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| i2mc |
| Posted: Jul 8 2003, 11:28 PM |
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Unregistered
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Hi
My problem (which I believe is a bug) is as follows;
I have a standard set of filters I automatically apply to clips, I've started noticing problems with bold captions as follows;
I start with a white (not 100%) on black caption which is 720 x 576
Filter 1 is de-interlace
Filter 2 is resize to 352 x 288 (standard PAL MPEG1 size)
The preview shows fine, but the actual AVI produced (using MPEG4 V2 codec) exhibits blocky corruptions - kind of as if some macro blocks are being put in the wrong place.
If I resize to 360 x 288 (the neat division by 2) the problem seems to go away.
I've tried various options on the resize such as bilinear / bicubic etc but all that does is move the corrupt blocks to a different part of the screen.
Also, I've tried cropping the image as well and it causes really weird things to happen - for example the caption shifts maybe 1/3rd of the way across the screen and wraps around to the start again.
I've posted a before and after processing image to show what the fault looks like.
http://www.moffatt.uk.net/vdubfault.gif
Any thoughts?
Thanks
Roger
PS. Version in use is VirtualDubMod_1_5_1_1a, system runs XP home with windows media player 9.
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| fccHandler |
| Posted: Jul 9 2003, 12:26 AM |
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Administrator n00b
Group: Moderators
Posts: 3961
Member No.: 280
Joined: 13-September 02
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Ah, I know it well. This is not a fault with VirtualDub, it's a known fault of the MS MPEG4 codecs. Pardon my language, but the technical term for it is "shit." IIRC Nandub had an "anti-shit" checkbox that was supposed to correct exactly this artifact. It mostly occurs in high-contrast areas (like credits) and the general belief is that it's caused by an overflow error in the codec. It can also be seen in the DivX ;-) hacked codecs.
I recommend upgrading to the latest DivX.
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May the FOURCC be with you... |
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| i2mc |
| Posted: Jul 9 2003, 12:00 PM |
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Unregistered
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| QUOTE (fccHandler @ Jul 8 2003, 06:26 PM) | | Ah, I know it well. This is not a fault with VirtualDub, it's a known fault of the MS MPEG4 codecs. |
Many thanks for the speedy reply :-) I actually end up coding MPEG1 and MPEG2 and was just using the MPEG4 as an intermediate codec for the deinterlaced AVI to help out on disk space. It seemed like a good idea at the time ...
I'll swap codecs
Thanx Again
Roger |
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| fccHandler |
| Posted: Jul 9 2003, 05:30 PM |
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Administrator n00b
Group: Moderators
Posts: 3961
Member No.: 280
Joined: 13-September 02
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Depending on the MPEG encoder, you might be able to frameserve VirtualDub's output and avoid using an intermediate file. I know this works great with TMPGEnc (not sure about other encoders).
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May the FOURCC be with you... |
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