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Author Topic: Convert Binaural recording to Stereo?  (Read 10602 times)

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Offline MartyMo

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Convert Binaural recording to Stereo?
« on: January 19, 2011, 07:03:48 PM »
I have been taping for quite a while and have many great shows under my belt.  Since my mics are binaural the sound on headphones of course is phenomenal.  I really have to do a LOT of work in post however to get a decent sounding CD, but even then it falls way short.  Is there any good or better way to convert a binaural recording for good sounding playback in stereo?  By the way I am ditching the binaurals and have some nice cards on order right now.  Thank you...
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Offline Moke

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Re: Convert Binaural recording to Stereo?
« Reply #1 on: January 19, 2011, 07:22:49 PM »
Binaural is a technique, not a product. You likely have omnidirectional  mics that you can use in binaural recording. 
What kind of binaural recordings were you doing?
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Offline MartyMo

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Re: Convert Binaural recording to Stereo?
« Reply #2 on: January 19, 2011, 07:34:55 PM »
True, they are omnidirectional mics.  Most mic manufacturers do list them however as "Binaural Mics".  Anyway they are always separated by my head or neck depending on venue.  I get permission but can't always use a mic stand.  Just normal taping of concerts.  I also do a lot of nature sound recording, with the same problem.  I want to listen on a CD so I am looking for a better way to convert from binaural to stereo without all the hours and hours of post time.
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Offline 12milluz

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Re: Convert Binaural recording to Stereo?
« Reply #3 on: January 19, 2011, 07:36:55 PM »
True, they are omnidirectional mics.  Most mic manufacturers do list them however as "Binaural Mics".  Anyway they are always separated by my head or neck depending on venue.  I get permission but can't always use a mic stand.  Just normal taping of concerts.  I also do a lot of nature sound recording, with the same problem.  I want to listen on a CD so I am looking for a better way to convert from binaural to stereo without all the hours and hours of post time.
What do you mean convert from binaural to stereo?  Binaural recording is a stereo technique. The recording is in stereo if you record binaurally. Binaural is a method of recording in stereo using two omnidirectional mics to closely replicate a pair of ears.
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Offline MartyMo

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Re: Convert Binaural recording to Stereo?
« Reply #4 on: January 19, 2011, 07:44:57 PM »
Binaural recording is intended for replay using headphones.  With headphones all of my concerts sound fantastic.  However when you play back on speakers it does not sound good.  I guess my subject should have said "Convert Binaural recording for loudspeaker playback"
Rig: R-09HR  W  Audioreality Binaural mics & BB

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Offline 12milluz

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Re: Convert Binaural recording to Stereo?
« Reply #5 on: January 19, 2011, 07:54:39 PM »
Yes,  binaural is meant for headphone playback but I don't know how you can "convert" them.  You get phase cancellation when played back with speakers, but that is not something one can really fix- It is the nature of binaural recording.
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Offline Moke

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Re: Convert Binaural recording to Stereo?
« Reply #6 on: January 19, 2011, 08:02:17 PM »
Well, IMO, you're already at one of the most pure stereo recordings that can be made.  Any altering and you end up with far less. Binaural is a very true stereo recording.

Do they really sound that bad through speakers?

Binaural is a long fascination of mine, like 30 years worth.  I can't imagine that there is much that I could do to my recordings that wouldn't have some negative impact.
You might try a touch of EQ'ing in the high-mids, and low-highs region. I would really suggest being light handed though, as there is so much crucial true stereo detail already there, and it would be real easy to smudge it.

Regarding the binaural terminology as it applies to a product,...
true binaural:
Neumann binaural stereo head
Sennheiser binaural stereo head
AKG binaural stereo head

Core Sounds has called their product binaural, but its just a pair of omnis; not even a baffle.
Sonic Studios has a round pillow and omni mics, but designed for HRTF stereo (baffled omnis at ear width spacing)
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Offline PeteJE

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Re: Convert Binaural recording to Stereo?
« Reply #7 on: January 19, 2011, 08:07:00 PM »
What makes a binaural recording a great technique for headphones is all the inherent phase interrelationships (cancellation and additive) at various frequencies.   As the other poster said, this is a stereo technique, not really a unique format.  Some stereo binaural recordings are just fine in loudspeakers, others quite lackluster.  This depends on technique / placement used. 

