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| sswroom |
| Posted: May 30 2003, 04:56 PM |
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Unregistered
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Test file:
http://sswroom.uhome.net/test-.avi
Procedure 1:
1 open the file
2 Video > Direct Stream Copy
3 Video > Framerate
4 Frame rate conversion > Convert to fps: 119.88 (source rate = 23.976, 1:5)
5 Save AVI
Result 1:
Source file contains 3 frames only. The output AVI file contains 14 frames (not 15 frames??).
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Procedure 2:
1 open the file (same file)
2 Video > Direct Stream Copy
3 Video > Framerate
4 Source framerate adjustment > Change to 29.97 frames per second
5 Frame rate conversion > Convert to fps: 59.94
6 Save AVI
Result 2:
Source Frame type: (K = Key frame, D = Drop frame, d = delta frame)
0 K
1 D
2 d
Output Frame type:
0 K
1 D
2 D
3 D
4 D <-- Why add drop frame here, not adding after delta frame?
5 d
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| phaeron |
| Posted: May 31 2003, 02:15 AM |
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Virtualdub Developer
Group: Administrator
Posts: 7773
Member No.: 61
Joined: 30-July 02
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These aren't bugs, I'm afraid -- they're caused by roundoff errors due to mixing rational and decimal frame rates.
In your first case, your file is NTSC FILM (24000/1001 fps), but your actual target is 11988/100 fps. The actual ratio between the two is a tiny bit less than 5:1, which with point sampling is enough to ensure you get one frame less than you expected. This is a UI issue -- the engine itself receives the conversion target rate in rational form and you can specify the exact value by editing the script.
In your second case, the problem is that the "adjust frame rate" value actually sets frame period in microseconds rather than rational or decimal. (This is a legacy adjustment that needs to be fixed.) The actual frame rate is 1000000 / round(1000000 / 29.97) = 29.9697 fps, meaning your conversion ratio is 59.94 / 29.9697 = 2.000004:1. As it happens, that 0.000004 resulted in an extra frame early in the process. Unfortunately, in this case you can't easily work around the issue as the engine only accepts periods in microseconds. You can, however, edit the dwRate/dwScale values in the AVI file directly to (30 75 00 00 E9 03 00 00) without too much difficulty.
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