Recording line level audio

[Jeremy Neish]

PS- If this camera is supposed to revolutionize the non-linear video world and possibly replace the film camera, then why the hell did they bother putting an audio section on it. Leave the audio to the Sound Dept. and the video to the Camera Dept.

Because this camera is designed to be flexible enough for more than just film style shooting. There are many times when I am using the camera without a sound department at all (in fact most of my shoots which are industrial, ENG or one man shoots, and have a dedicated sound department). Sometimes I get a little tired of so many folks viewing the camera as just a film-replacement camera, I see it as much more.

 

[Scott C.]

... then why the hell did they bother putting an audio section on it. Leave the audio to the Sound Dept. and the video to the Camera Dept.

I can think of a couple reasons:

1. For projects like Jeremy's a direct feed to camera is practical, efficient and adequate. This group is a large part of the camera's target audience.

2. Dailies- having synched scratch audio embedded into the files makes turning out dailies quicker. I'm guessing that assistant editors love this.

You seem worried but don't fret; this doesn't threaten sound jobs. Good sound techs are still required to capture a good feed whether it is going only to camera, or also to outboard multitrack.

 

[Jon Frost]

I would strongly advise going 2 system audio with the RED build 17... You can still get decent audio at Line Level by adjusting the output from a SD442 Mixer and the input of the RED. You have to experiment (before actual production of course) with your mics/mixer/camera settings to obtain the best audio. I still think it makes sense to have 24-bit 48K audio recorded on an SD or Deva recorder sunc with a smart slate and planning for the time to sync dailies until RED can come up with a stable audio card/recording system that can handle the same quality of a Sound Devices or Deva recorder without the hassles.

 

[Meryem Ersoz]

PS- If this camera is supposed to revolutionize the non-linear video world and possibly replace the film camera, then why the hell did they bother putting an audio section on it. Leave the audio to the Sound Dept. and the video to the Camera Dept.

Uh, because they listen to their customer base. You're a tad late to the party....

I just sent in one of my cameras for the audio board upgrade, and this thread has me a tad concerned...and confused. Oh well, I guess I'll refer back to it once I have a chance to test the new board.

 

[zach nasits]

New Audio Board Upgrade- To Do? Or, not to do?

New Audio Board Upgrade- To Do? Or, not to do?

I am trying to figure out whether or not to upgrade the audio board on my Red One. We were contacted by Red to let us know that we are up for the "RED One upgrade program." A lot of the program sounds great! However, I am hesitant to upgrade the "audio boards."

My reasons are as listed:

1) Our sound mixer has had problems working with the new audio boards and says that we should "keep ours as is!" We currently have great audio recording to the camera, via mixer and some -20db pad cables. Our sound mixer says that with the new audio boards, he insists on recording dual-source and has now incorporated -30db padded cables.

2) 2 of our other sound mixers say that they still prefer the original audio boards, now that they know how to "work them."

3) I am a cameraman and listen to my sound mixers who have provided me great sound so far!

I want to hear about other experiences. Anyone?

And to the RED Bomb Squad (with much respect), may I send in my RED ONE under the following circumstances?

a) for the i-pin install and "a tuneup that will include full camera diagnostics, re-seating of joystick knob, upgrading CF reader/writer to current gen with 16 GB CF card support, replacing many hex screws with Torx Plus screws, cleaning of OLPF and ventilation chamber, etc?"
b) leaving the original audio boards and follow my "if it ain't broke don't fix it" philosphy?

Thank you RED for producing a digital cinema package that I love to work with.

Zach Nasits
RedONE (2501) /MKII's / Angenieux HR / 2060

 

[Tom Visser]

I think part of the the problem is that an analog mixer at 0 dBu is not the same as sending a -20 signal from a digital device like a Sound Devices recorder which you can set the menu at a specific tone level.

If I send a signal from a digital source at -20 dBFS, out at analog +4 line level from a 702T it hits the right hash mark. It is a simple TA3 to TA3 connection.

