From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx3.redhat.com (mx3.redhat.com [172.16.48.32]) by int-mx2.corp.redhat.com (8.13.1/8.13.1) with ESMTP id m7MKXXVw012562 for ; Fri, 22 Aug 2008 16:33:33 -0400 Received: from mail.gmx.net (mail.gmx.net [213.165.64.20]) by mx3.redhat.com (8.13.8/8.13.8) with SMTP id m7MKXVtD022621 for ; Fri, 22 Aug 2008 16:33:31 -0400 Date: Fri, 22 Aug 2008 22:32:47 +0200 From: Daniel =?iso-8859-1?Q?Gl=F6ckner?= To: Andy Walls Message-ID: <20080822203247.GA928@daniel.bse> References: <200808181918.05975.jdelvare@suse.de> <200808202334.20872.jdelvare@suse.de> <200808211114.27290.jdelvare@suse.de> <1219407994.2855.24.camel@morgan.walls.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1219407994.2855.24.camel@morgan.walls.org> Cc: video4linux-list@redhat.com, v4l-dvb-maintainer@linuxtv.org, Trent Piepho , Jean Delvare Subject: Re: [v4l-dvb-maintainer] bttv driver errors List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: video4linux-list-bounces@redhat.com Errors-To: video4linux-list-bounces@redhat.com List-ID: On Fri, Aug 22, 2008 at 08:26:34AM -0400, Andy Walls wrote: > What are the benefits of using the moving average filters before > decimation? The benefit is that the upper spectrum is attenuated before it is mirrored into the lower spectrum by the decimation. After the decimation you have no way of removing those artifacts in a mathematically correct way. There are better FIR filters than 0.5 * x(0) + 0.5 * x(1), which will avoid aliasing even more and preserve more of the lower spectrum. This is just the simplest. Btw., enabling the chroma comb filter in bttv will result in alternating 0.5*x(-2)+0.5*x(0) and 0.5*x(-1)+0.5*x(1) for frame captures and 0.5*x(-1)+0.5*x(0) for field captures. I have once tried to modify bttv_risc_planar to be closer to MPEG chroma subsampling when the comb filter is enabled, because I was annoyed by the gray first line. On Thu, Aug 21, 2008 at 01:50:05AM -0700, Trent Piepho wrote: > A better question would be how does the bt878 do horizontal and vertical > scaling? If you look at the description of ultralock and the number of > taps avaiable for the vertical scaling filters, the chip must have some > kind of multi-line buffer before the scaler. But this buffer, and the > delay it must introduce, is never mentioned in the datasheet. The buffer is "mentioned" in figure 2-4 of the Fusion 878A datasheet available on the Conexant website. Its size can be derived from the restrictions placed on the luma filters. It should be 768 luma samples. The decimation then has another full line buffer for luma and chroma to perform the linear luma interpolation and the chroma comb filter. Daniel -- video4linux-list mailing list Unsubscribe mailto:video4linux-list-request@redhat.com?subject=unsubscribe https://www.redhat.com/mailman/listinfo/video4linux-list