Re: fast frame grab

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Andrew Wilson (a_wilson@xxxxxxx):

> I'm trying to grab a 640x480 BW frame as fast as possible, it
> currently takes roughly 100milliseconds per grab.    The live video
> feed straight to the monitor runs smoothly at 60fps though, shouldn't
> a frame grab be 17 milliseconds?

  Video is interlaced, so for NTSC you'll only get 240 scanlines per
field.  If you're capturing at 640x480, you're probably capturing
frames, so you'll only get one frame every 33ms.  If you want <33ms
delays, you'll need one of the new bttv drivers with V4L2 support that
allows you to ask for field-rate capture, then you can get a new frame
every 16.6ms.

  It shouldn't take 100ms per grab though, something sounds wrong.  Post
your code somewhere and maybe someone can take a look at it.

  -Billy





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