Main Page | Class Hierarchy | Alphabetical List | Class List | Directories | File List | Class Members | File Members

dv1394.h

Go to the documentation of this file.
00001 /*
00002  * dv1394.h - DV input/output over IEEE 1394 on OHCI chips
00003  *   Copyright (C)2001 Daniel Maas <dmaas@dcine.com>
00004  *     receive by Dan Dennedy <dan@dennedy.org>
00005  *
00006  * based on:
00007  *   video1394.h - driver for OHCI 1394 boards
00008  *   Copyright (C)1999,2000 Sebastien Rougeaux <sebastien.rougeaux@anu.edu.au>
00009  *                          Peter Schlaile <udbz@rz.uni-karlsruhe.de>
00010  *
00011  * This program is free software; you can redistribute it and/or modify
00012  * it under the terms of the GNU General Public License as published by
00013  * the Free Software Foundation; either version 2 of the License, or
00014  * (at your option) any later version.
00015  *
00016  * This program is distributed in the hope that it will be useful,
00017  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00018  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00019  * GNU General Public License for more details.
00020  *
00021  * You should have received a copy of the GNU General Public License
00022  * along with this program; if not, write to the Free Software Foundation,
00023  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
00024  */
00025 
00026 #ifndef _DV_1394_H
00027 #define _DV_1394_H
00028 
00029 /* This is the public user-space interface. Try not to break it. */
00030 
00031 #define DV1394_API_VERSION 0x20011127
00032 
00033 /* ********************
00034    **                **
00035    **   DV1394 API   **
00036    **                **
00037    ********************
00038 
00039    There are two methods of operating the DV1394 DV output device.
00040 
00041    1)
00042 
00043    The simplest is an interface based on write(): simply write
00044    full DV frames of data to the device, and they will be transmitted
00045    as quickly as possible. The FD may be set for non-blocking I/O,
00046    in which case you can use select() or poll() to wait for output
00047    buffer space.
00048 
00049    To set the DV output parameters (e.g. whether you want NTSC or PAL
00050    video), use the DV1394_INIT ioctl, passing in the parameters you
00051    want in a struct dv1394_init.
00052  
00053    Example 1:
00054          To play a raw .DV file:   cat foo.DV > /dev/dv1394
00055          (cat will use write() internally)
00056 
00057    Example 2:
00058            static struct dv1394_init init = {
00059               0x63,        (broadcast channel)
00060               4,           (four-frame ringbuffer)
00061               DV1394_NTSC, (send NTSC video)
00062               0, 0         (default empty packet rate)
00063            }
00064 
00065            ioctl(fd, DV1394_INIT, &init);
00066 
00067            while (1) {
00068                   read( <a raw DV file>, buf, DV1394_NTSC_FRAME_SIZE );
00069                   write( <the dv1394 FD>, buf, DV1394_NTSC_FRAME_SIZE );
00070            }
00071 
00072    2)
00073 
00074    For more control over buffering, and to avoid unnecessary copies
00075    of the DV data, you can use the more sophisticated the mmap() interface. 
00076    First, call the DV1394_INIT ioctl to specify your parameters, 
00077    including the number of frames in the ringbuffer. Then, calling mmap() 
00078    on the dv1394 device will give you direct access to the ringbuffer
00079    from which the DV card reads your frame data.
00080 
00081    The ringbuffer is simply one large, contiguous region of memory
00082    containing two or more frames of packed DV data. Each frame of DV data
00083    is 120000 bytes (NTSC) or 144000 bytes (PAL).
00084 
00085    Fill one or more frames in the ringbuffer, then use the DV1394_SUBMIT_FRAMES
00086    ioctl to begin I/O. You can use either the DV1394_WAIT_FRAMES ioctl
00087    or select()/poll() to wait until the frames are transmitted. Next, you'll
