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Re: Some Ambisonics questions
by Brian Willkie
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> - looks like I could use BFEncode2 to encode the
> sources, then BFDecode1 to decode onto the speaker ring.
Not sure about the exact ugens
Also, Josh Parmenter just recently released a new set of ugens you
should check out. (JoshAmbiUgensUB.scx in the sc3-plugins, part of
the optional installs???).
> * How do I turn many point sources into one single B-format feed? Do I
> encode each one separately and then just add the feeds together? (Or
> multiply the feeds together? Or...)
You need one encoder for each point source. I believe you can sum
the output for all of the encoders the same way you would mix any
multi-channel audio, then feed the mixed/scaled multi-channel
signal to one decoder.
> * In terms of the audio outcome, is the only difference between the
> different "orders" of Ambisonics the sound quality?
Not so much sound quality as "localization quality." Higher order
Ambisonics gives a more accurate image of the location of a sound.
It also uses more speakers. If you decode a B-format signal to a
smaller set of speakers, then you simply throw out the extra
localization information.
> * For projecting the ring down to headphones, what is needed? In the
> archive there's discussion of downloading the Kemar HRTFs from MIT -
> fine. But is there a specific UGen that would take my 8 channels and
> apply the HRTFs? Or otherwise how would it work?
I think for this you want Christopher Frauenberger's ambiem package
http://sonenvir.at/downloads/sc3/ambiem/
A couple of additional points, ambisonics typically places sound
only on the unit circle, so if you want to work with positions
inside (or outside) the circle, most implementations of ambisonics
won't support it. Josh's implementation does.
Ambisonics utilizes all of the speakers, all of the time, to give a
sense of location. Some people feel that this system makes it
difficult to get a very narrowly focused sound (if that's what you
want). Finally, the math behind it introduces delay in some of the
signals (by design), so there's a bit of built in reverb.
Good luck.
-Brian
> ----- Original Message -----
> From: "Dan Stowell" <danstowell@...>
> To: "SuperCollider users mailing list" <sc-users@...>
> Subject: [sc-users] Some Ambisonics questions
> Date: Sat, 8 Mar 2008 10:07:47 +0000
>
>
> Hi -
>
> I've never used Ambisonics before, but I'm wondering about how
> possible it would be to implement the following setup using SC's
> Ambisonics stuff:
>
> I have 20 or 30 point sources, each of which has a location in the x-y
> plane (and may move about in this plane). I'd like to encode them into
> an Ambisonic representation, then decode this to a ring-of-8-speakers.
> Then for convenience I'd also like to be able to project this
> ring-of-8 down to stereo headphones using a HRTF.
>
> Looking back over the mailing list archives it looks like this is
> probably possible - looks like I could use BFEncode2 to encode the
> sources, then BFDecode1 to decode onto the speaker ring. But I have
> some questions:
>
> * How do I turn many point sources into one single B-format feed? Do I
> encode each one separately and then just add the feeds together? (Or
> multiply the feeds together? Or...)
>
> * In terms of the audio outcome, is the only difference between the
> different "orders" of Ambisonics the sound quality?
>
> * For projecting the ring down to headphones, what is needed? In the
> archive there's discussion of downloading the Kemar HRTFs from MIT -
> fine. But is there a specific UGen that would take my 8 channels and
> apply the HRTFs? Or otherwise how would it work?
>
> I'd be grateful for any tips
> Dan
> _______________________________________________
> sc-users mailing list
> sc-users@...
> http://lists.create.ucsb.edu/mailman/listinfo/sc-users
>
_______________________________________________
sc-users mailing list
sc-users@...
http://lists.create.ucsb.edu/mailman/listinfo/sc-users
> sources, then BFDecode1 to decode onto the speaker ring.
Not sure about the exact ugens
Also, Josh Parmenter just recently released a new set of ugens you
should check out. (JoshAmbiUgensUB.scx in the sc3-plugins, part of
the optional installs???).
> * How do I turn many point sources into one single B-format feed? Do I
> encode each one separately and then just add the feeds together? (Or
> multiply the feeds together? Or...)
You need one encoder for each point source. I believe you can sum
the output for all of the encoders the same way you would mix any
multi-channel audio, then feed the mixed/scaled multi-channel
signal to one decoder.
> * In terms of the audio outcome, is the only difference between the
> different "orders" of Ambisonics the sound quality?
Not so much sound quality as "localization quality." Higher order
Ambisonics gives a more accurate image of the location of a sound.
It also uses more speakers. If you decode a B-format signal to a
smaller set of speakers, then you simply throw out the extra
localization information.
> * For projecting the ring down to headphones, what is needed? In the
> archive there's discussion of downloading the Kemar HRTFs from MIT -
> fine. But is there a specific UGen that would take my 8 channels and
> apply the HRTFs? Or otherwise how would it work?
I think for this you want Christopher Frauenberger's ambiem package
http://sonenvir.at/downloads/sc3/ambiem/
A couple of additional points, ambisonics typically places sound
only on the unit circle, so if you want to work with positions
inside (or outside) the circle, most implementations of ambisonics
won't support it. Josh's implementation does.
Ambisonics utilizes all of the speakers, all of the time, to give a
sense of location. Some people feel that this system makes it
difficult to get a very narrowly focused sound (if that's what you
want). Finally, the math behind it introduces delay in some of the
signals (by design), so there's a bit of built in reverb.
Good luck.
-Brian
> ----- Original Message -----
> From: "Dan Stowell" <danstowell@...>
> To: "SuperCollider users mailing list" <sc-users@...>
> Subject: [sc-users] Some Ambisonics questions
> Date: Sat, 8 Mar 2008 10:07:47 +0000
>
>
> Hi -
>
> I've never used Ambisonics before, but I'm wondering about how
> possible it would be to implement the following setup using SC's
> Ambisonics stuff:
>
> I have 20 or 30 point sources, each of which has a location in the x-y
> plane (and may move about in this plane). I'd like to encode them into
> an Ambisonic representation, then decode this to a ring-of-8-speakers.
> Then for convenience I'd also like to be able to project this
> ring-of-8 down to stereo headphones using a HRTF.
>
> Looking back over the mailing list archives it looks like this is
> probably possible - looks like I could use BFEncode2 to encode the
> sources, then BFDecode1 to decode onto the speaker ring. But I have
> some questions:
>
> * How do I turn many point sources into one single B-format feed? Do I
> encode each one separately and then just add the feeds together? (Or
> multiply the feeds together? Or...)
>
> * In terms of the audio outcome, is the only difference between the
> different "orders" of Ambisonics the sound quality?
>
> * For projecting the ring down to headphones, what is needed? In the
> archive there's discussion of downloading the Kemar HRTFs from MIT -
> fine. But is there a specific UGen that would take my 8 channels and
> apply the HRTFs? Or otherwise how would it work?
>
> I'd be grateful for any tips
> Dan
> _______________________________________________
> sc-users mailing list
> sc-users@...
> http://lists.create.ucsb.edu/mailman/listinfo/sc-users
>
_______________________________________________
sc-users mailing list
sc-users@...
http://lists.create.ucsb.edu/mailman/listinfo/sc-users
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