actually if drift stays constant, then it is very simple to fix in cinelerra.. just right click on asset, and change frequency from 48000 to 48002 or some similar value - depending on the scale of your drift.
The only trick is that you have to do that _before_ you start dragging edits to the timeline and before creating clips. bye andraz On Mon, 2007-02-12 at 09:11 +1030, Jonathan Woithe wrote: > Hi Scott > > > > I'm glad to hear it. The symptoms were a little strange though, even for > > > a TOC issue. Oh well, at least the result is consistent now. > > :) > > > > > > No problem. Even though things appear to be working now you will still > > > suffer from the problems I mentioned. You might just be lucky in that in > > > this particular case your sources were sufficiently close in frequency > > > such > > > that the drift over the 4 minutes of footage wasn't particularly audible. > > > As your clips get longer it is guaranteed that your sync will drift unless > > > all digital audio recording sources are locked to the same clock. The > > > amount of drift (and therefore the maximum clip length before you notice > > > it) > > > depends on how close the recorders' clocks were, which is indeterminant > > > since there's a temperature dependency in the frequencies. > > > > Interesting. This drift stuff is a nightmare. Next recording, we'll > > sync to a clock source! :) > > Yes, it is a pain. Syncing everything to a master clock is the best > solution. However, since only high end cameras have an external syncing > options and the external clock units themselves can be quite expensive it's > often not possible to do this. That in the end is why I use the workflow > described eariler; it's a little more time consuming but still a lot cheaper > than an externally clockable camera. :) > > FYI one thing I've thought of doing is making an audio clock generator which > locks to the camcorder. The idea is to take the video output from the > camcorder (which by definition is locked to the *video* clock) and detect > the sync pulses (probably vertical). This will give a 50 Hz signal. This > would then be fed into a phase locked loop (PLL) which would generate the 48 > kHz clock signal for the audio hardware. It's a good theory but there are > issues. It assumes that the PLL can be made incredibly stable; if it > jitters any more than the internal clock of the audio interface it will have > a negative impact on the recorded audio quality - to achieve this it might > be necessary to go into temperature control. It also assumes that the > vertical sync pulses out of the camcorder are stable. > > Unfortunately I've had no time to pursue this further than thinking about > it, so I don't know how feasible it is in practice. Some day I might get > around to it though. > > Anyway, we're getting a bit off-topic here. Best of luck with your future > projects and feel free to follow up privately on these matters and to let > me know how you get on. > > Best regards > jonathan > > _______________________________________________ > Cinelerra mailing list > [email protected] > https://init.linpro.no/mailman/skolelinux.no/listinfo/cinelerra _______________________________________________ Cinelerra mailing list [email protected] https://init.linpro.no/mailman/skolelinux.no/listinfo/cinelerra
