>>> As far as the processing chain is concerned, separate
> channels might as well be separate mono radio stations.
>
> If the "processing chain" implements a reverb, that is not true.
> Example: Take a standard stereo-capable reverb unit from the music shop,
> feed a signal into left channel and put an unused cable in the right
> channel (to force it to stereo mode).
> The output signal appears on both outputs, although stronger on the left
> channel. In other words, it CANNOT be used as two independent mono reverb
> units.
Reverb, cross-fade, and other effects aside, the ideal crosstalk between
channels is zero. That goes for equalizers and other filters.
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
> If the "processing chain" implements a reverb, that is not true.
> Example: Take a standard stereo-capable reverb unit from the music shop,
> feed a signal into left channel and put an unused cable in the right
> channel (to force it to stereo mode).
> The output signal appears on both outputs, although stronger on the left
> channel. In other words, it CANNOT be used as two independent mono reverb
> units.
>
> -mn
Thanks,
O.K. this was more like my original question, it makes a lot of convolution
kit, that use just stereo impulses, look less appealing. So I guess I need a
stereo impulse from a source in the left of the room, for example, and a
stereo impulse from the right of the room, and feed each of the user's
stereo inputs to both, and mix them?
VC
Reply by mnentwig●October 16, 20072007-10-16
>> As far as the processing chain is concerned, separate
channels might as well be separate mono radio stations.
If the "processing chain" implements a reverb, that is not true.
Example: Take a standard stereo-capable reverb unit from the music shop,
feed a signal into left channel and put an unused cable in the right
channel (to force it to stereo mode).
The output signal appears on both outputs, although stronger on the left
channel. In other words, it CANNOT be used as two independent mono reverb
units.
-mn
Reply by VelociChicken●October 15, 20072007-10-15
Thanks for all the replies guys. It's clear to me now.
"Jerry Avins" <jya@ieee.org> wrote in message
news:M6SdneVXRfP1EI_anZ2dnUVZ_ryqnZ2d@rcn.net...
> VelociChicken wrote:
>>> Stereo channels are independent. There must be an error in your code.
>>
>> I was asking what to do for stereo, but O.K. thanks for the reply - they
>> are separate? So... If I have a stereo impulse of a large hall, and
>> process the channels independently on a stereo sound like a hand-clap but
>> the clap is panned to the far left - then independent convolution will
>> sound fine on the left but silent on the right, which is wrong as this
>> does not mimic the space itself. Downloading a few convolution plug-in
>> demos do indeed show the channels to be independent though. Surprised me
>> a little I guess. : )
>
> It is up to the microphones to pick up the stereophonic aspects of the
> sound in the room. As far as the processing chain is concerned, separate
> channels might as well be separate mono radio stations.
>
> Jerry
> --
> Engineering is the art of making what you want from things you can get.
> �����������������������������������������������������������������������
Reply by Jerry Avins●October 14, 20072007-10-14
VelociChicken wrote:
>> Stereo channels are independent. There must be an error in your code.
>
> I was asking what to do for stereo, but O.K. thanks for the reply - they are
> separate? So... If I have a stereo impulse of a large hall, and process the
> channels independently on a stereo sound like a hand-clap but the clap is
> panned to the far left - then independent convolution will sound fine on the
> left but silent on the right, which is wrong as this does not mimic the
> space itself. Downloading a few convolution plug-in demos do indeed show the
> channels to be independent though. Surprised me a little I guess. : )
It is up to the microphones to pick up the stereophonic aspects of the
sound in the room. As far as the processing chain is concerned, separate
channels might as well be separate mono radio stations.
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Reply by mnentwig●October 14, 20072007-10-14
Hi,
In the general case, a 2 input 2 output system has four independent
impulse responses. Probably you can simplify things (turn an cross-impulse
response into a constant factor, for example) but that really depends on
your application.
-mn
Reply by Randy Yates●October 14, 20072007-10-14
"VelociChicken" <bob@yahoob.com> writes:
>> Stereo channels are independent. There must be an error in your code.
>
> I was asking what to do for stereo, but O.K. thanks for the reply - they are
> separate? So... If I have a stereo impulse of a large hall, and process the
> channels independently on a stereo sound like a hand-clap but the clap is
> panned to the far left - then independent convolution will sound fine on the
> left but silent on the right, which is wrong as this does not mimic the
> space itself. Downloading a few convolution plug-in demos do indeed show the
> channels to be independent though. Surprised me a little I guess. : )
>
> Cheers,
> VC
You need to examine your assumptions more closely. Are you positing that
the two input channels (l and r) are emitting into an acoustic space and
you want to reproduce the resulting signal that arrives at a listener's
left and right ears?
If so, then you're right - there has to be some interchannel crossfeed
for the general case (and for any practical acoustic space
simulation). Specifically, you'll need Hll(f), Hlr(f), Hrr(f), and
Hrl(f), where Hxy denotes the system function from input channel x to
ear y. Where you would get such system functions is another story.
--
% Randy Yates % "Midnight, on the water...
%% Fuquay-Varina, NC % I saw... the ocean's daughter."
%%% 919-577-9882 % 'Can't Get It Out Of My Head'
%%%% <yates@ieee.org> % *El Dorado*, Electric Light Orchestra
http://www.digitalsignallabs.com
Reply by VelociChicken●October 14, 20072007-10-14
> Stereo channels are independent. There must be an error in your code.
I was asking what to do for stereo, but O.K. thanks for the reply - they are
separate? So... If I have a stereo impulse of a large hall, and process the
channels independently on a stereo sound like a hand-clap but the clap is
panned to the far left - then independent convolution will sound fine on the
left but silent on the right, which is wrong as this does not mimic the
space itself. Downloading a few convolution plug-in demos do indeed show the
channels to be independent though. Surprised me a little I guess. : )
Cheers,
VC
Reply by Jerry Avins●October 14, 20072007-10-14
VelociChicken wrote:
> Hello, I've written my own convolution algorithm using FFT, all seems to
> work nicely and it's fairly fast. But I've got a little stuck on making it
> true stereo. Originally I thought I just simply use two convolutions, but
> that does not work because the impulses fed into the system work on the left
> AND right hand sides. So there needs to be some kind of cross feed at work.
> I've tried in vain looking around the net, and was wondering if some kind
> person could nudge me in the right direction on this. Can this be
> pre-processed into the stereo impulse itself? How's this done?
Stereo channels are independent. There must be an error in your code.
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