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1 | .. -*- coding: utf-8; mode: rst -*- |
2 | ||
af4a4d0d | 3 | .. _VIDIOC_G_JPEGCOMP: |
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4 | |
5 | ****************************************** | |
6 | ioctl VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP | |
7 | ****************************************** | |
8 | ||
9 | *man VIDIOC_G_JPEGCOMP(2)* | |
10 | ||
11 | VIDIOC_S_JPEGCOMP | |
12 | ||
13 | Synopsis | |
14 | ======== | |
15 | ||
b7e67f6c | 16 | .. cpp:function:: int ioctl( int fd, int request, v4l2_jpegcompression *argp ) |
5377d91f | 17 | |
b7e67f6c | 18 | .. cpp:function:: int ioctl( int fd, int request, const v4l2_jpegcompression *argp ) |
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19 | |
20 | Arguments | |
21 | ========= | |
22 | ||
23 | ``fd`` | |
24 | File descriptor returned by :ref:`open() <func-open>`. | |
25 | ||
26 | ``request`` | |
27 | VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP | |
28 | ||
29 | ``argp`` | |
30 | ||
31 | ||
32 | Description | |
33 | =========== | |
34 | ||
35 | These ioctls are **deprecated**. New drivers and applications should use | |
36 | :ref:`JPEG class controls <jpeg-controls>` for image quality and JPEG | |
37 | markers control. | |
38 | ||
39 | [to do] | |
40 | ||
41 | Ronald Bultje elaborates: | |
42 | ||
43 | APP is some application-specific information. The application can set it | |
44 | itself, and it'll be stored in the JPEG-encoded fields (eg; interlacing | |
45 | information for in an AVI or so). COM is the same, but it's comments, | |
46 | like 'encoded by me' or so. | |
47 | ||
48 | jpeg_markers describes whether the huffman tables, quantization tables | |
49 | and the restart interval information (all JPEG-specific stuff) should be | |
50 | stored in the JPEG-encoded fields. These define how the JPEG field is | |
51 | encoded. If you omit them, applications assume you've used standard | |
52 | encoding. You usually do want to add them. | |
53 | ||
54 | ||
55 | .. _v4l2-jpegcompression: | |
56 | ||
57 | .. flat-table:: struct v4l2_jpegcompression | |
58 | :header-rows: 0 | |
59 | :stub-columns: 0 | |
60 | :widths: 1 1 2 | |
61 | ||
62 | ||
63 | - .. row 1 | |
64 | ||
65 | - int | |
66 | ||
67 | - ``quality`` | |
68 | ||
69 | - Deprecated. If | |
70 | :ref:`V4L2_CID_JPEG_COMPRESSION_QUALITY <jpeg-quality-control>` | |
71 | control is exposed by a driver applications should use it instead | |
72 | and ignore this field. | |
73 | ||
74 | - .. row 2 | |
75 | ||
76 | - int | |
77 | ||
78 | - ``APPn`` | |
79 | ||
80 | - | |
81 | ||
82 | - .. row 3 | |
83 | ||
84 | - int | |
85 | ||
86 | - ``APP_len`` | |
87 | ||
88 | - | |
89 | ||
90 | - .. row 4 | |
91 | ||
92 | - char | |
93 | ||
94 | - ``APP_data``\ [60] | |
95 | ||
96 | - | |
97 | ||
98 | - .. row 5 | |
99 | ||
100 | - int | |
101 | ||
102 | - ``COM_len`` | |
103 | ||
104 | - | |
105 | ||
106 | - .. row 6 | |
107 | ||
108 | - char | |
109 | ||
110 | - ``COM_data``\ [60] | |
111 | ||
112 | - | |
113 | ||
114 | - .. row 7 | |
115 | ||
116 | - __u32 | |
117 | ||
118 | - ``jpeg_markers`` | |
119 | ||
120 | - See :ref:`jpeg-markers`. Deprecated. If | |
121 | :ref:`V4L2_CID_JPEG_ACTIVE_MARKER <jpeg-active-marker-control>` | |
122 | control is exposed by a driver applications should use it instead | |
123 | and ignore this field. | |
124 | ||
125 | ||
126 | ||
127 | .. _jpeg-markers: | |
128 | ||
129 | .. flat-table:: JPEG Markers Flags | |
130 | :header-rows: 0 | |
131 | :stub-columns: 0 | |
132 | :widths: 3 1 4 | |
133 | ||
134 | ||
135 | - .. row 1 | |
136 | ||
137 | - ``V4L2_JPEG_MARKER_DHT`` | |
138 | ||
139 | - (1<<3) | |
140 | ||
141 | - Define Huffman Tables | |
142 | ||
143 | - .. row 2 | |
144 | ||
145 | - ``V4L2_JPEG_MARKER_DQT`` | |
146 | ||
147 | - (1<<4) | |
148 | ||
149 | - Define Quantization Tables | |
150 | ||
151 | - .. row 3 | |
152 | ||
153 | - ``V4L2_JPEG_MARKER_DRI`` | |
154 | ||
155 | - (1<<5) | |
156 | ||
157 | - Define Restart Interval | |
158 | ||
159 | - .. row 4 | |
160 | ||
161 | - ``V4L2_JPEG_MARKER_COM`` | |
162 | ||
163 | - (1<<6) | |
164 | ||
165 | - Comment segment | |
166 | ||
167 | - .. row 5 | |
168 | ||
169 | - ``V4L2_JPEG_MARKER_APP`` | |
170 | ||
171 | - (1<<7) | |
172 | ||
173 | - App segment, driver will always use APP0 | |
174 | ||
175 | ||
176 | ||
177 | Return Value | |
178 | ============ | |
179 | ||
180 | On success 0 is returned, on error -1 and the ``errno`` variable is set | |
181 | appropriately. The generic error codes are described at the | |
182 | :ref:`Generic Error Codes <gen-errors>` chapter. | |
183 | ||
184 | ||
185 | .. ------------------------------------------------------------------------------ | |
186 | .. This file was automatically converted from DocBook-XML with the dbxml | |
187 | .. library (https://github.com/return42/sphkerneldoc). The origin XML comes | |
188 | .. from the linux kernel, refer to: | |
189 | .. | |
190 | .. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook | |
191 | .. ------------------------------------------------------------------------------ |