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1 | <refentry id="vidioc-decoder-cmd"> |
2 | <refmeta> | |
3 | <refentrytitle>ioctl VIDIOC_DECODER_CMD, VIDIOC_TRY_DECODER_CMD</refentrytitle> | |
4 | &manvol; | |
5 | </refmeta> | |
6 | ||
7 | <refnamediv> | |
8 | <refname>VIDIOC_DECODER_CMD</refname> | |
9 | <refname>VIDIOC_TRY_DECODER_CMD</refname> | |
10 | <refpurpose>Execute an decoder command</refpurpose> | |
11 | </refnamediv> | |
12 | ||
13 | <refsynopsisdiv> | |
14 | <funcsynopsis> | |
15 | <funcprototype> | |
16 | <funcdef>int <function>ioctl</function></funcdef> | |
17 | <paramdef>int <parameter>fd</parameter></paramdef> | |
18 | <paramdef>int <parameter>request</parameter></paramdef> | |
19 | <paramdef>struct v4l2_decoder_cmd *<parameter>argp</parameter></paramdef> | |
20 | </funcprototype> | |
21 | </funcsynopsis> | |
22 | </refsynopsisdiv> | |
23 | ||
24 | <refsect1> | |
25 | <title>Arguments</title> | |
26 | ||
27 | <variablelist> | |
28 | <varlistentry> | |
29 | <term><parameter>fd</parameter></term> | |
30 | <listitem> | |
31 | <para>&fd;</para> | |
32 | </listitem> | |
33 | </varlistentry> | |
34 | <varlistentry> | |
35 | <term><parameter>request</parameter></term> | |
36 | <listitem> | |
37 | <para>VIDIOC_DECODER_CMD, VIDIOC_TRY_DECODER_CMD</para> | |
38 | </listitem> | |
39 | </varlistentry> | |
40 | <varlistentry> | |
41 | <term><parameter>argp</parameter></term> | |
42 | <listitem> | |
43 | <para></para> | |
44 | </listitem> | |
45 | </varlistentry> | |
46 | </variablelist> | |
47 | </refsect1> | |
48 | ||
49 | <refsect1> | |
50 | <title>Description</title> | |
51 | ||
6b4f1252 HV |
52 | <para>These ioctls control an audio/video (usually MPEG-) decoder. |
53 | <constant>VIDIOC_DECODER_CMD</constant> sends a command to the | |
54 | decoder, <constant>VIDIOC_TRY_DECODER_CMD</constant> can be used to | |
55 | try a command without actually executing it. To send a command applications | |
56 | must initialize all fields of a &v4l2-decoder-cmd; and call | |
57 | <constant>VIDIOC_DECODER_CMD</constant> or <constant>VIDIOC_TRY_DECODER_CMD</constant> | |
58 | with a pointer to this structure.</para> | |
59 | ||
60 | <para>The <structfield>cmd</structfield> field must contain the | |
61 | command code. Some commands use the <structfield>flags</structfield> field for | |
62 | additional information. | |
63 | </para> | |
64 | ||
65 | <para>A <function>write</function>() or &VIDIOC-STREAMON; call sends an implicit | |
66 | START command to the decoder if it has not been started yet. | |
67 | </para> | |
68 | ||
69 | <para>A <function>close</function>() or &VIDIOC-STREAMOFF; call of a streaming | |
70 | file descriptor sends an implicit immediate STOP command to the decoder, and all | |
71 | buffered data is discarded.</para> | |
72 | ||
73 | <para>These ioctls are optional, not all drivers may support | |
74 | them. They were introduced in Linux 3.3.</para> | |
75 | ||
76 | <table pgwide="1" frame="none" id="v4l2-decoder-cmd"> | |
77 | <title>struct <structname>v4l2_decoder_cmd</structname></title> | |
78 | <tgroup cols="5"> | |
79 | &cs-str; | |
80 | <tbody valign="top"> | |
81 | <row> | |
82 | <entry>__u32</entry> | |
83 | <entry><structfield>cmd</structfield></entry> | |
84 | <entry></entry> | |
85 | <entry></entry> | |
86 | <entry>The decoder command, see <xref linkend="decoder-cmds" />.</entry> | |
87 | </row> | |
88 | <row> | |
89 | <entry>__u32</entry> | |
90 | <entry><structfield>flags</structfield></entry> | |
91 | <entry></entry> | |
92 | <entry></entry> | |
93 | <entry>Flags to go with the command. If no flags are defined for | |
94 | this command, drivers and applications must set this field to zero.</entry> | |
