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/*
* Copy a YUV4MPEG stream to a v4l2 output device.
* The stream is read from standard input.
* The device can be specified as argument; it defaults to /dev/video0.
*
* Example using mplayer as a producer for the v4l2loopback driver:
*
* $ mkfifo /tmp/pipe
* $ ./yuv4mpeg_to_v4l2 < /tmp/pipe &
* $ mplayer movie.mp4 -vo yuv4mpeg:file=/tmp/pipe
*
* Copyright (C) 2011 Eric C. Cooper <ecc@cmu.edu>
* Released under the GNU General Public License
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>
char *prog;
char *device;
int dev_fd;
int frame_width;
int frame_height;
int frame_bytes;
void
usage(void)
{
fprintf(stderr, "Usage: %s [/dev/videoN]\n", prog);
exit(1);
}
void
process_args(int argc, char **argv)
{
prog = argv[0];
switch (argc) {
case 1:
device = "/dev/video0";
break;
case 2:
device = argv[1];
break;
default:
usage();
break;
}
}
void
sysfail(char *msg)
{
perror(msg);
exit(1);
}
void
fail(char *msg)
{
fprintf(stderr, "%s: %s\n", prog, msg);
exit(1);
}
void
bad_header(char *kind)
{
char msg[64];
sprintf(msg, "malformed %s header", kind);
fail(msg);
}
void
do_tag(char tag, char *value)
{
switch (tag) {
case 'W':
frame_width = strtoul(value, NULL, 10);
break;
case 'H':
frame_height = strtoul(value, NULL, 10);
break;
}
}
int
read_header(char *magic)
{
char *p, *q, *p0;
size_t n;
int first, done;
p0 = NULL;
if (getline(&p0, &n, stdin) == -1) {
free(p0);
return 0;
}
q = p = p0;
first = 1;
done = 0;
while (!done) {
while (*q != ' ' && *q != '\n')
if (*q++ == '\0') bad_header(magic);
done = (*q == '\n');
*q = '\0';
if (first)
if (strcmp(p, magic) == 0) first = 0;
else bad_header(magic);
else
do_tag(*p, p + 1);
p = ++q;
}
free(p0);
return 1;
}
void
process_header(void)
{
if (!read_header("YUV4MPEG2")) fail("missing YUV4MPEG2 header");
frame_bytes = 3 * frame_width * frame_height / 2;
if (frame_bytes == 0) fail("frame width or height is missing");
}
void
copy_frames(void)
{
char *frame;
frame = malloc(frame_bytes);
if (frame == NULL) fail("cannot malloc frame");
while (read_header("FRAME")) {
if (fread(frame, 1, frame_bytes, stdin) != frame_bytes) {
free(frame);
fail("malformed frame");
}
else if (write(dev_fd, frame, frame_bytes) != frame_bytes) {
free(frame);
sysfail("write");
}
}
free(frame);
}
#define vidioc(op, arg) \
if (ioctl(dev_fd, VIDIOC_##op, arg) == -1) \
sysfail(#op); \
else
void
open_video(void)
{
struct v4l2_format v;
dev_fd = open(device, O_RDWR);
if (dev_fd == -1) sysfail(device);
v.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
vidioc(G_FMT, &v);
v.fmt.pix.width = frame_width;
v.fmt.pix.height = frame_height;
v.fmt.pix.pixelformat = V4L2_PIX_FMT_YUV420;
v.fmt.pix.sizeimage = frame_bytes;
vidioc(S_FMT, &v);
}
int
main(int argc, char **argv)
{
process_args(argc, argv);
process_header();
open_video();
copy_frames();
return 0;
}
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