Hi all, I am interested in implementing a Digital Mixer(mixing 2 voice signals). But I had HARD luck in finding the relevant material so far....I could only find filters in abundance. Can anyone suggest me ANY book/link which would have the implementation of the Mixer? Currently I have the following books: i)DSP by Oppenheim & Schafer. ii)Theory and Application of Digital Signal Processing - Rabiner and Gold iii) DSP - Salivahanan,Vallavaraj,Gnanapriya But there is nothing about Mixers in these books.... Also what are the basics in DSP that I can learn from these books before going into the Mixer implementation/algorithm? I need your suggestions.....Please reply....... Thanks in advance, Prakash.
Digital Mixer.
Started by ●August 19, 2002
Reply by ●August 19, 20022002-08-19
Ulrich Prakash-
> I am interested in implementing a Digital
Mixer(mixing 2 voice signals).
> But I had HARD luck in finding the relevant material so far....I could only
> find filters in abundance.
>
> Can anyone suggest me ANY book/link which would have the implementation of
> the Mixer?
>
> Currently I have the following books:
> i)DSP by Oppenheim & Schafer.
> ii)Theory and Application of Digital Signal Processing - Rabiner and Gold
> iii) DSP - Salivahanan,Vallavaraj,Gnanapriya
>
> But there is nothing about Mixers in these books....
>
> Also what are the basics in DSP that I can learn from these books before
> going into the Mixer implementation/algorithm?
Mix == add. Add your signals together, like this:
y[n] = a*x1[n] + b*x2[n]
Suggest that you maintain a + b = 1. Then put a dial on your MATLAB GUI that
allows
the user to adjust between a and b. All the way to left, a = 1. All the way to
right, b = 1.
Jeff Brower
DSP sw/hw engineer
Signalogic
Reply by ●August 19, 20022002-08-19
Hi Jeff, Thanks for the reply. I have some queries,pls see inline..... At 07:34 AM 8/19/02 -0500, Jeff Brower wrote: >Ulrich Prakash- > > > I am interested in implementing a Digital Mixer(mixing 2 voice signals). > > But I had HARD luck in finding the relevant material so far....I could only > > find filters in abundance. > > > > Can anyone suggest me ANY book/link which would have the implementation of > > the Mixer? > > > > Currently I have the following books: > > i)DSP by Oppenheim & Schafer. > > ii)Theory and Application of Digital Signal Processing - Rabiner and Gold > > iii) DSP - Salivahanan,Vallavaraj,Gnanapriya > > > > But there is nothing about Mixers in these books.... > > > > Also what are the basics in DSP that I can learn from these books before > > going into the Mixer implementation/algorithm? > >Mix == add. Add your signals together, like this: > > y[n] = a*x1[n] + b*x2[n] > >Suggest that you maintain a + b = 1. [Prakash] Can I take a = 0.5 and b = 0.5,or is there any particular factor to evaluate the value of a and b? > Then put a dial on your MATLAB GUI that allows >the user to adjust between a and b. All the way to left, a = 1. All the >way to >right, b = 1. [Prakash] From what you have said,I assume,if x1 = {4,2,6} and x2 = {8,10,12},and a=0.5,b=0.5then y = {2+4, 1+5, 3+6} = {6, 6, 9} Is that so straight-forward?Will I hear both samples x1 and x2 from y output? But I didn't understand what you mean to the LEFT and RIGHT here. Thanks in advance, Prakash. >Jeff Brower >DSP sw/hw engineer >Signalogic > > >_____________________________________ >Note: If you do a simple "reply" with your email client, only the author >of this message will receive your answer. You need to do a "reply all" if >you want your answer to be distributed to the entire group. > >_____________________________________ >About this discussion group: > >To Join: audiodsp-subscribe@audi... > >To Post: audiodsp@audi... > >To Leave: audiodsp-unsubscribe@audi... > >Archives: http://groups.yahoo.com/group/audiodsp > >Other DSP-Related Groups: http://www.dsprelated.com > > >">http://docs.yahoo.com/info/terms/
