</structname></title>
113	      <tgroup cols="3">
114		&cs-str;
115		<tbody valign="top">
116		  <row>
117		    <entry>__u64</entry>
118		    <entry><structfield>offset</structfield></entry>
119		    <entry>The offset in bytes from the beginning of the
120	compressed video stream to the beginning of this picture, that is a
121	<wordasword>PES packet header</wordasword> as defined in <xref
122		    linkend="mpeg2part1" /> or a <wordasword>picture
123	header</wordasword> as defined in <xref linkend="mpeg2part2" />. When
124	the encoder is stopped, the driver resets the offset to zero.</entry>
125		  </row>
126		  <row>
127		    <entry>__u64</entry>
128		    <entry><structfield>pts</structfield></entry>
129		    <entry>The 33 bit <wordasword>Presentation Time
130	Stamp</wordasword> of this picture as defined in <xref
131			linkend="mpeg2part1" />.</entry>
132		  </row>
133		  <row>
134		    <entry>__u32</entry>
135		    <entry><structfield>length</structfield></entry>
136		    <entry>The length of this picture in bytes.</entry>
137		  </row>
138		  <row>
139		    <entry>__u32</entry>
140		    <entry><structfield>flags</structfield></entry>
141		    <entry>Flags containing the coding type of this picture, see <xref
142			linkend="enc-idx-flags" />.</entry>
143		  </row>
144		  <row>
145		    <entry>__u32</entry>
146		    <entry><structfield>reserved</structfield>[2]</entry>
147		    <entry>Reserved for future extensions.
148	Drivers must set the array to zero.</entry>
149		  </row>
150		</tbody>
151	      </tgroup>
152	    </table>
153	
154	    <table pgwide="1" frame="none" id="enc-idx-flags">
155	      <title>Index Entry Flags</title>
156	      <tgroup cols="3">
157		&cs-def;
158		<tbody valign="top">
159		  <row>
160		    <entry><constant>V4L2_ENC_IDX_FRAME_I</constant></entry>
161		    <entry>0x00</entry>
162		    <entry>This is an Intra-coded picture.</entry>
163		  </row>
164		  <row>
165		    <entry><constant>V4L2_ENC_IDX_FRAME_P</constant></entry>
166		    <entry>0x01</entry>
167		    <entry>This is a Predictive-coded picture.</entry>
168		  </row>
169		  <row>
170		    <entry><constant>V4L2_ENC_IDX_FRAME_B</constant></entry>
171		    <entry>0x02</entry>
172		    <entry>This is a Bidirectionally predictive-coded
173	picture.</entry>
174		  </row>
175		  <row>
176		    <entry><constant>V4L2_ENC_IDX_FRAME_MASK</constant></entry>
177		    <entry>0x0F</entry>
178		    <entry><wordasword>AND</wordasword> the flags field with
179	this mask to obtain the picture coding type.</entry>
180		  </row>
181	       </tbody>
182	      </tgroup>
183	    </table>
184	  </refsect1>
185	
186	  <refsect1>
187	    &return-value;
188	  </refsect1>
189	</refentry>
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