libavformat/dv1394.h

   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 #define DV1394_DEFAULT_CHANNEL 0x63
  30 #define DV1394_DEFAULT_CARD    0
  31 #define DV1394_RING_FRAMES     20
  32
  33 #define DV1394_WIDTH  720
  34 #define DV1394_HEIGHT 480
  35
  36 /* This is the public user-space interface. Try not to break it. */
  37
  38 #define DV1394_API_VERSION 0x20011127
  39
  40 /* ********************
  41    **                **
  42    **   DV1394 API   **
  43    **                **
  44    ********************
  45
  46    There are two methods of operating the DV1394 DV output device.
  47
  48    1)
  49
  50    The simplest is an interface based on write(): simply write
  51    full DV frames of data to the device, and they will be transmitted
  52    as quickly as possible. The FD may be set for non-blocking I/O,
  53    in which case you can use select() or poll() to wait for output
  54    buffer space.
  55
  56    To set the DV output parameters (e.g. whether you want NTSC or PAL
  57    video), use the DV1394_INIT ioctl, passing in the parameters you
  58    want in a struct dv1394_init.
  59
  60    Example 1:
  61          To play a raw .DV file:   cat foo.DV > /dev/dv1394
  62          (cat will use write() internally)
  63
  64    Example 2:
  65            static struct dv1394_init init = {
  66               0x63,        (broadcast channel)
  67               4,           (four-frame ringbuffer)
  68               DV1394_NTSC, (send NTSC video)
  69               0, 0         (default empty packet rate)
  70            }
  71
  72            ioctl(fd, DV1394_INIT, &init);
  73
  74            while(1) {
  75                   read( <a raw DV file>, buf, DV1394_NTSC_FRAME_SIZE );
  76                   write( <the dv1394 FD>, buf, DV1394_NTSC_FRAME_SIZE );
  77            }
  78
  79    2)
  80
  81    For more control over buffering, and to avoid unnecessary copies
  82    of the DV data, you can use the more sophisticated the mmap() interface.
  83    First, call the DV1394_INIT ioctl to specify your parameters,
  84    including the number of frames in the ringbuffer. Then, calling mmap()
  85    on the dv1394 device will give you direct access to the ringbuffer
  86    from which the DV card reads your frame data.
  87
  88    The ringbuffer is simply one large, contiguous region of memory
  89    containing two or more frames of packed DV data. Each frame of DV data
  90    is 120000 bytes (NTSC) or 144000 bytes (PAL).
  91
  92    Fill one or more frames in the ringbuffer, then use the DV1394_SUBMIT_FRAMES
  93    ioctl to begin I/O. You can use either the DV1394_WAIT_FRAMES ioctl
  94    or select()/poll() to wait until the frames are transmitted. Next, you'll
  95    need to call the DV1394_GET_STATUS ioctl to determine which ringbuffer
  96    frames are clear (ready to be filled with new DV data). Finally, use
  97    DV1394_SUBMIT_FRAMES again to send the new data to the DV output.
  98
  99
 100    Example: here is what a four-frame ringbuffer might look like
 101             during DV transmission:
 102
 103
 104          frame 0   frame 1   frame 2   frame 3
 105
 106         *--------------------------------------*
 107         | CLEAR   | DV data | DV data | CLEAR  |
 108         *--------------------------------------*
 109                    <ACTIVE>
 110
 111         transmission goes in this direction --->>>
 112
 113
 114    The DV hardware is currently transmitting the data in frame 1.
 115    Once frame 1 is finished, it will automatically transmit frame 2.
 116    (if frame 2 finishes before frame 3 is submitted, the device
 117    will continue to transmit frame 2, and will increase the dropped_frames
 118    counter each time it repeats the transmission).
 119
 120
 121    If you called DV1394_GET_STATUS at this instant, you would
 122    receive the following values:
 123
 124                   n_frames          = 4
 125                   active_frame      = 1
 126                   first_clear_frame = 3
 127                   n_clear_frames    = 2
 128
 129    At this point, you should write new DV data into frame 3 and optionally
 130    frame 0. Then call DV1394_SUBMIT_FRAMES to inform the device that
 131    it may transmit the new frames.
