1/* 2 * dv1394.h - DV input/output over IEEE 1394 on OHCI chips 3 * Copyright (C)2001 Daniel Maas <dmaas@dcine.com> 4 * receive, proc_fs by Dan Dennedy <dan@dennedy.org> 5 * 6 * based on: 7 * video1394.h - driver for OHCI 1394 boards 8 * Copyright (C)1999,2000 Sebastien Rougeaux <sebastien.rougeaux@anu.edu.au> 9 * Peter Schlaile <udbz@rz.uni-karlsruhe.de> 10 * 11 * This program is free software; you can redistribute it and/or modify 12 * it under the terms of the GNU General Public License as published by 13 * the Free Software Foundation; either version 2 of the License, or 14 * (at your option) any later version. 15 * 16 * This program is distributed in the hope that it will be useful, 17 * but WITHOUT ANY WARRANTY; without even the implied warranty of 18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19 * GNU General Public License for more details. 20 * 21 * You should have received a copy of the GNU General Public License 22 * along with this program; if not, write to the Free Software Foundation, 23 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 24 */ 25 26#ifndef _DV_1394_H 27#define _DV_1394_H 28 29/* This is the public user-space interface. Try not to break it. */ 30 31#define DV1394_API_VERSION 0x20011127 32 33/* ******************** 34 ** ** 35 ** DV1394 API ** 36 ** ** 37 ******************** 38 39 There are two methods of operating the DV1394 DV output device. 40 41 1) 42 43 The simplest is an interface based on write(): simply write 44 full DV frames of data to the device, and they will be transmitted 45 as quickly as possible. The FD may be set for non-blocking I/O, 46 in which case you can use select() or poll() to wait for output 47 buffer space. 48 49 To set the DV output parameters (e.g. whether you want NTSC or PAL 50 video), use the DV1394_INIT ioctl, passing in the parameters you 51 want in a struct dv1394_init. 52 53 Example 1: 54 To play a raw .DV file: cat foo.DV > /dev/dv1394 55 (cat will use write() internally) 56 57 Example 2: 58 static struct dv1394_init init = { 59 0x63, (broadcast channel) 60 4, (four-frame ringbuffer) 61 DV1394_NTSC, (send NTSC video) 62 0, 0 (default empty packet rate) 63 } 64 65 ioctl(fd, DV1394_INIT, &init); 66 67 while(1) { 68 read( <a raw DV file>, buf, DV1394_NTSC_FRAME_SIZE ); 69 write( <the dv1394 FD>, buf, DV1394_NTSC_FRAME_SIZE ); 70 } 71 72 2) 73 74 For more control over buffering, and to avoid unnecessary copies 75 of the DV data, you can use the more sophisticated the mmap() interface. 76 First, call the DV1394_INIT ioctl to specify your parameters, 77 including the number of frames in the ringbuffer. Then, calling mmap() 78 on the dv1394 device will give you direct access to the ringbuffer 79 from which the DV card reads your frame data. 80 81 The ringbuffer is simply one large, contiguous region of memory 82 containing two or more frames of packed DV data. Each frame of DV data 83 is 120000 bytes (NTSC) or 144000 bytes (PAL). 84 85 Fill one or more frames in the ringbuffer, then use the DV1394_SUBMIT_FRAMES 86 ioctl to begin I/O. You can use either the DV1394_WAIT_FRAMES ioctl 87 or select()/poll() to wait until the frames are transmitted. Next, you'll 88 need to call the DV1394_GET_STATUS ioctl to determine which ringbuffer 89 frames are clear (ready to be filled with new DV data). Finally, use 90 DV1394_SUBMIT_FRAMES again to send the new data to the DV output. 91 92 93 Example: here is what a four-frame ringbuffer might look like 94 during DV transmission: 95 96 97 frame 0 frame 1 frame 2 frame 3 98 99 *--------------------------------------* 100 | CLEAR | DV data | DV data | CLEAR | 101 *--------------------------------------* 102 <ACTIVE> 103 104 transmission goes in this direction --->>> 105 106 107 The DV hardware is currently transmitting the data in frame 1. 108 Once frame 1 is finished, it will automatically transmit frame 2. 