Problems with cropping, scaling and positioning using V4L

dc90210

1) The overlay size does not change with VIDIOC_S_FMT. The command reports success and the window width and height look like there were changed with a subsequent VIDIOC_G_FMT but the video overlay does not scale.

2) Cropping with VIDIOC_S_CROP and positioning with VIDIOC_S_FMT work but not reliably. Again, the command reports success and the values look like there were changed with a subsequent query, but the video overlay does not update. It can sometimes take 5-6 retries of the command for the overlay changes to actually take effect.

Anyone else see similar problems? I am trying the latest EZSDK.

over 13 years ago

0 Deepthy Ravi over 13 years ago

Prodigy 80 points

Hi,

Could you please give us more details of your test setup and the application that you are using.

0 dc90210 over 13 years ago in reply to Deepthy Ravi

Prodigy 180 points

A short program (test-v4l) is at the bottom of the post which you can use to see the issue. I use a simple gstreamer line to start playing video while testing the following commands.

# gst-launch playbin2 uri="file:///test.h264"

1) The following tries to scale the video overlay using VIDIOC_S_FMT. When run the size of the video does not change.

# test-v4l setpos 0 0 320 240

2) The following command lines try to change the overlay (x,y) with VIDIOC_S_FMT. If you toggle between the lines you will see sometimes the video does not change. You sometimes need to repeat a command several times before the video will change position.

# dv4l setpos 0 0 320 240
# dv4l setpos 200 200 320 240

The VIDIOC_S_FMT ioctl does not fail. If you read back the overlay window it looks like the (x,y) was successfully changed.

3) The following command lines try to crop with VIDIOC_S_CROP. If you toggle between the lines you will see sometimes the cropping does not change. You sometimes need to repeat a command several times before the video will change postion.

# dv4l crop 0 0 720 480
# dv4l crop 100 100 200 200

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/ioctl.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <linux/videodev.h>

#include <linux/videodev2.h>

#include <string.h>

#define exit_if(expr, s) do{ if (expr) { perror(s); exit(-1); } } while(0)

int crop(int fd, int x, int y, int w, int h)

{

struct v4l2_crop crop;

crop.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;

crop.c.left = x;

crop.c.top = y;

crop.c.width = w;

crop.c.height = h;

int rc = ioctl(fd, VIDIOC_S_CROP, &crop);

exit_if(rc < 0, "VIDIOC_S_CROP:");

return rc;

}

int getpos(int fd)

{

struct v4l2_format fmt;

fmt.type = V4L2_BUF_TYPE_VIDEO_OVERLAY;

int rc = ioctl(fd, VIDIOC_G_FMT, &fmt);

exit_if(rc < 0, "VIDIOC_G_FMT:");

printf( "%d %d %d %d\n", fmt.fmt.win.w.left, fmt.fmt.win.w.top, fmt.fmt.win.w.width, fmt.fmt.win.w.height);

return rc;

}

int setpos(int fd, int x, int y, int w, int h)

{

struct v4l2_format fmt;

fmt.type = V4L2_BUF_TYPE_VIDEO_OVERLAY;

int rc = ioctl(fd, VIDIOC_G_FMT, &fmt);

exit_if(rc < 0, "VIDIOC_G_FMT:");

fmt.fmt.win.w.left = x;

fmt.fmt.win.w.top = y;

fmt.fmt.win.w.width = w;

fmt.fmt.win.w.height = h;

rc = ioctl(fd, VIDIOC_S_FMT, &fmt);

exit_if(rc < 0, "VIDIOC_S_FMT:");

return rc;

}

int main(int argc, char *argv[])

{

const char *dev = "/dev/video1";

int fd = open(dev, O_RDWR);

exit_if(fd < 0, "Failed to open display device:");

if (strcmp("crop", argv[1]) == 0)

crop(fd, atoi(argv[2]), atoi(argv[3]), atoi(argv[4]), atoi(argv[5]));

else if (strcmp("setpos", argv[1]) == 0)

setpos(fd, atoi(argv[2]), atoi(argv[3]), atoi(argv[4]), atoi(argv[5]));

else if (strcmp("getpos", argv[1]) == 0)

getpos(fd);

close(fd);

return 0;

}

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Problems with cropping, scaling and positioning using V4L