1.. SPDX-License-Identifier: GPL-2.0 2 3The cx2341x driver 4================== 5 6Non-compressed file format 7-------------------------- 8 9The cx23416 can produce (and the cx23415 can also read) raw YUV output. The 10format of a YUV frame is 16x16 linear tiled NV12 (V4L2_PIX_FMT_NV12_16L16). 11 12The format is YUV 4:2:0 which uses 1 Y byte per pixel and 1 U and V byte per 13four pixels. 14 15The data is encoded as two macroblock planes, the first containing the Y 16values, the second containing UV macroblocks. 17 18The Y plane is divided into blocks of 16x16 pixels from left to right 19and from top to bottom. Each block is transmitted in turn, line-by-line. 20 21So the first 16 bytes are the first line of the top-left block, the 22second 16 bytes are the second line of the top-left block, etc. After 23transmitting this block the first line of the block on the right to the 24first block is transmitted, etc. 25 26The UV plane is divided into blocks of 16x8 UV values going from left 27to right, top to bottom. Each block is transmitted in turn, line-by-line. 28 29So the first 16 bytes are the first line of the top-left block and 30contain 8 UV value pairs (16 bytes in total). The second 16 bytes are the 31second line of 8 UV pairs of the top-left block, etc. After transmitting 32this block the first line of the block on the right to the first block is 33transmitted, etc. 34 35The code below is given as an example on how to convert V4L2_PIX_FMT_NV12_16L16 36to separate Y, U and V planes. This code assumes frames of 720x576 (PAL) pixels. 37 38The width of a frame is always 720 pixels, regardless of the actual specified 39width. 40 41If the height is not a multiple of 32 lines, then the captured video is 42missing macroblocks at the end and is unusable. So the height must be a 43multiple of 32. 44 45Raw format c example 46~~~~~~~~~~~~~~~~~~~~ 47 48.. code-block:: c 49 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 54 static unsigned char frame[576*720*3/2]; 55 static unsigned char framey[576*720]; 56 static unsigned char frameu[576*720 / 4]; 57 static unsigned char framev[576*720 / 4]; 58 59 static void de_macro_y(unsigned char* dst, unsigned char *src, int dstride, int w, int h) 60 { 61 unsigned int y, x, i; 62 63 // descramble Y plane 64 // dstride = 720 = w 65 // The Y plane is divided into blocks of 16x16 pixels 66 // Each block in transmitted in turn, line-by-line. 67 for (y = 0; y < h; y += 16) { 68 for (x = 0; x < w; x += 16) { 69 for (i = 0; i < 16; i++) { 70 memcpy(dst + x + (y + i) * dstride, src, 16); 71 src += 16; 72 } 73 } 74 } 75 } 76 77 static void de_macro_uv(unsigned char *dstu, unsigned char *dstv, unsigned char *src, int dstride, int w, int h) 78 { 79 unsigned int y, x, i; 80 81 // descramble U/V plane 82 // dstride = 720 / 2 = w 83 // The U/V values are interlaced (UVUV...). 84 // Again, the UV plane is divided into blocks of 16x16 UV values. 85 // Each block in transmitted in turn, line-by-line. 86 for (y = 0; y < h; y += 16) { 87 for (x = 0; x < w; x += 8) { 88 for (i = 0; i < 16; i++) { 89 int idx = x + (y + i) * dstride; 90 91 dstu[idx+0] = src[0]; dstv[idx+0] = src[1]; 92 dstu[idx+1] = src[2]; dstv[idx+1] = src[3]; 93 dstu[idx+2] = src[4]; dstv[idx+2] = src[5]; 94 dstu[idx+3] = src[6]; dstv[idx+3] = src[7]; 95 dstu[idx+4] = src[8]; dstv[idx+4] = src[9]; 96 dstu[idx+5] = src[10]; dstv[idx+5] = src[11]; 97 dstu[idx+6] = src[12]; dstv[idx+6] = src[13]; 98 dstu[idx+7] = src[14]; dstv[idx+7] = src[15]; 99 src += 16; 100 } 101 } 102 } 103 } 104 105 /*************************************************************************/ 106 int main(int argc, char **argv) 107 { 108 FILE *fin; 109 int i; 110 111 if (argc == 1) fin = stdin; 112 else fin = fopen(argv[1], "r"); 113 114 if (fin == NULL) { 115 fprintf(stderr, "cannot open input\n"); 116 exit(-1); 117 } 118 while (fread(frame, sizeof(frame), 1, fin) == 1) { 119 de_macro_y(framey, frame, 720, 720, 576); 120 de_macro_uv(frameu, framev, frame + 720 * 576, 720 / 2, 720 / 2, 576 / 2); 121 fwrite(framey, sizeof(framey), 1, stdout); 122 fwrite(framev, sizeof(framev), 1, stdout); 123 fwrite(frameu, sizeof(frameu), 1, stdout); 124 } 125 fclose(fin); 126 return 0; 127 } 128 129 130Format of embedded V4L2_MPEG_STREAM_VBI_FMT_IVTV VBI data 131--------------------------------------------------------- 132 133Author: Hans Verkuil <hverkuil@xs4all.nl> 134 135 136This section describes the V4L2_MPEG_STREAM_VBI_FMT_IVTV format of the VBI data 137embedded in an MPEG-2 program stream. This format is in part dictated by some 138hardware limitations of the ivtv driver (the driver for the Conexant cx23415/6 139chips), in particular a maximum size for the VBI data. Anything longer is cut 140off when the MPEG stream is played back through the cx23415. 141 142The advantage of this format is it is very compact and that all VBI data for 143all lines can be stored while still fitting within the maximum allowed size. 144 145The stream ID of the VBI data is 0xBD. The maximum size of the embedded data is 1464 + 43 * 36, which is 4 bytes for a header and 2 * 18 VBI lines with a 1 byte 147header and a 42 bytes payload each. Anything beyond this limit is cut off by 148the cx23415/6 firmware. Besides the data for the VBI lines we also need 36 bits 149for a bitmask determining which lines are captured and 4 bytes for a magic cookie, 150signifying that this data package contains V4L2_MPEG_STREAM_VBI_FMT_IVTV VBI data. 151If all lines are used, then there is no longer room for the bitmask. To solve this 152two different magic numbers were introduced: 153 154'itv0': After this magic number two unsigned longs follow. Bits 0-17 of the first 155unsigned long denote which lines of the first field are captured. Bits 18-31 of 156the first unsigned long and bits 0-3 of the second unsigned long are used for the 157second field. 158 159'ITV0': This magic number assumes all VBI lines are captured, i.e. it implicitly 160implies that the bitmasks are 0xffffffff and 0xf. 161 162After these magic cookies (and the 8 byte bitmask in case of cookie 'itv0') the 163captured VBI lines start: 164 165For each line the least significant 4 bits of the first byte contain the data type. 166Possible values are shown in the table below. The payload is in the following 42 167bytes. 168 169Here is the list of possible data types: 170 171.. code-block:: c 172 173 #define IVTV_SLICED_TYPE_TELETEXT 0x1 // Teletext (uses lines 6-22 for PAL) 174 #define IVTV_SLICED_TYPE_CC 0x4 // Closed Captions (line 21 NTSC) 175 #define IVTV_SLICED_TYPE_WSS 0x5 // Wide Screen Signal (line 23 PAL) 176 #define IVTV_SLICED_TYPE_VPS 0x7 // Video Programming System (PAL) (line 16) 177 178