Audio at Different Frame Rates

[MDP16]

Hey I was wondering if the RED was going to be able to record audio at all the frame rates. I have been using the HVX and there are no audio capabilites using under or over cranked frame rates. It would be amazing if RED could solve that problem. Slow motion audio is key for action sports stuff.
Thanks,
Mike McEntire

[David Mullen ASC]

Yes, but the notion of "sync sound" is sort of meaningless in a slow-motion shot which is why usually when you shoot a slow-motion shot, you only record the audio as a guide track, if at all, just in case they want to slow-down the sound in post to match. But usually you aren't shooting a dialogue shot in slow-motion anyway, other than the classic "Nooooooooo...." when someone sees someone getting killed, shot, etc... Most sound effects for a slow-motion action scene are created in post -- the production audio isn't that interesting usually (since people don't really hit each other, for example, and stuntmen land on pads, half the gunfire sound is added later, etc.). Production sound is primarily concerned with recording dialogue, leaving things like footsteps, body crunches, explosions, etc. to post.

Assuming you can even lay down audio as the RED camera is running at 48 fps, let's say, the question is whether when it's played back in a 24 fps timeline, will the audio be equally slowed-down.

[Desert Rune]

Planet Earth HD on BBC and Discovery Channel has some of the best sounding slow-motion audio I've ever heard, especially the super slow motion shot of the Great Whites. Fantastic stuff. I think all of it is foley and post audio... amazing work.

Guess what I am saying is for variable frame rate video, audio post is the only route possible to achieve the best sounding tracks.

[MDP16]

Yes, but the notion of "sync sound" is sort of meaningless in a slow-motion shot which is why usually when you shoot a slow-motion shot, you only record the audio as a guide track, if at all, just in case they want to slow-down the sound in post to match. But usually you aren't shooting a dialogue shot in slow-motion anyway, other than the classic "Nooooooooo...." when someone sees someone getting killed, shot, etc... Most sound effects for a slow-motion action scene are created in post -- the production audio isn't that interesting usually (since people don't really hit each other, for example, and stuntmen land on pads, half the gunfire sound is added later, etc.). Production sound is primarily concerned with recording dialogue, leaving things like footsteps, body crunches, explosions, etc. to post.

Assuming you can even lay down audio as the RED camera is running at 48 fps, let's say, the question is whether when it's played back in a 24 fps timeline, will the audio be equally slowed-down.

David for the type of work I do it is really helpful to have slow motion sync sound. I shoot action sports and it is a real benefit to have the action sounds in sync with the shot whether they are shot in real time or slow motion. It adds a lot to the shot. Also we are in pretty remote locations where extra sound equipment is not going to be used. I really hope that the camera has this capability.
Thanks
Mike McEntire

[Jeff Kilgroe]

This same question and discussion can be found in this older thread (http://www.reduser.net/forum/showthread.php?t=328).

But the question was never answered. I want to assume that audio will be recorded, regardless of which frame rate the camera is shooting at. It would also be nice to have additional sampling abilities beyond 48KHz. To be able to record sync'd audio at any frame rate, would be a godsend.

[Alex Boothby]

Just did some digging. About 8 months ago there was a similar thread on dvxuser:

http://www.dvxuser.com/V6/showthread.php?t=72815

I asked:

" ...would it still be possible to record standard audio when shooting offspeed? Even if it's just a primative "wild audio grab" of the event that we have to re-synch later? You know - for those great 60fps shots of people screaming "Nooooooooo...." that are a must for every serious film."

Greame replied:

" I think all we can do for audio in off-speed modes is record it to a seperate file and let you do with it what you will. Does that make sense?

Graeme"

- hope that helps.

[Jeff Kilgroe]

That's really all we can expect though, isn't it? You record 10 seconds of footage, the camera writes that and the corresponding 10 seconds of audio to your storage media of choice. It doesn't matter if you were shooting 2fps, 24fps or 60fps. Any audio squeezing, stretching or FX will have to be done in post. It would be nice to have higher sampling rates too, especially for shooting overcranked and then stretching the audio to match slower frame rate playback...

[tj williams]

AV
AS we use overcranking the system is getting closer to the max it can record.
so probably that is the very point where we may not get higher audio data rates. Hey fit to fill for the audio should make anyone happy... how much off speed sound is violins anyway???

[Jeff Kilgroe]

AV
AS we use overcranking the system is getting closer to the max it can record.

I agree... And right now, we can only speculate as to just how much head room there is when recording data to the RED DRIVE and other media. We also don't know if the audio processor is even capable of rates higher than the 48KHz that has been mentioned or if audio processing may be sacrificed as the requirements for image capture increase (higher frame rates). Lots we don't know... Two threads on this subject over the past 2 months and no answer from RED. Also no audio functions enabled for the PJ shoot... There's a good bet that all audio functions are still very much in development and there's no firm answers yet.


so probably that is the very point where we may not get higher audio data rates. Hey fit to fill for the audio should make anyone happy... how much off speed sound is violins anyway???

I think the fit to fill is all we can realistically ask for. And that should be fine for everyone -- I can just see where higher rates to match overcranked frame rates would be a great thing. But that may just be something that needs external audio systems to get it done.

[I Bloom]

It doesn't make a lot of sense to complicate the audio hardware to compensate for frame rate changes. Especially since this is very undesirable when switching between 30, 29.97, 24, 23.98 and PAL frame rates. We really just need 48Khz matched up to the first frame of each video file.

In an earlier thread Stuart mentioned that RED video audio and metadata are all stored together in roughly 2GB file chunks. Based on that my guess is that a higher frame rate just means fewer audio samples per frame but still running at 48khz.

This makes more sense than overcranking audio sampling rates to match the frame rate. Since the frame rate is included in metadata it might be possible to automatically resample audio in post to get it in sync.

Here's a feature I'm interested to see what peoplpe would think of: Wild sound/room tone mode. No picture. Yay or Nay?

[Alex Boothby]

Here's a feature I'm interested to see what peoplpe would think of: Wild sound/room tone mode. No picture. Yay or Nay?

Right on! That would be very useful.

[David Mullen ASC]

Well, just as with an HD camera, you could just put the lens cap on and run the camera to record sound with a black picture (or switch to color bars).

The advantage though of the sound recordist also carrying a separate recorder, not just sending audio to the camera's recorder (which makes sense in order to not have to sync dailies) is that he is free to record material during the day without bothering the camera crew, like a wild line here and there, in some corner with the actor, while the crew is out to lunch or setting up the next shot. Or he can playback the audio whenever he feels like checking something, without touching the picture recording.

[I Bloom]

Well, just as with an HD camera, you could just put the lens cap on and run the camera to record sound with a black picture (or switch to color bars).

The advantage though of the sound recordist also carrying a separate recorder, not just sending audio to the camera's recorder (which makes sense in order to not have to sync dailies) is that he is free to record material during the day without bothering the camera crew, like a wild line here and there, in some corner with the actor, while the crew is out to lunch or setting up the next shot. Or he can playback the audio whenever he feels like checking something, without touching the picture recording.

That's definitely the way to do it. Unfortunately sometimes the trend on HD shoots seems to be just a mixer/boom operator. Sometimes even just mixing in camera. The no picture feature isn't one I'd push to hard for, or even at all, besides if audio is always running you could get roughly the same thing by just undercranking heavily.

IBloom

[Caesar]

Hey I was wondering if the RED was going to be able to record audio at all the frame rates. Me too. Any update?