 132
 133    ERROR HANDLING
 134
 135    An error (buffer underflow/overflow or a break in the DV stream due
 136    to a 1394 bus reset) can be detected by checking the dropped_frames
 137    field of struct dv1394_status (obtained through the
 138    DV1394_GET_STATUS ioctl).
 139
 140    The best way to recover from such an error is to re-initialize
 141    dv1394, either by using the DV1394_INIT ioctl call, or closing the
 142    file descriptor and opening it again. (note that you must unmap all
 143    ringbuffer mappings when closing the file descriptor, or else
 144    dv1394 will still be considered 'in use').
 145
 146    MAIN LOOP
 147
 148    For maximum efficiency and robustness against bus errors, you are
 149    advised to model the main loop of your application after the
 150    following pseudo-code example:
 151
 152    (checks of system call return values omitted for brevity; always
 153    check return values in your code!)
 154
 155    while( frames left ) {
 156
 157     struct pollfd *pfd = ...;
 158
 159     pfd->fd = dv1394_fd;
 160     pfd->revents = 0;
 161     pfd->events = POLLOUT | POLLIN; (OUT for transmit, IN for receive)
 162
 163     (add other sources of I/O here)
 164
 165     poll(pfd, 1, -1); (or select(); add a timeout if you want)
 166
 167     if(pfd->revents) {
 168          struct dv1394_status status;
 169
 170          ioctl(dv1394_fd, DV1394_GET_STATUS, &status);
 171
 172          if(status.dropped_frames > 0) {
 173               reset_dv1394();
 174          } else {
 175               for(int i = 0; i < status.n_clear_frames; i++) {
 176                   copy_DV_frame();
 177               }
 178          }
 179     }
 180    }
 181
 182    where copy_DV_frame() reads or writes on the dv1394 file descriptor
 183    (read/write mode) or copies data to/from the mmap ringbuffer and
 184    then calls ioctl(DV1394_SUBMIT_FRAMES) to notify dv1394 that new
 185    frames are availble (mmap mode).
 186
 187    reset_dv1394() is called in the event of a buffer
 188    underflow/overflow or a halt in the DV stream (e.g. due to a 1394
 189    bus reset). To guarantee recovery from the error, this function
 190    should close the dv1394 file descriptor (and munmap() all
 191    ringbuffer mappings, if you are using them), then re-open the
 192    dv1394 device (and re-map the ringbuffer).
 193
 194 */
 195
 196
 197 /* maximum number of frames in the ringbuffer */
 198 #define DV1394_MAX_FRAMES 32
 199
 200 /* number of *full* isochronous packets per DV frame */
 201 #define DV1394_NTSC_PACKETS_PER_FRAME 250
 202 #define DV1394_PAL_PACKETS_PER_FRAME  300
 203
 204 /* size of one frame's worth of DV data, in bytes */
 205 #define DV1394_NTSC_FRAME_SIZE (480 * DV1394_NTSC_PACKETS_PER_FRAME)
 206 #define DV1394_PAL_FRAME_SIZE  (480 * DV1394_PAL_PACKETS_PER_FRAME)
 207
 208
 209 /* ioctl() commands */
 210
 211 enum {
 212         /* I don't like using 0 as a valid ioctl() */
 213         DV1394_INVALID = 0,
 214
 215
 216         /* get the driver ready to transmit video.
