1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 The cx2341x driver 3 The cx2341x driver
4 ================== 4 ==================
5 5
6 Non-compressed file format 6 Non-compressed file format
7 -------------------------- 7 --------------------------
8 8
9 The cx23416 can produce (and the cx23415 can a 9 The cx23416 can produce (and the cx23415 can also read) raw YUV output. The
10 format of a YUV frame is 16x16 linear tiled NV 10 format of a YUV frame is 16x16 linear tiled NV12 (V4L2_PIX_FMT_NV12_16L16).
11 11
12 The format is YUV 4:2:0 which uses 1 Y byte pe 12 The format is YUV 4:2:0 which uses 1 Y byte per pixel and 1 U and V byte per
13 four pixels. 13 four pixels.
14 14
15 The data is encoded as two macroblock planes, 15 The data is encoded as two macroblock planes, the first containing the Y
16 values, the second containing UV macroblocks. 16 values, the second containing UV macroblocks.
17 17
18 The Y plane is divided into blocks of 16x16 pi 18 The Y plane is divided into blocks of 16x16 pixels from left to right
19 and from top to bottom. Each block is transmit 19 and from top to bottom. Each block is transmitted in turn, line-by-line.
20 20
21 So the first 16 bytes are the first line of th 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 22 second 16 bytes are the second line of the top-left block, etc. After
23 transmitting this block the first line of the 23 transmitting this block the first line of the block on the right to the
24 first block is transmitted, etc. 24 first block is transmitted, etc.
25 25
26 The UV plane is divided into blocks of 16x8 UV 26 The UV plane is divided into blocks of 16x8 UV values going from left
27 to right, top to bottom. Each block is transmi 27 to right, top to bottom. Each block is transmitted in turn, line-by-line.
28 28
29 So the first 16 bytes are the first line of th 29 So the first 16 bytes are the first line of the top-left block and
30 contain 8 UV value pairs (16 bytes in total). 30 contain 8 UV value pairs (16 bytes in total). The second 16 bytes are the
31 second line of 8 UV pairs of the top-left bloc 31 second line of 8 UV pairs of the top-left block, etc. After transmitting
32 this block the first line of the block on the 32 this block the first line of the block on the right to the first block is
33 transmitted, etc. 33 transmitted, etc.
34 34
35 The code below is given as an example on how t 35 The code below is given as an example on how to convert V4L2_PIX_FMT_NV12_16L16
36 to separate Y, U and V planes. This code assum 36 to separate Y, U and V planes. This code assumes frames of 720x576 (PAL) pixels.
37 37
38 The width of a frame is always 720 pixels, reg 38 The width of a frame is always 720 pixels, regardless of the actual specified
39 width. 39 width.
40 40
41 If the height is not a multiple of 32 lines, t 41 If the height is not a multiple of 32 lines, then the captured video is
42 missing macroblocks at the end and is unusable 42 missing macroblocks at the end and is unusable. So the height must be a
43 multiple of 32. 43 multiple of 32.
44 44
45 Raw format c example 45 Raw format c example
46 ~~~~~~~~~~~~~~~~~~~~ 46 ~~~~~~~~~~~~~~~~~~~~
47 47
48 .. code-block:: c 48 .. code-block:: c
49 49
50 #include <stdio.h> 50 #include <stdio.h>
51 #include <stdlib.h> 51 #include <stdlib.h>
52 #include <string.h> 52 #include <string.h>
53 53
54 static unsigned char frame[576*720*3/2 54 static unsigned char frame[576*720*3/2];
55 static unsigned char framey[576*720]; 55 static unsigned char framey[576*720];
56 static unsigned char frameu[576*720 / 56 static unsigned char frameu[576*720 / 4];
57 static unsigned char framev[576*720 / 57 static unsigned char framev[576*720 / 4];
58 58
59 static void de_macro_y(unsigned char* 59 static void de_macro_y(unsigned char* dst, unsigned char *src, int dstride, int w, int h)
60 { 60 {
61 unsigned int y, x, i; 61 unsigned int y, x, i;
62 62
63 // descramble Y plane 63 // descramble Y plane
64 // dstride = 720 = w 64 // dstride = 720 = w
65 // The Y plane is divided into blocks 65 // The Y plane is divided into blocks of 16x16 pixels
66 // Each block in transmitted in turn, 66 // Each block in transmitted in turn, line-by-line.
