On Sun, Mar 8, 2020 at 8:02 PM Spencer Russell wrote:
> In fact, the the standard STFT analysis/synthesis pipeline is the same
> thing as overlap-add "fast convolution" if you:
>
> 1. Use a rectangular window with a length equal to your hop size
> 2. zero-pad each input frame by the length of you
Nowhere was it mentioned that there was an across the frame multiplication
with a scalar as far as manipulating the transform coefficients. That
might make it time variant. My concept was in the domain of audio
engineering which reads a side-chain signal to obtain attenuation factors
in the conte
On Sun, Mar 8, 2020, at 7:41 PM, Ethan Duni wrote:
> FFT filterbanks are time variant due to framing effects and the circular
> convolution property. They exhibit “perfect reconstruction” if you design the
> windows correctly, but this only applies if the FFT coefficients are not
> altered betwe
so Ethan, what is your definition of time invariance? because you say it's
not time invariant because of time domain aliasing but then you say there
is delay due to compute time. delay due to window and compute time is
unavoidable and not to be factored into time invariance / variance. coding
no
>
> If the system is suitably designed (e.g. correct window and overlap),
> you can filter using an FFT and get identical results to a time domain
> FIR filter (up-to rounding/precision limits, of course). The
> appropriate window and overlap process will cause all circular
> convolution artefact
On Sun, Mar 8, 2020 at 11:41 PM Ethan Duni wrote:
> FFT filterbanks are time variant due to framing effects and the circular
> convolution property. They exhibit “perfect reconstruction” if you design the
> windows correctly, but this only applies if the FFT coefficients are not
> altered betwe
No, MDCT TDAC is the same. Perfect reconstruction only obtains if the
coefficients are not changed at all. Coding noise causes (uncancelled) time
domain aliasing that is shaped according to the window design. Limiting this
effect is a primary aspect of MDCT codec design.
Ethan
> On Mar 8, 202
Audio compression by definition 'alters' the transform coefficients and
they get perfect reconstruction with no aliasing due to the transform
alone. In fact 'TDAC' or time domain aliasing cancellation is a hallmark
of the MDCT or DCT type IV which is ubiquitous in audio codecs.
On Sun, Mar 8, 202
FFT filterbanks are time variant due to framing effects and the circular
convolution property. They exhibit “perfect reconstruction” if you design the
windows correctly, but this only applies if the FFT coefficients are not
altered between analysis and synthesis. If you alter the FFT coefficient
The system is memoryless just because it is based on the DFT and nothing
else, which is also why it's time-invariant. unless you alter certain
parameters in real-time like the window size or hop size or windowing
function, etc, any input gives you the same output at any given time, which
is the de
Well I believe the system is LTI just because the DFT is LTI by
definition. The impulse response of a rectangular window I believe is that
of a sinc function, which has ripple artifacts. Actually, the overlap-add
method (sorry I don't have time to dig into the differences between
overlap-add and
> On March 8, 2020 2:00 PM Zhiguang Eric Zhang wrote:
>
> it is not causal because the zero-phase system does not depend on past samples
>
>
> On Sun, Mar 8, 2020 at 1:58 PM Zhiguang Eric Zhang wrote:
> > the frequency response is a function of the windowing function
> >
> >
what frequenc
it is not causal because the zero-phase system does not depend on past
samples
On Sun, Mar 8, 2020 at 1:58 PM Zhiguang Eric Zhang wrote:
> the frequency response is a function of the windowing function
>
> On Sun, Mar 8, 2020 at 10:34 AM robert bristow-johnson <
> r...@audioimagination.com> wrot
the frequency response is a function of the windowing function
On Sun, Mar 8, 2020 at 10:34 AM robert bristow-johnson <
r...@audioimagination.com> wrote:
>
>
> > On March 8, 2020 10:05 AM Ethan Duni wrote:
> >
> >
> > It is physically impossible to build a causal, zero-phase system with
> non-tr
> On March 8, 2020 10:05 AM Ethan Duni wrote:
>
>
> It is physically impossible to build a causal, zero-phase system with
> non-trivial frequency response.
a system that operates in real time. when processing sound files you can
pretend that you're looking at some "future" samples. i gues
It is physically impossible to build a causal, zero-phase system with
non-trivial frequency response.
Ethan
> On Mar 7, 2020, at 7:42 PM, Zhiguang Eric Zhang wrote:
>
>
> Not to threadjack from Alan Wolfe, but the FFT EQ was responsive written in C
> and running on a previous gen MacBook P
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