00088    need to call the DV1394_GET_STATUS ioctl to determine which ringbuffer
00089    frames are clear (ready to be filled with new DV data). Finally, use
00090    DV1394_SUBMIT_FRAMES again to send the new data to the DV output.
00091 
00092 
00093    Example: here is what a four-frame ringbuffer might look like
00094             during DV transmission:
00095 
00096 
00097          frame 0   frame 1   frame 2   frame 3
00098 
00099         *--------------------------------------*
00100         | CLEAR   | DV data | DV data | CLEAR  |
00101         *--------------------------------------*
00102                    <ACTIVE> 
00103 
00104         transmission goes in this direction --->>>
00105 
00106 
00107    The DV hardware is currently transmitting the data in frame 1.
00108    Once frame 1 is finished, it will automatically transmit frame 2.
00109    (if frame 2 finishes before frame 3 is submitted, the device
00110    will continue to transmit frame 2, and will increase the dropped_frames
00111    counter each time it repeats the transmission).
00112 
00113  
00114    If you called DV1394_GET_STATUS at this instant, you would
00115    receive the following values:
00116    
00117                   n_frames          = 4
00118                   active_frame      = 1
00119                   first_clear_frame = 3
00120                   n_clear_frames    = 2
00121 
00122    At this point, you should write new DV data into frame 3 and optionally
00123    frame 0. Then call DV1394_SUBMIT_FRAMES to inform the device that
00124    it may transmit the new frames.
00125 
00126    ERROR HANDLING
00127 
00128    An error (buffer underflow/overflow or a break in the DV stream due
00129    to a 1394 bus reset) can be detected by checking the dropped_frames
00130    field of struct dv1394_status (obtained through the
00131    DV1394_GET_STATUS ioctl).
00132 
00133    The best way to recover from such an error is to re-initialize
00134    dv1394, either by using the DV1394_INIT ioctl call, or closing the
00135    file descriptor and opening it again. (note that you must unmap all
00136    ringbuffer mappings when closing the file descriptor, or else
00137    dv1394 will still be considered 'in use').
00138 
00139    MAIN LOOP
00140 
00141    For maximum efficiency and robustness against bus errors, you are
00142    advised to model the main loop of your application after the
00143    following pseudo-code example:
00144 
00145    (checks of system call return values omitted for brevity; always
00146    check return values in your code!)
00147    
00148    while ( frames left ) {
00149    
00150     struct pollfd *pfd = ...;
00151 
00152     pfd->fd = dv1394_fd;
00153     pfd->revents = 0;
00154     pfd->events = POLLOUT | POLLIN; (OUT for transmit, IN for receive)
00155 
00156     (add other sources of I/O here)
00157     
00158     poll(pfd, 1, -1); (or select(); add a timeout if you want)
00159 
00160     if (pfd->revents) {
00161          struct dv1394_status status;
00162          
00163          ioctl(dv1394_fd, DV1394_GET_STATUS, &status);
00164 
00165          if (status.dropped_frames > 0) {
00166               reset_dv1394();
00167          } else {
00168               for (int i = 0; i < status.n_clear_frames; i++) {
00169                   copy_DV_frame();
00170               }
00171          }
00172     }
00173    }
00174 
00175    where copy_DV_frame() reads or writes on the dv1394 file descriptor
00176    (read/write mode) or copies data to/from the mmap ringbuffer and
00177    then calls ioctl(DV1394_SUBMIT_FRAMES) to notify dv1394 that new
00178    frames are availble (mmap mode).
00179 
00180    reset_dv1394() is called in the event of a buffer
00181    underflow/overflow or a halt in the DV stream (e.g. due to a 1394
00182    bus reset). To guarantee recovery from the error, this function
00183    should close the dv1394 file descriptor (and munmap() all
00184    ringbuffer mappings, if you are using them), then re-open the
00185    dv1394 device (and re-map the ringbuffer).
