There's a related discussion here:
http://virtualdub.everwicked.com/index.php?act=ST&f=2&t=1770&s=853e0dc4057cb0ceebbeca155182fe1b
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| Unofficial VirtualDub Support Forums > Testing / Bug Reports > Incorrectly Calculated Frametimes(?) |
| Posted by: mashadar Jan 30 2003, 06:32 AM |
| 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. |
| Posted by: phaeron Jan 30 2003, 07:56 AM |
| 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. |
| Posted by: wanderering Feb 24 2003, 09:39 PM |
| 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.) |
| Posted by: phaeron Feb 25 2003, 03:18 AM |
| 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. |
| Posted by: fccHandler Feb 25 2003, 03:56 AM |
| Actually, 29.96973 (1000000/33367) is a tiny bit closer. There's a related discussion here: http://virtualdub.everwicked.com/index.php?act=ST&f=2&t=1770&s=853e0dc4057cb0ceebbeca155182fe1b |