Interlaced images

jameswilson · Post by **jameswilson** » Mon Jun 13, 2005 11:23 am

I have been trying to setup my zm box to emulate a dm digital sprite. It captures at 720x512. I can set zm to do the same but on fast moving images i get motion blur. I have read elsewhere this is to do with interlacing, but i dont get this blur on a sprite. Can this be removed, or is it that my machine is not powerful enough to capture quick enough succesive frames. If i drop to 320 x 240 this stops but the resolution is poor then compared to the srites.
Anyone any ideas??

James

Post by **zoneminder** » Mon Jun 13, 2005 4:19 pm

There are several threads that discuss interlaced images in some depth. If you search hopefully you can find something useful in one of them. v1.21.1 (out later today or tomorrow) includes a contributed patch which addresses one cause of this on some hardware, at the cost of a slower frame rate.

Phil

jameswilson · Post by **jameswilson** » Mon Jun 13, 2005 7:21 pm

thanks phil but im not getting the problem of the odds and evens being mixed up i get bluring on high speed motion ie cars going past this even happens when only using 1 input at 20 fps

maciekc · Post by **maciekc** » Mon Jun 13, 2005 8:30 pm

I think that there is no solution to this. Use low resolution that's the only one.

jameswilson · Post by **jameswilson** » Mon Jun 13, 2005 10:06 pm

how do they get over this then in the dvr's we use at work. Do they grap 2 frames bedore switching to the next input. i pume e fuzziness appears because it grabs field odd from 1 then 2 then 3 then 4 then evens? Then there is quite a gap between odd 1 capture and even 1. Hope i have explained what i mean.

James

Post by **zoneminder** » Tue Jun 14, 2005 8:27 am

The patch that was contributed discards some captured frames as some hardware gets even and odd frames backwards after a switch. It appears to take a short while to settle down to a decent image.

Even with that though, if an object is moving you will probably get an interlaced image as the only way some devices can get large image sizes is by combining two frames which will have a short delay between them.

Phil

jameswilson · Post by **jameswilson** » Tue Jun 14, 2005 9:49 am

i have been googleing and am i right in thinking what i need to stop this is deinterlace. It appears the osprey 100 (my card rebadged version of this) has deinterlacing built into it and can be turned on in wndows. I also notice that XawTV have written a deinterlace script for bt878 cards. Am i way off with this or should i keep looking??

Post by **zoneminder** » Tue Jun 14, 2005 9:59 am

There are various method of manual de-interlacing. If you look on google, or here it explains some. They are mostly just fudges though and can be a lot of work for little effect. Currently ZM doesn't do any of them but if one method was found to be exceptional then it's not hard to do.

Phil

jameswilson · Post by **jameswilson** » Tue Jun 14, 2005 10:41 am

Thanks Phil. The reason im looking at it is because i want to use zm at home (i dont want to shell out for a dm sprite) cheapskate i know. BUt sprites record at high res and dont have the interlacing problem. do you know how they do it or do they bend the truth about the resolution they capture. I have spoken to another of the manufacturese we use and they told me thay capture at 768 x 288 or 768 x520 can be setup and that doesnt do this either. Can i get a card that doesnt do this or can one of the 'bodges'actuall work?

James

Post by **cordel** » Tue Jun 14, 2005 11:16 am

The least expencive way might be looking into the Axis IP cams. The higher end boards are not supported in linux kernel yet at least alot of them are not (Could be wrong).

jameswilson · Post by **jameswilson** » Tue Jun 14, 2005 11:24 am

DO you know of a capture card that does this i dont like the idea of anything that expensive being outside my house and alarm

Post by **cordel** » Tue Jun 14, 2005 12:48 pm

I don't know of any supported by the kernel. Don't mean it don't exist though. Something else you could consider is a video server. Axis makes those too. You can run coax far enough to secure the little box.

jameswilson · Post by **jameswilson** » Tue Jun 14, 2005 12:51 pm

Yeah true hadnt thought of that but arnt they a bit expensive?

Post by **cordel** » Tue Jun 14, 2005 12:53 pm

A quality card can run $700 USD, and you can do quiet a bit with a video server.

jameswilson · Post by **jameswilson** » Tue Jun 14, 2005 1:18 pm

i should bl**dy hope so for that, does that come with cameras, a 200Gb hard disk and an fx55??