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>
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>
11 * This library is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU Lesser General Public
13 * License as published by the Free Software Foundation; either
14 * version 2 of the License, or (at your option) any later version.
16 * This library 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 GNU
19 * Lesser General Public License for more details.
21 * You should have received a copy of the GNU Lesser General Public
22 * License along with this library; if not, write to the Free Software
23 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
30 #define DV1394_DEFAULT_CHANNEL 63
31 #define DV1394_DEFAULT_CARD 0
32 #define DV1394_RING_FRAMES 20
34 #define DV1394_WIDTH 720
35 #define DV1394_NTSC_HEIGHT 480
36 #define DV1394_PAL_HEIGHT 576
38 /* This is the public user-space interface. Try not to break it. */
40 #define DV1394_API_VERSION 0x20011127
42 /* ********************
48 There are two methods of operating the DV1394 DV output device.
52 The simplest is an interface based on write(): simply write
53 full DV frames of data to the device, and they will be transmitted
54 as quickly as possible. The FD may be set for non-blocking I/O,
55 in which case you can use select() or poll() to wait for output
58 To set the DV output parameters (e.g. whether you want NTSC or PAL
59 video), use the DV1394_INIT ioctl, passing in the parameters you
60 want in a struct dv1394_init.
63 To play a raw .DV file: cat foo.DV > /dev/dv1394
64 (cat will use write() internally)
67 static struct dv1394_init init = {
68 0x63, (broadcast channel)
69 4, (four-frame ringbuffer)
70 DV1394_NTSC, (send NTSC video)
71 0, 0 (default empty packet rate)
74 ioctl(fd, DV1394_INIT, &init);
77 read( <a raw DV file>, buf, DV1394_NTSC_FRAME_SIZE );
78 write( <the dv1394 FD>, buf, DV1394_NTSC_FRAME_SIZE );
83 For more control over buffering, and to avoid unnecessary copies
84 of the DV data, you can use the more sophisticated the mmap() interface.
85 First, call the DV1394_INIT ioctl to specify your parameters,
86 including the number of frames in the ringbuffer. Then, calling mmap()
87 on the dv1394 device will give you direct access to the ringbuffer
88 from which the DV card reads your frame data.
90 The ringbuffer is simply one large, contiguous region of memory
91 containing two or more frames of packed DV data. Each frame of DV data
92 is 120000 bytes (NTSC) or 144000 bytes (PAL).
94 Fill one or more frames in the ringbuffer, then use the DV1394_SUBMIT_FRAMES
95 ioctl to begin I/O. You can use either the DV1394_WAIT_FRAMES ioctl
96 or select()/poll() to wait until the frames are transmitted. Next, you'll
97 need to call the DV1394_GET_STATUS ioctl to determine which ringbuffer
98 frames are clear (ready to be filled with new DV data). Finally, use
99 DV1394_SUBMIT_FRAMES again to send the new data to the DV output.
102 Example: here is what a four-frame ringbuffer might look like
103 during DV transmission:
106 frame 0 frame 1 frame 2 frame 3
108 *--------------------------------------*
109 | CLEAR | DV data | DV data | CLEAR |
110 *--------------------------------------*
113 transmission goes in this direction --->>>
116 The DV hardware is currently transmitting the data in frame 1.
117 Once frame 1 is finished, it will automatically transmit frame 2.
118 (if frame 2 finishes before frame 3 is submitted, the device
119 will continue to transmit frame 2, and will increase the dropped_frames
120 counter each time it repeats the transmission).
123 If you called DV1394_GET_STATUS at this instant, you would
124 receive the following values:
128 first_clear_frame = 3
131 At this point, you should write new DV data into frame 3 and optionally
132 frame 0. Then call DV1394_SUBMIT_FRAMES to inform the device that
133 it may transmit the new frames.
137 An error (buffer underflow/overflow or a break in the DV stream due
138 to a 1394 bus reset) can be detected by checking the dropped_frames
139 field of struct dv1394_status (obtained through the
140 DV1394_GET_STATUS ioctl).
142 The best way to recover from such an error is to re-initialize
143 dv1394, either by using the DV1394_INIT ioctl call, or closing the
144 file descriptor and opening it again. (note that you must unmap all
145 ringbuffer mappings when closing the file descriptor, or else
146 dv1394 will still be considered 'in use').
150 For maximum efficiency and robustness against bus errors, you are
151 advised to model the main loop of your application after the
152 following pseudo-code example:
154 (checks of system call return values omitted for brevity; always
155 check return values in your code!)
157 while( frames left ) {
159 struct pollfd *pfd = ...;
163 pfd->events = POLLOUT | POLLIN; (OUT for transmit, IN for receive)
165 (add other sources of I/O here)
167 poll(pfd, 1, -1); (or select(); add a timeout if you want)
170 struct dv1394_status status;
172 ioctl(dv1394_fd, DV1394_GET_STATUS, &status);
174 if(status.dropped_frames > 0) {
177 for(int i = 0; i < status.n_clear_frames; i++) {
184 where copy_DV_frame() reads or writes on the dv1394 file descriptor
185 (read/write mode) or copies data to/from the mmap ringbuffer and
186 then calls ioctl(DV1394_SUBMIT_FRAMES) to notify dv1394 that new
187 frames are availble (mmap mode).
