media/drivers/cx2341x-uapi.rst

1 .. SPDX-License-Identifier: GPL-2.0
6 Non-compressed file format
7 --------------------------
15 The data is encoded as two macroblock planes, the first containing the Y
19 and from top to bottom. Each block is transmitted in turn, line-by-line.
21 So the first 16 bytes are the first line of the top-left block, the
22 second 16 bytes are the second line of the top-left block, etc. After
27 to right, top to bottom. Each block is transmitted in turn, line-by-line.
29 So the first 16 bytes are the first line of the top-left block and
31 second line of 8 UV pairs of the top-left block, etc. After transmitting
41 If the height is not a multiple of 32 lines, then the captured video is
48 .. code-block:: c
66 	// Each block in transmitted in turn, line-by-line.
85 	// Each block in transmitted in turn, line-by-line.
116 		exit(-1);
130 Format of embedded V4L2_MPEG_STREAM_VBI_FMT_IVTV VBI data
131 ---------------------------------------------------------
136 This section describes the V4L2_MPEG_STREAM_VBI_FMT_IVTV format of the VBI data
137 embedded in an MPEG-2 program stream. This format is in part dictated by some
139 chips), in particular a maximum size for the VBI data. Anything longer is cut
142 The advantage of this format is it is very compact and that all VBI data for
143 all lines can be stored while still fitting within the maximum allowed size.
145 The stream ID of the VBI data is 0xBD. The maximum size of the embedded data is
146 4 + 43 * 36, which is 4 bytes for a header and 2 * 18 VBI lines with a 1 byte
148 the cx23415/6 firmware. Besides the data for the VBI lines we also need 36 bits
149 for a bitmask determining which lines are captured and 4 bytes for a magic cookie,
150 signifying that this data package contains V4L2_MPEG_STREAM_VBI_FMT_IVTV VBI data.
151 If all lines are used, then there is no longer room for the bitmask. To solve this
154 'itv0': After this magic number two unsigned longs follow. Bits 0-17 of the first
155 unsigned long denote which lines of the first field are captured. Bits 18-31 of
156 the first unsigned long and bits 0-3 of the second unsigned long are used for the
159 'ITV0': This magic number assumes all VBI lines are captured, i.e. it implicitly
163 captured VBI lines start:
165 For each line the least significant 4 bits of the first byte contain the data type.
169 Here is the list of possible data types:
171 .. code-block:: c
173 	#define IVTV_SLICED_TYPE_TELETEXT       0x1     // Teletext (uses lines 6-22 for PAL)