[music-dsp] Job openings at Cirrus Logic

[Earl Vickers]

Here are a few audio / DSP job openings at Cirrus Logic:

Algorithm Research Engineer   (Stockholm, Sweden)
Audio and Acoustic Applications Engineer   (Austin, TX)
Audio Machine Learning Engineer   (Salt Lake City, UT)
DSP Applications Engineer   (Edinburgh, Scotland)
DSP Firmware Engineer   (Austin)
Intern, Acoustics Systems Engineer   (Austin)
Manager, Acoustic Applications Engineering   (Austin)
Mixed Signal Audio Applications Engineer   (Austin)
Mixed Signal Audio Applications Engineer - Audio Tuning   (Austin)
Principal DSP Design Engineer   (Edinburgh, Scotland)
Principal Research Engineer   (Madrid, Spain)
Senior DSP Development Engineer   (Mesa, Arizona)
Senior DSP Firmware Engineer   (Austin)
Senior DSP Researcher   (Richmond, Victoria, Australia)
Senior/Principal Acoustics Applications Engineer   (Edinburgh or Newbury)
Speech Researcher   (Edinburgh)

For more info or to apply, go to:
http://app.jobvite.com/m?3V6DIjwa

(I’m not the recruiter, so don’t contact me.)


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Re: [music-dsp] (Novel?) "Modal Phase Rotation Synthesis"

[gm]

After looking at it I think probably you can but you need trig 
calculations every sample
when you change the frequency and quite some additional calculations for 
the WGR every sample

in this case.
So its cheaper to use a standard oscillator with a sine aproximation for 
phase mod.  in both cases.


The MCF seems lighter on CPU then what I do if you insist that the rotation
must be on a perfect circle instead of the parapolic shape,
but I think when used as an oscillator it has issues
with frequency accuracy or amplitude rescaling or something similar?

And it appears not to rotate on a perfect circle internally either
but just from looking at the paper I can't tell if and how that matters.

I remember years ago I investigated both for use as an undamped 
oscillator and
came to the conclusion that a fast sine approximation is superior for 
phase modulation.

But I dont recall the details.

The sine approximation I use only needs 4 multiplies so I am not sure
if I am on the right path using filters.

There seems to be an advantage with voice stealing though, the click
you get is masked and blurred by the filters response


Am 03.04.2018 um 14:37 schrieb Corey K:
Yes, I think you can do phase modulation with those filters. They are 
referred to colloquially as "phasor filters", because their phase is 
manipulated in order to rotate a vector around the complex plane...


On Tue, Apr 3, 2018 at 8:16 AM, gm > wrote:



Yes it's related, I dont recall if I used one of these filters
in my first implementation which was several years ago.
I used a complex filter before I used the SVF and AP.

But I think you can't do full phase modulation with such filters?
I think that was my motivation to apply the rotation outside of
the filter.

Either way it seems lighter on cpu when you use the external
rotation with
parabolas instead of trig operations since you dont have to constantly
adapt the internal state of the filter.

A drawback of the method in general with either filter is that
you can cancel the internal state with an impulse.

I havent figured out what the best excitation signal is.

The paper you linked suggests to delay the impulse until a zero
crossing
but that is not an option in my use cases.


Am 03.04.2018 um 01:46 schrieb Corey K:

Your idea seems to bear a few similarities to this (just in case
you haven't seen it already):
https://ccrma.stanford.edu/~jos/smac03maxjos/




On Mon, Apr 2, 2018 at 2:46 PM, gm > wrote:


I don't know if this idea is new, I had it for some time but
have never seen it mentioned anywhere:

Use a filter with high q and rotate it's (complex) output by
the (real) output
of another filter to obtain a phase modulated sine wave.
Excite with an impulse or impact signal.

It's basically crossed between modal and phase modulation
synthesis.

Now there are some ideas to this to make it practical and a
useful substitute for phase modulation and FM:

You can use a state variable filter with an additional
allpass instead of
the complex filter to obtain a filter you can pitch modulate
in audio
(useful for drum synthesis ect) (or maybe the 90 shift can be
designed more efficiently
into the SVF IDK.)

Instead of expensive trig calculations for the rotation, or using
the normalized complex signal form the other filter (also
expensive)
just use a very coarse parabolic sine/cosine approximation
and the real signal,
the difference is really very small sonically, since the
modulator is still sine
and the radius stays around 1 so it's the effect of a small
amplitude modulation on the modulator
caused by the slight deviation of the circle.
I couldnt tell the difference when I tested it first.

You need 7 mults and 4 adds in addition to the SVF for the AP
and rotation per carrier.

But you save an envelope for each operator and have a pretty
efficient sine operator with the SVF.
And you get all the benfits of phase modulation over
frequency modulation of the
filter cutoff.
It's very useful for drum synthesis but also useful for some
other percussive sounds like "FM" pianos etc.

Here is an audio demo, with cheap "soundboard" and some other
fx added:
https://soundcloud.com/traumlos_kalt/smoke-piano-test-1-01/s-W54wz


I wonder if this idea is new?

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Re: [music-dsp] (Novel?) "Modal Phase Rotation Synthesis"

[Corey K]

Yes, I think you can do phase modulation with those filters. They are
referred to colloquially as "phasor filters", because their phase is
manipulated in order to rotate a vector around the complex plane...

