examples/wss.c

WSS capture example.

/*
 *  libzvbi WSS capture example
 *
 *  Copyright (C) 2005 Michael H. Schimek
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/* $Id: wss.c,v 1.4 2006/10/27 04:52:08 mschimek Exp $ */

/* This example shows how to extract Wide Screen Signalling data
   (EN 300 294) from video images. The signal is transmitted on the
   first half of PAL/SECAM scan line 23, which ITU-R BT.601 defines
   as the first line of a 576 line picture.

   The author is not aware of any drivers which can capture a scan
   line as raw VBI and video data at the same time, and sliced VBI
   capturing is not supported yet by libzvbi. Note some drivers like
   saa7134 cannot capture line 23 at all.

   gcc -o wss wss.c `pkg-config zvbi-0.2 --cflags --libs` */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#ifdef ENABLE_V4L2

#include <fcntl.h>              /* low-level i/o */
#include <unistd.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sys/ioctl.h>

#include <libzvbi.h>

#include <asm/types.h>          /* for videodev2.h */
#include "videodev2k.h"

#define CLEAR(x) memset (&(x), 0, sizeof (x))

struct buffer {
        void *                  start;
        size_t                  length;
};

static const char *     dev_name = "/dev/video";

static int              fd;
static struct buffer *  buffers;
static unsigned int     n_buffers;

static int              quit;

static vbi_raw_decoder  rd;

static void
errno_exit                      (const char *           s)
{
        fprintf (stderr, "%s error %d, %s\n",
                 s, errno, strerror (errno));

        exit (EXIT_FAILURE);
}

static int
xioctl                          (int                    fd,
                                 int                    request,
                                 void *                 p)
{
        int r;

        do r = ioctl (fd, request, p);
        while (-1 == r && EINTR == errno);

        return r;
}

static void
decode_wss_625                  (uint8_t *              buf)
{
        static const char *formats [] = {
                "Full format 4:3, 576 lines",
                "Letterbox 14:9 centre, 504 lines",
                "Letterbox 14:9 top, 504 lines",
                "Letterbox 16:9 centre, 430 lines",
                "Letterbox 16:9 top, 430 lines",
                "Letterbox > 16:9 centre",
                "Full format 14:9 centre, 576 lines",
                "Anamorphic 16:9, 576 lines"
        };
        static const char *subtitles [] = {
                "none",
                "in active image area",
                "out of active image area",
                "<invalid>"
        };
        int g1;
        int parity;

        g1 = buf[0] & 15;

        parity = g1;
        parity ^= parity >> 2;
        parity ^= parity >> 1;
        g1 &= 7;

        printf ("WSS PAL: ");
        if (!(parity & 1))
                printf ("<parity error> ");
        printf ("%s; %s mode; %s colour coding; %s helper; "
                "reserved b7=%d; %s Teletext subtitles; "
                "open subtitles: %s; %s surround sound; "
                "copyright %s; copying %s\n",
                formats[g1],
                (buf[0] & 0x10) ? "film" : "camera",
                (buf[0] & 0x20) ? "MA/CP" : "standard",
                (buf[0] & 0x40) ? "modulated" : "no",
                !!(buf[0] & 0x80),
                (buf[1] & 0x01) ? "have" : "no",
                subtitles[(buf[1] >> 1) & 3],
                (buf[1] & 0x08) ? "have" : "no",
                (buf[1] & 0x10) ? "asserted" : "unknown",
                (buf[1] & 0x20) ? "restricted" : "not restricted");
}

static void
process_image                   (const void *           p)
{
        vbi_sliced sliced[1];
        unsigned int n_lines;

        n_lines = vbi_raw_decode (&rd, (uint8_t *) p, sliced);
        if (0 /* test */) {
                /* Error ignored. */
                write (STDOUT_FILENO, p, rd.bytes_per_line);
        } else if (n_lines > 0) {
                assert (VBI_SLICED_WSS_625 == sliced[0].id);
                assert (1 == n_lines);
                decode_wss_625 (sliced[0].data);
        } else {
                fputc ('.', stdout);
                fflush (stdout);
        }
}

static void
init_decoder                    (void)
{
        unsigned int services;

        vbi_raw_decoder_init (&rd);

        rd.scanning = 625;
        rd.sampling_format = VBI_PIXFMT_YUYV;

