[Clam-devel] Spectral Analysis/Synthesis problem

Xavier Amatriain xavier at amatriain.net
Fri Nov 30 05:24:11 PST 2007

globot wrote:
> with the small modif i mad in the patch i send previously i got 
> exactly what i want... with 0 glitch...
What patch are you referring to? Sorry if I missed something but all 
your latest patches don't seam
to deal with spectral processing at all.

And what do you mean now by 0 glitch... you solved the problem?
> 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
That sounds good.
> 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 :)
So, what ever happened to the periodic glitch you were reporting? I am 

>> - Use an analysis hop size of at most windowSize/4... that is 64 in 
>> your case
>> - 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...
This has to be a problem with sampling rate interpreting something 
wrong. A change in hop size should
not produce this kind of error.

Pau, maybe it is worth it to reproduce it and nail it with a tes
> 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 seting)
If you use the same window for analysis and synthesis the sound should 
be perfectly reconstructed. If not, it
means that you are basically doing something wrong... like using the 
wrong hop size :-)

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