RCX-P Audio syncing - 48khz question

[alexo]

Hi,

I`ve been learning the timecode dual system auto match feature in RCX-P. I`ve recorded my RED footage at 23.98 and my audio at 48.000 hz with a 23.98 timebase. Both are jammed with timecode.

After running automatch, in the control section of the audio tab, it shows 48hz as the frequency, but it shows 48.048 as the TC frequency.

Do I need to override this to get both the "frequency" and "TC frequency" to match and both display 48.000hz?

Or is RCX handing the compensation correctly already, due to the footage being shot at 23.98, and I should leave it alone? I would be rendering the synced clips to ProRes with the synced audio attached for a Final Cut 7 project.

Thanks

 

[Alcove Audio]

I'm not up on RED/SCARLET work flows, but I've heard that there are some issues when using any audio format other than BWAV.

I noticed that you also posted at RedUser; if they can't help you I don't know who can, except maybe http://jwsoundgroup.net/.

One thing from my own experience is that there is usually a missed "button" in the menu, a conversion problem, or misunderstood (or poorly given) instructions. I remember that when the Yamaha DX-7 synthesizer came out the manual was almost incomprehensible. One issue was that the Japanese manual was translated into French and from there into English - by native Korean speakers.

And, of course, the old movie joke where the hero is defusing a bomb;

"Cut the green wire..."

Snip

"..but first..."

 

[AudioPostExpert]

After running automatch, in the control section of the audio tab, it shows 48hz as the frequency, but it shows 48.048 as the TC frequency.

The terminology here is unclear. I take it the audio sample rate is 48kFs/s, which is entirely standard for film/TV audio and the frame rate is 23.98 (23.976), standard for HD video. There is a frequency associated with LTC (Longitudinal Time Code), the frequency of the bi-phase modulated signal but that ranges from 960Hz to 2400Hz depending on frame rate, there is not as far as I'm aware a 48.048 LTC frequency.

However, I am familiar with an audio sample rate of 48.048kFs/S. 48.048kFs/S is the pull up rate used to convert audio recorded at 23.976fps to match a frame rate of 24fps. Conversely when recording to film at 24fps and then editing with a HD intermediate a sample rate of 48.048kFs/s should be used when recording the production sound so it can be pulled down to 48kFs/S in audio post to sync with the 23.976fps digital intermediate. So for some reason your software is trying to perform this sample rate conversion where it shouldn't be necessary as you are working to 23.976pfs throughout.

So, there are 3 possibilities:

1. You recorded your video at 24fps and your software is informing you or has already pulled up the audio to match.
2. There is some incorrect setting in your software which is making it believe you are running at 24fps and/or telling it to pull up your audio on import.
3. Your software has a bug.

If your video is at 23.976 and your audio has been pulled up to 48.048kFs/S, the audio will drift relative to the picture by 0.1%. It's still the incorrect terminology though, to call it TC frequency.

G