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diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-jpegcomp.rst b/Documentation/userspace-api/media/v4l/vidioc-g-jpegcomp.rst new file mode 100644 index 000000000..d4565d2cc --- /dev/null +++ b/Documentation/userspace-api/media/v4l/vidioc-g-jpegcomp.rst @@ -0,0 +1,124 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _VIDIOC_G_JPEGCOMP: + +****************************************** +ioctl VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP +****************************************** + +Name +==== + +VIDIOC_G_JPEGCOMP - VIDIOC_S_JPEGCOMP + +Synopsis +======== + +.. c:macro:: VIDIOC_G_JPEGCOMP + +``int ioctl(int fd, VIDIOC_G_JPEGCOMP, v4l2_jpegcompression *argp)`` + +.. c:macro:: VIDIOC_S_JPEGCOMP + +``int ioctl(int fd, VIDIOC_S_JPEGCOMP, const v4l2_jpegcompression *argp)`` + +Arguments +========= + +``fd`` + File descriptor returned by :c:func:`open()`. + +``argp`` + Pointer to struct :c:type:`v4l2_jpegcompression`. + +Description +=========== + +These ioctls are **deprecated**. New drivers and applications should use +:ref:`JPEG class controls <jpeg-controls>` for image quality and JPEG +markers control. + +[to do] + +Ronald Bultje elaborates: + +APP is some application-specific information. The application can set it +itself, and it'll be stored in the JPEG-encoded fields (eg; interlacing +information for in an AVI or so). COM is the same, but it's comments, +like 'encoded by me' or so. + +jpeg_markers describes whether the huffman tables, quantization tables +and the restart interval information (all JPEG-specific stuff) should be +stored in the JPEG-encoded fields. These define how the JPEG field is +encoded. If you omit them, applications assume you've used standard +encoding. You usually do want to add them. + +.. tabularcolumns:: |p{1.2cm}|p{3.0cm}|p{13.1cm}| + +.. c:type:: v4l2_jpegcompression + +.. flat-table:: struct v4l2_jpegcompression + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + * - int + - ``quality`` + - Deprecated. If + :ref:`V4L2_CID_JPEG_COMPRESSION_QUALITY <jpeg-quality-control>` + control is exposed by a driver applications should use it instead + and ignore this field. + * - int + - ``APPn`` + - + * - int + - ``APP_len`` + - + * - char + - ``APP_data``\ [60] + - + * - int + - ``COM_len`` + - + * - char + - ``COM_data``\ [60] + - + * - __u32 + - ``jpeg_markers`` + - See :ref:`jpeg-markers`. Deprecated. If + :ref:`V4L2_CID_JPEG_ACTIVE_MARKER <jpeg-active-marker-control>` + control is exposed by a driver applications should use it instead + and ignore this field. + +.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}| + +.. _jpeg-markers: + +.. flat-table:: JPEG Markers Flags + :header-rows: 0 + :stub-columns: 0 + :widths: 3 1 4 + + * - ``V4L2_JPEG_MARKER_DHT`` + - (1<<3) + - Define Huffman Tables + * - ``V4L2_JPEG_MARKER_DQT`` + - (1<<4) + - Define Quantization Tables + * - ``V4L2_JPEG_MARKER_DRI`` + - (1<<5) + - Define Restart Interval + * - ``V4L2_JPEG_MARKER_COM`` + - (1<<6) + - Comment segment + * - ``V4L2_JPEG_MARKER_APP`` + - (1<<7) + - App segment, driver will always use APP0 + +Return Value +============ + +On success 0 is returned, on error -1 and the ``errno`` variable is set +appropriately. The generic error codes are described at the +:ref:`Generic Error Codes <gen-errors>` chapter. |