From owner-freebsd-multimedia Mon Apr 26 22:59:11 1999 Delivered-To: freebsd-multimedia@freebsd.org Received: from fleming.cs.strath.ac.uk (fleming.cs.strath.ac.uk [130.159.196.126]) by hub.freebsd.org (Postfix) with ESMTP id 2142B14E16 for ; Mon, 26 Apr 1999 22:59:08 -0700 (PDT) (envelope-from roger@cs.strath.ac.uk) Received: from cs.strath.ac.uk (scary.dmem.strath.ac.uk [130.159.202.5]) by fleming.cs.strath.ac.uk (8.8.8/8.8.8) with ESMTP id GAA13090 Tue, 27 Apr 1999 06:58:55 +0100 (BST) Message-ID: <372551F6.E328D2A0@cs.strath.ac.uk> Date: Tue, 27 Apr 1999 06:58:14 +0100 From: Roger Hardiman Organization: Strathclyde University X-Mailer: Mozilla 4.04 [en] (X11; I; FreeBSD 3.1-STABLE i386) MIME-Version: 1.0 To: Juha.Nurmela@quicknet.inet.fi Cc: multimedia@FreeBSD.ORG Subject: Re: brooktree driver problems?? References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-multimedia@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org Juha I agree that the bktr_intr() codes attempt to work out if the interrupt was ODD or EVEN is a bit of a cludge and we should be modifying the risc program to use the special signal bits. I found all this recently when writing the VBI support for teletext capture. > I got so confused about the even/odd things. > Does VRE _follow_ even field ? Yes it does. The bt878 datasheet contradicts itself but I wrote a test to find the real meaning. VRE is at the END of the even field. VRO is at the end of the odd field. > Which field produces the first visible scanline ? In PAL, the odd field is transmitted first, then the even. So a RISC program should be grab to odd data buffer, check for VRO, grab to even data, check for VRE > Circles in still pictures look correct but moving objects > generate an effect which led me to think the fields are > from differing frames (maybe this is just the way television works ?) The fields (odd and even) are "sampled" in the camera 1/50th of a second appart. On a real TV, the phosphor from the odd lines has faded away before the even lines are drawn. Of course this does not happen on a VGA screen, so you see each moving object in two positions. > Can we get vbi data without the corresponding field of pixel data ? Not sure what you mean, but I have preliminary VBI capture on my site now. http://telepresence.dmem.strath.ac.uk/bt848 Do you mean "get VBI from even and odd fields, but just video from the odd field?" If so, in theory yes. But the RISC program I wrote did not work right. I kept getting interrputs due to an error in executing the RISC program. Bye Roger To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-multimedia" in the body of the message