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| virtualxx |
| Posted: Oct 9 2002, 03:13 PM |
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Unregistered
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Using Win2K on a 1.5Ghz Dell Precision 330 and a AverTVStudio board and using BtWinCap drivers for the board with Vdub 1.4.10, why does 320x240 capture frame drop like crazy, but 640x480 capture fine? 288x352 captures fine too (no frame drops), but it has a bad case of the jaggies.
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| BaronVlad |
| Posted: Oct 10 2002, 07:17 PM |
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Terrorhörnchen
Group: Moderators
Posts: 335
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Joined: 12-July 02
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Higher resolution is btter anyway, but you have to deinterlace then.
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Hochachtungsvoll
BaronVlad
Deutsch >> Capture FAQ - Capture Guide
Englisch >> Capture FAQ - Capture Guide |
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| Kippesoep |
| Posted: Oct 11 2002, 05:36 AM |
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Moderator of the Virtualdub support forum
Group: Moderators
Posts: 447
Member No.: 441
Joined: 6-October 02
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This is apparently a problem with the Bt8xx hardware and certain unsynchronised video source, such as VHS tapes. Not much you can do about it except experiment which video format is captured correctly and then resize to whatever size you need. |
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| JanMann82 |
| Posted: Oct 25 2002, 03:57 PM |
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From Virtualdub.org
Why do I get errors when I try to capture with a height above 240 (288 for PAL/SECAM)?
The BT8x8(A) can only DMA to one destination at a time, and the output pixel format can only be set on a per-field basis. If you specify Overlay mode, then the capture driver will instruct the chip to DMA one field to memory for capture, and the other field to the video card. The catch is that if you are capturing both fields, both DMA lists have to point to main memory. This means that overlay mode is impossible when both fields are captured, and depending on your exact driver, you will either have overlay disabled when the capture starts, or, as is more often the case, get a cryptic error about being out of memory. Note that this is not a bandwidth issue -- you can capture 640x240 in overlay mode, but not 80x480.
To "fix" the problem, specify Preview mode; this unfortunately is slower since the CPU is now doing a blit from the captured frame to the video card. It may be that your system is not fast enough to handle this, in which case you will need to disable the video preview entirely and capture blind. A secondary consequence of all of this is that you see exactly what is being captured in Preview mode, while you are actually seeing the other field in Overlay. If you have a strange source where one field is much cleaner than the other, it is possible with an Overlay display that you will see a clean display on screen and end up capturing crap. (I have had this happen.)
Perhaps it will help you
Jan
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| Kippesoep |
| Posted: Oct 25 2002, 04:00 PM |
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Moderator of the Virtualdub support forum
Group: Moderators
Posts: 447
Member No.: 441
Joined: 6-October 02
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JanMann, I think you have it backwards. In this case, high resolution works, but low resolution doesn't. This has nothing to do with the DMA restriction and happens no matter whether overlay and/or preview are enabled or not. |
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