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-   -   ATI MMC and 704/720 resolution thoughts? (http://www.digitalfaq.com/forum/video-capture/163-ati-mmc-704-a.html)

admin 02-15-2005 09:19 AM

ATI MMC and 704/720 resolution thoughts?
 
ATI AIW cards, and ATI MMC, can run into 720 vs 704 resolution problems. :unsure:

Others here may find this informative:

Quote:

You may or may not know that the correct full PAL capture resolution with a Radeon card is 704x576. That's the resolution ATI MMC offers for AVI capturing. If you capture 720x576 the picture gets stretched a little and the aspect ratio won't be 100% correct anymore on your TV when you author a DVD. To keep the correct aspect ratio the picture should not get stretched, but black bars should be added to the left and right. Those black bars should be eight pixels wide: 8+704+8=720. However, 704x576 is a DVD compliant resolution, so adding black bars is unnecessary, as long as you don't resize 704x576 to 720x576.

Unfortunately, 704x576 is not available for MPEG-2 capturing: 720x576 is available but this causes a slightly wrong aspect ratio on a TV if you use the 720x576 MPEG-2 file for DVD authoring because the picture gets stretched. I've explained this in Dutch (with a little German thrown in) on this Web page. Dutch is gibberish to most people, but if you scroll all the way down to the bottom of that page you can see the distortion it causes. The picture switches between te correct aspect ratio (with black bars) and the wrong aspect ratio (without black bars) continuously. The area inside the yellow rectangle is approximately what you see on your TV, the rest (including the black bars) is hidden by your TV's overscan. Maybe most people don't mind a small distortion like that, but I do! ATI MMC should offer a 704x576 MPEG-2 template.

There is a way to capture 704x576 MPEG-2 with ATI MMC 8.7 by changing a registry key though. (I once tried it with an older version of MMC but it didn't work then.) Here's what you have to do to capture full PAL 704x576 MPEG-2:

1. Create a custom MPEG-2 template with ATI MMC by editing the available DVD template. Keep the 720x576 resolution for now. Give the template a new name, like DVD 704 or something like that. Make this template your default capture template.

2. Now close MMC and locate the following key in the registry:
[HKEY_CURRENT_USER\Software\ATI Technologies\MultiMedia\Features\TV\Video Capture\MPEG]
That's where MMC stores your custom MPEG-2 templates. Select your new template and change the Width key to 704 decimal (or 2c0 hexadecimal). You may notice that the Height is set to 288 (120 hex). Don't change that!

3. Now run MMC again and start capturing. You should get a 704x576 MPEG-2 file. I've tried it and it definitely works on my system. That file is DVD compliant and any good DVD authoring program should accept it without complaining and - very important! - without resizing it to 720x576 and re-encoding it.

If you look at the settings for your new template with MMC's Personal Video Recorder you will notice that it's listed as 704x288. Don't worry about that, 704x576 is what will be captured. If you edit your new custom template with MMC the 704x576 resolution will not be retained however. You will have to use the 720x576 resolution again and afterwards change the width to 704 in the registry. A small price to pay for perfection.

I assume this also works for NTSC 704x480. You may have noticed that 720x480 AVI is no longer available in MMC 8.7. I'm sure ATI had a good reason for changing it to 704x480, but I can't test that myself. Anyway, the full 720x480 NTSC frame should contain small black bars to the left and right since analog NTSC has no more than 711 active pixels per scan line (analog PAL has no more than 702 active pixels per scan line). If the 720x576 frame doesn't contain any black bars, then 704x480 (NTSC Cropped as Vegas 4.0 calls it) is a better resolution than 720x480.

One more thing: the DVD Medium templates (352x576 PAL or 352x480 NTSC) don't need changing. Your DVD player will stretch 352x576/480 to 704x576/480 so the aspect ratio will be correct on your TV. The SVCD template is not correct, however, because 480 gets stretched to 720 by a DVD player, so anyone who uses MMC for capturing straight to SVCD MPEG-2 is creating SVCDs with a slightly wrong aspect ratio. I would change the SVCD template to 352x576/480 and make a CVD instead.
from http://www.rage3d.com/board/showthre...eadid=33724603


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