Hi,
What you are trying code is V4l2 application rather than V4l. Below u
can find the code which will help u to grab a image and store the same
in ".ppm" format using V4l. You replace the V4l APIs with V4l2
accordingly.
// Capturing frames from tv tuner card
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <linux/videodev.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
char* deviceName = "/dev/video0";
int deviceHandle = 0;
int i; // temporary counter
struct video_capability capability;
struct video_channel queryChannel;
struct video_channel selectedChannel;
struct video_window captureWindow;
struct video_picture imageProperties;
struct video_mbuf memoryBuffer;
struct video_mmap* mmaps;
char* memoryMap;
int channelNumber = 0;
int width = 320;
int height = 240;
int depth;
int palette;
int bufferIndex;
char* NextFrame(); // function prototype
int main()
{
// open the device
deviceName = "/dev/video0";
deviceHandle = open (deviceName, O_RDWR);
if (deviceHandle == -1) // could not open device
{
// printf ("Could not open device %s - %s\n", deviceName,
sys_errlist[errno]);
printf ("Could not open device %s - %s\n", deviceName,
strerror(errno));
return -1;
}
// get device capabilities
if (ioctl (deviceHandle, VIDIOCGCAP, &capability) == -1)
{ // query failed
printf ("could not obtain device capabilities\n");
return -1;
}
printf("Number of channels = %d \n",capability.channels);
if ((capability.type & VID_TYPE_CAPTURE) == 0)
{ // this device cannot capture video to memory, exit
printf ("this device cannot capture video to memory\n");
return -1;
}
if ((capability.type & VID_TYPE_OVERLAY))
{ // this device cannot capture video to memory, exit
printf ("Can overlay its image onto the frame buffer\n");
}
// enumerate and print out the channels
printf ("Select a channel:\n");
i = 0;
while (i < capability.channels)
{
queryChannel.channel = i;
if (ioctl (deviceHandle, VIDIOCGCHAN, &queryChannel) != -1)
{ // ioctl success, queryChannel contains information about
this channel
printf ("%d. %s\n", queryChannel.channel,
queryChannel.name);
}
++ i;
}
// have the user select a channel
printf (": ");
fflush (stdout);
scanf ("%d", &channelNumber);
selectedChannel.channel = channelNumber; // set the selected
channel
//selectedChannel.norm = VIDEO_MODE_NTSC;
selectedChannel.norm = VIDEO_MODE_PAL;
if (ioctl (deviceHandle, VIDIOCSCHAN, &selectedChannel) == -1)
{ // could not set the selected channel
printf ("Could not set channel #%d\nNot a fatal error.",
channelNumber);
}
// set the desired width and height
if ((capability.type & VID_TYPE_SCALES) != 0)
{ // supports the ability to scale captured images have the
user enter a desired width
printf ("Enter the desired width (e.g. 320): ");
fflush (stdout);
scanf ("%d", &width);
printf ("Enter the desired height (e.g. 240): ");
fflush (stdout);
scanf ("%d", &height);
captureWindow.x = 0;
captureWindow.y = 0;
captureWindow.width = width;
captureWindow.height = height;
captureWindow.chromakey = 0;
captureWindow.flags = 0;
captureWindow.clips = 0;
captureWindow.clipcount = 0;
if (ioctl (deviceHandle, VIDIOCSWIN, &captureWindow) == -1)
{ // could not set window values for capture
printf ("Could not set desired dimensions\nNot a fatal
error.\n");
}
}
// retrieve the actual width and height of the capturing images
if (ioctl (deviceHandle, VIDIOCGWIN, &captureWindow) == -1)
{ // could not obtain specifics of capture window
printf ("Could not obtain capture window dimensions.\n");
}
width = captureWindow.width;
height = captureWindow.height;
printf ("Capturing dimensions are : %d, %d\n", width, height);
// request that we capture to 24bit RGB
// get image properties
if (ioctl (deviceHandle, VIDIOCGPICT, &imageProperties) != -1)
{ // successfully retrieved the default image properties
// the following values are for requesting 24bit RGB
imageProperties.depth = 24;
imageProperties.palette = VIDEO_PALETTE_RGB24;
if (ioctl (deviceHandle, VIDIOCSPICT, &imageProperties) == -1)
{ // failed to set the image properties
printf ("Could not set the video depth and palette.\nPerhaps
not a fatal error.\n");
}
}
// verify that the requested capture pixel depth and palette
succeeded
if (ioctl (deviceHandle, VIDIOCGPICT, &imageProperties) == -1)
{ // failed to retrieve default image properties
printf ("Failed to retrieve the video depth and