67 for (y = 0; y < h; y += 16) { 67 for (y = 0; y < h; y += 16) {
68 for (x = 0; x < w; x += 16) { 68 for (x = 0; x < w; x += 16) {
69 for (i = 0; i < 16; i++) { 69 for (i = 0; i < 16; i++) {
70 memcpy(dst + x + (y + 70 memcpy(dst + x + (y + i) * dstride, src, 16);
71 src += 16; 71 src += 16;
72 } 72 }
73 } 73 }
74 } 74 }
75 } 75 }
76 76
77 static void de_macro_uv(unsigned char 77 static void de_macro_uv(unsigned char *dstu, unsigned char *dstv, unsigned char *src, int dstride, int w, int h)
78 { 78 {
79 unsigned int y, x, i; 79 unsigned int y, x, i;
80 80
81 // descramble U/V plane 81 // descramble U/V plane
82 // dstride = 720 / 2 = w 82 // dstride = 720 / 2 = w
83 // The U/V values are interlaced (UVUV 83 // The U/V values are interlaced (UVUV...).
84 // Again, the UV plane is divided into 84 // Again, the UV plane is divided into blocks of 16x16 UV values.
85 // Each block in transmitted in turn, 85 // Each block in transmitted in turn, line-by-line.
86 for (y = 0; y < h; y += 16) { 86 for (y = 0; y < h; y += 16) {
87 for (x = 0; x < w; x += 8) { 87 for (x = 0; x < w; x += 8) {
88 for (i = 0; i < 16; i++) { 88 for (i = 0; i < 16; i++) {
89 int idx = x + (y + i) 89 int idx = x + (y + i) * dstride;
90 90
91 dstu[idx+0] = src[0]; 91 dstu[idx+0] = src[0]; dstv[idx+0] = src[1];
92 dstu[idx+1] = src[2]; 92 dstu[idx+1] = src[2]; dstv[idx+1] = src[3];
93 dstu[idx+2] = src[4]; 93 dstu[idx+2] = src[4]; dstv[idx+2] = src[5];
94 dstu[idx+3] = src[6]; 94 dstu[idx+3] = src[6]; dstv[idx+3] = src[7];
95 dstu[idx+4] = src[8]; 95 dstu[idx+4] = src[8]; dstv[idx+4] = src[9];
96 dstu[idx+5] = src[10]; 96 dstu[idx+5] = src[10]; dstv[idx+5] = src[11];
97 dstu[idx+6] = src[12]; 97 dstu[idx+6] = src[12]; dstv[idx+6] = src[13];
98 dstu[idx+7] = src[14]; 98 dstu[idx+7] = src[14]; dstv[idx+7] = src[15];
99 src += 16; 99 src += 16;
100 } 100 }
101 } 101 }
102 } 102 }
103 } 103 }
104 104
105 /************************************* 105 /*************************************************************************/
106 int main(int argc, char **argv) 106 int main(int argc, char **argv)
107 { 107 {
108 FILE *fin; 108 FILE *fin;
109 int i; 109 int i;
110 110
111 if (argc == 1) fin = stdin; 111 if (argc == 1) fin = stdin;
112 else fin = fopen(argv[1], "r"); 112 else fin = fopen(argv[1], "r");
113 113
114 if (fin == NULL) { 114 if (fin == NULL) {
115 fprintf(stderr, "cannot open i 115 fprintf(stderr, "cannot open input\n");
116 exit(-1); 116 exit(-1);
117 } 117 }
118 while (fread(frame, sizeof(frame), 1, 118 while (fread(frame, sizeof(frame), 1, fin) == 1) {
119 de_macro_y(framey, frame, 720, 119 de_macro_y(framey, frame, 720, 720, 576);
120 de_macro_uv(frameu, framev, fr 120 de_macro_uv(frameu, framev, frame + 720 * 576, 720 / 2, 720 / 2, 576 / 2);
121 fwrite(framey, sizeof(framey), 121 fwrite(framey, sizeof(framey), 1, stdout);
122 fwrite(framev, sizeof(framev), 122 fwrite(framev, sizeof(framev), 1, stdout);
123 fwrite(frameu, sizeof(frameu), 123 fwrite(frameu, sizeof(frameu), 1, stdout);
124 } 124 }
125 fclose(fin); 125 fclose(fin);
126 return 0; 126 return 0;
127 } 127 }
128 128
129 129
130 Format of embedded V4L2_MPEG_STREAM_VBI_FMT_IV 130 Format of embedded V4L2_MPEG_STREAM_VBI_FMT_IVTV VBI data
131 ---------------------------------------------- 131 ---------------------------------------------------------
132 132
