Re: capture.c example (multiple inputs)

["Brian Phelps" <lm317t@xxxxxxxxx>]

I did some digging and it looks like this single chip bt878 card must
cut the frame rate when switching inputs.  Is this correct?

I found a 4-chip version from bluecherry.com that seems to do this at
full 30 FPS per channel.

On Tue, Oct 7, 2008 at 9:15 AM, Brian Phelps <lm317t@xxxxxxxxx> wrote:
> Hi, I have a 4 input Hauppage ImpactVCB.
>
> I have modified capture.c to display frames from an input using SDL
> and the mmap method and this seems to work great.  I would like to
> modify capture.c to display video using 2 inputs.  The problem is that
> if I change inputs, I have to wait for another frame to enter the
> buffer.  This cuts the frame rate in half.
>
> How do I capture frames from two inputs without cutting the frame rate?
>
>
> static void
> mainloop                        (void)
> {
>   unsigned int count;
>
>   count = 1000;
>
>   //Frame_timer = SDL_AddTimer(INTERVAL, process_image, NULL);
>   while (count-- > 0)
>   {
>      for (;;)
>      {
>         fd_set fds;
>         struct timeval tv;
>         int r;
>
>         FD_ZERO (&fds);
>         FD_SET (fd, &fds);
>
>         /* Timeout. */
>         tv.tv_sec = 2;
>         tv.tv_usec = 0;
>
>         r = select (fd + 1, &fds, NULL, NULL, &tv);
>
>         if (-1 == r)
>         {
>            if (EINTR == errno)
>               continue;
>
>            errno_exit ("select");
>         }
>
>         if (0 == r)
>         {
>            fprintf (stderr, "select timeout\n");
>            exit (EXIT_FAILURE);
>         }
>
> //         if (read_frame (0))
>         {
>            ;
>            //r = select (fd + 1, &fds, NULL, NULL, &tv);
>         }
>
>
>         while(read_frame (0)==0)  // I modified read_frame to change
> the input: read_frame(int input_number)
>            r = select (fd + 1, &fds, NULL, NULL, &tv);
>
>         while(read_frame (1)==0)
>            r = select (fd + 1, &fds, NULL, NULL, &tv);
>            break;
>
>         /* EAGAIN - continue select loop. */
>      }
>      printf("Count is %d\n", count);
>   }
> }
>



-- 
Brian Phelps
System Design Engineer
Custom Light and Sound
919-286-0011
http://customlightandsound.com

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