I have used diko for ages now for skvcd's , but recently changed my cd writer for a dvd writer & bought some dvd-r's (£20 for 100 from blankdiscshop.com ) , now I tend to fit three hour & a half films on one dvd , some work great but alot of the time the films jump or turn blocky on every dvd player i try , the mpeg2 files play ok on the pc . could it be the blank discs or the burner or the software i use to burn (nero 6.6) ?

More probably the disc.

Look into Nero program group, under "Nero Toolkit". You will find "Nero CD-DVD speed". In this tool, you have a "Disc scan" in the menu "Extra". That will let you test the quality of you disc after you have burnt it. You will probably find some sector yellow (hard to read) or red (read error).

but why should it only happen with video & not data the data dvd's like games or just files seem to be ok on these discs , if it is the discs then people need to be aware of these crappy discs

Try the disc quality check in Nero Toolkit->Nero CD-DVD Speed. Set the scan speed to 4x and do the scan. If there are spikes above 4 in the lower chart (PIF), there an increased chance you'll get problems during playback. The test is a very good one when dealing with different DVD media, it will tell you very quickly whether you have the good or the bad ones.

EDIT: what comes to the difference between data and video is that standalone players are much more sensible, they don't like errors. They need to keep up a constant stream whereas the drive in your PC can re-read problemous parts or slow down to read them.

unrecognisable read error , graph lines went over 4x . great now I know not to buy these dvd's again from http://www.blankdiscshop.co.uk/ . im going to mail them for a refund , thanks for your help dialhot & boulder

just a thought , I allways have mcafee virus & firewall running on my pc would that interfear with burning ?

Most likely not.

Do you have an idea about why the "start" button is alays greyed in this window ? I never understood what to tool is waiting for.

It runs the whole set of tests when you insert a disc and then get to press Start. It's greyed out when there's no disc in the drive. It runs the basic tests (the ones under "Run test"), not the more important PI/PIF one which is at the extra tests.

I know ! That's in this extra tsest window that I never have the start button active. Whatever I put a blanck, a DVD video ou a DVD data disc
Do I have to run basic tests first ? I managed to run the extras once but don't know how

Hm, maybe your drive isn't supported, or there's some conflict with the different drivers since Windows comes with its own and Nero has some too? I've always had it working, but you could also try KProbe, which does exactly the same test, although I don't know if it works on any other drives than LiteOn's.