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[directfb-dev] Re: Hardware to videosurface copy


  • To: "Patrick.Debois" <Patrick.Debois@sos.be>
  • Subject: [directfb-dev] Re: Hardware to videosurface copy
  • From: Denis Oliver Kropp <dok@directfb.org>
  • Date: Mon, 10 Jun 2002 10:14:41 +0200
  • Cc: directfb-dev@directfb.org
  • Content-disposition: inline
  • Content-type: text/plain; charset=iso-8859-1
  • In-reply-to: <Pine.LNX.4.33.0205302038550.16420-100000@falcon.home.jedi.be>
  • References: <Pine.LNX.4.33.0205302038550.16420-100000@falcon.home.jedi.be>
  • Reply-to: Denis Oliver Kropp <dok@directfb.org>
  • Sender: directfb-dev-bounce@directfb.org
  • User-agent: Mutt/1.3.28i

Quoting Patrick.Debois (Patrick.Debois@sos.be):
> Hi,
> 
> i'm trying to adapt the avi videoprovider. While looking at the code
> i can not locate where the copy is done to the surface.

The avifile provider uses dfb_gfxcard_blit() to copy the data from
the pseudo surface wrapped around avifile's frame memory.

The code is a bit ugly because the was no support for preallocated
surfaces the time it was written.

> Being more familiar with v4l i started looking to that code but there also 
> i could not locate the place where the HW videobuffer is copied to the 
> surface rect. Or is it done through some pointer mechanism?

The v4l provider instructs the v4l hardware to write into the video
memory via DMA. This happens during v4l_to_surface(), after setting
everything up it uses the VIDIOCCAPTURE ioctl to start the DMA transfer.

> If this is an obvious question/answer i'm sorry but i'm really willing to 
> understand to add some effort in this project.

Both providers are not the best example, have a look at the libmpeg3 and
OpenQuicktime providers. Please excuse the late answer and don't hesitate
if you have further questions, we are always looking for developers willing
to help as there's still much to be done.

-- 
Best regards,
  Denis Oliver Kropp

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