On Wed, Oct 03, 2001 at 10:47:08AM +0200, Michael Zayats wrote:
> I will present my problem in it's full, may be you will help me:
>
> I am grabbing frames from bt848 and should both store them for future reuse
> and get them on the screen. The box is i810 based and has many other tasks
> to do.
> putting video on a screen should be fast and very low CPU consuming.
>
> what pisses off my boss is that in Windows using DirectShow we get any
> resolution we want with 2-3% of CPU. Is it someway copying bytes from the
> grabber to the video card via PCI/DMA without using CPU on it's way?
>
> Can I achieve something like it on Linux with or without DRI?
Yes. It's called V4L (Video 4 Linux) and the mode you want is called
OVERLAY. All the standard TV applications for Linux (eg, xawtv) have
support for this mode. What you are doing is called GRABBING and you
have already found out that it's CPU intensive.
In OVERLAY mode the bt848 becomes the PCI master and writes directly
into the framebuffer. You'll need a memory mapped PCI video card, of
course. Keep in mind that although the CPU usage is low, an 848 will
consume a large portion of your PCI bus bandwidth.
V4L is completely independent of DRI.
Now if you want to put data from system memory to the video screen I
suggest you look at XV (X Video). It can do various colour expansion
techniques in hardware (eg, YUV12 expansion).
XV is completely independent of V4L and the DRI.
--
The more I know about the WIN32 API the more I dislike it. It is complex and
for the most part poorly designed, inconsistent, and poorly documented.
- David Korn
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