95 | </row> | |
96 | <row> | |
97 | <entry>union</entry> | |
98 | <entry>(anonymous)</entry> | |
99 | <entry></entry> | |
100 | <entry></entry> | |
101 | <entry></entry> | |
102 | </row> | |
103 | <row> | |
104 | <entry></entry> | |
105 | <entry>struct</entry> | |
106 | <entry><structfield>start</structfield></entry> | |
107 | <entry></entry> | |
108 | <entry>Structure containing additional data for the | |
109 | <constant>V4L2_DEC_CMD_START</constant> command.</entry> | |
110 | </row> | |
111 | <row> | |
112 | <entry></entry> | |
113 | <entry></entry> | |
1b1301e6 | 114 | <entry>__s32</entry> |
6b4f1252 HV |
115 | <entry><structfield>speed</structfield></entry> |
116 | <entry>Playback speed and direction. The playback speed is defined as | |
117 | <structfield>speed</structfield>/1000 of the normal speed. So 1000 is normal playback. | |
118 | Negative numbers denote reverse playback, so -1000 does reverse playback at normal | |
119 | speed. Speeds -1, 0 and 1 have special meanings: speed 0 is shorthand for 1000 | |
120 | (normal playback). A speed of 1 steps just one frame forward, a speed of -1 steps | |
121 | just one frame back. | |
122 | </entry> | |
123 | </row> | |
124 | <row> | |
125 | <entry></entry> | |
126 | <entry></entry> | |
127 | <entry>__u32</entry> | |
128 | <entry><structfield>format</structfield></entry> | |
129 | <entry>Format restrictions. This field is set by the driver, not the | |
130 | application. Possible values are <constant>V4L2_DEC_START_FMT_NONE</constant> if | |
131 | there are no format restrictions or <constant>V4L2_DEC_START_FMT_GOP</constant> | |
132 | if the decoder operates on full GOPs (<wordasword>Group Of Pictures</wordasword>). | |
133 | This is usually the case for reverse playback: the decoder needs full GOPs, which | |
134 | it can then play in reverse order. So to implement reverse playback the application | |
135 | must feed the decoder the last GOP in the video file, then the GOP before that, etc. etc. | |
136 | </entry> | |
137 | </row> | |
138 | <row> | |
139 | <entry></entry> | |
140 | <entry>struct</entry> | |
141 | <entry><structfield>stop</structfield></entry> | |
142 | <entry></entry> | |
143 | <entry>Structure containing additional data for the | |
144 | <constant>V4L2_DEC_CMD_STOP</constant> command.</entry> | |
145 | </row> | |
146 | <row> | |
147 | <entry></entry> | |
148 | <entry></entry> | |
149 | <entry>__u64</entry> | |
150 | <entry><structfield>pts</structfield></entry> | |
151 | <entry>Stop playback at this <structfield>pts</structfield> or immediately | |
152 | if the playback is already past that timestamp. Leave to 0 if you want to stop after the | |
153 | last frame was decoded. | |
154 | </entry> | |
155 | </row> | |
156 | <row> | |
157 | <entry></entry> | |
158 | <entry>struct</entry> | |
159 | <entry><structfield>raw</structfield></entry> | |
160 | <entry></entry> | |
161 | <entry></entry> | |
162 | </row> | |
163 | <row> | |
164 | <entry></entry> | |
165 | <entry></entry> | |
166 | <entry>__u32</entry> | |
167 | <entry><structfield>data</structfield>[16]</entry> | |
168 | <entry>Reserved for future extensions. Drivers and | |
169 | applications must set the array to zero.</entry> | |
170 | </row> | |
171 | </tbody> | |
172 | </tgroup> | |
173 | </table> | |
174 | ||
175 | <table pgwide="1" frame="none" id="decoder-cmds"> | |
176 | <title>Decoder Commands</title> | |
177 | <tgroup cols="3"> | |
178 | &cs-def; | |
179 | <tbody valign="top"> | |
180 | <row> | |
181 | <entry><constant>V4L2_DEC_CMD_START</constant></entry> | |
182 | <entry>0</entry> | |
183 | <entry>Start the decoder. When the decoder is already | |
184 | running or paused, this command will just change the playback speed. | |