If I send a 0dBu 1k reference from my 302 Mixer it is slightly hotter. I am sure every analog mixer is going to send a different level. Early on back in build 12 when audio on Red was new, I was on a shoot where a PSC mixer was sending a level that had to be 30db hotter than my 302. And that was supposedly standard line level. So I know mixer to mixer the 0 dBu tone will vary, it isn't the camera.

If you send a known digital to analog line level signal like the first example (the 702) it will record and open up in FCP where it should. The analog source can be within a range. Analog mixers are all over the place. My 302 comes really close but it is not as exact as using the 702T.

And as to the Mackie references in this thread do they send a 0dBu 1k tone? I know none of my Mackies send tone, but they are older.

You can't really send a 0dBFs tone out of a mixer, unless your interconnection is digital. Once it comes out of an analog line output, it is now in the dBU power range, and the reference to dBFs where 0 is digital peak, no longer has any relevance. You can set you tone generator on something like the 702 to -20dBFS and if your outputs are +4dB, you happen to match up at the camera, great. It is actually great foresight on your company's part to make the Sound Devices levels the standard. As pointed out, there is the ugly truth that not all audio devices have agreed to use the same power level outputs for reference.

The 702t / 302 difference might simply be different ballistics of the meters or performance of the tone generator itself, the 7## being a digitally produced sine wave and the 302 using an analog oscillator. The advanced settings on the 302 have quite a few output adjustment options "hidden" in a documented setup mode.

Jason, that's exactly the way it works.

You can choose Line or Mic level, and each Mic level input has an adjustable pre-amp gain.

The only difference is on Line we don't give you adjustment. You set the levels on your mixer.

Here I would recommend that the camera should really have either a stepped or continuously variable attenuation pot on the camera. The whole point of calibration is to calibrate the downstream device to the upstream device. Maybe the mixer is a little bit out of spec, so you can use the pots to make a small adjustment to the levels. Maybe the audio has to go through several hundred feet of cabling and is a little attenuated. Maybe there is a distribution amplifier that is not quite unity gain and is boosting the levels a dB or two. In any event, I would recommend that fine adjustments should be available on the camera or any recording device. Trying to establish a standard on a camera is a bit dicey, as there are US standards, EU standards, and different standards based upon the era that a mixer was manufactured and the philosophy of the designers at that point in time.

It sounds like a few people on this thread might simply have defective boards. Especially those people that are reporting hot audio levels on the meters and actually experiencing -30dB or lower levels on the workstation.

I don't like to do this, but sometimes I have to set my 302 padded down to mic level and then use the mic inputs on the camera. Conceptually this gain strategy would be at a disadvantage to sending a hot line signals, but in fact some cameras perform better with mic inputs than line inputs. I don't think that the REDs that I have worked with, both old and new boards, have every been fed anything other than line level by me, and haven't had major problems with either version of the board once I knew what to look for. I have seen "damaged" boards where different inputs seemed to be all over the place with respect to their own levels relative to each other. Headroom can also be limited (perhaps due to electronic damage), but to play it safe, I always recommend recording double with scratch audio sent to the camera. Every effort is made to keep the scratch audio of the highest quality possible, but it keeps my mind at ease being able to know that I can do the job asked of me with as few technical glitches as possible. Camera department appreciates me staying away from their camera too, I'm sure, as my scratch audio is always sent via a wireless hop.

 

[James Brundige]

Just received my upgrade and ran a line level test. -20 tone from Sound Devices, line input to Red at 0dB. (the other option is +10)

tone hit the hash mark, maybe a touch hot. Audio was fine as long as I did not exceed -20 out of the mixer. Not much headroom above that. Got pretty crunchy if there was any red on the Sound devices meter, which corresponds to yellow on the Red Camera meter.

The test tone reads out as -16 in FCP, which is -28 below unity.

 

[Stuart English]

Headroom

Headroom

How much headroom are you estimating James ?

No comment on FCP audio level scale... we know a -20dBFS tone input delivers a -20dBFS output..

 

[James Brundige]

How much headroom are you estimating James ?

No comment on FCP audio level scale... we know a -20dBFS tone input delivers a -20dBFS output..

I've got a shoot today with Red audio. I'll test some more and give a more clear answer.

About FCP, I'm confused about their meter. It tops out at +12, which I think is 0 to the rest of the world. What's dBFS?