00186    
00187 */
00188 
00189 
00190 /* maximum number of frames in the ringbuffer */
00191 #define DV1394_MAX_FRAMES 32
00192 
00193 /* number of *full* isochronous packets per DV frame */
00194 #define DV1394_NTSC_PACKETS_PER_FRAME 250
00195 #define DV1394_PAL_PACKETS_PER_FRAME  300
00196 
00197 /* size of one frame's worth of DV data, in bytes */
00198 #define DV1394_NTSC_FRAME_SIZE (480 * DV1394_NTSC_PACKETS_PER_FRAME)
00199 #define DV1394_PAL_FRAME_SIZE  (480 * DV1394_PAL_PACKETS_PER_FRAME)
00200 
00201 
00202 /* ioctl() commands */
00203 #include "ieee1394-ioctl.h"
00204 
00205 
00206 enum pal_or_ntsc {
00207         DV1394_NTSC = 0,
00208         DV1394_PAL
00209 };
00210 
00211 
00212 
00213 
00214 /* this is the argument to DV1394_INIT */
00215 struct dv1394_init {
00216         /* DV1394_API_VERSION */
00217         unsigned int api_version;
00218         
00219         /* isochronous transmission channel to use */
00220         unsigned int channel;
00221 
00222         /* number of frames in the ringbuffer. Must be at least 2
00223            and at most DV1394_MAX_FRAMES. */
00224         unsigned int n_frames;
00225 
00226         /* send/receive PAL or NTSC video format */
00227         enum pal_or_ntsc format;
00228 
00229         /* the following are used only for transmission */
00230  
00231         /* set these to zero unless you want a
00232            non-default empty packet rate (see below) */
00233         unsigned long cip_n;
00234         unsigned long cip_d;
00235 
00236         /* set this to zero unless you want a
00237            non-default SYT cycle offset (default = 3 cycles) */
00238         unsigned int syt_offset;
00239 };
00240 
00241 /* NOTE: you may only allocate the DV frame ringbuffer once each time
00242    you open the dv1394 device. DV1394_INIT will fail if you call it a
00243    second time with different 'n_frames' or 'format' arguments (which
00244    would imply a different size for the ringbuffer). If you need a
00245    different buffer size, simply close and re-open the device, then
00246    initialize it with your new settings. */
00247    
00248 /* Q: What are cip_n and cip_d? */
00249 
00250 /*
00251   A: DV video streams do not utilize 100% of the potential bandwidth offered
00252   by IEEE 1394 (FireWire). To achieve the correct rate of data transmission,
00253   DV devices must periodically insert empty packets into the 1394 data stream.
00254   Typically there is one empty packet per 14-16 data-carrying packets.
00255 
00256   Some DV devices will accept a wide range of empty packet rates, while others
00257   require a precise rate. If the dv1394 driver produces empty packets at
00258   a rate that your device does not accept, you may see ugly patterns on the
00259   DV output, or even no output at all.
00260 
00261   The default empty packet insertion rate seems to work for many people; if
00262   your DV output is stable, you can simply ignore this discussion. However,
00263   we have exposed the empty packet rate as a parameter to support devices that
00264   do not work with the default rate. 
00265 
00266   The decision to insert an empty packet is made with a numerator/denominator
00267   algorithm. Empty packets are produced at an average rate of CIP_N / CIP_D.
00268   You can alter the empty packet rate by passing non-zero values for cip_n
00269   and cip_d to the INIT ioctl.
00270   
00271  */
00272 
00273 
00274 
00275 struct dv1394_status {
00276         /* this embedded init struct returns the current dv1394
00277            parameters in use */
00278         struct dv1394_init init;
00279 
00280         /* the ringbuffer frame that is currently being
00281            displayed. (-1 if the device is not transmitting anything) */
00282         int active_frame;
00283 
00284         /* index of the first buffer (ahead of active_frame) that
00285            is ready to be filled with data */
00286         unsigned int first_clear_frame;
00287 
00288         /* how many buffers, including first_clear_buffer, are
00289            ready to be filled with data */
00290         unsigned int n_clear_frames;
00291 
00292         /* how many times the DV stream has underflowed, overflowed,
00293            or otherwise encountered an error, since the previous call
00294            to DV1394_GET_STATUS */
00295         unsigned int dropped_frames;
00296 
00297         /* N.B. The dropped_frames counter is only a lower bound on the actual
00298            number of dropped frames, with the special case that if dropped_frames
00299            is zero, then it is guaranteed that NO frames have been dropped
00300            since the last call to DV1394_GET_STATUS.
00301         */
00302 };
00303 
00304 
00305 #endif /* _DV_1394_H */

Generated on Sun Jan 8 13:38:53 2006 for Cinelerra-svn by  doxygen 1.4.4