189 reset_dv1394() is called in the event of a buffer
190 underflow/overflow or a halt in the DV stream (e.g. due to a 1394
191 bus reset). To guarantee recovery from the error, this function
192 should close the dv1394 file descriptor (and munmap() all
193 ringbuffer mappings, if you are using them), then re-open the
194 dv1394 device (and re-map the ringbuffer).
199 /* maximum number of frames in the ringbuffer */
200 #define DV1394_MAX_FRAMES 32
202 /* number of *full* isochronous packets per DV frame */
203 #define DV1394_NTSC_PACKETS_PER_FRAME 250
204 #define DV1394_PAL_PACKETS_PER_FRAME 300
206 /* size of one frame's worth of DV data, in bytes */
207 #define DV1394_NTSC_FRAME_SIZE (480 * DV1394_NTSC_PACKETS_PER_FRAME)
208 #define DV1394_PAL_FRAME_SIZE (480 * DV1394_PAL_PACKETS_PER_FRAME)
211 /* ioctl() commands */
214 /* I don't like using 0 as a valid ioctl() */
218 /* get the driver ready to transmit video.
219 pass a struct dv1394_init* as the parameter (see below),
220 or NULL to get default parameters */
224 /* stop transmitting video and free the ringbuffer */
228 /* submit N new frames to be transmitted, where
229 the index of the first new frame is first_clear_buffer,
230 and the index of the last new frame is
231 (first_clear_buffer + N) % n_frames */
232 DV1394_SUBMIT_FRAMES,
235 /* block until N buffers are clear (pass N as the parameter)
236 Because we re-transmit the last frame on underrun, there
237 will at most be n_frames - 1 clear frames at any time */
240 /* capture new frames that have been received, where
241 the index of the first new frame is first_clear_buffer,
242 and the index of the last new frame is
243 (first_clear_buffer + N) % n_frames */
244 DV1394_RECEIVE_FRAMES,
247 DV1394_START_RECEIVE,
250 /* pass a struct dv1394_status* as the parameter (see below) */
264 /* this is the argument to DV1394_INIT */
266 /* DV1394_API_VERSION */
267 unsigned int api_version;
269 /* isochronous transmission channel to use */
270 unsigned int channel;
272 /* number of frames in the ringbuffer. Must be at least 2
273 and at most DV1394_MAX_FRAMES. */
274 unsigned int n_frames;
276 /* send/receive PAL or NTSC video format */
277 enum pal_or_ntsc format;
279 /* the following are used only for transmission */
281 /* set these to zero unless you want a
282 non-default empty packet rate (see below) */
286 /* set this to zero unless you want a
287 non-default SYT cycle offset (default = 3 cycles) */
288 unsigned int syt_offset;
291 /* NOTE: you may only allocate the DV frame ringbuffer once each time
292 you open the dv1394 device. DV1394_INIT will fail if you call it a
293 second time with different 'n_frames' or 'format' arguments (which
294 would imply a different size for the ringbuffer). If you need a
295 different buffer size, simply close and re-open the device, then
296 initialize it with your new settings. */
298 /* Q: What are cip_n and cip_d? */
301 A: DV video streams do not utilize 100% of the potential bandwidth offered
302 by IEEE 1394 (FireWire). To achieve the correct rate of data transmission,
303 DV devices must periodically insert empty packets into the 1394 data stream.
304 Typically there is one empty packet per 14-16 data-carrying packets.
306 Some DV devices will accept a wide range of empty packet rates, while others
307 require a precise rate. If the dv1394 driver produces empty packets at
308 a rate that your device does not accept, you may see ugly patterns on the
309 DV output, or even no output at all.
311 The default empty packet insertion rate seems to work for many people; if
312 your DV output is stable, you can simply ignore this discussion. However,
313 we have exposed the empty packet rate as a parameter to support devices that
314 do not work with the default rate.
316 The decision to insert an empty packet is made with a numerator/denominator
317 algorithm. Empty packets are produced at an average rate of CIP_N / CIP_D.
318 You can alter the empty packet rate by passing non-zero values for cip_n
319 and cip_d to the INIT ioctl.
325 struct dv1394_status {
326 /* this embedded init struct returns the current dv1394
328 struct dv1394_init init;
330 /* the ringbuffer frame that is currently being
331 displayed. (-1 if the device is not transmitting anything) */
334 /* index of the first buffer (ahead of active_frame) that
335 is ready to be filled with data */
336 unsigned int first_clear_frame;
338 /* how many buffers, including first_clear_buffer, are
339 ready to be filled with data */
340 unsigned int n_clear_frames;
342 /* how many times the DV stream has underflowed, overflowed,
343 or otherwise encountered an error, since the previous call
344 to DV1394_GET_STATUS */
345 unsigned int dropped_frames;
347 /* N.B. The dropped_frames counter is only a lower bound on the actual
348 number of dropped frames, with the special case that if dropped_frames
349 is zero, then it is guaranteed that NO frames have been dropped
350 since the last call to DV1394_GET_STATUS.
355 #endif /* _DV_1394_H */