 

[David Limpus]

dbFS is dB Full Scale, maximum of 0dbFS.
Reference level is -20 dBFS or -18 dBFS depending where you are in world and what standard you work to.

 

[James Brundige]

Another quick test while loading the van. This time a Wendt X3 mixer. 0dB tone from the mixer just lights the yellow in the camera.

In FCP, reads out as -14, -26 below unity.

Ran some dialogue tests. It seems you've got about 6 dB headroom after the camera meter hits yellow.

I can not run the Wendt, or the Sound Devices, at optimum levels. Normal output distorts the Red. If I run those mixers conservatively, it sounds fine. Since it's digital, the noise floor is low. Not ideal, but usable for now. Why not +4dB ????

Conclusion: Be very careful with the Red one meter. Keep it green. Yellow is dangerous and red is cooked.

 

[Stuart English]

Audio Levels

Audio Levels

...... a Wendt X3 mixer. 0dB tone from the mixer just lights the yellow in the camera.

Ran some dialogue tests. It seems you've got about 6 dB headroom after the camera meter hits yellow.

I can not run the Wendt, or the Sound Devices, at optimum levels. Normal output distorts the Red. If I run those mixers conservatively, it sounds fine. Since it's digital, the noise floor is low. Not ideal, but usable for now. Why not +4dB ????

Conclusion: Be very careful with the Red one meter. Keep it green. Yellow is dangerous and red is cooked.

That suggests your input level is too high or you have +10dB gain enabled for line input.

It shouldn't be lighting up yellow, as you are correct when it changes from green to yellow its indicating about 6dB of remaining headroom before clip...

When I run my Sound Devices 302 (I don't have it with me unfortunately) at -20dBFS, my camera indicates its hitting the witness mark right on the nail.....


What build of firmware are you on?

Is it possible you have +10dB Input Level gain enabled on the RED ONE?

There was a bug in earlier Builds (17 for example) where that was the default setting when the camera turned on....

 

[Stuart English]

FCP audio meters

FCP audio meters

Just received my upgrade and ran a line level test. -20 tone from Sound Devices, line input to Red at 0dB. (the other option is +10)

tone hit the hash mark, maybe a touch hot.....

The test tone reads out as -16 in FCP, which is -28 below unity.

So given that, if the scale logic of the meters in the camera and FCP are the same, you would expect to see a recording of a line level tone input that aligns with the witness mark of a Rev B audio card on the RED ONE (i.e a signal at -20dBFS) lining up to ( 12 - 20 = -8 ) - 8 on the FCP meters.

But a big caveat - this assumes they use the same logic to represent the data.

Does FCP have a 4 offset and 2:1 scale difference ?

 

[James Brundige]

That suggests your input level is too high or you have +10dB gain enabled for line input.

It shouldn't be lighting up yellow, as you are correct when it changes from green to yellow its indicating about 6dB of remaining headroom before clip...

When I run my Sound Devices 302 (I don't have it with me unfortunately) at -20dBFS, my camera indicates its hitting the witness mark right on the nail.....


What build of firmware are you on?

Is it possible you have +10dB Input Level gain enabled on the RED ONE?

There was a bug in earlier Builds (17 for example) where that was the default setting when the camera turned on....

latest build 20. +10 is NOT enabled.

Running dialogue through a pro mixer at the optimal level for the mixer is indeed too hot for the Red. Could be the difference between +4 dB and 0 dB.

I just shot a performance with a board feed to the Red. Kept it out of the yellow, nicely in the middle of the Red meter. I will be very interested to see how it moves into FCP. After that, I will take time to do some thorough tests. From other posts, I gather the mic level input, which has much more adjustment, may work better. The issue as I see it is lining up the mixer's headroom with the camera. My quick tests with tone have not accomplished that.

 

[Stuart English]

FCP audio meters

FCP audio meters

About FCP, I'm confused about their meter. It tops out at +12, which I think is 0 to the rest of the world. What's dBFS?

Can you post a JPEG of the meter that you are looking at in FCP?

Just so we know that we are talking about the same thing.. I'm looking at this - except its vertical. Range is - 96 to 0