ffmpeg/libavdevice/dv1394.h

   1 /*
   2  * 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 file is part of FFmpeg.
  12  *
  13  * FFmpeg is free software; you can redistribute it and/or
  14  * modify it under the terms of the GNU Lesser General Public
  15  * License as published by the Free Software Foundation; either
  16  * version 2.1 of the License, or (at your option) any later version.
  17  *
  18  * FFmpeg is distributed in the hope that it will be useful,
  19  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  21  * Lesser General Public License for more details.
  22  *
  23  * You should have received a copy of the GNU Lesser General Public
  24  * License along with FFmpeg; if not, write to the Free Software
  25  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  26  */
  27
  28 #ifndef AVDEVICE_DV1394_H
  29 #define AVDEVICE_DV1394_H
  30
  31 #define DV1394_DEFAULT_CHANNEL 63
  32 #define DV1394_DEFAULT_CARD    0
  33 #define DV1394_RING_FRAMES     20
  34
  35 #define DV1394_WIDTH  720
  36 #define DV1394_NTSC_HEIGHT 480
  37 #define DV1394_PAL_HEIGHT 576
  38
  39 /* This is the public user-space interface. Try not to break it. */
  40
  41 #define DV1394_API_VERSION 0x20011127
  42
  43 /* ********************
  44    **                **
  45    **   DV1394 API   **
  46    **                **
  47    ********************
  48
  49    There are two methods of operating the DV1394 DV output device.
  50
  51    1)
  52
  53    The simplest is an interface based on write(): simply write
  54    full DV frames of data to the device, and they will be transmitted
  55    as quickly as possible. The FD may be set for non-blocking I/O,
  56    in which case you can use select() or poll() to wait for output
  57    buffer space.
  58
  59    To set the DV output parameters (e.g. whether you want NTSC or PAL
  60    video), use the DV1394_INIT ioctl, passing in the parameters you
  61    want in a struct dv1394_init.
  62
  63    Example 1:
  64          To play a raw .DV file:   cat foo.DV > /dev/dv1394
  65          (cat will use write() internally)
  66
  67    Example 2:
  68            static struct dv1394_init init = {
  69               0x63,        (broadcast channel)
  70               4,           (four-frame ringbuffer)
  71               DV1394_NTSC, (send NTSC video)
  72               0, 0         (default empty packet rate)
  73            }
  74
  75            ioctl(fd, DV1394_INIT, &init);
  76
  77            while(1) {
  78                   read( <a raw DV file>, buf, DV1394_NTSC_FRAME_SIZE );
  79                   write( <the dv1394 FD>, buf, DV1394_NTSC_FRAME_SIZE );
  80            }
  81
  82    2)
  83
  84    For more control over buffering, and to avoid unnecessary copies
  85    of the DV data, you can use the more sophisticated the mmap() interface.
  86    First, call the DV1394_INIT ioctl to specify your parameters,
  87    including the number of frames in the ringbuffer. Then, calling mmap()
  88    on the dv1394 device will give you direct access to the ringbuffer
  89    from which the DV card reads your frame data.
  90
  91    The ringbuffer is simply one large, contiguous region of memory
  92    containing two or more frames of packed DV data. Each frame of DV data
  93    is 120000 bytes (NTSC) or 144000 bytes (PAL).
  94
  95    Fill one or more frames in the ringbuffer, then use the DV1394_SUBMIT_FRAMES
  96    ioctl to begin I/O. You can use either the DV1394_WAIT_FRAMES ioctl
  97    or select()/poll() to wait until the frames are transmitted. Next, you'll
  98    need to call the DV1394_GET_STATUS ioctl to determine which ringbuffer
  99    frames are clear (ready to be filled with new DV data). Finally, use
 100    DV1394_SUBMIT_FRAMES again to send the new data to the DV output.
 101
 102
 103    Example: here is what a four-frame ringbuffer might look like
 104             during DV transmission:
 105
 106
 107          frame 0   frame 1   frame 2   frame 3
 108
 109         *--------------------------------------*
 110         | CLEAR   | DV data | DV data | CLEAR  |
 111         *--------------------------------------*
 112                    <ACTIVE>
 113
 114         transmission goes in this direction --->>>
 115
 116
 117    The DV hardware is currently transmitting the data in frame 1.
 118    Once frame 1 is finished, it will automatically transmit frame 2.
 119    (if frame 2 finishes before frame 3 is submitted, the device
 120    will continue to transmit frame 2, and will increase the dropped_frames
 121    counter each time it repeats the transmission).
