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Re: Saving YUVY image from V4L2 buffer to file




Owen O' Hehir wrote:
> Hello All,
> 
> I'm trying to save a captured image from a USB camera to a file. The capture is based on V4L2 video capture example from the V4L2 API spec. http://v4l2spec.bytesex.org/spec/a16706.htm
> 
> The V4L2 set pointers (via mmap) to to the USB image (in YUV 4:2:2 (YUYV)) and as far as I can see the simplest way to save the image in a recognised format is in RGB format, specifically in PPM (Netpbm color image format).
> 
> As such I've expanded the process_image function:
> 
> 
> static void
> process_image                   (const void *           p)
> {
>     static int count = 0;
> 
>     static int r,g,b;
>     static int y1,y2,cb,cr;
> 
>     int pixel=0;
> 
>         FILE* fp = fopen("datadump", "w" );
>         // Write PNM header
>         fprintf( fp, "P6\n" );
>         fprintf( fp, "# YUV422 frame -> RGB \n" );
>         fprintf( fp, "%d %d\n", userfmt.fmt.pix.width, userfmt.fmt.pix.height );
> 
>         fprintf( fp, "255\n" );
> 
>         while(pixel < (userfmt.fmt.pix.width * userfmt.fmt.pix.height)){
> 
>         y1 = *(p+pixel);

Are you sure that's your real code? I don't think you should dereference
a void pointer like that.

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