media/drivers/cx2341x-uapi.rst

1 .. SPDX-License-Identifier: GPL-2.0
6 Non-compressed file format
7 --------------------------
17 The data is encoded as two macroblock planes, the first containing the Y
21 and from top to bottom. Each block is transmitted in turn, line-by-line.
23 So the first 16 bytes are the first line of the top-left block, the
24 second 16 bytes are the second line of the top-left block, etc. After
29 to right, top to bottom. Each block is transmitted in turn, line-by-line.
31 So the first 16 bytes are the first line of the top-left block and
33 second line of 8 UV pairs of the top-left block, etc. After transmitting
43 If the height is not a multiple of 32 lines, then the captured video is
50 .. code-block:: c
68 	// Each block in transmitted in turn, line-by-line.
87 	// Each block in transmitted in turn, line-by-line.
118 		exit(-1);
132 Format of embedded V4L2_MPEG_STREAM_VBI_FMT_IVTV VBI data
133 ---------------------------------------------------------
138 This section describes the V4L2_MPEG_STREAM_VBI_FMT_IVTV format of the VBI data
139 embedded in an MPEG-2 program stream. This format is in part dictated by some
141 chips), in particular a maximum size for the VBI data. Anything longer is cut
144 The advantage of this format is it is very compact and that all VBI data for
145 all lines can be stored while still fitting within the maximum allowed size.
147 The stream ID of the VBI data is 0xBD. The maximum size of the embedded data is
148 4 + 43 * 36, which is 4 bytes for a header and 2 * 18 VBI lines with a 1 byte
150 the cx23415/6 firmware. Besides the data for the VBI lines we also need 36 bits
151 for a bitmask determining which lines are captured and 4 bytes for a magic cookie,
152 signifying that this data package contains V4L2_MPEG_STREAM_VBI_FMT_IVTV VBI data.
153 If all lines are used, then there is no longer room for the bitmask. To solve this
156 'itv0': After this magic number two unsigned longs follow. Bits 0-17 of the first
157 unsigned long denote which lines of the first field are captured. Bits 18-31 of
158 the first unsigned long and bits 0-3 of the second unsigned long are used for the
161 'ITV0': This magic number assumes all VBI lines are captured, i.e. it implicitly
165 captured VBI lines start:
167 For each line the least significant 4 bits of the first byte contain the data type.
171 Here is the list of possible data types:
173 .. code-block:: c
175 	#define IVTV_SLICED_TYPE_TELETEXT       0x1     // Teletext (uses lines 6-22 for PAL)