drivers/ieee1394/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 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 #include "ieee1394-ioctl.h"
 204
 205
 206 enum pal_or_ntsc {
 207         DV1394_NTSC = 0,
 208         DV1394_PAL
 209 };
 210
 211
 212
 213
 214 /* this is the argument to DV1394_INIT */
 215 struct dv1394_init {
 216         /* DV1394_API_VERSION */
 217         unsigned int api_version;
 218
 219         /* isochronous transmission channel to use */
 220         unsigned int channel;
 221
 222         /* number of frames in the ringbuffer. Must be at least 2
 223            and at most DV1394_MAX_FRAMES. */
 224         unsigned int n_frames;
 225
 226         /* send/receive PAL or NTSC video format */
 227         enum pal_or_ntsc format;
 228
 229         /* the following are used only for transmission */
 230
 231         /* set these to zero unless you want a
 232            non-default empty packet rate (see below) */
 233         unsigned long cip_n;
 234         unsigned long cip_d;
 235
 236         /* set this to zero unless you want a
 237            non-default SYT cycle offset (default = 3 cycles) */
 238         unsigned int syt_offset;
 239 };
 240
 241 /* NOTE: you may only allocate the DV frame ringbuffer once each time
 242    you open the dv1394 device. DV1394_INIT will fail if you call it a
 243    second time with different 'n_frames' or 'format' arguments (which
 244    would imply a different size for the ringbuffer). If you need a
 245    different buffer size, simply close and re-open the device, then
 246    initialize it with your new settings. */
 247
 248 /* Q: What are cip_n and cip_d? */
 249
 250 /*
 251   A: DV video streams do not utilize 100% of the potential bandwidth offered
 252   by IEEE 1394 (FireWire). To achieve the correct rate of data transmission,
 253   DV devices must periodically insert empty packets into the 1394 data stream.
 254   Typically there is one empty packet per 14-16 data-carrying packets.
 255
 256   Some DV devices will accept a wide range of empty packet rates, while others
 257   require a precise rate. If the dv1394 driver produces empty packets at
 258   a rate that your device does not accept, you may see ugly patterns on the
 259   DV output, or even no output at all.
 260
 261   The default empty packet insertion rate seems to work for many people; if
 262   your DV output is stable, you can simply ignore this discussion. However,
 263   we have exposed the empty packet rate as a parameter to support devices that
 264   do not work with the default rate.
 265
 266   The decision to insert an empty packet is made with a numerator/denominator
 267   algorithm. Empty packets are produced at an average rate of CIP_N / CIP_D.
 268   You can alter the empty packet rate by passing non-zero values for cip_n
 269   and cip_d to the INIT ioctl.
 270
 271  */
 272
 273
 274
 275 struct dv1394_status {
 276         /* this embedded init struct returns the current dv1394
 277            parameters in use */
 278         struct dv1394_init init;
 279
 280         /* the ringbuffer frame that is currently being
 281            displayed. (-1 if the device is not transmitting anything) */
 282         int active_frame;
 283
 284         /* index of the first buffer (ahead of active_frame) that
 285            is ready to be filled with data */
 286         unsigned int first_clear_frame;
 287
 288         /* how many buffers, including first_clear_buffer, are
 289            ready to be filled with data */
 290         unsigned int n_clear_frames;
 291
 292         /* how many times the DV stream has underflowed, overflowed,
 293            or otherwise encountered an error, since the previous call
 294            to DV1394_GET_STATUS */
 295         unsigned int dropped_frames;
 296
 297         /* N.B. The dropped_frames counter is only a lower bound on the actual
 298            number of dropped frames, with the special case that if dropped_frames
 299            is zero, then it is guaranteed that NO frames have been dropped
 300            since the last call to DV1394_GET_STATUS.
 301         */
 302 };
 303
 304
 305 #endif /* _DV_1394_H */