109 (if frame 2 finishes before frame 3 is submitted, the device 110 will continue to transmit frame 2, and will increase the dropped_frames 111 counter each time it repeats the transmission). 112 113 114 If you called DV1394_GET_STATUS at this instant, you would 115 receive the following values: 116 117 n_frames = 4 118 active_frame = 1 119 first_clear_frame = 3 120 n_clear_frames = 2 121 122 At this point, you should write new DV data into frame 3 and optionally 123 frame 0. Then call DV1394_SUBMIT_FRAMES to inform the device that 124 it may transmit the new frames. 125 126 ERROR HANDLING 127 128 An error (buffer underflow/overflow or a break in the DV stream due 129 to a 1394 bus reset) can be detected by checking the dropped_frames 130 field of struct dv1394_status (obtained through the 131 DV1394_GET_STATUS ioctl). 132 133 The best way to recover from such an error is to re-initialize 134 dv1394, either by using the DV1394_INIT ioctl call, or closing the 135 file descriptor and opening it again. (note that you must unmap all 136 ringbuffer mappings when closing the file descriptor, or else 137 dv1394 will still be considered 'in use'). 138 139 MAIN LOOP 140 141 For maximum efficiency and robustness against bus errors, you are 142 advised to model the main loop of your application after the 143 following pseudo-code example: 144 145 (checks of system call return values omitted for brevity; always 146 check return values in your code!) 147 148 while( frames left ) { 149 150 struct pollfd *pfd = ...; 151 152 pfd->fd = dv1394_fd; 153 pfd->revents = 0; 154 pfd->events = POLLOUT | POLLIN; (OUT for transmit, IN for receive) 155 156 (add other sources of I/O here) 157 158 poll(pfd, 1, -1); (or select(); add a timeout if you want) 159 160 if(pfd->revents) { 161 struct dv1394_status status; 162 163 ioctl(dv1394_fd, DV1394_GET_STATUS, &status); 164 165 if(status.dropped_frames > 0) { 166 reset_dv1394(); 167 } else { 168 for(int i = 0; i < status.n_clear_frames; i++) { 169 copy_DV_frame(); 170 } 171 } 172 } 173 } 174 175 where copy_DV_frame() reads or writes on the dv1394 file descriptor 176 (read/write mode) or copies data to/from the mmap ringbuffer and 177 then calls ioctl(DV1394_SUBMIT_FRAMES) to notify dv1394 that new 178 frames are availble (mmap mode). 179 180 reset_dv1394() is called in the event of a buffer 181 underflow/overflow or a halt in the DV stream (e.g. due to a 1394 182 bus reset). To guarantee recovery from the error, this function 183 should close the dv1394 file descriptor (and munmap() all 184 ringbuffer mappings, if you are using them), then re-open the 185 dv1394 device (and re-map the ringbuffer). 186 187*/ 188 189 190/* maximum number of frames in the ringbuffer */ 191#define DV1394_MAX_FRAMES 32 192 193/* number of *full* isochronous packets per DV frame */ 194#define DV1394_NTSC_PACKETS_PER_FRAME 250 195#define DV1394_PAL_PACKETS_PER_FRAME 300 196 197/* size of one frame's worth of DV data, in bytes */ 198#define DV1394_NTSC_FRAME_SIZE (480 * DV1394_NTSC_PACKETS_PER_FRAME) 199#define DV1394_PAL_FRAME_SIZE (480 * DV1394_PAL_PACKETS_PER_FRAME) 200 201 202/* ioctl() commands */ 203 204enum { 205 /* I don't like using 0 as a valid ioctl() */ 206 DV1394_INVALID = 0, 207 208 209 /* get the driver ready to transmit video. 210 pass a struct dv1394_init* as the parameter (see below), 211 or NULL to get default parameters */ 212 DV1394_INIT, 213 214 215 /* stop transmitting video and free the ringbuffer */ 216 DV1394_SHUTDOWN, 217 218 219 /* submit N new frames to be transmitted, where 220 the index of the first new frame is first_clear_buffer, 221 and the index of the last new frame is 222 (first_clear_buffer + N) % n_frames */ 223 DV1394_SUBMIT_FRAMES, 224 225 226 /* block until N buffers are clear (pass N as the parameter) 227 Because we re-transmit the last frame on underrun, there 228 will at most be n_frames - 1 clear frames at any time */ 229 DV1394_WAIT_FRAMES, 