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               for(int i = 0; i < status.n_clear_frames; i++) {
 179                   copy_DV_frame();
 180               }
 181          }
 182     }
 183    }
 184
 185    where copy_DV_frame() reads or writes on the dv1394 file descriptor
 186    (read/write mode) or copies data to/from the mmap ringbuffer and
 187    then calls ioctl(DV1394_SUBMIT_FRAMES) to notify dv1394 that new
 188    frames are availble (mmap mode).
 189
 190    reset_dv1394() is called in the event of a buffer
 191    underflow/overflow or a halt in the DV stream (e.g. due to a 1394
 192    bus reset). To guarantee recovery from the error, this function
 193    should close the dv1394 file descriptor (and munmap() all
 194    ringbuffer mappings, if you are using them), then re-open the
 195    dv1394 device (and re-map the ringbuffer).
 196
 197 */
 198
 199
 200 /* maximum number of frames in the ringbuffer */
 201 #define DV1394_MAX_FRAMES 32
 202
 203 /* number of *full* isochronous packets per DV frame */
 204 #define DV1394_NTSC_PACKETS_PER_FRAME 250
 205 #define DV1394_PAL_PACKETS_PER_FRAME  300
 206
 207 /* size of one frame's worth of DV data, in bytes */
 208 #define DV1394_NTSC_FRAME_SIZE (480 * DV1394_NTSC_PACKETS_PER_FRAME)
 209 #define DV1394_PAL_FRAME_SIZE  (480 * DV1394_PAL_PACKETS_PER_FRAME)
 210
 211
 212 /* ioctl() commands */
 213
 214 enum {
 215         /* I don't like using 0 as a valid ioctl() */
 216         DV1394_INVALID = 0,
 217
 218
 219         /* get the driver ready to transmit video.
 220            pass a struct dv1394_init* as the parameter (see below),
 221            or NULL to get default parameters */
 222         DV1394_INIT,
 223
 224
 225         /* stop transmitting video and free the ringbuffer */
 226         DV1394_SHUTDOWN,
 227
 228
 229         /* submit N new frames to be transmitted, where
 230            the index of the first new frame is first_clear_buffer,
 231            and the index of the last new frame is
 232            (first_clear_buffer + N) % n_frames */
 233         DV1394_SUBMIT_FRAMES,
 234
 235
 236         /* block until N buffers are clear (pass N as the parameter)
 237            Because we re-transmit the last frame on underrun, there
 238            will at most be n_frames - 1 clear frames at any time */
 239         DV1394_WAIT_FRAMES,
 240
 241         /* capture new frames that have been received, where
 242            the index of the first new frame is first_clear_buffer,
 243            and the index of the last new frame is
 244            (first_clear_buffer + N) % n_frames */
 245         DV1394_RECEIVE_FRAMES,
 246
 247
 248         DV1394_START_RECEIVE,
 249
 250
 251         /* pass a struct dv1394_status* as the parameter (see below) */
 252         DV1394_GET_STATUS,
 253 };
 254
 255
 256
 257 enum pal_or_ntsc {
 258         DV1394_NTSC = 0,
 259         DV1394_PAL
 260 };
 261
 262
 263
 264
 265 /* this is the argument to DV1394_INIT */
 266 struct dv1394_init {
 267         /* DV1394_API_VERSION */
 268         unsigned int api_version;
 269
 270         /* isochronous transmission channel to use */
 271         unsigned int channel;
 272
 273         /* number of frames in the ringbuffer. Must be at least 2
 274            and at most DV1394_MAX_FRAMES. */
 275         unsigned int n_frames;
 276
 277         /* send/receive PAL or NTSC video format */
 278         enum pal_or_ntsc format;
 279
 280         /* the following are used only for transmission */
 281
 282         /* set these to zero unless you want a
 283            non-default empty packet rate (see below) */
 284         unsigned long cip_n;
 285         unsigned long cip_d;
 286
 287         /* set this to zero unless you want a
 288            non-default SYT cycle offset (default = 3 cycles) */
 289         unsigned int syt_offset;
 290 };
 291
 292 /* NOTE: you may only allocate the DV frame ringbuffer once each time
 293    you open the dv1394 device. DV1394_INIT will fail if you call it a
 294    second time with different 'n_frames' or 'format' arguments (which
 295    would imply a different size for the ringbuffer). If you need a
 296    different buffer size, simply close and re-open the device, then
 297    initialize it with your new settings. */
 298
 299 /* Q: What are cip_n and cip_d? */
 300
 301 /*
 302   A: DV video streams do not utilize 100% of the potential bandwidth offered
 303   by IEEE 1394 (FireWire). To achieve the correct rate of data transmission,
 304   DV devices must periodically insert empty packets into the 1394 data stream.
 305   Typically there is one empty packet per 14-16 data-carrying packets.
 306
 307   Some DV devices will accept a wide range of empty packet rates, while others
 308   require a precise rate. If the dv1394 driver produces empty packets at
 309   a rate that your device does not accept, you may see ugly patterns on the
 310   DV output, or even no output at all.
 311
 312   The default empty packet insertion rate seems to work for many people; if
 313   your DV output is stable, you can simply ignore this discussion. However,
 314   we have exposed the empty packet rate as a parameter to support devices that
 315   do not work with the default rate.
 316
 317   The decision to insert an empty packet is made with a numerator/denominator
 318   algorithm. Empty packets are produced at an average rate of CIP_N / CIP_D.
 319   You can alter the empty packet rate by passing non-zero values for cip_n
 320   and cip_d to the INIT ioctl.
 321
 322  */
 323
 324
 325
 326 struct dv1394_status {
 327         /* this embedded init struct returns the current dv1394
 328            parameters in use */
 329         struct dv1394_init init;
 330
 331         /* the ringbuffer frame that is currently being
 332            displayed. (-1 if the device is not transmitting anything) */
 333         int active_frame;
 334
 335         /* index of the first buffer (ahead of active_frame) that
 336            is ready to be filled with data */
 337         unsigned int first_clear_frame;
 338
 339         /* how many buffers, including first_clear_buffer, are
 340            ready to be filled with data */
 341         unsigned int n_clear_frames;
 342
 343         /* how many times the DV stream has underflowed, overflowed,
 344            or otherwise encountered an error, since the previous call
 345            to DV1394_GET_STATUS */
 346         unsigned int dropped_frames;
 347
 348         /* N.B. The dropped_frames counter is only a lower bound on the actual
 349            number of dropped frames, with the special case that if dropped_frames
 350            is zero, then it is guaranteed that NO frames have been dropped
 351            since the last call to DV1394_GET_STATUS.
 352         */
 353 };
 354
 355
 356 #endif /* AVDEVICE_DV1394_H */