 122
 123
 124    If you called DV1394_GET_STATUS at this instant, you would
 125    receive the following values:
 126
 127                   n_frames          = 4
 128                   active_frame      = 1
 129                   first_clear_frame = 3
 130                   n_clear_frames    = 2
 131
 132    At this point, you should write new DV data into frame 3 and optionally
 133    frame 0. Then call DV1394_SUBMIT_FRAMES to inform the device that
 134    it may transmit the new frames.
 135
 136    ERROR HANDLING
 137
 138    An error (buffer underflow/overflow or a break in the DV stream due
 139    to a 1394 bus reset) can be detected by checking the dropped_frames
 140    field of struct dv1394_status (obtained through the
 141    DV1394_GET_STATUS ioctl).
 142
 143    The best way to recover from such an error is to re-initialize
 144    dv1394, either by using the DV1394_INIT ioctl call, or closing the
 145    file descriptor and opening it again. (note that you must unmap all
 146    ringbuffer mappings when closing the file descriptor, or else
 147    dv1394 will still be considered 'in use').
 148
 149    MAIN LOOP
 150
 151    For maximum efficiency and robustness against bus errors, you are
 152    advised to model the main loop of your application after the
 153    following pseudo-code example:
 154
 155    (checks of system call return values omitted for brevity; always
 156    check return values in your code!)
 157
 158    while( frames left ) {
 159
 160     struct pollfd *pfd = ...;
 161
 162     pfd->fd = dv1394_fd;
 163     pfd->revents = 0;
 164     pfd->events = POLLOUT | POLLIN; (OUT for transmit, IN for receive)
 165
 166     (add other sources of I/O here)
 167
 168     poll(pfd, 1, -1); (or select(); add a timeout if you want)
 169
 170     if(pfd->revents) {
 171          struct dv1394_status status;
 172
 173          ioctl(dv1394_fd, DV1394_GET_STATUS, &status);
 174
 175          if(status.dropped_frames > 0) {
 176               reset_dv1394();
 177          } else {
 178               int i;
 179               for (i = 0; i < status.n_clear_frames; i++) {
 180                   copy_DV_frame();
 181               }
 182          }
 183     }
 184    }
 185
 186    where copy_DV_frame() reads or writes on the dv1394 file descriptor
 187    (read/write mode) or copies data to/from the mmap ringbuffer and
 188    then calls ioctl(DV1394_SUBMIT_FRAMES) to notify dv1394 that new
 189    frames are available (mmap mode).
 190
 191    reset_dv1394() is called in the event of a buffer
 192    underflow/overflow or a halt in the DV stream (e.g. due to a 1394
 193    bus reset). To guarantee recovery from the error, this function
 194    should close the dv1394 file descriptor (and munmap() all
 195    ringbuffer mappings, if you are using them), then re-open the
 196    dv1394 device (and re-map the ringbuffer).
 197
 198 */
 199
 200
 201 /* maximum number of frames in the ringbuffer */
 202 #define DV1394_MAX_FRAMES 32
 203
 204 /* number of *full* isochronous packets per DV frame */
 205 #define DV1394_NTSC_PACKETS_PER_FRAME 250
 206 #define DV1394_PAL_PACKETS_PER_FRAME  300
 207
 208 /* size of one frame's worth of DV data, in bytes */
 209 #define DV1394_NTSC_FRAME_SIZE (480 * DV1394_NTSC_PACKETS_PER_FRAME)
 210 #define DV1394_PAL_FRAME_SIZE  (480 * DV1394_PAL_PACKETS_PER_FRAME)
 211
 212
 213 /* ioctl() commands */
 214
 215 enum {
 216         /* I don't like using 0 as a valid ioctl() */
 217         DV1394_INVALID = 0,
 218
 219
 220         /* get the driver ready to transmit video.
