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dv1394.h
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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() */
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 */
224 
225 
226  /* stop transmitting video and free the ringbuffer */
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 */
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 */
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 */
247 
248 
250 
251 
252  /* pass a struct dv1394_status* as the parameter (see below) */
254 };
255 
256 
257 
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 */
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 
328  /* this embedded init struct returns the current dv1394
329  parameters in use */
331 
332  /* the ringbuffer frame that is currently being
333  displayed. (-1 if the device is not transmitting anything) */
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 */