185 | That means that calling <constant>V4L2_DEC_CMD_START</constant> when | |
186 | the decoder was paused will <emphasis>not</emphasis> resume the decoder. | |
187 | You have to explicitly call <constant>V4L2_DEC_CMD_RESUME</constant> for that. | |
188 | This command has one flag: | |
189 | <constant>V4L2_DEC_CMD_START_MUTE_AUDIO</constant>. If set, then audio will | |
190 | be muted when playing back at a non-standard speed. | |
191 | </entry> | |
192 | </row> | |
193 | <row> | |
194 | <entry><constant>V4L2_DEC_CMD_STOP</constant></entry> | |
195 | <entry>1</entry> | |
196 | <entry>Stop the decoder. When the decoder is already stopped, | |
197 | this command does nothing. This command has two flags: | |
198 | if <constant>V4L2_DEC_CMD_STOP_TO_BLACK</constant> is set, then the decoder will | |
199 | set the picture to black after it stopped decoding. Otherwise the last image will | |
8cee396b PZ |
200 | repeat. mem2mem decoders will stop producing new frames altogether. They will send |
201 | a <constant>V4L2_EVENT_EOS</constant> event when the last frame has been decoded | |
202 | and all frames are ready to be dequeued and will set the | |
203 | <constant>V4L2_BUF_FLAG_LAST</constant> buffer flag on the last buffer of the | |
204 | capture queue to indicate there will be no new buffers produced to dequeue. This | |
205 | buffer may be empty, indicated by the driver setting the | |
206 | <structfield>bytesused</structfield> field to 0. Once the | |
207 | <constant>V4L2_BUF_FLAG_LAST</constant> flag was set, the | |
208 | <link linkend="vidioc-qbuf">VIDIOC_DQBUF</link> ioctl will not block anymore, | |
209 | but return an &EPIPE;. | |
210 | If <constant>V4L2_DEC_CMD_STOP_IMMEDIATELY</constant> is set, then the decoder | |
6b4f1252 HV |
211 | stops immediately (ignoring the <structfield>pts</structfield> value), otherwise it |
212 | will keep decoding until timestamp >= pts or until the last of the pending data from | |
213 | its internal buffers was decoded. | |
214 | </entry> | |
215 | </row> | |
216 | <row> | |
217 | <entry><constant>V4L2_DEC_CMD_PAUSE</constant></entry> | |
218 | <entry>2</entry> | |
219 | <entry>Pause the decoder. When the decoder has not been | |
220 | started yet, the driver will return an &EPERM;. When the decoder is | |
221 | already paused, this command does nothing. This command has one flag: | |
222 | if <constant>V4L2_DEC_CMD_PAUSE_TO_BLACK</constant> is set, then set the | |
223 | decoder output to black when paused. | |
224 | </entry> | |
225 | </row> | |
226 | <row> | |
227 | <entry><constant>V4L2_DEC_CMD_RESUME</constant></entry> | |
228 | <entry>3</entry> | |
229 | <entry>Resume decoding after a PAUSE command. When the | |
230 | decoder has not been started yet, the driver will return an &EPERM;. | |
231 | When the decoder is already running, this command does nothing. No | |
232 | flags are defined for this command.</entry> | |
233 | </row> | |
234 | </tbody> | |
235 | </tgroup> | |
236 | </table> | |
237 | ||
238 | </refsect1> | |
239 | ||
240 | <refsect1> | |
241 | &return-value; | |
242 | ||
243 | <variablelist> | |
244 | <varlistentry> | |
245 | <term><errorcode>EINVAL</errorcode></term> | |
246 | <listitem> | |
247 | <para>The <structfield>cmd</structfield> field is invalid.</para> | |
248 | </listitem> | |
249 | </varlistentry> | |
250 | <varlistentry> | |
251 | <term><errorcode>EPERM</errorcode></term> | |
252 | <listitem> | |
253 | <para>The application sent a PAUSE or RESUME command when | |
254 | the decoder was not running.</para> | |
255 | </listitem> | |
256 | </varlistentry> | |
257 | </variablelist> | |
258 | </refsect1> | |
259 | </refentry> |