        /* Should be calculated from VIDIOC_CROPCAP information.
           Common sampling rates are 14.75 MHz to get 768 PAL/SECAM
           square pixels per line, and 13.5 MHz according to ITU-R Rec.
           BT.601 with 720 pixels/line. Note BT.601 overscans the line:
           13.5e6 / 720 > 14.75e6 / 768. Don't be fooled by a driver
           scaling 768 square pixels to 720. */
        rd.sampling_rate = 768 * 14750000 / 768;

        rd.bytes_per_line = 768 * 2;

        /* Should be calculated from VIDIOC_CROPCAP information. */
        rd.offset = 0;

        rd.start[0] = 23;
        rd.count[0] = 1;

        rd.start[1] = 0;
        rd.count[1] = 0;

        rd.interlaced = FALSE; /* just one line */
        rd.synchronous = TRUE;

        services = vbi_raw_decoder_add_services (&rd,
                                                 VBI_SLICED_WSS_625,
                                                 /* strict */ 2);
        if (0 == services) {
                fprintf (stderr, "Cannot decode WSS\n");
                exit (EXIT_FAILURE);
        }
}

static void
mainloop                        (void)
{
        quit = 0;

        while (!quit) {
                struct v4l2_buffer buf;

                for (;;) {
                        fd_set fds;
                        struct timeval tv;
                        int r;

                        FD_ZERO (&fds);
                        FD_SET (fd, &fds);

                        tv.tv_sec = 2;
                        tv.tv_usec = 0;

                        r = select (fd + 1, &fds, NULL, NULL, &tv);

                        if (-1 == r) {
                                if (EINTR == errno) {
                                        /* XXX should subtract the elapsed
                                           time from timeout here. */
                                        continue;
                                }

                                errno_exit ("select");
                        }

                        if (0 == r) {
                                fprintf (stderr, "select timeout\n");
                                exit (EXIT_FAILURE);
                        }

                        break;
                }

                CLEAR (buf);

                buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;
                buf.memory      = V4L2_MEMORY_MMAP;

                if (-1 == xioctl (fd, VIDIOC_DQBUF, &buf)) {
                        if (EAGAIN == errno)
                                continue;

                        errno_exit ("VIDIOC_DQBUF");
                }

                assert (buf.index < n_buffers);

                process_image (buffers[buf.index].start);

                if (-1 == xioctl (fd, VIDIOC_QBUF, &buf))
                        errno_exit ("VIDIOC_QBUF");
        }
}

static void
start_capturing                 (void)
{
        unsigned int i;
        enum v4l2_buf_type type;

        for (i = 0; i < n_buffers; ++i) {
                struct v4l2_buffer buf;

                CLEAR (buf);

                buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;
                buf.memory      = V4L2_MEMORY_MMAP;
                buf.index       = i;

                if (-1 == xioctl (fd, VIDIOC_QBUF, &buf))
                        errno_exit ("VIDIOC_QBUF");
        }

        type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

        if (-1 == xioctl (fd, VIDIOC_STREAMON, &type))
                errno_exit ("VIDIOC_STREAMON");
}

static void
init_device                     (void)
{
        struct v4l2_capability cap;
        v4l2_std_id std_id;
        struct v4l2_format fmt;
        struct v4l2_requestbuffers req;

        if (-1 == xioctl (fd, VIDIOC_QUERYCAP, &cap)) {
                if (EINVAL == errno) {
                        fprintf (stderr, "%s is no V4L2 device\n",
                                 dev_name);
                        exit (EXIT_FAILURE);
                } else {
                        errno_exit ("VIDIOC_QUERYCAP");
                }
        }

        if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
                fprintf (stderr, "%s is no video capture device\n",
                         dev_name);
                exit (EXIT_FAILURE);
        }

        if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
                fprintf (stderr, "%s does not support streaming I/O\n",
                         dev_name);
                exit (EXIT_FAILURE);
        }

        std_id = V4L2_STD_PAL;

        if (-1 == xioctl (fd, VIDIOC_S_STD, &std_id))
                errno_exit ("VIDIOC_S_STD");