On Tue, Apr 3, 2018 at 8:16 AM, gm  wrote:

>
> Yes it's related, I dont recall if I used one of these filters
> in my first implementation which was several years ago.
> I used a complex filter before I used the SVF and AP.
>
> But I think you can't do full phase modulation with such filters?
> I think that was my motivation to apply the rotation outside of the filter.
>
> Either way it seems lighter on cpu when you use the external rotation with
> parabolas instead of trig operations since you dont have to constantly
> adapt the internal state of the filter.
>
> A drawback of the method in general with either filter is that
> you can cancel the internal state with an impulse.
>
> I havent figured out what the best excitation signal is.
>
> The paper you linked suggests to delay the impulse until a zero crossing
> but that is not an option in my use cases.
>
> Am 03.04.2018 um 01:46 schrieb Corey K:
>
> Your idea seems to bear a few similarities to this (just in case you
> haven't seen it already):
> https://ccrma.stanford.edu/~jos/smac03maxjos/
>
>
>
> On Mon, Apr 2, 2018 at 2:46 PM, gm  wrote:
>
>>
>> I don't know if this idea is new, I had it for some time but have never
>> seen it mentioned anywhere:
>>
>> Use a filter with high q and rotate it's (complex) output by the (real)
>> output
>> of another filter to obtain a phase modulated sine wave.
>> Excite with an impulse or impact signal.
>>
>> It's basically crossed between modal and phase modulation synthesis.
>>
>> Now there are some ideas to this to make it practical and a useful
>> substitute for phase modulation and FM:
>>
>> You can use a state variable filter with an additional allpass instead of
>> the complex filter to obtain a filter you can pitch modulate in audio
>> (useful for drum synthesis ect) (or maybe the 90 shift can be designed
>> more efficiently
>> into the SVF IDK.)
>>
>> Instead of expensive trig calculations for the rotation, or using
>> the normalized complex signal form the other filter (also expensive)
>> just use a very coarse parabolic sine/cosine approximation and the real
>> signal,
>> the difference is really very small sonically, since the modulator is
>> still sine
>> and the radius stays around 1 so it's the effect of a small amplitude
>> modulation on the modulator
>> caused by the slight deviation of the circle.
>> I couldnt tell the difference when I tested it first.
>>
>> You need 7 mults and 4 adds in addition to the SVF for the AP and
>> rotation per carrier.
>>
>> But you save an envelope for each operator and have a pretty efficient
>> sine operator with the SVF.
>> And you get all the benfits of phase modulation over frequency modulation
>> of the
>> filter cutoff.
>> It's very useful for drum synthesis but also useful for some other
>> percussive sounds like "FM" pianos etc.
>>
>> Here is an audio demo, with cheap "soundboard" and some other fx added:
>> https://soundcloud.com/traumlos_kalt/smoke-piano-test-1-01/s-W54wz
>>
>> I wonder if this idea is new?
>>
>> ___
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>>
>>
>
>
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>
>
>
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Re: [music-dsp] (Novel?) "Modal Phase Rotation Synthesis"

[gm]

Yes it's related, I dont recall if I used one of these filters
in my first implementation which was several years ago.
I used a complex filter before I used the SVF and AP.

But I think you can't do full phase modulation with such filters?
I think that was my motivation to apply the rotation outside of the filter.

Either way it seems lighter on cpu when you use the external rotation with
parabolas instead of trig operations since you dont have to constantly
adapt the internal state of the filter.

A drawback of the method in general with either filter is that
you can cancel the internal state with an impulse.

I havent figured out what the best excitation signal is.

The paper you linked suggests to delay the impulse until a zero crossing
but that is not an option in my use cases.


Am 03.04.2018 um 01:46 schrieb Corey K:
Your idea seems to bear a few similarities to this (just in case you 
haven't seen it already):
https://ccrma.stanford.edu/~jos/smac03maxjos/ 





On Mon, Apr 2, 2018 at 2:46 PM, gm > wrote:



I don't know if this idea is new, I had it for some time but have
never seen it mentioned anywhere:

Use a filter with high q and rotate it's (complex) output by the
(real) output
of another filter to obtain a phase modulated sine wave.
Excite with an impulse or impact signal.

It's basically crossed between modal and phase modulation synthesis.

Now there are some ideas to this to make it practical and a useful
substitute for phase modulation and FM:

You can use a state variable filter with an additional allpass
instead of
the complex filter to obtain a filter you can pitch modulate in audio
(useful for drum synthesis ect) (or maybe the 90 shift can be
designed more efficiently
into the SVF IDK.)

Instead of expensive trig calculations for the rotation, or using
the normalized complex signal form the other filter (also expensive)
just use a very coarse parabolic sine/cosine approximation and the
real signal,
the difference is really very small sonically, since the modulator
is still sine
and the radius stays around 1 so it's the effect of a small
amplitude modulation on the modulator
caused by the slight deviation of the circle.
I couldnt tell the difference when I tested it first.

You need 7 mults and 4 adds in addition to the SVF for the AP and
rotation per carrier.

But you save an envelope for each operator and have a pretty
efficient sine operator with the SVF.
And you get all the benfits of phase modulation over frequency
modulation of the
filter cutoff.
It's very useful for drum synthesis but also useful for some other
percussive sounds like "FM" pianos etc.

Here is an audio demo, with cheap "soundboard" and some other fx
added:
https://soundcloud.com/traumlos_kalt/smoke-piano-test-1-01/s-W54wz


I wonder if this idea is new?

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