Re: [music-dsp] Fractional delay filters in Python?

[robert bristow-johnson]

On 3/2/17 6:45 PM, Stefan Sullivan wrote:

Fractional sample delays are simply integer sample delays with
interpolators at the back of them. It's common to implement it as a
delay followed by an allpass filter. Take a look at Julius Smith's
book: 
https://ccrma.stanford.edu/~jos/Interpolation/Simple_Interpolators_suitable_Real.html.

For the delay part, it really depends on your application. You could
just prepend a bunch of zeros to a signal. For the interpolator, you
can implement it as a filter using scipy.signal.lfilter()
https://docs.scipy.org/doc/scipy-0.18.1/reference/generated/scipy.signal.lfilter.html#scipy.signal.lfilter

i can't help regarding Python, but i just wanted to add something to 
what Stefan said.  i wanna kinda give it the canonical FIR spin.


a precision delay can be split into an integer delay and, what i would 
call, a fractional delay.  the fractional delay is conceptually the 
fractional part of the total precision delay.


let D = the delay amount measured in units of the sampling period.

D_i = floor(D)   // integer part
D_f = D - D_i// fractional part

so D = D_i + D_f  and it turns out that  0 <= D_f < 1

then

y[n] = \sum_{m=0}^{M-1} h[k,m] x[n-m-(D_i-M/2)]

and k = floor(D_f r)  where r is the upsampling ratio (to the highest 
upsampling factor)  r might be something like 512 to get enough 
fractional delays.  and 0 <= k < r .


so you have a family of different impulse responses.  fix k to some 
value then h[k,n] is a causal impulse response that is a delay of M/2 + 
D_f samples.


getting that family of curves takes an LPF filter design program like 
Parks-McClellan or, if you want a closed-form solution, a 
Kaiser-windowed sinc function.  maybe the JOS stuff can tell you exactly 
how to do that.  if you want me to spell out how to do a Kaiser-windowed 
sinc(), i guess i can do that.  but i think i've done it before 
somewhere (maybe comp.dsp).


--

r b-j  r...@audioimagination.com

"Imagination is more important than knowledge."



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Re: [music-dsp] Fractional delay filters in Python?

[Stefan Sullivan]

Fractional sample delays are simply integer sample delays with
interpolators at the back of them. It's common to implement it as a
delay followed by an allpass filter. Take a look at Julius Smith's
book: 
https://ccrma.stanford.edu/~jos/Interpolation/Simple_Interpolators_suitable_Real.html.

For the delay part, it really depends on your application. You could
just prepend a bunch of zeros to a signal. For the interpolator, you
can implement it as a filter using scipy.signal.lfilter()
https://docs.scipy.org/doc/scipy-0.18.1/reference/generated/scipy.signal.lfilter.html#scipy.signal.lfilter

-stefan


On Thu, Mar 2, 2017 at 8:50 AM, Olivier Bélanger  wrote:
> Hi Leonardo,
>
> Don't know if this can be of any help, but I've implemented one in the
> pyo module:
>
> http://ajaxsoundstudio.com/pyodoc/api/classes/effects.html#waveguide
>
> It's not in pure python (would be too slow to compute) but you can
> take a look at the C implementation (line 975+):
>
> https://github.com/belangeo/pyo/blob/master/src/objects/delaymodule.c
>
> Olivier
>
> http://ajaxsoundstudio.com/software/pyo/
>
>
> On Thu, Mar 2, 2017 at 9:51 AM, Leonardo Gabrielli
>  wrote:
>> Dear all,
>> I'm looking into a fractional delay filter design implemented in python, if
>> it exists... If not, well I will need to implement one, and since I'm new to
>> numeric stuff in python pointers and tips will be highly appreciated!
>> BTW: My goal is to implement a simple digital waveguide string model.
>>
>> Best regards,
>> Leonardo
>>
>>
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Re: [music-dsp] Job: Audio and Video Project Manager at Google

[Ross Bencina]

Hi Don,

> I work as an engineer in the Pro Audio team here at Google.
[snip]
> Mobile is the future of how people consume media

There seems to be a contradiction here. Typically, "Pro Audio" includes 
the production and broadcast side of things. The job ad mentions only 
consumption and consumer media applications.


What exactly does "Pro Audio" mean in the context of Android's mission, 
and your team in particular?


Thanks,

Ross.


On 3/03/2017 2:55 AM, Don Turner wrote:

I work as an engineer in the Pro Audio team here at Google. We are
looking for a Project Manager in the Android audio and video framework
engineering team. I thought someone on this list might be interested.
The role is not yet advertised publicly.