Once recorded, there is very little you can do to alter these phase relationships inherent in the recordings.  They are, however, still true stereo.  If you are comparing listening on headphones to loudspeakers, you will always be disappointed as you won't experience the same dimensional "stage" that exists on headphone monitoring.  The sound, on loudspeakers, is now subject to re-interpretation through the air-outer ear-ear canal and more phase inter-relationships that will alter the already printed phase information that gives such a great sound stage when fed directly to the eardrum with headphones.

This is just the nature of binaural.  One decent way to preserve some of this dimension on loudspeakers is with 5.1 sound systems and decoding of the original stereo binaural.  The recordings can be decoded with a Dolby PL2 decoder which splits the "dimensions" of the recording out to a discreet 5.1 output; L, C, R, L surround, R surround.  This works surprisingly well, but, obviously gets into a different format, not a simple stereo to CD for stereo loudspeaker playback.

There is nothing in post you can do to resolve the phase information to make a more satisfying stereo loudspeaker playback.  Binaural recordings will always sound better on headphones.  Frequency dependent phase cancellation and additive qualities are complex and really printed forever.  This is why there are so many different and differently satisfying stereo recording techniques - this is a quality that is made with the recordings forever.

You can use a simple plug-in decoder, splitting the sound out to more discreet channels (L,C,R or 5.1 and then re-sum these into a new L,R stereo subjectively controlling the amount of center or side information you mix to the new L,R.  Sometimes you can get some decent results with this, but it is entirely subjective and requires mixing and experimenting.  Many of these decoders and decoder plug-ins use phase information in their algorithms to expand sound of the dimensional binaural sound stage to more discreet places in a loudspeaker L,C,R or 5.1 set up.  These split outs can then be mixed back and controlled to affect the L,R mix quality.

http://www.soundonsound.com/sos/jun07/articles/ptencoders.htm
http://www.neyrinck.com/
http://www.minnetonkaaudio.com/index.php?option=com_content&view=article&id=49&Itemid=76

Offline Moke

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Re: Convert Binaural recording to Stereo?
« Reply #8 on: January 19, 2011, 08:32:44 PM »
True, they are omnidirectional mics.  Most mic manufacturers do list them however as "Binaural Mics".  Anyway they are always separated by my head or neck depending on venue.  I get permission but can't always use a mic stand.  Just normal taping of concerts.  I also do a lot of nature sound recording, with the same problem.  I want to listen on a CD so I am looking for a better way to convert from binaural to stereo without all the hours and hours of post time.

This is a variant of binaural, called, Head Reference Transfer Function, HRTF.  Its my favorite of the binaural techniques, and is quite favorable to speaker playback, at least compared to the in-ear canal true binaural recordings with the stereo heads.  I've done those binaural stereo head recordings, and HRTF, and HRTF is a much better speaker playback representation.
Try some real light EQ'ing as earlier suggested, and it could change your mind about binaural.  That's where I've noticed the greatest deficit in translating to speakers.
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Offline MartyMo

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Re: Convert Binaural recording to Stereo?
« Reply #9 on: January 19, 2011, 09:15:57 PM »
Huge thanks to everyone who posted!  Great suggestions, live and learn.  Much appreciated.
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Offline Moke

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Re: Convert Binaural recording to Stereo?
« Reply #10 on: January 19, 2011, 09:26:11 PM »
What do you do for playback? near field, far field? Speakers angled inward, or straight forward?
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Offline Gutbucket

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Re: Convert Binaural recording to Stereo?
« Reply #11 on: January 20, 2011, 12:42:09 PM »
What do you do for playback? near field, far field? Speakers angled inward, or straight forward?

