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     40 >Video for Linux Two API Specification: Revision 0.24</TH
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     71 ><H1
     72 ><A
     73 NAME="VIDIOC-G-JPEGCOMP"
     74 ></A
     75 >ioctl VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP</H1
     76 ><DIV
     77 CLASS="REFNAMEDIV"
     78 ><A
     79 NAME="AEN11289"
     80 ></A
     81 ><H2
     82 >Name</H2
     83 >VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP&nbsp;--&nbsp;</DIV
     84 ><DIV
     85 CLASS="REFSYNOPSISDIV"
     86 ><A
     87 NAME="AEN11293"
     88 ></A
     89 ><H2
     90 >Synopsis</H2
     91 ><DIV
     92 CLASS="FUNCSYNOPSIS"
     93 ><P
     94 ></P
     95 ><A
     96 NAME="AEN11294"
     97 ></A
     98 ><P
     99 ><CODE
    100 ><CODE
    101 CLASS="FUNCDEF"
    102 >int ioctl</CODE
    103 >(int fd, int request, v4l2_jpegcompression *argp);</CODE
    104 ></P
    105 ><P
    106 ></P
    107 ></DIV
    108 ><DIV
    109 CLASS="FUNCSYNOPSIS"
    110 ><P
    111 ></P
    112 ><A
    113 NAME="AEN11304"
    114 ></A
    115 ><P
    116 ><CODE
    117 ><CODE
    118 CLASS="FUNCDEF"
    119 >int ioctl</CODE
    120 >(int fd, int request, const v4l2_jpegcompression *argp);</CODE
    121 ></P
    122 ><P
    123 ></P
    124 ></DIV
    125 ></DIV
    126 ><DIV
    127 CLASS="REFSECT1"
    128 ><A
    129 NAME="AEN11314"
    130 ></A
    131 ><H2
    132 >Arguments</H2
    133 ><P
    134 ></P
    135 ><DIV
    136 CLASS="VARIABLELIST"
    137 ><DL
    138 ><DT
    139 ><CODE
    140 CLASS="PARAMETER"
    141 >fd</CODE
    142 ></DT
    143 ><DD
    144 ><P
    145 >File descriptor returned by <A
    146 HREF="r14090.htm"
    147 ><CODE
    148 CLASS="FUNCTION"
    149 >open()</CODE
    150 ></A
    151 >.</P
    152 ></DD
    153 ><DT
    154 ><CODE
    155 CLASS="PARAMETER"
    156 >request</CODE
    157 ></DT
    158 ><DD
    159 ><P
    160 >VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP</P
    161 ></DD
    162 ><DT
    163 ><CODE
    164 CLASS="PARAMETER"
    165 >argp</CODE
    166 ></DT
    167 ><DD
    168 ><P
    169 ></P
    170 ></DD
    171 ></DL
    172 ></DIV
    173 ></DIV
    174 ><DIV
    175 CLASS="REFSECT1"
    176 ><A
    177 NAME="AEN11334"
    178 ></A
    179 ><H2
    180 >Description</H2
    181 ><P
    182 >[to do]</P
    183 ><P
    184 >Ronald Bultje elaborates:</P
    185 ><P
    186 >APP is some application-specific information. The
    187 application can set it itself, and it'll be stored in the JPEG-encoded
    188 fields (eg; interlacing information for in an AVI or so). COM is the
    189 same, but it's comments, like 'encoded by me' or so.</P
    190 ><P
    191 >jpeg_markers describes whether the huffman tables,
    192 quantization tables and the restart interval information (all
    193 JPEG-specific stuff) should be stored in the JPEG-encoded fields.
    194 These define how the JPEG field is encoded. If you omit them,
    195 applications assume you've used standard encoding. You usually do want
    196 to add them.</P
    197 ><DIV
    198 CLASS="TABLE"
    199 ><A
    200 NAME="V4L2-JPEGCOMPRESSION"
    201 ></A
    202 ><P
    203 ><B
    204 >Table 1. struct <CODE
    205 CLASS="STRUCTNAME"
    206 >v4l2_jpegcompression</CODE
    207 ></B
    208 ></P
    209 ><TABLE
    210 BORDER="0"
    211 FRAME="void"
    212 WIDTH="100%"
    213 CLASS="CALSTABLE"
    214 ><COL
    215 WIDTH="25%"
    216 TITLE="C1"><COL
    217 WIDTH="25%"
    218 TITLE="C2"><COL
    219 WIDTH="50%"
    220 TITLE="C3"><TBODY
    221 VALIGN="TOP"
    222 ><TR
    223 ><TD
    224 >int</TD
    225 ><TD
    226 ><CODE
    227 CLASS="STRUCTFIELD"
