Em Sat, 15 Aug 2009 20:23:43 +0200
"Rath" <mailings@xxxxxxxxxxxxxxxxxxxxx> escreveu:
> With the example from the api specifications I get this output:
> root@beagleboard:~# ./capture -d /dev/video0
> ....................................................................................................
> Where can I find the captured images?
It would better to use v4l2grab instead.
>
> ----- Original Message -----
> From: "Dongsoo, Nathaniel Kim" <dongsoo.kim@xxxxxxxxx>
> To: "Rath" <mailings@xxxxxxxxxxxxxxxxxxxxx>
> Cc: <linux-media@xxxxxxxxxxxxxxx>
> Sent: Saturday, August 15, 2009 11:53 AM
> Subject: Re: V4L image grab
>
>
> On Sat, Aug 15, 2009 at 6:36 AM, Rath<mailings@xxxxxxxxxxxxxxxxxxxxx> wrote:
> > Hi,
> >
> > with this code from the internet I only get pictures with some undefined
> > pixels on the top and black pixels on the bottom.
> >
> > Where's the problem? I only want a simple example for image captureing.
> >
> > Here is the code:
> >
> > #include <stdio.h>
> > #include <unistd.h>
> > #include <fcntl.h>
> > #include <sys/ioctl.h>
> > #include <libv4l1.h>
> > #include <linux/videodev.h>
> >
> > #define GES_LAENGE (640*480)
> >
> > unsigned char bild[GES_LAENGE];
> >
> > int main()
> > {
> > int fd;
> > long laenge;
> > struct video_window video_win;
> > FILE *bilddatei;
> >
> > if((fd = v4l1_open("/dev/video0", O_RDONLY)) == -1)
> > {
> > printf("Fehler beim Oeffnen von /dev/video0\r\n");
> > return 1;
> > }
> > if( v4l1_ioctl( fd, VIDIOCGWIN, &video_win) == -1)
> > {
> > printf("Fehler beim setzen der Einstellungen\r\n");
> > return 1;
> > }
> > laenge = video_win.width * video_win.height;
> > if( laenge > GES_LAENGE)
> > {
> > printf("Bild ist groesser als angegeben\r\n");
> > return 1;
> > }
> >
> >
> > if( v4l1_read( fd, bild, laenge) == -1)
> > {
> > printf("Auslesen der Kamera nicht möglch\r\n");
> > return 1;
> > }
> > if((bilddatei = fopen( "bild.ppm", "w+b")) == NULL)
> > {
> > printf("Konnte die datei zum schreiben nicht öffnen\r\n");
> > return 1;
> > }
> > v4l1_close(fd);
> > fprintf( bilddatei, "P6\n%d %d\n255\n",video_win.width,
> > video_win.height);
> > fwrite( bild, 1, video_win.width*video_win.height,bilddatei);
> > fclose(bilddatei);
> > return 0;
> > }
> >
>
>
> Hi Joern,
>
> That code seems to be using v4l1 APIs. How about using current version
> of video4linux?
> You can find a simple example code at following document:
> http://www.linuxtv.org/downloads/video4linux/API/V4L2_API/spec-single/v4l2.html#CAPTURE-EXAMPLE
>
> And about the weird image you got from the v4l1 example code, could be
> a pixelformat missmatch or just some noise fetched but I can't say any
> further without knowing your environment :-)
> Cheers,
>
> Nate
>
> > Regards, Joern
> > --
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> >
>
>
>
Cheers,
Mauro
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