IMO, This may be the best way to approach the issue- ie: adapting the way you play the recordings back over speakers, rather than trying to manipulate the recording to sound best with traditional stereo speaker playback.  One approach is what M0k3 mentions above- using a matrix surround decoder such as Dolby PLII, DTS Neo6, Logic-&, Circle-Surround, Hafler-matrix, etc. for multi-channel playback and playing around with the settings. 
 
Another is simulating headphone listening over two speakers using cross-cancellation techniques.  These are techniques for speaker playback which eliminate the cross-talk between each speaker and the ear on the 'wrong' or opposite side of the head.  There are electronic means of doing this over standard 60 degree stereo speaker triangle such as the old Carver Sonic Hologram system and Lexicon's cross-talk cancellation program among others like in some Meridian and Tact gear, as well as speakers specifically built to do this like a model Polk made some years ago.  Those methods work, but can be quirky and require very specific placement of speakers and a listener glued to the sweet spot.

There are other, typically newer cancellation methods that work better partially because they move the speakers very close together so that they are only 10-20 degrees apart, and partially because they use improved cross-cancellation algorithms.  Most of these are referred to as stereo dipole systems. Some are plug-in based and can be easily used for computer playback if you move your speakers close together.  I haven't used it, but here is a free VST version that can be used via Foobar/Winamp with the appropriate VST wrapper- http://www.weldroid.net/2010/02/ambiophonics-processor-vst-ambioone.html  There are a good number of other available plug-ins available using various cancelation algorithms.  Some are better than others. Something like that is pretty simple to setup and may possibly be a practical solution for you.
 
Some stereo dipoles are built into a single speaker enclosure that includes the cross talk cancellation circuitry like the Emes owl-



Arguably the best cross talk cancelation (and a simple, cheap method, if somewhat funny looking) is accomplished by using a physical baffle sandwiched between near-spaced point-source speakers which runs right to the nose of the listener. You can do this with a sheet of plywood or heavy cardboard.  I recommend that anyone interested in how stereo works give this a try, the results are enlightening.  It 'turns-stereo inside out' by placing the physical speakers directly in front of you, and produces phantom images extending out to the sides, much wider than the traditional stereo triangle.  Just don't let anyone catch you doing it or you'll never hear the end of the ridicule.  Here's a sketch I made a few years back to explain it in another post here at TS-



The low-frequency speakers on the sides are optional and just improve the imersion, it's the two small speakers and the barrier between them that are important.  If at all interested, I suggest whipping out the plywood to see how it works, then give some of the plugins a try to see how close they can come to emulating the physical barrier.

Information on cross-talk cancellation: http://www.isvr.soton.ac.uk/fdag/vap/html/xtalk.html
Try searches with the following terms:
stereo cross-talk cancellation
stereo dipole
ambiphonics

The Ambiophonics technique goes so far as to adapt binaural/HRTF recording techniques with additional baffling to exclude everything but front arrival, then add a second head or additional mics behind the baffle, or room convolution for the room sound.

Have fun exploring the rabbit hole.
« Last Edit: January 21, 2011, 09:24:10 AM by Gutbucket »
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Offline andromedanwarmachine

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Re: Convert Binaural recording to Stereo?
« Reply #12 on: January 21, 2011, 08:42:46 AM »
right...

how about M-S to binaural conversion?

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Offline Gutbucket

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Re: Convert Binaural recording to Stereo?
« Reply #13 on: January 21, 2011, 10:53:46 AM »
apologies for the audio geek overload..

However, this is cutting edge reproduction tech for which the prefered source is binaural (or rather HRTF recordings made excluding the ears) and is relatively simple to implement.  Your material is absolutely perfect for this.

Here's a photo of the latest 4.0 Ambiophone, a HRTF 4 channel microphone that is basically an ear-less dummy head with an additional binaural mic pair on the back side of the front/rear baffleing-

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Offline andromedanwarmachine

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Re: Convert Binaural recording to Stereo?
« Reply #14 on: January 25, 2011, 08:40:21 AM »
that's really incredible- I don't imagine that would have much use outside of large classical recording projects...

I wonder what a Rycote would look like for that!!

JimP
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