    228 >quality</CODE
    229 ></TD
    230 ><TD
    231 >&nbsp;</TD
    232 ></TR
    233 ><TR
    234 ><TD
    235 >int</TD
    236 ><TD
    237 ><CODE
    238 CLASS="STRUCTFIELD"
    239 >APPn</CODE
    240 ></TD
    241 ><TD
    242 >&nbsp;</TD
    243 ></TR
    244 ><TR
    245 ><TD
    246 >int</TD
    247 ><TD
    248 ><CODE
    249 CLASS="STRUCTFIELD"
    250 >APP_len</CODE
    251 ></TD
    252 ><TD
    253 >&nbsp;</TD
    254 ></TR
    255 ><TR
    256 ><TD
    257 >char</TD
    258 ><TD
    259 ><CODE
    260 CLASS="STRUCTFIELD"
    261 >APP_data</CODE
    262 >[60]</TD
    263 ><TD
    264 >&nbsp;</TD
    265 ></TR
    266 ><TR
    267 ><TD
    268 >int</TD
    269 ><TD
    270 ><CODE
    271 CLASS="STRUCTFIELD"
    272 >COM_len</CODE
    273 ></TD
    274 ><TD
    275 >&nbsp;</TD
    276 ></TR
    277 ><TR
    278 ><TD
    279 >char</TD
    280 ><TD
    281 ><CODE
    282 CLASS="STRUCTFIELD"
    283 >COM_data</CODE
    284 >[60]</TD
    285 ><TD
    286 >&nbsp;</TD
    287 ></TR
    288 ><TR
    289 ><TD
    290 >__u32</TD
    291 ><TD
    292 ><CODE
    293 CLASS="STRUCTFIELD"
    294 >jpeg_markers</CODE
    295 ></TD
    296 ><TD
    297 >See <A
    298 HREF="r11285.htm#JPEG-MARKERS"
    299 >Table 2</A
    300 >.</TD
    301 ></TR
    302 ></TBODY
    303 ></TABLE
    304 ></DIV
    305 ><DIV
    306 CLASS="TABLE"
    307 ><A
    308 NAME="JPEG-MARKERS"
    309 ></A
    310 ><P
    311 ><B
    312 >Table 2. JPEG Markers Flags</B
    313 ></P
    314 ><TABLE
    315 BORDER="0"
    316 FRAME="void"
    317 WIDTH="100%"
    318 CLASS="CALSTABLE"
    319 ><COL
    320 WIDTH="38%"
    321 TITLE="C1"><COL
    322 WIDTH="12%"
    323 TITLE="C2"><COL
    324 WIDTH="50%"
    325 TITLE="C3"><TBODY
    326 VALIGN="TOP"
    327 ><TR
    328 ><TD
    329 ><CODE
    330 CLASS="CONSTANT"
    331 >V4L2_JPEG_MARKER_DHT</CODE
    332 ></TD
    333 ><TD
    334 >(1&lt;&lt;3)</TD
    335 ><TD
    336 >Define Huffman Tables</TD
    337 ></TR
    338 ><TR
    339 ><TD
    340 ><CODE
    341 CLASS="CONSTANT"
    342 >V4L2_JPEG_MARKER_DQT</CODE
    343 ></TD
    344 ><TD
    345 >(1&lt;&lt;4)</TD
    346 ><TD
    347 >Define Quantization Tables</TD
    348 ></TR
    349 ><TR
    350 ><TD
    351 ><CODE
    352 CLASS="CONSTANT"
    353 >V4L2_JPEG_MARKER_DRI</CODE
    354 ></TD
    355 ><TD
    356 >(1&lt;&lt;5)</TD
    357 ><TD
    358 >Define Restart Interval</TD
    359 ></TR
    360 ><TR
    361 ><TD
    362 ><CODE
    363 CLASS="CONSTANT"
    364 >V4L2_JPEG_MARKER_COM</CODE
    365 ></TD
    366 ><TD
    367 >(1&lt;&lt;6)</TD
    368 ><TD
    369 >Comment segment</TD
    370 ></TR
    371 ><TR
    372 ><TD
    373 ><CODE
    374 CLASS="CONSTANT"
    375 >V4L2_JPEG_MARKER_APP</CODE
    376 ></TD
    377 ><TD
    378 >(1&lt;&lt;7)</TD
    379 ><TD
    380 >App segment, driver will always use APP0</TD
    381 ></TR
    382 ></TBODY
    383 ></TABLE
    384 ></DIV
    385 ></DIV
    386 ><DIV
    387 CLASS="REFSECT1"
    388 ><A
    389 NAME="AEN11418"
    390 ></A
    391 ><H2
    392 >Return Value</H2
    393 ><P
    394 >On success <SPAN
    395 CLASS="RETURNVALUE"
    396 >0</SPAN
    397 > is returned, on error <SPAN
    398 CLASS="RETURNVALUE"
    399 >-1</SPAN
    400 > and the <CODE
    401 CLASS="VARNAME"
    402 >errno</CODE
    403 > variable is set appropriately:</P
    404 ><P
    405 ></P
    406 ><DIV
    407 CLASS="VARIABLELIST"
    408 ><DL
    409 ><DT
    410 ><SPAN
    411 CLASS="ERRORCODE"
    412 >EINVAL</SPAN
    413 ></DT
    414 ><DD
    415 ><P
    416 >This ioctl is not supported.</P
    417 ></DD
    418 ></DL
    419 ></DIV
    420 ></DIV
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