1 .. SPDX-License-Identifier: GPL-2.0
6 Non-compressed file format
7 --------------------------
9 The cx23416 can produce (and the cx23415 can also read) raw YUV output. The
10 format of a YUV frame is specific to this chip and is called HM12. 'HM' stands
11 for 'Hauppauge Macroblock', which is a misnomer as 'Conexant Macroblock' would
14 The format is YUV 4:2:0 which uses 1 Y byte per pixel and 1 U and V byte per
17 The data is encoded as two macroblock planes, the first containing the Y
18 values, the second containing UV macroblocks.
20 The Y plane is divided into blocks of 16x16 pixels from left to right
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
25 transmitting this block the first line of the block on the right to the
26 first block is transmitted, etc.
28 The UV plane is divided into blocks of 16x8 UV values going from left
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
32 contain 8 UV value pairs (16 bytes in total). The second 16 bytes are the
33 second line of 8 UV pairs of the top-left block, etc. After transmitting
34 this block the first line of the block on the right to the first block is
37 The code below is given as an example on how to convert HM12 to separate
38 Y, U and V planes. This code assumes frames of 720x576 (PAL) pixels.
40 The width of a frame is always 720 pixels, regardless of the actual specified
43 If the height is not a multiple of 32 lines, then the captured video is
44 missing macroblocks at the end and is unusable. So the height must be a
56 static unsigned char frame[576*720*3/2];
57 static unsigned char framey[576*720];
58 static unsigned char frameu[576*720 / 4];
59 static unsigned char framev[576*720 / 4];
61 static void de_macro_y(unsigned char* dst, unsigned char *src, int dstride, int w, int h)
67 // The Y plane is divided into blocks of 16x16 pixels
68 // Each block in transmitted in turn, line-by-line.
69 for (y = 0; y < h; y += 16) {
70 for (x = 0; x < w; x += 16) {
71 for (i = 0; i < 16; i++) {
72 memcpy(dst + x + (y + i) * dstride, src, 16);
79 static void de_macro_uv(unsigned char *dstu, unsigned char *dstv, unsigned char *src, int dstride, int w, int h)
83 // descramble U/V plane
84 // dstride = 720 / 2 = w
85 // The U/V values are interlaced (UVUV...).
86 // Again, the UV plane is divided into blocks of 16x16 UV values.
87 // Each block in transmitted in turn, line-by-line.
88 for (y = 0; y < h; y += 16) {
89 for (x = 0; x < w; x += 8) {
90 for (i = 0; i < 16; i++) {
91 int idx = x + (y + i) * dstride;
93 dstu[idx+0] = src[0]; dstv[idx+0] = src[1];
94 dstu[idx+1] = src[2]; dstv[idx+1] = src[3];
95 dstu[idx+2] = src[4]; dstv[idx+2] = src[5];
96 dstu[idx+3] = src[6]; dstv[idx+3] = src[7];
97 dstu[idx+4] = src[8]; dstv[idx+4] = src[9];
98 dstu[idx+5] = src[10]; dstv[idx+5] = src[11];
99 dstu[idx+6] = src[12]; dstv[idx+6] = src[13];
100 dstu[idx+7] = src[14]; dstv[idx+7] = src[15];
107 /*************************************************************************/
108 int main(int argc, char **argv)
113 if (argc == 1) fin = stdin;
114 else fin = fopen(argv[1], "r");
117 fprintf(stderr, "cannot open input\n");
120 while (fread(frame, sizeof(frame), 1, fin) == 1) {
121 de_macro_y(framey, frame, 720, 720, 576);
122 de_macro_uv(frameu, framev, frame + 720 * 576, 720 / 2, 720 / 2, 576 / 2);
123 fwrite(framey, sizeof(framey), 1, stdout);
124 fwrite(framev, sizeof(framev), 1, stdout);
125 fwrite(frameu, sizeof(frameu), 1, stdout);
132 Format of embedded V4L2_MPEG_STREAM_VBI_FMT_IVTV VBI data
133 ---------------------------------------------------------
135 Author: Hans Verkuil <hverkuil@xs4all.nl>
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
140 hardware limitations of the ivtv driver (the driver for the Conexant cx23415/6
141 chips), in particular a maximum size for the VBI data. Anything longer is cut
142 off when the MPEG stream is played back through the cx23415.
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
149 header and a 42 bytes payload each. Anything beyond this limit is cut off by
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
154 two different magic numbers were introduced:
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
162 implies that the bitmasks are 0xffffffff and 0xf.
164 After these magic cookies (and the 8 byte bitmask in case of cookie 'itv0') the
165 captured VBI lines start:
167 For each line the least significant 4 bits of the first byte contain the data type.
168 Possible values are shown in the table below. The payload is in the following 42
171 Here is the list of possible data types:
175 #define IVTV_SLICED_TYPE_TELETEXT 0x1 // Teletext (uses lines 6-22 for PAL)
176 #define IVTV_SLICED_TYPE_CC 0x4 // Closed Captions (line 21 NTSC)
177 #define IVTV_SLICED_TYPE_WSS 0x5 // Wide Screen Signal (line 23 PAL)
178 #define IVTV_SLICED_TYPE_VPS 0x7 // Video Programming System (PAL) (line 16)