133 Author: Hans Verkuil <hverkuil@xs4all.nl> 133 Author: Hans Verkuil <hverkuil@xs4all.nl>
134 134
135 135
136 This section describes the V4L2_MPEG_STREAM_VB 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 for 137 embedded in an MPEG-2 program stream. This format is in part dictated by some
138 hardware limitations of the ivtv driver (the d 138 hardware limitations of the ivtv driver (the driver for the Conexant cx23415/6
139 chips), in particular a maximum size for the V 139 chips), in particular a maximum size for the VBI data. Anything longer is cut
140 off when the MPEG stream is played back throug 140 off when the MPEG stream is played back through the cx23415.
141 141
142 The advantage of this format is it is very com 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 wi 143 all lines can be stored while still fitting within the maximum allowed size.
144 144
145 The stream ID of the VBI data is 0xBD. The max 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 146 4 + 43 * 36, which is 4 bytes for a header and 2 * 18 VBI lines with a 1 byte
147 header and a 42 bytes payload each. Anything b 147 header and a 42 bytes payload each. Anything beyond this limit is cut off by
148 the cx23415/6 firmware. Besides the data for t 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 capt 149 for a bitmask determining which lines are captured and 4 bytes for a magic cookie,
150 signifying that this data package contains V4L 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 151 If all lines are used, then there is no longer room for the bitmask. To solve this
152 two different magic numbers were introduced: 152 two different magic numbers were introduced:
153 153
154 'itv0': After this magic number two unsigned l 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 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 se 156 the first unsigned long and bits 0-3 of the second unsigned long are used for the
157 second field. 157 second field.
158 158
159 'ITV0': This magic number assumes all VBI line 159 'ITV0': This magic number assumes all VBI lines are captured, i.e. it implicitly
160 implies that the bitmasks are 0xffffffff and 0 160 implies that the bitmasks are 0xffffffff and 0xf.
161 161
162 After these magic cookies (and the 8 byte bitm 162 After these magic cookies (and the 8 byte bitmask in case of cookie 'itv0') the
163 captured VBI lines start: 163 captured VBI lines start:
164 164
165 For each line the least significant 4 bits of 165 For each line the least significant 4 bits of the first byte contain the data type.
166 Possible values are shown in the table below. 166 Possible values are shown in the table below. The payload is in the following 42
167 bytes. 167 bytes.
168 168
169 Here is the list of possible data types: 169 Here is the list of possible data types:
170 170
171 .. code-block:: c 171 .. code-block:: c
172 172
173 #define IVTV_SLICED_TYPE_TELETEXT 173 #define IVTV_SLICED_TYPE_TELETEXT 0x1 // Teletext (uses lines 6-22 for PAL)
174 #define IVTV_SLICED_TYPE_CC 174 #define IVTV_SLICED_TYPE_CC 0x4 // Closed Captions (line 21 NTSC)
175 #define IVTV_SLICED_TYPE_WSS 175 #define IVTV_SLICED_TYPE_WSS 0x5 // Wide Screen Signal (line 23 PAL)
176 #define IVTV_SLICED_TYPE_VPS 176 #define IVTV_SLICED_TYPE_VPS 0x7 // Video Programming System (PAL) (line 16)
177 177
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