230 231 /* capture new frames that have been received, where 232 the index of the first new frame is first_clear_buffer, 233 and the index of the last new frame is 234 (first_clear_buffer + N) % n_frames */ 235 DV1394_RECEIVE_FRAMES, 236 237 238 DV1394_START_RECEIVE, 239 240 241 /* pass a struct dv1394_status* as the parameter (see below) */ 242 DV1394_GET_STATUS, 243}; 244 245 246 247enum pal_or_ntsc { 248 DV1394_NTSC = 0, 249 DV1394_PAL 250}; 251 252 253 254 255/* this is the argument to DV1394_INIT */ 256struct dv1394_init { 257 /* DV1394_API_VERSION */ 258 unsigned int api_version; 259 260 /* isochronous transmission channel to use */ 261 unsigned int channel; 262 263 /* number of frames in the ringbuffer. Must be at least 2 264 and at most DV1394_MAX_FRAMES. */ 265 unsigned int n_frames; 266 267 /* send/receive PAL or NTSC video format */ 268 enum pal_or_ntsc format; 269 270 /* the following are used only for transmission */ 271 272 /* set these to zero unless you want a 273 non-default empty packet rate (see below) */ 274 unsigned long cip_n; 275 unsigned long cip_d; 276 277 /* set this to zero unless you want a 278 non-default SYT cycle offset (default = 3 cycles) */ 279 unsigned int syt_offset; 280}; 281 282/* NOTE: you may only allocate the DV frame ringbuffer once each time 283 you open the dv1394 device. DV1394_INIT will fail if you call it a 284 second time with different 'n_frames' or 'format' arguments (which 285 would imply a different size for the ringbuffer). If you need a 286 different buffer size, simply close and re-open the device, then 287 initialize it with your new settings. */ 288 289/* Q: What are cip_n and cip_d? */ 290 291/* 292 A: DV video streams do not utilize 100% of the potential bandwidth offered 293 by IEEE 1394 (FireWire). To achieve the correct rate of data transmission, 294 DV devices must periodically insert empty packets into the 1394 data stream. 295 Typically there is one empty packet per 14-16 data-carrying packets. 296 297 Some DV devices will accept a wide range of empty packet rates, while others 298 require a precise rate. If the dv1394 driver produces empty packets at 299 a rate that your device does not accept, you may see ugly patterns on the 300 DV output, or even no output at all. 301 302 The default empty packet insertion rate seems to work for many people; if 303 your DV output is stable, you can simply ignore this discussion. However, 304 we have exposed the empty packet rate as a parameter to support devices that 305 do not work with the default rate. 306 307 The decision to insert an empty packet is made with a numerator/denominator 308 algorithm. Empty packets are produced at an average rate of CIP_N / CIP_D. 309 You can alter the empty packet rate by passing non-zero values for cip_n 310 and cip_d to the INIT ioctl. 311 312 */ 313 314 315 316struct dv1394_status { 317 /* this embedded init struct returns the current dv1394 318 parameters in use */ 319 struct dv1394_init init; 320 321 /* the ringbuffer frame that is currently being 322 displayed. (-1 if the device is not transmitting anything) */ 323 int active_frame; 324 325 /* index of the first buffer (ahead of active_frame) that 326 is ready to be filled with data */ 327 unsigned int first_clear_frame; 328 329 /* how many buffers, including first_clear_buffer, are 330 ready to be filled with data */ 331 unsigned int n_clear_frames; 332 333 /* how many times the DV stream has underflowed, overflowed, 334 or otherwise encountered an error, since the previous call 335 to DV1394_GET_STATUS */ 336 unsigned int dropped_frames; 337 338 /* N.B. The dropped_frames counter is only a lower bound on the actual 339 number of dropped frames, with the special case that if dropped_frames 340 is zero, then it is guaranteed that NO frames have been dropped 341 since the last call to DV1394_GET_STATUS. 342 */ 343}; 344 345 346#endif /* _DV_1394_H */ 347