 221            pass a struct dv1394_init* as the parameter (see below),
 222            or NULL to get default parameters */
 223         DV1394_INIT,
 224
 225
 226         /* stop transmitting video and free the ringbuffer */
 227         DV1394_SHUTDOWN,
 228
 229
 230         /* submit N new frames to be transmitted, where
 231            the index of the first new frame is first_clear_buffer,
 232            and the index of the last new frame is
 233            (first_clear_buffer + N) % n_frames */
 234         DV1394_SUBMIT_FRAMES,
 235
 236
 237         /* block until N buffers are clear (pass N as the parameter)
 238            Because we re-transmit the last frame on underrun, there
 239            will at most be n_frames - 1 clear frames at any time */
 240         DV1394_WAIT_FRAMES,
 241
 242         /* capture new frames that have been received, where
 243            the index of the first new frame is first_clear_buffer,
 244            and the index of the last new frame is
 245            (first_clear_buffer + N) % n_frames */
 246         DV1394_RECEIVE_FRAMES,
 247
 248
 249         DV1394_START_RECEIVE,
 250
 251
 252         /* pass a struct dv1394_status* as the parameter (see below) */
 253         DV1394_GET_STATUS,
 254 };
 255
 256
 257
 258 enum pal_or_ntsc {
 259         DV1394_NTSC = 0,
 260         DV1394_PAL
 261 };
 262
 263
 264
 265
 266 /* this is the argument to DV1394_INIT */
 267 struct dv1394_init {
 268         /* DV1394_API_VERSION */
 269         unsigned int api_version;
 270
 271         /* isochronous transmission channel to use */
 272         unsigned int channel;
 273
 274         /* number of frames in the ringbuffer. Must be at least 2
 275            and at most DV1394_MAX_FRAMES. */
 276         unsigned int n_frames;
 277
 278         /* send/receive PAL or NTSC video format */
 279         enum pal_or_ntsc format;
 280
 281         /* the following are used only for transmission */
 282
 283         /* set these to zero unless you want a
 284            non-default empty packet rate (see below) */
 285         unsigned long cip_n;
 286         unsigned long cip_d;
 287
 288         /* set this to zero unless you want a
 289            non-default SYT cycle offset (default = 3 cycles) */
 290         unsigned int syt_offset;
 291 };
 292
 293 /* NOTE: you may only allocate the DV frame ringbuffer once each time
 294    you open the dv1394 device. DV1394_INIT will fail if you call it a
 295    second time with different 'n_frames' or 'format' arguments (which
 296    would imply a different size for the ringbuffer). If you need a
 297    different buffer size, simply close and re-open the device, then
 298    initialize it with your new settings. */
 299
 300 /* Q: What are cip_n and cip_d? */
 301
 302 /*
 303   A: DV video streams do not utilize 100% of the potential bandwidth offered
 304   by IEEE 1394 (FireWire). To achieve the correct rate of data transmission,
 305   DV devices must periodically insert empty packets into the 1394 data stream.
 306   Typically there is one empty packet per 14-16 data-carrying packets.
 307
 308   Some DV devices will accept a wide range of empty packet rates, while others
 309   require a precise rate. If the dv1394 driver produces empty packets at
 310   a rate that your device does not accept, you may see ugly patterns on the
 311   DV output, or even no output at all.
 312
 313   The default empty packet insertion rate seems to work for many people; if
 314   your DV output is stable, you can simply ignore this discussion. However,
 315   we have exposed the empty packet rate as a parameter to support devices that
 316   do not work with the default rate.
 317
 318   The decision to insert an empty packet is made with a numerator/denominator
 319   algorithm. Empty packets are produced at an average rate of CIP_N / CIP_D.
 320   You can alter the empty packet rate by passing non-zero values for cip_n
 321   and cip_d to the INIT ioctl.
 322
 323  */
 324
 325
 326
 327 struct dv1394_status {
 328         /* this embedded init struct returns the current dv1394
 329            parameters in use */
 330         struct dv1394_init init;
 331
 332         /* the ringbuffer frame that is currently being
 333            displayed. (-1 if the device is not transmitting anything) */
 334         int active_frame;
 335
 336         /* index of the first buffer (ahead of active_frame) that
 337            is ready to be filled with data */
 338         unsigned int first_clear_frame;
 339
 340         /* how many buffers, including first_clear_buffer, are
 341            ready to be filled with data */
 342         unsigned int n_clear_frames;
 343
 344         /* how many times the DV stream has underflowed, overflowed,
 345            or otherwise encountered an error, since the previous call
 346            to DV1394_GET_STATUS */
 347         unsigned int dropped_frames;
 348
 349         /* N.B. The dropped_frames counter is only a lower bound on the actual
 350            number of dropped frames, with the special case that if dropped_frames
 351            is zero, then it is guaranteed that NO frames have been dropped
 352            since the last call to DV1394_GET_STATUS.
 353         */
 354 };
 355
 356
 357 #endif /* AVDEVICE_DV1394_H */