Reply by ●August 19, 20022002-08-19
Ulrich Prakash- > >Mix == add. Add your signals together, like this: > > > > y[n] = a*x1[n] + b*x2[n] > > > >Suggest that you maintain a + b = 1. > > [Prakash] > Can I take a = 0.5 and b = 0.5,or is there any particular factor to > evaluate the value of a and b? > > > Then put a dial on your MATLAB GUI that allows > >the user to adjust between a and b. All the way to left, a = 1. All the > >way to > >right, b = 1. > > [Prakash] > From what you have said,I assume,if > x1 = {4,2,6} and x2 = {8,10,12},and a=0.5,b=0.5then > y = {2+4, 1+5, 3+6} = {6, 6, 9} > Is that so straight-forward? Yep. >Will I hear both samples x1 and x2 from y output? Yep. > But I didn't understand what you mean to the LEFT and RIGHT here. When the user turns the dial. You can put a dial (knob) on your GUI to easily demonstrate the effect; better than asking your users to enter values of a and b. Jeff Brower DSP sw/hw engineer Signalogic
Reply by ●August 19, 20022002-08-19
Have a look at: 1) Watkinson, J., The art of digital audio, 2nd ed., Focal Press (Butterworth), 1993. 2) Zzer, U., Digital audio signal processing, John Wiley & Sons, Ltd., 1995. Regards Sigmund. -----Original Message----- From: Ulrich Prakash To: Audiodsp@Audi... Sent: 8/19/2002 11:01 AM Subject: [audiodsp] Digital Mixer. Hi all, I am interested in implementing a Digital Mixer(mixing 2 voice signals). But I had HARD luck in finding the relevant material so far....I could only find filters in abundance. Can anyone suggest me ANY book/link which would have the implementation of the Mixer? Currently I have the following books: i)DSP by Oppenheim & Schafer. ii)Theory and Application of Digital Signal Processing - Rabiner and Gold iii) DSP - Salivahanan,Vallavaraj,Gnanapriya But there is nothing about Mixers in these books.... Also what are the basics in DSP that I can learn from these books before going into the Mixer implementation/algorithm? I need your suggestions.....Please reply....... Thanks in advance, Prakash. _____________________________________ Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. _____________________________________ About this discussion group: To Join: audiodsp-subscribe@audi... To Post: audiodsp@audi... To Leave: audiodsp-unsubscribe@audi... Archives: http://groups.yahoo.com/group/audiodsp Other DSP-Related Groups: http://www.dsprelated.com ">http://docs.yahoo.com/info/terms/
Reply by ●August 19, 20022002-08-19
On Mon, Aug 19, 2002 at 08:20:16AM -0500, Jeff Brower wrote:
> Ulrich Prakash-
>
> > >Mix == add. Add your signals together, like this:
> > >
> > > y[n] = a*x1[n] + b*x2[n]
> > >
> > >Suggest that you maintain a + b = 1.
> >
> > [Prakash]
> > Can I take a = 0.5 and b = 0.5,or is there any particular factor to
> > evaluate the value of a and b?
> >
> > > Then put a dial on your MATLAB GUI that allows
> > >the user to adjust between a and b. All the way to left, a = 1.
All the
> > >way to
> > >right, b = 1.
> >
> > [Prakash]
> > From what you have said,I assume,if
> > x1 = {4,2,6} and x2 = {8,10,12},and a=0.5,b=0.5then
> > y = {2+4, 1+5, 3+6} = {6, 6, 9}
> > Is that so straight-forward?
>
> Yep.
>
> >Will I hear both samples x1 and x2 from y output?
>
> Yep.
>
> > But I didn't understand what you mean to the LEFT and RIGHT here.
>
> When the user turns the dial. You can put a dial (knob) on your GUI to
easily
> demonstrate the effect; better than asking your users to enter values of a
and b.
>
Jeff,
Ulrich didn't say he was using Matlab.
Ulrich,
Don't read so many books. Experiment more. Look at the waveforms and listen
to them.