        CLEAR (fmt);

        /* We need the top field without vertical scaling,
           width must be at least 320 pixels. */

        fmt.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        fmt.fmt.pix.width       = 768; 
        fmt.fmt.pix.height      = 576;
        fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
        fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;

        if (-1 == xioctl (fd, VIDIOC_S_FMT, &fmt))
                errno_exit ("VIDIOC_S_FMT");

        /* XXX the driver may adjust width and height, some
           even change the pixelformat, that should be checked here. */

        CLEAR (req);

        req.count               = 4;
        req.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        req.memory              = V4L2_MEMORY_MMAP;

        if (-1 == xioctl (fd, VIDIOC_REQBUFS, &req)) {
                if (EINVAL == errno) {
                        fprintf (stderr, "%s does not support "
                                 "memory mapping\n", dev_name);
                        exit (EXIT_FAILURE);
                } else {
                        errno_exit ("VIDIOC_REQBUFS");
                }
        }

        if (req.count < 2) {
                fprintf (stderr, "Insufficient buffer memory on %s\n",
                         dev_name);
                exit (EXIT_FAILURE);
        }

        buffers = calloc (req.count, sizeof (*buffers));

        if (!buffers) {
                fprintf (stderr, "Out of memory\n");
                exit (EXIT_FAILURE);
        }

        for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {
                struct v4l2_buffer buf;

                CLEAR (buf);

                buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;
                buf.memory      = V4L2_MEMORY_MMAP;
                buf.index       = n_buffers;

                if (-1 == xioctl (fd, VIDIOC_QUERYBUF, &buf))
                        errno_exit ("VIDIOC_QUERYBUF");

                buffers[n_buffers].length = buf.length;
                buffers[n_buffers].start =
                        mmap (NULL /* start anywhere */,
                              buf.length,
                              PROT_READ | PROT_WRITE /* required */,
                              MAP_SHARED /* recommended */,
                              fd, buf.m.offset);

                if (MAP_FAILED == buffers[n_buffers].start)
                        errno_exit ("mmap");
        }
}

static void
open_device                     (void)
{
        struct stat st; 

        if (-1 == stat (dev_name, &st)) {
                fprintf (stderr, "Cannot identify '%s': %d, %s\n",
                         dev_name, errno, strerror (errno));
                exit (EXIT_FAILURE);
        }

        if (!S_ISCHR (st.st_mode)) {
                fprintf (stderr, "%s is no device\n", dev_name);
                exit (EXIT_FAILURE);
        }

        fd = open (dev_name, O_RDWR | O_NONBLOCK, 0);

        if (-1 == fd) {
                fprintf (stderr, "Cannot open '%s': %d, %s\n",
                         dev_name, errno, strerror (errno));
                exit (EXIT_FAILURE);
        }
}

int
main                            (void)
{
        /* Helps debugging. */
        vbi_set_log_fn (/* mask: log everything */ -1,
                        vbi_log_on_stderr,
                        /* user_data */ NULL);

        open_device ();

        init_device ();

        init_decoder ();

        start_capturing ();

        mainloop ();

        exit (EXIT_SUCCESS);

        return 0;
}

#else /* !ENABLE_V4L2 */

int
main                            (int                    argc,
                                 char **                argv)
{
        fprintf (stderr, "Sorry, V4L2 only. Patches welcome.\n");

        exit (EXIT_FAILURE);
        
        return 0;
}

#endif /* !ENABLE_V4L2 */

---