Hi, Thanks to all who replied to 'wierd effects'. I am pretty convinced now that it is the PCI/DMA etc and I shall try some of the suggestions - but I really must get a better PC for this kind of work! Thanks again Ivor ----- Original Message ----- From: "Justin Schoeman" <justin@xxxxxxxxxxxxxxxxxxxx> To: <video4linux-list@xxxxxxxxxx> Sent: Friday, April 20, 2001 7:50 AM Subject: Re: weird effects > Ivor Cox wrote: > > > > Hi Ben > > > > I only tried full size, but the effect is that of a grid - but intermittent. > > The PCI latency idea seems reasonable as my PC is a bit skinny. > > > > I am familiar with the effects of interlaced fields - it is definitely more > > nasty than that. > > > > The effect is best described as getting a blotchy image with the blotches in > > the correct location and black in the gaps and the blotches fit into small > > rectangular zones so that repeated captures on a still scene gradually fill > > out the blotches to full rectangles but never completes the picture, leaving > > the dark grid. > > The horizontal lines get deeper going right at quarter width steps. The > > vertical lines are concentrated in the middle two quarter widths and are > > pretty constant over the full height. > > The rectangles are of the order of 16-32 pixels. Also I capture the whole > > image but am only delivering one field in my test. > > > > Cheers, and thanks for your attention > > > > Ivor > > I don't think any P75 came out with a PCI2.1 bus which is a requirement > for bt848 cards. I have used a bt848 on a PCI2.0 bus before, but had > serious problems with DMA (black lines/dropped data). > > If you are feeling lucky, you could try the following (in > bttv-driver.c): > > Search for the only occurence of BT848_GPIO_DMA_CTL_PKTP_32 , and > replace the _32 with _16 or _8 or _4 . Each of these progressively > increase the "greedyness" of the Bt848, and may get you slightly better > performance (at the expense of the performance of the rest of the > system. > > -justin > > > > _______________________________________________ > Video4linux-list mailing list > Video4linux-list@xxxxxxxxxx > https://listman.redhat.com/mailman/listinfo/video4linux-list
