1.. Permission is granted to copy, distribute and/or modify this 2.. document under the terms of the GNU Free Documentation License, 3.. Version 1.1 or any later version published by the Free Software 4.. Foundation, with no Invariant Sections, no Front-Cover Texts 5.. and no Back-Cover Texts. A copy of the license is included at 6.. Documentation/userspace-api/media/fdl-appendix.rst. 7.. 8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections 9 10.. _VIDIOC_G_JPEGCOMP: 11 12****************************************** 13ioctl VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP 14****************************************** 15 16Name 17==== 18 19VIDIOC_G_JPEGCOMP - VIDIOC_S_JPEGCOMP 20 21 22Synopsis 23======== 24 25.. c:function:: int ioctl( int fd, VIDIOC_G_JPEGCOMP, v4l2_jpegcompression *argp ) 26 :name: VIDIOC_G_JPEGCOMP 27 28.. c:function:: int ioctl( int fd, VIDIOC_S_JPEGCOMP, const v4l2_jpegcompression *argp ) 29 :name: VIDIOC_S_JPEGCOMP 30 31 32Arguments 33========= 34 35``fd`` 36 File descriptor returned by :ref:`open() <func-open>`. 37 38``argp`` 39 Pointer to struct :c:type:`v4l2_jpegcompression`. 40 41 42Description 43=========== 44 45These ioctls are **deprecated**. New drivers and applications should use 46:ref:`JPEG class controls <jpeg-controls>` for image quality and JPEG 47markers control. 48 49[to do] 50 51Ronald Bultje elaborates: 52 53APP is some application-specific information. The application can set it 54itself, and it'll be stored in the JPEG-encoded fields (eg; interlacing 55information for in an AVI or so). COM is the same, but it's comments, 56like 'encoded by me' or so. 57 58jpeg_markers describes whether the huffman tables, quantization tables 59and the restart interval information (all JPEG-specific stuff) should be 60stored in the JPEG-encoded fields. These define how the JPEG field is 61encoded. If you omit them, applications assume you've used standard 62encoding. You usually do want to add them. 63 64 65.. tabularcolumns:: |p{1.2cm}|p{3.0cm}|p{13.3cm}| 66 67.. c:type:: v4l2_jpegcompression 68 69.. flat-table:: struct v4l2_jpegcompression 70 :header-rows: 0 71 :stub-columns: 0 72 :widths: 1 1 2 73 74 * - int 75 - ``quality`` 76 - Deprecated. If 77 :ref:`V4L2_CID_JPEG_COMPRESSION_QUALITY <jpeg-quality-control>` 78 control is exposed by a driver applications should use it instead 79 and ignore this field. 80 * - int 81 - ``APPn`` 82 - 83 * - int 84 - ``APP_len`` 85 - 86 * - char 87 - ``APP_data``\ [60] 88 - 89 * - int 90 - ``COM_len`` 91 - 92 * - char 93 - ``COM_data``\ [60] 94 - 95 * - __u32 96 - ``jpeg_markers`` 97 - See :ref:`jpeg-markers`. Deprecated. If 98 :ref:`V4L2_CID_JPEG_ACTIVE_MARKER <jpeg-active-marker-control>` 99 control is exposed by a driver applications should use it instead 100 and ignore this field. 101 102 103.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}| 104 105.. _jpeg-markers: 106 107.. flat-table:: JPEG Markers Flags 108 :header-rows: 0 109 :stub-columns: 0 110 :widths: 3 1 4 111 112 * - ``V4L2_JPEG_MARKER_DHT`` 113 - (1<<3) 114 - Define Huffman Tables 115 * - ``V4L2_JPEG_MARKER_DQT`` 116 - (1<<4) 117 - Define Quantization Tables 118 * - ``V4L2_JPEG_MARKER_DRI`` 119 - (1<<5) 120 - Define Restart Interval 121 * - ``V4L2_JPEG_MARKER_COM`` 122 - (1<<6) 123 - Comment segment 124 * - ``V4L2_JPEG_MARKER_APP`` 125 - (1<<7) 126 - App segment, driver will always use APP0 127 128 129Return Value 130============ 131 132On success 0 is returned, on error -1 and the ``errno`` variable is set 133appropriately. The generic error codes are described at the 134:ref:`Generic Error Codes <gen-errors>` chapter. 135