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/*
* How to test v4l2loopback:
* 1. launch this test program (even in background), it will initialize the
* loopback device and keep it open so it won't loose the settings.
* 2. Feed the video device with data according to the settings specified
* below: size, pixelformat, etc.
* For instance, you can try the default settings with this command:
* mencoder video.avi -ovc raw -nosound -vf scale=640:480,format=yuy2 -o /dev/video1
* TODO: a command that limits the fps would be better :)
*
* Test the video in your favourite viewer, for instance:
* luvcview -d /dev/video1 -f yuyv
*/
#include <linux/videodev2.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <assert.h>
#define ROUND_UP_2(num) (((num)+1)&~1)
#define ROUND_UP_4(num) (((num)+3)&~3)
#define ROUND_UP_8(num) (((num)+7)&~7)
#define ROUND_UP_16(num) (((num)+15)&~15)
#define ROUND_UP_32(num) (((num)+31)&~31)
#define ROUND_UP_64(num) (((num)+63)&~63)
#if 0
# define CHECK_REREAD
#endif
#define VIDEO_DEVICE "/dev/video0"
#if 1
# define FRAME_WIDTH 640
# define FRAME_HEIGHT 480
#else
# define FRAME_WIDTH 512
# define FRAME_HEIGHT 512
#endif
#if 0
# define FRAME_FORMAT V4L2_PIX_FMT_YUYV
#else
# define FRAME_FORMAT V4L2_PIX_FMT_YVU420
#endif
static int debug = 0;
int format_properties(const unsigned int format,
const unsigned int width,
const unsigned int height,
size_t*linewidth,
size_t*framewidth) {
size_t lw, fw;
switch(format) {
case V4L2_PIX_FMT_YUV420: case V4L2_PIX_FMT_YVU420:
lw = width; /* ??? */
fw = ROUND_UP_4 (width) * ROUND_UP_2 (height);
fw += 2 * ((ROUND_UP_8 (width) / 2) * (ROUND_UP_2 (height) / 2));
break;
case V4L2_PIX_FMT_UYVY: case V4L2_PIX_FMT_Y41P: case V4L2_PIX_FMT_YUYV: case V4L2_PIX_FMT_YVYU:
lw = (ROUND_UP_2 (width) * 2);
fw = lw * height;
break;
default:
return 0;
}
if(linewidth)*linewidth=lw;
if(framewidth)*framewidth=fw;
return 1;
}
void print_format(struct v4l2_format*vid_format) {
printf(" vid_format->type =%d\n", vid_format->type );
printf(" vid_format->fmt.pix.width =%d\n", vid_format->fmt.pix.width );
printf(" vid_format->fmt.pix.height =%d\n", vid_format->fmt.pix.height );
printf(" vid_format->fmt.pix.pixelformat =%d\n", vid_format->fmt.pix.pixelformat);
printf(" vid_format->fmt.pix.sizeimage =%d\n", vid_format->fmt.pix.sizeimage );
printf(" vid_format->fmt.pix.field =%d\n", vid_format->fmt.pix.field );
printf(" vid_format->fmt.pix.bytesperline=%d\n", vid_format->fmt.pix.bytesperline );
printf(" vid_format->fmt.pix.colorspace =%d\n", vid_format->fmt.pix.colorspace );
}
int main(int argc, char**argv)
{
struct v4l2_capability vid_caps;
struct v4l2_format vid_format;
size_t framesize = 0;
size_t linewidth = 0;
__u8*buffer;
__u8*check_buffer;
const char*video_device=VIDEO_DEVICE;
int fdwr = 0;
int ret_code = 0;
int i;
if(argc>1) {
video_device=argv[1];
printf("using output device: %s\n", video_device);
}
fdwr = open(video_device, O_RDWR);
assert(fdwr >= 0);
ret_code = ioctl(fdwr, VIDIOC_QUERYCAP, &vid_caps);
assert(ret_code != -1);
memset(&vid_format, 0, sizeof(vid_format));
ret_code = ioctl(fdwr, VIDIOC_G_FMT, &vid_format);
if(debug)print_format(&vid_format);
vid_format.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
vid_format.fmt.pix.width = FRAME_WIDTH;
vid_format.fmt.pix.height = FRAME_HEIGHT;
vid_format.fmt.pix.pixelformat = FRAME_FORMAT;
vid_format.fmt.pix.sizeimage = framesize;
vid_format.fmt.pix.field = V4L2_FIELD_NONE;
vid_format.fmt.pix.bytesperline = linewidth;
vid_format.fmt.pix.colorspace = V4L2_COLORSPACE_SRGB;
if(debug)print_format(&vid_format);
ret_code = ioctl(fdwr, VIDIOC_S_FMT, &vid_format);
assert(ret_code != -1);
if(debug)printf("frame: format=%d\tsize=%lu\n", FRAME_FORMAT, framesize);
print_format(&vid_format);
if(!format_properties(vid_format.fmt.pix.pixelformat,
vid_format.fmt.pix.width, vid_format.fmt.pix.height,
&linewidth,
&framesize)) {
printf("unable to guess correct settings for format '%d'\n", FRAME_FORMAT);
}
buffer=(__u8*)malloc(sizeof(__u8)*framesize);
check_buffer=(__u8*)malloc(sizeof(__u8)*framesize);
memset(buffer, 0, framesize);
memset(check_buffer, 0, framesize);
for (i = 0; i < framesize; ++i) {
//buffer[i] = i % 2;
check_buffer[i] = 0;
}
write(fdwr, buffer, framesize);
#ifdef CHECK_REREAD
do {
/* check if we get the same data on output */
int fdr = open(video_device, O_RDONLY);
read(fdr, check_buffer, framesize);
for (i = 0; i < framesize; ++i) {
if (buffer[i] != check_buffer[i])
assert(0);
}
close(fdr);
} while(0);
#endif
pause();
close(fdwr);
free(buffer);
free(check_buffer);
return 0;
}
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