 217            pass a struct dv1394_init* as the parameter (see below),
 218            or NULL to get default parameters */
 219         DV1394_INIT,
 220
 221
 222         /* stop transmitting video and free the ringbuffer */
 223         DV1394_SHUTDOWN,
 224
 225
 226         /* submit N new frames to be transmitted, where
 227            the index of the first new frame is first_clear_buffer,
 228            and the index of the last new frame is
 229            (first_clear_buffer + N) % n_frames */
 230         DV1394_SUBMIT_FRAMES,
 231
 232
 233         /* block until N buffers are clear (pass N as the parameter)
 234            Because we re-transmit the last frame on underrun, there
 235            will at most be n_frames - 1 clear frames at any time */
 236         DV1394_WAIT_FRAMES,
 237
 238         /* capture new frames that have been received, where
 239            the index of the first new frame is first_clear_buffer,
 240            and the index of the last new frame is
 241            (first_clear_buffer + N) % n_frames */
 242         DV1394_RECEIVE_FRAMES,
 243
 244
 245         DV1394_START_RECEIVE,
 246
 247
 248         /* pass a struct dv1394_status* as the parameter (see below) */
 249         DV1394_GET_STATUS,
 250 };
 251
 252
 253
 254 enum pal_or_ntsc {
 255         DV1394_NTSC = 0,
 256         DV1394_PAL
 257 };
 258
 259
 260
 261
 262 /* this is the argument to DV1394_INIT */
 263 struct dv1394_init {
 264         /* DV1394_API_VERSION */
 265         unsigned int api_version;
 266
 267         /* isochronous transmission channel to use */
 268         unsigned int channel;
 269
 270         /* number of frames in the ringbuffer. Must be at least 2
 271            and at most DV1394_MAX_FRAMES. */
 272         unsigned int n_frames;
 273
 274         /* send/receive PAL or NTSC video format */
 275         enum pal_or_ntsc format;
 276
 277         /* the following are used only for transmission */
 278
 279         /* set these to zero unless you want a
 280            non-default empty packet rate (see below) */
 281         unsigned long cip_n;
 282         unsigned long cip_d;
 283
 284         /* set this to zero unless you want a
 285            non-default SYT cycle offset (default = 3 cycles) */
 286         unsigned int syt_offset;
 287 };
 288
 289 /* NOTE: you may only allocate the DV frame ringbuffer once each time
 290    you open the dv1394 device. DV1394_INIT will fail if you call it a
 291    second time with different 'n_frames' or 'format' arguments (which
 292    would imply a different size for the ringbuffer). If you need a
 293    different buffer size, simply close and re-open the device, then
 294    initialize it with your new settings. */
 295
 296 /* Q: What are cip_n and cip_d? */
 297
 298 /*
 299   A: DV video streams do not utilize 100% of the potential bandwidth offered
 300   by IEEE 1394 (FireWire). To achieve the correct rate of data transmission,
 301   DV devices must periodically insert empty packets into the 1394 data stream.
 302   Typically there is one empty packet per 14-16 data-carrying packets.
 303
 304   Some DV devices will accept a wide range of empty packet rates, while others
 305   require a precise rate. If the dv1394 driver produces empty packets at
 306   a rate that your device does not accept, you may see ugly patterns on the
 307   DV output, or even no output at all.
 308
 309   The default empty packet insertion rate seems to work for many people; if
 310   your DV output is stable, you can simply ignore this discussion. However,
 311   we have exposed the empty packet rate as a parameter to support devices that
 312   do not work with the default rate.
 313
 314   The decision to insert an empty packet is made with a numerator/denominator
 315   algorithm. Empty packets are produced at an average rate of CIP_N / CIP_D.
 316   You can alter the empty packet rate by passing non-zero values for cip_n
 317   and cip_d to the INIT ioctl.
 318
 319  */
 320
 321
 322
 323 struct dv1394_status {
 324         /* this embedded init struct returns the current dv1394
 325            parameters in use */
 326         struct dv1394_init init;
 327
 328         /* the ringbuffer frame that is currently being
 329            displayed. (-1 if the device is not transmitting anything) */
 330         int active_frame;
 331
 332         /* index of the first buffer (ahead of active_frame) that
 333            is ready to be filled with data */
 334         unsigned int first_clear_frame;
 335
 336         /* how many buffers, including first_clear_buffer, are
 337            ready to be filled with data */
 338         unsigned int n_clear_frames;
 339
 340         /* how many times the DV stream has underflowed, overflowed,
 341            or otherwise encountered an error, since the previous call
 342            to DV1394_GET_STATUS */
 343         unsigned int dropped_frames;
 344
 345         /* N.B. The dropped_frames counter is only a lower bound on the actual
 346            number of dropped frames, with the special case that if dropped_frames
 347            is zero, then it is guaranteed that NO frames have been dropped
 348            since the last call to DV1394_GET_STATUS.
 349         */
 350 };
 351
 352
 353 #endif /* _DV_1394_H */