[Clam-devel] Spectral Analysis/Synthesis problem

globot gglobot at gmail.com
Fri Nov 30 04:05:06 PST 2007

>I am surprised that with those settings all you get is a "small glitch". 
>Is that with the filter
>active? I would predict that as soon as you start doing noticeable 
>transformations to the spectrum
>with those settings you would have more problems including a sort of 
>phasiness. But if not, let me
>know. My advice:
with the small modif i mad in the patch i send previously i got exactly 
what i want... with 0 glitch...
my global latency is 8ms, including network, jackdmp (64frames) next 
week i will drop latency to 4ms by rewrting  and regrouping some 
processing and decrising jackd buffer...
now i use a stable kernel 2.6.17 without patch of any kind on an old AMD 
64 3200+. I will try on low latency patched kernel 2.6.23 with a Pentium 
core 2 duo to see what happen :)
sound card = M-Audio 1010Lt

the only glitch i have is when the network scanner of my application 
start, it cause a lot of Xrun because launch a lot of thread....I Will 
rewrite it i guess :)

>- Use an analysis hop size of at most windowSize/4... that is 64 in your 
>- Use the same analysis and synthesis hop size (again 64)
I know i should do that but strangely when i use the same, the sound is 
play at half speed on output, and it is very ugly...

>- In general an FFTSize of 226 is really, really small to do anything 
>meaningful but
>it might work decently on a 3Band filter so you might want to keep it 
>this way to
>reduce latency.
Yes it is low, but the minimum i need to apply the transformation i 
want... Plus i need low latency...

>- As Pau suggested, the "None" window is not the most advisable (maybe 
>the least) because of
>the characteristics of its transform. Again in a simple filter and if 
>you don't go to extreme settings
>you will get by with it but I don't see any reason you should want to 
>use it instead of a more reasonable
>window such as BH92,

For the Window, each time i apply an other type, the output wave form is 
modified.... and i need to get a similar wave because at this stage i 
just apply a custom equalizer that will also in some case act like high 
or low pass filter.... so what i expect from the Analysis is just a good 
spectrum, and i expect the Synthetyzer rebuild something that look like 
the original wave if my transformation is null (the user could use this 

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