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Re: Surround Sound Recording

Subject: Re: Surround Sound Recording
From: "umashankar" umashanks
Date: Wed Dec 31, 2014 7:40 pm ((PST))
that looks=C2=A0to me like four stereo pairs, 90 degrees apart. I do not kn=
ow what kind of imaging it gets.
I have been working with surround for years now, but most with ambisonics -=
 first order, with four capsules=C2=A0in a tetrahedral array. there are oth=
er ways of doing surround with height, but I think ambisonics is the most e=
legant, and there are now plenty of four channel recorders. (at the moment,=
 I am modifying the zoom H2n to build a tetrahedral array inside so you hav=
e pocketable ambisonics system) I have posted a brief bird call recording o=
n ambisonia.com. The files there are of the .amb format (four channel wave,=
 B-format) but plenty of free players to play them with.
future plans include building a very low noise 25 mm tetrahedral array, whi=
ch can be plugged into a modified zoom H2n or into any four channel recorde=
r.
umashankar
=C2=A0      From: "Dan Dugan  [naturerecordists]" <naturere=
>
 To: 
 Sent: Thursday, January 1, 2015 6:40 AM
 Subject: Re: [Nature Recordists] Surround Sound Recording

> I'm starting to record surround sound alongside with panoramic videos. On=
e of the sample MP4's has an audio file structure of
>
> 0L.wav
> 0R.wav
> 90L.wav
> 90R.wav
> 180L.wav
> 180R.wav
> 270L.wav
> 270R.wav
>
> Have any of you seen this structure

Where did that sample come from? I've never seen those track names. Looks l=
ike degrees of azimuth, but what are two at zero and 180?

> and if so, how are these signal sources positioned (i.e. is 90L/R on the =
right or on the left when looking down on it)? How are they recorded (I'm a=
ssuming 4 pairs of stereo mics)? And most importantly, how are they process=
ed, edited and embedded into the mp4 file so that they are positionally cor=
rect?

They don't make sense to me, I'd just be guessing. Ask the source.

There are three different standard sequences for surround channels on the r=
ecorder and studio console, Dolby, DTS, and I think SMPTE. I'm not sure whe=
ther encoding of the output goes by the channel names or sequence. When I m=
ade a surround DVD I let the authoring software (Apple Final Cut Pro and Co=
mpressor) encode the audio channels so I don't know what happened there. I =
wouldn't be surprised if authoring software has a preference to set for you=
r preferred working sequence. Obviously the output medium has a standard ch=
annel sequence. I'd use the Dolby sequence.

> If any of you have worked with this kind of format I'd be very thankful i=
f you could give me a hint for where to start.

I've been recording soundscapes in surround for many years, using the stand=
ard Dolby channel names L, R, Ls, Rs. I use a technique described by former=
 list subscriber Rich Peet:

Your favorite stereo array for L and R
Omni mics spaced 40' to the left and 40' to the right for Ls and Rs.

Thus the front pair is imaging and the rear pair are uncorrelated (very muc=
h so, 80' apart).

I use a Jecklin Disk for my front array thus four identical omni mics in th=
e system.

The original Rich Peet technique is great for being on a trail. It only rev=
eals its "defective" geometry when a jogger comes through! In an open space=
 I usually pull the rears back 20' or so. Or position them opportunisticall=
y, like that bunch of trees there and those bushes.

Steve Sergeant, a nature recordist who works at Dolby, has been encouraging=
 us to add height channels to our recordings. I've done it once but I don't=
 have proper playback set up yet to evaluate it. The minimum would be a ste=
reo pair raised say 14', axis left and right, pointing up. A bit of a hardw=
are challenge.

The LFE channels is created in production when desired, there is no need to=
 record an LFE channel in the field.

I like time-space in my recordings and rarely use one-point techniques.

-Dan

------------------------------------
Posted by: Dan Dugan <>
------------------------------------

"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.


------------------------------------

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