7f3521d6e8e17b9e033eb5c0241866298c281bc0
[libav.git] / libavdevice / 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, 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 FFMPEG_DV1394_H
29 #define FFMPEG_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 /* FFMPEG_DV1394_H */