Date: Tue, 18 Feb 1997 17:49:25 -0800 From: Amancio Hasty <hasty@rah.star-gate.com> To: Randall Hopper <rhh@ct.picker.com> Cc: Jamie Bowden <jamie@inna.net>, multimedia@FreeBSD.org Subject: Re: bt848 Message-ID: <199702190149.RAA01510@rah.star-gate.com> In-Reply-To: Your message of "Tue, 18 Feb 1997 19:22:59 EST." <19970218192259.57917@ct.picker.com>
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>From The Desk Of Randall Hopper : > You may want to look at both STB board and the WinCast/TV and > WinCast/TVdbx boards. From what I've seen/heard, Hauppauge has better tech > support and more stable drivers than STB, which is why I went with them. > > Also, one thing to be aware of when scanning the Hauppauge promo info > on their web site: > > http://www.hauppauge.com/hcw/index.htm > http://206.149.250.27/index.htm > > What they refer to as Overlay mode is different than what Amancio's > referring to. > > When doing video-in-window, their MSW95 drivers always do PCI-to-PCI > transfer over the bus. Their "Overlay Mode" refers to transferring YUV to > the video card and letting the video card do any scaling/quantization (thus > scaling is only limitied by the video card). Their "Primary Surface Mode" > on the other hand refers to transferring raw pixel data to the video card > in its frame buffer's formats, doing any necessary scaling and quantization > on the WinCast card (which the Bt848 limits to 640x480 for NTSC). Their > Overlay Mode requires a video card that supports a YUV port and they say > this eats about half a meg of memory on the video card to store YUV frames > as they come in. Hi, "Overlay" means that the Bt848 has access to the video frame buffer. The bit about yuv to rgb and scaling has to deal with the video display cards capability. If Hauppage is using video for windows, the "Primay Surface Mode" means that the Bt848 has to transfer the capture frame to the system and then to the vga display mode. If this is not the case, then Hauppage either has a modified version of video for windows or their own video driver subsystem which augmenst "Video For Windows" which would not surprise me at all. "Primary Surface Mode" is just a technical term to abstract the video display's frame buffer. You can also have a "Back Surface" which is typically used for double or triple buffering video display. With directdraw you can specified to flip surfaces on "VSYNC" among many things for accurate video display. That is every time that the vga card generats a "VSYNC" interrupt you have the option of changing the address of the frame buffer . Cheers, Amancio frame to the host and then
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