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 Libav.
12  *
13  * Libav 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  * Libav 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 Libav; 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() */
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 */
223 
224 
225  /* stop transmitting video and free the ringbuffer */
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 */
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 */
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 */
246 
247 
249 
250 
251  /* pass a struct dv1394_status* as the parameter (see below) */
253 };
254 
255 
256 
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 */
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 
327  /* this embedded init struct returns the current dv1394
328  parameters in use */
330 
331  /* the ringbuffer frame that is currently being
332  displayed. (-1 if the device is not transmitting anything) */
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 */