You would do well to learn a little analog signal processing as well.
Regards,
Mark
Reply by ●August 19, 20022002-08-19
Mark-
> > > >Mix == add. Add your signals
together, like this:
> > > >
> > > > y[n] = a*x1[n] + b*x2[n]
>
> Ulrich didn't say he was using Matlab.
I did not assume he was. Above is standard textbook notation, used widely.
Jeff Brower
DSP sw/hw engineer
Signalogic
Reply by ●August 20, 20022002-08-20
Hi Jeff,
In that case,if I need to mix 'm' voice channels(in the form of RTP
packets),then
y(n) = a1*x1 + a2*x2 + ... am*xm
= SIGMA ai*xi,where i = 1 to m (SIGMA - i don't have SIGMA symbol
in my mail editor)
And SIGMA ai = 1,where i = 1 to m.
In that case,if there are 10 input voice channels,then the amplitude of
original sample x1 in output y will be around x1/10.Will this not affect
the fidelity of x1?
Regards,
Prakash.
At 08:20 AM 8/19/02 -0500, Jeff Brower wrote:
>Ulrich Prakash-
>
> > >Mix == add. Add your signals together, like this:
> > >
> > > y[n] = a*x1[n] + b*x2[n]
> > >
> > >Suggest that you maintain a + b = 1.
> >
> > [Prakash]
> > Can I take a = 0.5 and b = 0.5,or is there any particular factor to
> > evaluate the value of a and b?
> >
> > > Then put a dial on your MATLAB GUI that allows
> > >the user to adjust between a and b. All the way to left, a = 1.
All the
> > >way to
> > >right, b = 1.
> >
> > [Prakash]
> > From what you have said,I assume,if
> > x1 = {4,2,6} and x2 = {8,10,12},and a=0.5,b=0.5then
> > y = {2+4, 1+5, 3+6} = {6, 6, 9}
> > Is that so straight-forward?
>
>Yep.
>
> >Will I hear both samples x1 and x2 from y output?
>
>Yep.
>
> > But I didn't understand what you mean to the LEFT and RIGHT here.
>
>When the user turns the dial. You can put a dial (knob) on your GUI to
easily
>demonstrate the effect; better than asking your users to enter values of a
>and b.
>
>Jeff Brower
>DSP sw/hw engineer
>Signalogic
Reply by ●August 20, 20022002-08-20
Ulrich- > In that case,if I need to mix 'm' voice channels(in the form of RTP > packets),then > y(n) = a1*x1 + a2*x2 + ... am*xm > > = SIGMA ai*xi,where i = 1 to m (SIGMA - i don't have SIGMA symbol > in my mail editor) > > And SIGMA ai = 1,where i = 1 to m. > In that case,if there are 10 input voice channels,then the amplitude of > original sample x1 in output y will be around x1/10.Will this not affect > the fidelity of x1? Ahh, now you not mixing, but conferencing -- you should have said so earlier. You need some type of algorithm that dynamically looks for "most energetic voice" and give that channel more weight. I've seen some conferencing algorithms that will look for most 2 or 3 dominant channels and give them weight. Clearly if you just constantly multiply every channel by 0.1 you will not hear the speaker -- he/she will be averaged with noise/silence. Not everyone talks at once, right? Or at least you hope that your algorithm does not cause them to do that :-) -Jeff > At 08:20 AM 8/19/02 -0500, Jeff Brower wrote: > >Ulrich Prakash- > > > > > >Mix == add. Add your signals together, like this: > > > > > > > > y[n] = a*x1[n] + b*x2[n] > > > > > > > >Suggest that you maintain a + b = 1. > > > > > > [Prakash] > > > Can I take a = 0.5 and b = 0.5,or is there any particular factor to > > > evaluate the value of a and b? > > > > > > > Then put a dial on your MATLAB GUI that allows > > > >the user to adjust between a and b. All the way to left, a = 1. All the > > > >way to > > > >right, b = 1. > > > > > > [Prakash] > > > From what you have said,I assume,if > > > x1 = {4,2,6} and x2 = {8,10,12},and a=0.5,b=0.5then > > > y = {2+4, 1+5, 3+6} = {6, 6, 9} > > > Is that so straight-forward? > > > >Yep. > > > > >Will I hear both samples x1 and x2 from y output? > > > >Yep. > > > > > But I didn't understand what you mean to the LEFT and RIGHT here. > > > >When the user turns the dial. You can put a dial (knob) on your GUI to easily > >demonstrate the effect; better than asking your users to enter values of a > >and b. > > > >Jeff Brower > >DSP sw/hw engineer > >Signalogic
