We had time code to sync a number of separate A/V recorders so that during editing you can cut from one to another seamlessly. I didn't calculate or look at how tight the sync had to be. The mobile cams could be out there for a while, maybe an hour or more, starting and stopping to change tapes and batteries, but with the time code it just worked.
On 05/07/12, J. Forster<[email protected]> wrote: A movie may be 7000 seconds, and you may need a fairly stable timebase, but every movie I've watched is made up of short (<300 second) scenes that are placed sequentially on the framework. You are not meshing together a pair or multiplicity of 7000 second event sequences. E#very time you edit in another scene, you put the bricks end to end, so to speak. -John =============== > One area where accuracy is important is not because of pitch (nobody can > hear 1ppm differences), but because of the need to synchronize sound > from different sources, particularly with video or motion picture frames. > > > 1000 seconds (20 minutes, give or take) with the sampler off by 1ppm > will be 1 millisecond out of sync, which is probably hearable, and is > 1/30th of a frame time. A 2 hour movie (about 7000 seconds) would be 7 > ms out of sync. > > Yes, we're not looking at needing Cs accuracy, but 10-20 ppm probably > isn't good enough. So you're pretty much not going to be able to use > the $10 oscillator in a can. > > So maybe a decent Rb, which is good to 1E-9 without doing anything > special, wouldn't be a bad thing. > > > And yes, there's a whole art to synchronizing stuff which was recorded > or filmed with incorrect sample rates, or ones that are "slightly off". > It wasn't too long ago that "quartz lock" for a motion picture camera > was something that was a "special order" from the camera rental house. > I used to modify PC video cards for external clock input so I could > adjust the refresh rate to match the camera speed (aka gen lock). > There's a time nuts challenge... synchronizing something normally driven > off a quartz oscillator (however crummy) to a mechanical device (the > movie camera shutter). > > And given the creative hierarchy on a set, it's going to be you that > adjusts to them, not vice versa. > > > There are directors who (for whatever motivation) also don't want things > like timebase correction used. Since I used to work for a physical > effects company, I thought that these guys and gals who are hung up on > the "purity of the process" were wonderful, since they typically wanted > "real" special effects, not something composited in later by optical or > computer techniques. > > There's a whole industry supplying 24/48 Hz refresh hardware, as > well. Well.. there used to be.. I'm not in that business anymore, and I > don't see credits for 24fps video as much, so they probably just paint > the screen blue or green or put registration dots on it and comp in the > images later. (Yes, I'm one of those people who watch all the obscure > credits at the end for things like assistant hod carrier and such.) > > _______________________________________________ > time-nuts mailing list -- [1][email protected] > To unsubscribe, go to > [2]https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- [3][email protected] To unsubscribe, go to [4]https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. References 1. mailto:[email protected] 2. https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts 3. mailto:[email protected] 4. https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
