RED Camera Audio Capability

[10s]

I'm curious, how good should the RED camera's audio be?

In other words, compared to Sony's f900 and other available models, what would be considered acceptable performance and features?

What should be left for the audio mixer and his/her gear? Where should the line be drawn?


thanks!

 

[Evin Grant]

I think cinema quality is a must, and I mean I should be able to record dialog on board that could be used in a theatrical release. As far as I can tell it's not bad even in this first incarnation, but I'm sure it'll get better.

 

[philper]

I think cinema quality is a must, and I mean I should be able to record dialog on board that could be used in a theatrical release. As far as I can tell it's not bad even in this first incarnation, but I'm sure it'll get better.

If they can make it as good as what an F900 records they've done a great thing considering how difficult it is to process analog audio within such a busy digital device in such a small chassis. When you say "cinema quality" I'm guessing you mean as good as the finest recorders used in film sound, the Aaton Cantar etc.. That's a great goal, but maybe a bit unrealistic in that the basic RED camera costs less than a Cantar. In any case, I've worked on many projects including feature films that went to theatrical with camera audio and got away with it. The more carefully recorded the production sound is and the more time is given to audio post to fix the inevitable problems the better the results will be. If Red can do better than the F900 on audio then they rock. Let's see some specs.

Philip Perkins CAS

 

[DNomer]

A few capabilities

A few capabilities

Here are three capabilities that are worth considering:

1. It might be nice to have some sort of audio clip indicator. What I envision is a purely digital thing where a DSP would count the samples whose absolute value is above a certain value (very near to clip), and give a little red line maybe at the top of the audio meter, or a red dot somewhere indicating some clipping if there were more than (some number) of samples considered 'too hot'. I think it would be cool if it would also show you how many samples were too hot, so you could have a good idea of the magnitude of clipping. This is analogous to zebra on video. If a limiter is part of the signal chain, this would affect the settings on this part. My view is that if only a few samples are too hot, it is probably not worth turning on the red line, and this would take some playing with to establish what is a reasonable number. The algorithm is utterly simple, just reset the counter when a new take is begun, then count every sample whose value (plus or minus) exceeds the threshold. When and how to display it could be discussed. I am not sure that the 'too hot' level needs to be user-settable. The sound guy on location has to listen for a bunch of things that could be wrong, and if you are shooting without a sound person it is even harder, so some sort of indication like this can be helpful. If you are running single system sound, and you see that a lot of samples were too hot, you might want to review the audio or notate the problem at a minimum in your audio log. Note that this is purely a digital thing, done by a DSP, and it would take almost no CPU power to implement, but it would be useful in the field, in my view.

2. A peak hold feature, to show how you are doing during audio setup, when someone is looking at the meters while sound is being measured, setting their audio levels. This could be shown with a little bar on the level meter, like other apps do it. You need to have an easy way to reset it, of course. This also is purely a digital thing, and it mostly needs to be operative during setup, although if processing power is available (it probably is), many people would probably like to have it working during takes, as well. The algorithm for this is somewhat fancier than the one above, but not by a whole lot.

3. Also worth considering, I think, would be a selectable (in or out) low cut, or high pass filter, as an analog filter, for recording dialog. Since a great deal of what actually gets shot, whether on high end or low budget productions, is dialog, optimizing for it to some extent is worthwhile. Let's explore some of the considerations in this area. I realize that you usually want to capture a certain amount of ambient sound as part of your location recording, and typically a noticeable amount of ambient sound is low frequency, precisely because it carries better (think distant traffic sounds). I also realize that this apparently violates the principle of 'Just give me all of the data, let me deal with it later in post, when I have the best tools.' Even so, there are two opposing considerations in this case:
a. In audio, higher frequencies 'ride' on lower frequencies, and too much level in lower frequencies can push the overall level too high. In other words, if there is an ambient low frequency sound, it can interfere with your dialog to the point of messing it up, so you are not 'getting all of the data' like you want.
b. In a way, this is somewhat like using a shotgun mic instead of an omni. We are providing a better 'focus' by filtering out some of the diffuse 'mud' that can exist in ambient sound. In particular, when people are going for top quality and willing to do what it takes, they normally want their dialog pristine, and they take extraordinary measures to reduce the environmental sound to near zero. They will then add a believable ambient sound in later. For example, when recording two people dancing amongst many others, the director might have all other dancers move their mouths as if talking, but say nothing, plus the 'music' will not exist on the set, and they get good takes of the principle actors talking, then later in post they add in the rest of it with extraordinary control, so that you can easily hear the actors.

The reason that some high end microphones have low-cut filters is that it can make sense to use them. In the case of location audio, it is not handy to dig into a blimp to mess with one there, and lav belt-packs are not a good place for one, so I think having one on the camera could be a nice tool. If a CMOS op amp was used on the high-level audio signal to do the filtering, it would take negligible power, cost only maybe 50 cents in manufacturing (I know it has to be in the shielded area, but these chips can be very small), and if the switching of it were rigged properly, you would not get into ugly signal routing. I am talking about a simple (not steep) filter that might have its corner at about 80 hz or so.

So anyway, the items above are a few talking points.

Dennis Nomer

 

[Evin Grant]

If they can make it as good as what an F900 records they've done a great thing considering how difficult it is to process analog audio within such a busy digital device in such a small chassis. When you say "cinema quality" I'm guessing you mean as good as the finest recorders used in film sound, the Aaton Cantar etc.. That's a great goal, but maybe a bit unrealistic in that the basic RED camera costs less than a Cantar. In any case, I've worked on many projects including feature films that went to theatrical with camera audio and got away with it. The more carefully recorded the production sound is and the more time is given to audio post to fix the inevitable problems the better the results will be. If Red can do better than the F900 on audio then they rock. Let's see some specs.

Philip Perkins CAS

I don't think as good as a Cantar is necessary but an F900 definitely, and it's already got a better DR so even if it's as good it's still better.

 

[10s]

Dennis, the high pass, or should I say, Dialog pass filter is a really nice idea. Often times the low freqs < 125 hz or so mud everything up while a slight 1 to 2 db bump up on 140 hz helps adds a little meat to the voice. While I use the mic roll off to loose the mud, the idea of a customized EQ for the voice could be very handy. Maybe one for men (low), another for men/women (mid) and then one for women, (high). And then another that is flat, but rolls off the low end.

 

[DNomer]

Camera Audio Capabilities

Camera Audio Capabilities

There is a great post by Ty Ford (all of his stuff is excellent) on this subject, in the Shotgun thread, of all places! (Post #65 of that thread).

dn