Reply by ●August 20, 20022002-08-20
Last year I went to SPIE's AeroSense conference and learned about Independent Component Analysis and an application called the 'Cocktail Party.' Basically, it's a method to assume that n multiple signals are recorded by n microphones. ICA is the method that allows the signals to be separated into n discrete signals. Perhaps a look down this path may be what you need... Regards,/s/neil Neil E. Van de Voorde, Ph.D. Senior Scientist Planning Systems Inc. 228.689.8775 -----Original Message----- From: Jeff Brower [mailto:jbrower@jbro...] Sent: Tuesday, August 20, 2002 7:21 AM To: Ulrich Prakash Cc: audiodsp@audi... Subject: Re: [audiodsp] Digital Mixer. Ulrich- > In that case,if I need to mix 'm' voice channels(in the form of RTP > packets),then > y(n) = a1*x1 + a2*x2 + ... am*xm > > = SIGMA ai*xi,where i = 1 to m (SIGMA - i don't have SIGMA symbol > in my mail editor) > > And SIGMA ai = 1,where i = 1 to m. > In that case,if there are 10 input voice channels,then the amplitude of > original sample x1 in output y will be around x1/10.Will this not affect > the fidelity of x1? Ahh, now you not mixing, but conferencing -- you should have said so earlier. You need some type of algorithm that dynamically looks for "most energetic voice" and give that channel more weight. I've seen some conferencing algorithms that will look for most 2 or 3 dominant channels and give them weight. Clearly if you just constantly multiply every channel by 0.1 you will not hear the speaker -- he/she will be averaged with noise/silence. Not everyone talks at once, right? Or at least you hope that your algorithm does not cause them to do that :-) -Jeff > At 08:20 AM 8/19/02 -0500, Jeff Brower wrote: > >Ulrich Prakash- > > > > > >Mix == add. Add your signals together, like this: > > > > > > > > y[n] = a*x1[n] + b*x2[n] > > > > > > > >Suggest that you maintain a + b = 1. > > > > > > [Prakash] > > > Can I take a = 0.5 and b = 0.5,or is there any particular factor to > > > evaluate the value of a and b? > > > > > > > Then put a dial on your MATLAB GUI that allows > > > >the user to adjust between a and b. All the way to left, a = 1. All the > > > >way to > > > >right, b = 1. > > > > > > [Prakash] > > > From what you have said,I assume,if > > > x1 = {4,2,6} and x2 = {8,10,12},and a=0.5,b=0.5then > > > y = {2+4, 1+5, 3+6} = {6, 6, 9} > > > Is that so straight-forward? > > > >Yep. > > > > >Will I hear both samples x1 and x2 from y output? > > > >Yep. > > > > > But I didn't understand what you mean to the LEFT and RIGHT here. > > > >When the user turns the dial. You can put a dial (knob) on your GUI to easily > >demonstrate the effect; better than asking your users to enter values of a > >and b. > > > >Jeff Brower > >DSP sw/hw engineer > >Signalogic _____________________________________ Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. _____________________________________ About this discussion group: To Join: audiodsp-subscribe@audi... To Post: audiodsp@audi... To Leave: audiodsp-unsubscribe@audi... Archives: http://groups.yahoo.com/group/audiodsp Other DSP-Related Groups: http://www.dsprelated.com ">http://docs.yahoo.com/info/terms/