palette.\n");
return -1;
}
depth = imageProperties.depth;
palette = imageProperties.palette;
if ((depth != 24) || (palette != VIDEO_PALETTE_RGB24))
{ // not a format our program supports
printf ("Format is not 24bit RGB.\n");
return -1;
}
printf ("Capture depth is 24bit RGB\n");
// obtain memory about capture space
if (ioctl (deviceHandle, VIDIOCGMBUF, &memoryBuffer) == -1)
{ // failed to retrieve information about capture memory space
printf ("Failed to retrieve information about MMIO space.\n");
return -1;
}
// obtain memory mapped area
memoryMap = (char*)mmap (0, // start address
memoryBuffer.size, // length in bytes
PROT_READ | PROT_WRITE, // memory protection
MAP_SHARED, // type of the mapped object
deviceHandle, // file descriptor
0 // offset of the buffer in device memory
);
printf("memoryMap = %u \n", memoryMap);
if ((int)memoryMap == -1)
{ // failed to retrieve pointer to memory mapped area
printf ("Failed to obtain MMIO space.\n");
return -1;
}
// allocate structures
mmaps = (struct video_mmap*)(malloc (memoryBuffer.frames *
sizeof (struct video_mmap)));
// fill out the fields
printf("No of frames = %d \n", memoryBuffer.frames);
i = 0;
while (i < memoryBuffer.frames)
{
mmaps[i].frame = i;
mmaps[i].width = width;
mmaps[i].height = height;
mmaps[i].format = palette;
++ i;
}
// request capture to each buffer except the last one
i = 0;
while (i < (memoryBuffer.frames-1))
{
if (ioctl (deviceHandle, VIDIOCMCAPTURE, &mmaps[i]) == -1)
{ // capture request failed
}
++ i;
}
// set our index to the last buffer
bufferIndex = memoryBuffer.frames-1;
// capture and write out frames
printf ("Capture is ready; capturing 10 images.\n");
int i = 0;
while (i < 10)
{
char* frame = NextFrame();
char fname[80]; // write out PPM file
sprintf (fname, "output%02d.ppm", i);
printf ("Writing out PPM file %s\n", fname);
FILE* fp;
if ((fp = fopen (fname, "w")) == NULL)
{
printf ("Could not open file %s for writing.\n", fname);
return -1;
}
fprintf (fp, "P6\n%d %d\n255\n", width, height);
int n = width * height;
int index=0;
for (index;index < n;++ index)
{
frame[index*3+2]=0;
frame[index*3+1]=255;
frame[index*3+2]=0;
putc (frame[index*3+2], fp);
putc (frame[index*3+1], fp);
putc (frame[index*3+0], fp);
}
fflush (fp);
fclose (fp);
++ i;
}
printf ("Use 'xv output*' to view output.\n");
free (mmaps); // free the video_mmap structures
munmap (memoryMap, memoryBuffer.size); // unmap the capture
memory
close (deviceHandle); // close the device
return 0;
}
char* NextFrame()
{
// send a request to begin capturing to the currently indexed buffer
if (ioctl (deviceHandle, VIDIOCMCAPTURE, &mmaps[bufferIndex]) == -1)
{ // capture request failed
}
++ bufferIndex; // move bufferIndex to the next frame
if (bufferIndex == memoryBuffer.frames)
{ // bufferIndex is indexing beyond the last buffer
// set it to index the first buffer
bufferIndex = 0;
}
// wait for the currently indexed frame to complete capture
if (ioctl (deviceHandle, VIDIOCSYNC, &mmaps[bufferIndex]) == -1)
{ // sync request failed
}
// return the address of the frame data for the current buffer index
return (memoryMap + memoryBuffer.offsets[bufferIndex]);
}
Try this one out. All the best.
On Tue, 2003-12-30 at 07:04, Garrett Kajmowicz wrote:
> I'm trying to write my first v4l application. The goal right now is to simply
> do individual image capturing. As you might suspect, it isn't working
> properly.
>
> This is being done on a Hauppauge tuner card with the bt878 chipset.
>
> So far, I am able to open the device, set the video input and set the video
> standard to V4L2_STD_NTSC_M;
>
> My next step is to try and set the capture format
>
> My code is roughly:
>
> v4l2_format retval
> retval.fmt.pix.sizeimage=0;
> retval.fmt.pix.bytesperline = 0;
> retval.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
> retval.fmt.pix.width = 640;
> retval.fmt.pix.height = 480;
> retval.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB24;
> retval.fmt.pix.field = V4L2_FIELD_ANY;
> retval.fmt.pix.priv = 0;
>
> Unfortunately, the ioctl fails with EINVAL
>
> Where am I going wrong?
>
> Thanks for the help.
>
> - Garrett Kajmowicz
>
>
> --
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--
S.Suriya Mohan, MCA.
Software Engineer,
Insys Technologies,
Coimbatore-641001.
India.
There is no substitution for hard work.
