[Numpy-discussion] "Dynamic convolution" in Numpy

David Huard david.huard@gmail....
Thu Jun 3 08:17:37 CDT 2010


Hi Arthur,

I've no experience whatsoever with what you are doing, but my first thought
was why don't you compute all possible versions beforehand and then
progressively switch from one version to another by interpolation between
the different versions. If the resolution is 15 degrees, there aren't that
many versions to compute beforehand.

David

On Thu, Jun 3, 2010 at 6:49 AM, arthur de conihout <
arthurdeconihout@gmail.com> wrote:

> Hello everybody
>
> i m fighting with a dynamic binaural synthesis(can give more hints on it if
> necessary).
>
> i would like to modify the sound playing according to listener's head
> position. I got special filters(binaural ones) per head position that i
> convolve in real time with a monophonic sound.When the head moves i want to
> be able to play the next position version of the stereo generated sound but
> from the playing position(bit number in the unpacked datas) of the previous
> one.My problem is to hamper audible artefacts due to transition.
> At moment i m only using *short audio wav* that i play and repeat if
> necessary entirely because my positionning resolution is 15°
> degrees.Evolution of head angle position let time for the whole process to
> operate (getting position->choosing corresponding filter->convolution->play
> sound)
>
> *For long **audio wav* I could make a fade-in fade-out from the transition
> point but i have no idea how to implement it(i m using audiolab and numpy
> for convolution)
>
> An other solution could be dynamic filtering means when i change position i
> convolve the next position filter from the place the playing must stop for
> the previous one(but won't pratically stop to let the next convolution
> operates on enough frames) in accordance with the filter frame length(all
> the filters are impulse response of the same lenght 128).
>
> The "drawing" i introduce just below is my mental representation of what i
> m looking to implement, i already apologize for its crapitude (and one of my
> brain too):
>
>
> t0_________t1__t2__t3___________________________________________________________t=len(stimulus)
> monophonic sound(time and bit position in the unpacked datas)
>
> C1C1C1C1C1C1C1C1C1C1C1...
> running convolution with filter 1 corresponding to position 1 (ex: angle
> from reference=15°)
>
>    P1_______
>    sound playing 1
>
>                    ^
>                    position 2 detection(angle=30°)
>
>                    C2C2C2C2C2C2C2C2C2C2C2...
>                    running convolution with filter 2
>
>                    P1_____x
>                    keep playing 1 for convolution 2 to operate on enough
> frames (latency)
>
>                            FIFO
>                            fade in fade out
>
>                                 P2_________
>                                 sound playing 2
>
>
> I don't know if i made myself very clear.
>
> if anyone has suggestions or has already operated a dynamic filtering i
> would be well interested.
>
> Cheers
>
> Arthur
>
>
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