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Re: new panning algorithm
by Chris Robinson-5
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On Sunday 25 January 2009 12:04:44 pm Joss Sanglier wrote:
> I am resending this as looking at another post, this may not have gone
> through a few days ago - sorry!
>
> Not sure if this is any help in working out what your final effect
> should achieve:
>
> http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professio
>nal/44_SuroundMixing.pdf
>
> This is the manual for one of the pro dolby studio units. It discusses
> true speaker placement as well as use.
It's an interesting read, regardless. Thanks. :)
> In theory, in a cinema, if everyone in the audience could sit in the
> precise middle of the screen, then there would be no need for a centre
> speaker, as the combined left and right pairing would give the correct
> balance. However, sitting left or right means that the voice would be
> imbalanced. So a centre channel is added to a dedicated speaker to fix
> the voice to the centre of the screen.
>
> The down side of this is that because a stereo sound (music for
> instance) also contains a lot of mono L+R information, this will also
> use this channel and result in a narrowing of the stereo field.
> Consequently, we often produced stereo tracks that were "wider" than
> would be mixed for normal stereo to compensate, or occasionally add a
> very small delay to the right channel (not good on music).
So does that mean stereo sounds should mix into the center channel? Or is that
mainly for 5.1-mixed tracks? I ask because at least some in rendered music
(like MIDI-to-wave, or module formats, that are played in real-time), mixing
the left and right channels into the center would dull the perceived stereo
effect, causing notes that are panned left to become panned halfway between
center and left.
> The other problem with games, (and I think this is especially affecting
> MMOs now) is panning through centre which is a little too fast. In real
> life, though we may turn our head slightly from left to right when
> talking to someone, we perceive the sound as still being in front of us
> until we move our head to either the extreme left or right. This is
> something that the brain sorts out for us in some way. However, with the
> artificial movement of sound created in a surround field in respect to
> an avatar the brain does not have the same information as it would in a
> real life situation and does not do this. In consequence the sound seems
> to move very quickly from centre to left or right.
I think this could be mostly resolved on the application side. For example,
keeping the listener orientation facing auditory points of interest (eg.
someone talking) even if the camera moves around a bit. Then reorient it when
you look far enough away.
> There is another problem in games which is the binaural or dummy-head
> effect (or lack of it). Sounds behind your avatar should be duller than
> the sounds ahead. There is an argument that says that since the two main
> SS speakers are placed behind the listener then this real life
> positioning should do the job. However, since it is common for the rear
> speakers to be not directly behind but very nearly to the side of the
> listener then I am not convinced this is happening appropriately. It
> was actually easier with the older true dolby stereo (LCRS). With only
> one mono surround channel (even if split over several speakers) the
> sound was naturally duller. But with a true stereo pair, the sound is
> normally as fresh sounding as the front speakers.
I've thought about the idea of a listener cone before for a similar reason.
But I also somewhat dismissed it for the similar thought, "a real surround
sound setup would naturally dull the sound anyway". I don't think it would
actually be too difficult to add listener cones to OpenAL.. but it may not
interact well since as you say, you can't know the user's speaker setup
(enabling it for stereo may produce good results, but perhaps not as good for
surround sound setups).
> However, it would be interesting if a switch could be added to the
> output of the mix that perhaps is called something like "enhanced
> binaural positioning" where is reduces the bandwidth of the SS tracks
> and changed the way the front panning worked. Something like that.
Not sure changing the way panning works is a good idea, as a game designer can
have proper control over it and they would know best what to focus on. Though,
I probably could add a config option that applies the cone logic to the
listener->source position (similar to the logic there for
source->listener) that's left for the user, not the app. It can modulate the
gain and high frequencies with the low-pass filter that's already being used.
> Anyway - it was the manual that was the important bit! Sorry!
No need to apologize. You brought up some interesting points. :)
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> I am resending this as looking at another post, this may not have gone
> through a few days ago - sorry!
>
> Not sure if this is any help in working out what your final effect
> should achieve:
>
> http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professio
>nal/44_SuroundMixing.pdf
>
> This is the manual for one of the pro dolby studio units. It discusses
> true speaker placement as well as use.
It's an interesting read, regardless. Thanks. :)
> In theory, in a cinema, if everyone in the audience could sit in the
> precise middle of the screen, then there would be no need for a centre
> speaker, as the combined left and right pairing would give the correct
> balance. However, sitting left or right means that the voice would be
> imbalanced. So a centre channel is added to a dedicated speaker to fix
> the voice to the centre of the screen.
>
> The down side of this is that because a stereo sound (music for
> instance) also contains a lot of mono L+R information, this will also
> use this channel and result in a narrowing of the stereo field.
> Consequently, we often produced stereo tracks that were "wider" than
> would be mixed for normal stereo to compensate, or occasionally add a
> very small delay to the right channel (not good on music).
So does that mean stereo sounds should mix into the center channel? Or is that
mainly for 5.1-mixed tracks? I ask because at least some in rendered music
(like MIDI-to-wave, or module formats, that are played in real-time), mixing
the left and right channels into the center would dull the perceived stereo
effect, causing notes that are panned left to become panned halfway between
center and left.
> The other problem with games, (and I think this is especially affecting
> MMOs now) is panning through centre which is a little too fast. In real
> life, though we may turn our head slightly from left to right when
> talking to someone, we perceive the sound as still being in front of us
> until we move our head to either the extreme left or right. This is
> something that the brain sorts out for us in some way. However, with the
> artificial movement of sound created in a surround field in respect to
> an avatar the brain does not have the same information as it would in a
> real life situation and does not do this. In consequence the sound seems
> to move very quickly from centre to left or right.
I think this could be mostly resolved on the application side. For example,
keeping the listener orientation facing auditory points of interest (eg.
someone talking) even if the camera moves around a bit. Then reorient it when
you look far enough away.
> There is another problem in games which is the binaural or dummy-head
> effect (or lack of it). Sounds behind your avatar should be duller than
> the sounds ahead. There is an argument that says that since the two main
> SS speakers are placed behind the listener then this real life
> positioning should do the job. However, since it is common for the rear
> speakers to be not directly behind but very nearly to the side of the
> listener then I am not convinced this is happening appropriately. It
> was actually easier with the older true dolby stereo (LCRS). With only
> one mono surround channel (even if split over several speakers) the
> sound was naturally duller. But with a true stereo pair, the sound is
> normally as fresh sounding as the front speakers.
I've thought about the idea of a listener cone before for a similar reason.
But I also somewhat dismissed it for the similar thought, "a real surround
sound setup would naturally dull the sound anyway". I don't think it would
actually be too difficult to add listener cones to OpenAL.. but it may not
interact well since as you say, you can't know the user's speaker setup
(enabling it for stereo may produce good results, but perhaps not as good for
surround sound setups).
> However, it would be interesting if a switch could be added to the
> output of the mix that perhaps is called something like "enhanced
> binaural positioning" where is reduces the bandwidth of the SS tracks
> and changed the way the front panning worked. Something like that.
Not sure changing the way panning works is a good idea, as a game designer can
have proper control over it and they would know best what to focus on. Though,
I probably could add a config option that applies the cone logic to the
listener->source position (similar to the logic there for
source->listener) that's left for the user, not the app. It can modulate the
gain and high frequencies with the low-pass filter that's already being used.
> Anyway - it was the manual that was the important bit! Sorry!
No need to apologize. You brought up some interesting points. :)
_______________________________________________
Openal-devel mailing list
Openal-devel@...
http://opensource.creative.com/mailman/listinfo/openal-devel
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