*Job description*

Do you absolutely love music and video? Come join the team building the
world’s most popular OS.


We are looking for a PM to own Android Media, including all our OS
features around audio and video. Mobile is the future of how people
consume media - depending on which benchmark you read, we are about to
cross over (mobile greater than TV for media consumption) or we already
have. And yet, this space remains incredibly nascent. Audio and video
experiences are nowhere near the quality and richness they need to
reach; further, mobile unlocks a richness of new potential use cases
that we've barely begun to tap. And if that isn't enough, Android's
Media stack powers Chromecast - now the world's most popular set-top
connectors to TVs - as well as AndroidTV. This is a great career
opportunity if you are passionate about music and video and also have
the technical chops to envision moonshots about what this platform looks
like in the long run.


Ideal candidates are strongly user focused and great at cross-team
collaboration and vision. Requirements:

  *

BA/BS in Computer Science (or equivalent)

  *

Passionate about music and video

Bonus points for:

  *

Domain knowledge / expertise in Media frameworks

  *

Exceptional analytical skills

  *

Experience working as a developer, and/or as PM on technical products

Note: the role is based in Mountain View, US (Google HQ) and only
available to applicants who have permission to work in the US.

Please email dontur...@google.com  with
your CV if interested.

Many thanks,

Don


Don Turner | Developer Advocate | dontur...@google.com
 | +44 7939 287199 


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Re: [music-dsp] Fractional delay filters in Python?

[Olivier Bélanger]

Hi Leonardo,

Don't know if this can be of any help, but I've implemented one in the
pyo module:

http://ajaxsoundstudio.com/pyodoc/api/classes/effects.html#waveguide

It's not in pure python (would be too slow to compute) but you can
take a look at the C implementation (line 975+):

https://github.com/belangeo/pyo/blob/master/src/objects/delaymodule.c

Olivier

http://ajaxsoundstudio.com/software/pyo/


On Thu, Mar 2, 2017 at 9:51 AM, Leonardo Gabrielli
 wrote:
> Dear all,
> I'm looking into a fractional delay filter design implemented in python, if
> it exists... If not, well I will need to implement one, and since I'm new to
> numeric stuff in python pointers and tips will be highly appreciated!
> BTW: My goal is to implement a simple digital waveguide string model.
>
> Best regards,
> Leonardo
>
>
> ___
> dupswapdrop: music-dsp mailing list
> music-dsp@music.columbia.edu
> https://lists.columbia.edu/mailman/listinfo/music-dsp
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[music-dsp] Job: Audio and Video Project Manager at Google

[Don Turner]

I work as an engineer in the Pro Audio team here at Google. We are looking
for a Project Manager in the Android audio and video framework engineering
team. I thought someone on this list might be interested. The role is not
yet advertised publicly.

*Job description*

Do you absolutely love music and video? Come join the team building the
world’s most popular OS.


We are looking for a PM to own Android Media, including all our OS features
around audio and video. Mobile is the future of how people consume media -
depending on which benchmark you read, we are about to cross over (mobile
greater than TV for media consumption) or we already have. And yet, this
space remains incredibly nascent. Audio and video experiences are nowhere
near the quality and richness they need to reach; further, mobile unlocks a
richness of new potential use cases that we've barely begun to tap. And if
that isn't enough, Android's Media stack powers Chromecast - now the
world's most popular set-top connectors to TVs - as well as AndroidTV. This
is a great career opportunity if you are passionate about music and video
and also have the technical chops to envision moonshots about what this
platform looks like in the long run.


Ideal candidates are strongly user focused and great at cross-team
collaboration and vision. Requirements:

   -

   BA/BS in Computer Science (or equivalent)
   -

   Passionate about music and video

Bonus points for:

   -

   Domain knowledge / expertise in Media frameworks
   -

   Exceptional analytical skills
   -

   Experience working as a developer, and/or as PM on technical products

Note: the role is based in Mountain View, US (Google HQ) and only available
to applicants who have permission to work in the US.

Please email dontur...@google.com with your CV if interested.

Many thanks,

Don


Don Turner | Developer Advocate | dontur...@google.com | +44 7939 287199
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[music-dsp] Fractional delay filters in Python?

[Leonardo Gabrielli]

Dear all,
I'm looking into a fractional delay filter design implemented in python, if
it exists... If not, well I will need to implement one, and since I'm new
to numeric stuff in python pointers and tips will be highly appreciated!
BTW: My goal is to implement a simple digital waveguide string model.

Best regards,
Leonardo
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