Hello again, I'm still using my ATI AIWPro 8mb AGP2x card to capture from pal vhs to make pal vcd's. Normally i capture at 352*240 44.1/16/stereo with ativcr2 codec, which results in good quality avi's. Which i then put straight into TMpegEnc or Panasonic and finally burn with Nero. However, i have the option of these settings BEFORE capture..... Interlaced Both Fields One Field

I have always used 'Both Fields' in the past, but last night i tried 'interlaced' @ 352*288 and the picture had some terrible horizontal lines/banding, which TMpegEnc couldn't quite remove 100%. The horizontal lines always appear at 352*288, so if i was to capture at 352*288 in the future, should i choose Interlaced or Both Fields? And would it make any difference if i chose Interlaced along with my USUAL settings?

Any info would be grateful, with perhaps an explanation of the different types of 'field settings' for my card.

Many thanks,

Andy.

ps. Lots of people have emailed me asking if i sell vcd's, NO i dont.

-- Andy (andy@snes.freeserve.co.uk), October 08, 2000

Answers

As far as I'm aware ATI has separate models of All-in-Wonder Pro for NTSC and PAL/SECAM. If you have the NTSC model you can't successfully capture anything other than NTSC and same for the PAL/SECAM model. Which is why I returned the one I bought and opted instead for the Matrox Marvel G200 at that time, which allows you to freely choose between PAL, SECAM, & NTSC with only one model. With ATI less expensive than the Matrox I knew there was something amiss all along. When capturing at CIF (352x240/288) for VCD purposes or something, do note that ONLY one field is being captured out of the two that makes the frame (one frame is 480/576, one field is 240/288, get it?). So, interlace has little value here, except probably when you are presented with which field (odd or even) you want to capture. When the VCD is played back later on, the player's DACs repeat that one field which was captured to make one frame, which is why apart from a tendency to be blocky, VCD picture quality also shows coarse structure on lines in the picture that are at a diagonal already near the horizontal. Information in the field which wasn't captured that could have gracefully smoothed out the picture isn't there; in its place is simply the same info from the one and same field. When you do capture a full frame the MPEG-1 encoder simply ignores every other field, whichever was the one you didn't choose in the encoding parameters. SVCD and DVD in contrast both use MPEG-2 which employs interlaced 480/576 full frame making it one of the reasons these two formats give better quality compared with VCD.

-- Mehmet Tekdemir (turk690@yahoo.com), October 08, 2000.

Hi Andy,

I have the same card as you and can tell you the banding has nothing to do with whether u capture single, Interlaced or both fields, but is actually a driver flaw from ATI, when ever you try to capture above 352 X 280 you will always get banding in the clip, no matter what u do, the only way round this if you want to capture at 352 X 288 is to capture at 352 X 280, then use the panasonic mpeg encoder to add the additional 8 lines, 4 top and bottom when you`re converting to mpeg making it VCD compliant....I`ve contacted ATI about this problem and have been sent several new sets of drivers, none of which solve this problem...so your best bet is as i said above hope this helps....

Alan.

-- Alan MacRae (alansam@lineone.net), October 08, 2000.

Hi Andy, I have a different type of ATI AIW .. the 128 rage chipset 32 mb model. And the three selections in my case do make a difference. It depends what your final source is going to be. IF you intend to encode it to SVCD then you need to use Interlaced. If you are doing VCD it should NOT be interlaced. Whether you use one or two fields may not be applicable in your case as the other poster said. But in my case when doing direct capture to VCD compatible Mpeg-1 I get best results from using dual fields. The important thing is the "interlacing" The mpeg specs for VCD requires "non-interlaced". Whereas SVCD (which is MPEG-2 and variable bit rate) should be "interlaced".

Try one and both fields and see which is best for you. Stay away from "interlaced" for VCD work. HTH

-- Rich (rich@pcphotovideo.com), October 08, 2000.