All keyframes off by 2 frames

[argentine_target]

Sometimes Virtualdub will make all the keyframes in an avi file be off by 2 keyframes. I know the keyframes are wrong because they are always 2 frames before a change in the scene, which is where keyframes are put most of the time.

Closing and restarting Virtualdub doesn't change things. If Virtualdub has the keyframes correctly, it will always have them that way for that file. If it has them messed up, it will always show them in the same messed up way.

If I save a segment of the avi with direct stream, at the beginning of the new movie clip there will be a very quick flash of the previous scene (the 2 frames from just before the scene changed).

[squid_80]

Questions:
a) What codec does the avi file use?
b) Which version of virtualdub? Latest is 1.6.11.

[stephanV]

I'm pretty sure that this is caused by using b-frames, although it should be impossible to show a flash of the previous scene because those frames are not decodable if the first one is not actually a keyframe (in which case VirtualDub would be correct)

[bond]

you could show flashes if the keyframes are actually on the wrong position (eg 2 frames before the scenechange) :D

[argentine_target]

None of you have ever experienced this? It happens to me every 30 or so files.

[Haze_NZ]

Could this have anything to do with NTSC and the 29.97fps as opposed to 30fps?

[stephanV]

None of you have ever experienced this? It happens to me every 30 or so files.
Upload a sample somewhere, I really have never seen this.