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| spockminov |
| Posted: Sep 2 2002, 11:03 PM |
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Newb question #2:
Relates to NTSC capture resolution. Intent is to burn to SVCD (480x480). I've read 2 conflicting things:
1) Just capture to 320x240, anything else is overkill.
2) Always capture at least as big (or bigger) than intended output resolution.
Which is correct? If 2) is correct, then I should at least try to capture at 320x480, right?
Also, I've read that vertical lo-rez vertical (240) vs. hi-rez (480) does make a difference, but horizontal rez (320, 352, 640) makes no difference. True?
Last question:
I use a BT878 card and in VDub at 320x240, get no dropped frames. But if I bump up to 320x480, frame rate jumps to above 30 (??) and frame drop takes off. I didn't think LOGICALLY that frame rate could go above 30. Is this jus a sign that my card can't support anything above 320x480??
THANKS |
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| avih |
| Posted: Sep 3 2002, 10:42 AM |
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if your cpu/hd can afford this, capture at the highest res possible, nothing is an overkill. since when you resize (while re-encoding), let's say to 320x240, the quality will be MUCH better than if capturing directly to 320x240 (you can try for yourself) because the averaging of the pixels that occure while resizing gives much more noise resistance and more details than if capturing directly to 320x240.
the vertical resolution does make a difference. the horizontal resolution depends on your driver. i.e. if you capture at 320x480 it depends on the method in which your driver resizes horizontally. if it uses billinear, then it's relatively ok, but if, i.e., it resizes using nearest neighbour, then the quality is affected. you'll have to try for yourself.
also, if you intend to use some filters before you re-encode, then sometimes it's better to use them on the full resolution, in which case, capping direcly to low res would harm your filterring efforts.
also very important, whether you should cap full vertical res (i.e. 480 for ntsc / 576 pal) is if the source video is interlaced or not. if it is, then to get most temporal details you'll HAVE to cap at full vertical res, while if the source is progressive, you can live (but still get lower quality) when capping half vertical res.
hope it helps
avi |
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| spockminov |
| Posted: Sep 3 2002, 03:05 PM |
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avih:
Thanks for the response. I tried capturing in full vertical-rez (x480) and then burned to SVCD, and you're right, it DOES look better. Guess that's the way to go. Also, I said my card couldn't handle (x480) capturing, but i figured out that's b/c I was trying to capture to DivX....capturing via Huffyuv it seems to work fine w/ no dropped frames.
In terms of horizontal capture rez:
" the horizontal resolution depends on your driver. i.e. if you capture at 320x480 it depends on the method in which your driver resizes horizontally. if it uses billinear, then it's relatively ok..."
How do I find this out?, you mentioned bilinear and "nearest neighbor". I use a std. Brooktree/Conexant 878 capture card/driver. Any ideas?
Thanks -- |
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| avih |
| Posted: Sep 3 2002, 03:46 PM |
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| QUOTE (spockminov @ Sep 3 2002, 05:05 PM) | In terms of horizontal capture rez:
" the horizontal resolution depends on your driver. i.e. if you capture at 320x480 it depends on the method in which your driver resizes horizontally. if it uses billinear, then it's relatively ok..."
How do I find this out?, you mentioned bilinear and "nearest neighbor". I use a std. Brooktree/Conexant 878 capture card/driver. Any ideas?
Thanks -- |
1. there's no such thing as 'standard bt8x8 driver'. the closest thing you'll get is the (much used and appreciated) opensource driver btwincap at http://btwincap.sf.net (and i don't know for sure what kind or resize method it uses)
2. just make the comparision yourself: cap at 640x480, and then resize to 480x480 (use billinear or bicubic resize) and keep the resulting clip. then cap directly to 480x480, and [encode to svcd if u need] and just choose the one that looks better/appeals more to u.
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