1/2 frame difference audio

[William Hohauser]

You are correct, there is no way to notice an audio sync issue on a sub-frame level if that's the only audio track in use. However if you are combining tracks there will be a delay effect.

[Brian Drysdale]

That's ok, I was wondering about the reasoning behind the concern.

[Paul R Johnson]

FCP, like Premiere mentioned above has the ability to shift the audio track in smaller increments.
From Apple:

While the smallest unit of video is a single frame, the smallest adjustable unit of audio in Final Cut Pro is 1/100 of a frame. Audio level and pan keyframes, as well as the sync between the video and audio tracks of a clip, can be set with an accuracy of 1/100 of a frame.

[Mark Watson]

Originally Posted by David Slingerland

hello everyone,

I used my 5D and put on a rode videomic, I have been using a transmitter as a second source. I used a clap as reference. In fcp7 i tried to put the audio together, but there seems to be a half frame difference. Does any body see a solution? do I need to get plural eyes?

I don't know how to eliminate the problem, other than placing a wired mic close to the source. Due to the speed of sound being 1,126ft/sec, video shot at 24fps, will have an audio delay of 1/2 frame for every 23 feet of distance between the source and the mic. I haven't done any testing with my wireless, but I'd think the processing electronics would introduce a small amount of delay which would be more constant (easier to fix in post) as opposed to shooting near and far subjects where the distance the sound travels causes a variable amount of delay.

[David Slingerland]

hello , again, I also seem to have some performance issues with fcp(7). I used to be able to listen to audo playing at a faster speed in the viewer, but that seems to be gone. And material in the timeline will sometimes not play directly but show the colorball and for several seconds not play, then I will hear the mediadrive. Now I have a 2011 27 inch Imac full specs, two drives 1 TB Sata drive (MEDIA) and flash drive for the programs and OS. I maxed out the memory and have a good benchmark score so I cannot be the computer. I edit in proress material from my 5D. Could it be the speed difference between the flash drive and SATA drive?

[William Hohauser]

A flash drive? I hope you don't mean one of those USB sticks. Those are much too slow and the USB connection isn't so fast either. Preferably the OS (and by default the programs) should be on the internal drive but it can be on an external drive connected by FireWire800 or Thunderbolt. USB can be used but it will slow down the computer.

[Paul R Johnson]

There's no delay in analogue processing, and to be honest, my digital radios to all intents and purposes have negligible delay. Distance is the key.

[David Slingerland]

no both are internal drives, latest fastest technology.

[William Hohauser]

Download the free AJA system test program from their website, run the tests with the file dimensions you are using (probably 1920x1080) and see what speeds you are getting from your media drives. How are your SATA drives connected to the iMac, FireWire or Thunderbolt? Generally if you have high quality solid state drives you should call them SSDs so not to confuse them with the cheap thumb flash drives that are everywhere.

[David Slingerland]

yes I have one SSD drive and one sata drive, they came preinstalled. The disk whack test score is 80 mb/s for the media(sata) drive. How well is that ? I have also one lacie external sata drive, firewire connected (800) that gives almost the same score.

[William Hohauser]

80 is good. More than enough for ProRes. How full are the drives? Have you ever run a disk repair program such as Diskwarrior?

[David Slingerland]

Thanks William, I figured it out, everytime I could hear the drive starting up and because of that the color ball appeared. Its a new computer and I simply forgot to change the settings !! my drive kept going in to sleep mode....I feel a bit stupid...