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| mashadar |
| Posted: Jan 30 2003, 06:32 AM |
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Unregistered
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Frame: 32271
FPS: 2997/125 (23.976000...)
Time calculated: 22:25.970970970...
Time shown in vdub: 22:25.959
depending on rounding or cropping of value, that means 11-12 ms off from the correct value.
Since this is a proper OpenDML avi, vdub should be able to read the correct exact fps by the num/denum values, instead of relying on the time per frame value.
The error grows bigger the more frames there are in the avi.
I found this one while trying to figure out why textsub+avisynth didn't show subs on a frame where vdub+textsub did.
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| phaeron |
| Posted: Jan 30 2003, 07:56 AM |
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Virtualdub Developer
Group: Administrator
Posts: 7773
Member No.: 61
Joined: 30-July 02
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VirtualDub internally converts the video stream rate from rational form to microsecond form (scale*10^6/rate) for display and filter timing purposes. The roundoff error is thus(1000000*125/2997 - 41708) * 32271 = 12103 us.
Fortunately, I can improve the accuracy of some of the calculations without much trouble.
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| wanderering |
| Posted: Feb 24 2003, 09:39 PM |
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Unregistered
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Is this related?... When I try to set the capture frame rate to 29.97 VDub comes back with 29.9706? (Subsequently DVD2SVCD/AVI2SVCD complains about frame rate of the captured avi.) |
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| phaeron |
| Posted: Feb 25 2003, 03:18 AM |
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Virtualdub Developer
Group: Administrator
Posts: 7773
Member No.: 61
Joined: 30-July 02
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The framerate accuracy problem should be solved in 1.5.
As for the capture issue, that's a different problem -- Video for Windows accepts capture rates in microseconds, so 29.9706 is the closest you can get to NTSC rate.
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| fccHandler |
| Posted: Feb 25 2003, 03:56 AM |
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Administrator n00b
Group: Moderators
Posts: 3961
Member No.: 280
Joined: 13-September 02
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Actually, 29.96973 (1000000/33367) is a tiny bit closer. 
There's a related discussion here:
True Frame Rates?
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May the FOURCC be with you... |
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