Questions about sound in Red One

[GlennChan]

1- Throwing out an idea here: It might be better to have 2 independent headphone outputs, as opposed to XLR outputs. Some mixers like the Sound Devices stuff take headphone/mini-jack as the return feed, not XLR.

If you want to record sync sound, a reasonable setup would be:
Two audio persons. Each sound operator holds a boom and a single wireless lav (or handle two wireless lavs). They also handle their own levels and mix their feeds. They can monitor right off the camera (via the return on their mixer).
This works well with the Sound Devices mixers, since they can't output more than 2 channels. They can have 2+ inputs, so you can have a boom and at least one lav. As well, if you make a custom snake/cable for a Sound Devices mixer (Trew Audio / Remote Audio does this), it will have a headphone jack (not XLR).

1b- If you are going wireless in and out of the camera (from your mixer[s]), 2 X mini-plug will still be ok?

2- Another situation would be using double system, where you might just record 2 tracks of guide audio, plus timecode. In this case 2 independent headphones feeds should still be fine.

3- Menu-wise, you'd need controls for:
*Monitoring/mixing. 4 channels of inputs, and 4 channels of monitoring (L+R on headphone out 1, L+R on headphone out 2) would mean a 4x4 matrix. A joystick-like control like on the DVX100 would be a sensible way of setting this if using a menu system.
*Line/mic on each input.
*Limiters on inputs 1 & 2. (I don't forsee needing limiters on inputs 3&4.)
*Phantom power (Probably ok to omit T power.)

I think with this many settings (24 or more), you'd need a menu system. Ideally, the menu system would be so intuitive that you can look at the camera and figure out how to setup the audio.

4- Stereo linking of the limiters can likely be omitted.

Flexibility about what channels to monitor implies that a 4 -> 2 channel monitor downmix is not possible?

My interpretation is that it implies that it IS possible.

[Graeme Nattress]

http://www.paia.com/ProdArticles/msmicwrk.htm

http://forums.dvdoctor.net/showthread.php?t=39513

Describes how the Mid - Side system works, which to me would be a great alternative to the tetrahedral technique linked to above.

Graeme

[Bruce Allen]

Graeme, I totally agreee about MS.

To be honest, for useful production sound, the Red should either have:
- really great preamps + DAC plus MS matrix monitoring for headphones
OR
- digital input (so that you can use an external mixer / preamp / DAC chain).
OR
- take $500 off the price of the camera, have 2 channels with cheap-ass preamps which we just record a reference track to and then we put that $500 towards a Sound Devices compact-flash timecode recorder with great pre-amps, MS monitoring and 192khz / 24bit recording (costs $2000-$4000 depending on how many channels you want)

...actually why don't you just cut a deal with the Sound Devices people to include their audio system on your camera?

The current system looks suspiciously like it has just low enough quality to not be useful.

All of this stuff about holographic 3D sound recording is likewise not that useful for real jobs. If you want to record stereo, MS is the way to go (especially with youtube, phones, video ipods, etc you always want a good mono-compatible signal).

[Emmanuel Cambier]

- digital input (so that you can use an external mixer / preamp / DAC chain).

This sure seems like a possibly good solution.

Yours Emmanuel

[Chris Kenny]

Because of the approach we have taken we have a fair bit of flexibility regarding what channel(s) can be monitored on the L and R outputs of the headphone and XLR outputs.

It would be interesting to collect inputs to what you guys would like, so we can compare it to what we've come up with as the first priority for product implimentation.

This is admittedly a fairly minor quibble, but... does the camera always record four channels, even when there's no input? It would be nice if channels could be disabled individually, to save a bit of storage space and make things just a little neater in post.

[Martin Drew]

I think well engineered 24bit 48khz is fine, 96khz would be nice but 48khz is good enough given that onboard sound will always be a bit of a compromise. If you are in pursuit of ultimate quality you will probably be using separate audio anyway. I think it is more important that the solution is implemented well and the AD stage is well engineered than pushing for maximum spec, that may lead to compromised performance.

There is an interesting paper here about 192kHz and why it maybe isn't such a great idea.
http://www.lavryengineering.com/documents/Sampling_Theory.pdf


Martin

[REDHKSC]

Stuart,
may I say that RED one has the options to go for Surround Sound live recording from all the inputs ?

No Camera on earth can record surround sound from the Camera but THE RED ONE ?

Stewart

[Stuart English]

The RED_ONE camera has four discreet channels of audio at 48KHz 16 or 24 bits. What you do with that - 2 channels spilt high / low gain or surround sound matrixed recording is for the user to descide.

These user choices do have some impact on monitoring to headphones etc, which is why we'd like to gather likely use data for our consideration.

[Stuart English]

We can turn off channels 3 / 4 ( i.e not record those) if its required.

To answer the follow up question - does that mean we can use that "unused bandwidth" to record Channel 1 & 2 at 96Khz ?

That issue is not related to the above. The audio spec is 48KHz at 16 or 24 bits per channel.

(Usual rider - that all specifications subject to change)

[Jochen Schmidt-Hambrock]

Ok, if you want to monitor the surround mix somehow, the camera would have to do a downmix from 4 channels into the 2 channels of the headphones.

So a simple matrix (which input of the 4 provided do I want to hear on my left output channel, which one on the right) would not enough. You´d have to be able to adjust volume and pan for the 4 inputs.

That would indeed be nice also in a non-surround setup with maybe 2 Lav´s plus a stereo ambience mike

Anything more for the surround field would require the ability to encode the 4 inputs into some sort of Dolby-ish matrix for monitoring - bit of an overkill IMHO.

I´d be perfectly happy with the simple I/O matrix for monitoring.
Onscreen metering for all 4 channels though is necessary (to check for dead mikes, cables, etc.)

Jochen