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| Unofficial VirtualDub Support Forums > Testing / Bug Reports > Rolled Edges On Resize V1.9.11 |
| Posted by: MrSmite May 8 2011, 06:02 AM |
| While resizing a video I noticed that the edges have this "rolled over" appearance. I initially thought it might be an artifact in the editor but unfortunately it carries over to the rendered video as well. Here is a screenshot of the original vid in MPC HomeCinema and the resized version in VirtualDub. I've hilighted the area in question: http://imageshack.us/photo/my-images/695/rollededge.jpg/ You can see in the larger version that the edge between the image and black has a wide "rolled" look to it. Video details: Type: AVI (hex editor shows standard RIFF header with 'vids MSVC' listed) Original Size: 320x156 Decompressor: Internal DIB decoder (original is uncompressed) Resize: 720x351 (preserve aspect, lanczos3, letterbox / crop to 720x480) Edit: If I open the video using the DirectShowInputDriver, the "rolling" only occurrs on the bottom rather than bot bottom and top. |
| Posted by: pintcat May 8 2011, 10:57 AM |
| I assume this effect is part of the resizing. Do you really need those black bars at the top and bottom of the picture? You should reduce the frame to it's actual size by cropping them away. |
| Posted by: MrSmite May 8 2011, 06:28 PM | ||
The original video doesn't have the black bars. I can see though that the image I posted might be a bit misleading. The part of the image that shows the video playing in MPC HomeCinema only has bars because I dragged the corner of the player to make it a little larger. The normal playback has no bars as seen here: http://imageshack.us/photo/my-images/156/originalud.jpg/ The VirtualDub portion has bars because I added them to make the video DVD compliant (720x480) because when I resized the width to 720 the height only went to 351. My ultimate goal is to make the video 16:9. I guess I don't understand the process. |
| Posted by: pintcat May 9 2011, 07:20 AM |
| Are you planning to make a DivX or XviD video for your DVD player? In that case you don't need to resize the video to a perfect 16:9 aspect ratio. The only thing you have to consider is that all edges have to be divisible by at least 2 (hence 720x351 won't work; change it to 720x 352). |
| Posted by: MrSmite May 9 2011, 09:32 PM | ||
I use TMPGenc to compress the video and then Sony DVD Architect to create the actual DVD with menu. I thought I had to make a 16:9 so that it doesn't look like a postage stamp when played on a 16:9 TV. What I'm trying to replicate is something like the Widescreen Lord of the Rings. I can play that on a 4:3 TV and it has black bars on top/bottom or I can play it on a 16:9 TV. I just can't seem to figure out the math to make a proper 720x480 anamorphic video when the source is a non standard size. |
| Posted by: pintcat May 10 2011, 12:57 AM |
| Ah, now I get it: an anamorphic DVD display! OK, assuming the pixel aspect ratio (PAR) of the source video is 1:1, you should try the following procedure: First of all you need to know the pixel aspect ratio used by your anamorphic 720x480 (16:9) display. The formula should look like this: (16/9) / (720/480) ~ 1.1852 So your PAR is about 1:1.1852. The next step would be to multiply this with the vertical number of pixels (156) which should result 184.8912 and then scale the new frame size 320x184.8912 to the desired size (in your case 720x416; remember: always round to the next value divisible by 2) - that's it. Two little points: 1. When usin TMPGEnc you don't need to add black bars by hand to fill the aspect corrected frame. Just resize the picture as you like and then save it as a standard DVD video. TMPGEnc will automatically center the picture and add black bars if necessary. 2. IIRC the DVD standard accepts the old VCD standard resolutions too. And since up-scaling doesn't actually improve the picture quality, but increases the amount of data to be processed/stored, you might want to use one of these lower resolutions. |
| Posted by: MrSmite May 10 2011, 04:09 AM |
| @pintcat Thanks for that, I'll give it a shot. The only reason I was adding the bars is because I found the bars that TMPGenc added weren't black but grey. They were clearly visible on the TV (an old 4:3 CRT, not one of the new LCD ones). Two questions though: 1) When you say "scale to your desired size", how does this play out in VDub? If I type "184" into the height on the resize filter, it changes the width to 377. Should I disable the aspect ratio option? After that, do I then simply type "720x416" into a second resize filter? 2) Is the rolling edge I posted an artifact with VDub or is it because my calculations are wrong? |
| Posted by: pintcat May 10 2011, 09:14 AM |
1: Yes, disable the aspect option, because you don't want to keep the old aspect ration, but stretch the picture to fit into the new (16:9 anamorphic). And no, you don't have to use a second resize filter. If you still want to scale th picture to 720x416 then simply do it in one step  2: As mentioned before, I assume this edge effect is part of the scaling and might occur in other tools as well. Did you test other resize algorithms? I.e. "Nearest neighbor" which gives a pretty ugly picture quality, but shouldn't have "rolled edges". Also make sure that if you play back the video (no matter if with MPC or VDub preview or whatever) you always watch it with it's original size - no enlarging or fullscreen - for the most accurate effect. |