[Clam-devel] does ladspa increase latency ?

[globot]

hi,

today i was testing ladspa plugins (because there is a lot of usefull 
things in ladspa), but i still need realtime processing, and i have 
mesured some increase in latency when using ladspa plugin. The increase 
is made in such a way i can't get my network running under 310 frames of 
latency between a micro and outputs.

the network is simple: input -> gainIn -> EQ -> gainOut -> output
all measurements are done with a sample rate of 48000Hz
____________________________________________________
if EQ = FFT_fftw3 -> 3BandFilter -> IFFT_fftw3
and gain is made with the CLAM::AudioMixer
buffersize is set to 32
i get around 150 frame of latency.
_____________________________________________________
if EQ = FFT_fftw3 -> 3BandFilter -> IFFT_fftw3
if i remove gainIn and gainOut and connect directly
i get aroud 118 frames of latency.
_____________________________________________________
if EQ = FFT_fftw3 -> 3BandFilter -> IFFT_fftw3
if for gainIn and Out i use ladspa plugins (id 1181, simple amplifier)
i get around 320 frames of latency
_____________________________________________________
if EQ =  multiBandEQ (ladspa plugin id 1197)
and use ladspa plugins (id 1181, simple amplifier) for GainIn and Out
with buffer size of 32
i get around 329 frames of latency
_____________________________________________________
if EQ =  multiBandEQ (ladspa plugin id 1197)
and gain is made with the CLAM::AudioMixer
with buffer size of 32
i get around 329 frames of latency
_____________________________________________________

the thing that seem strange here is for the test 4 and 5, because if i 
increase the buffersize for the ladspa Equalizer, my latency change (if 
i set 64 for the ladspa EQ buffer size, i got around 360 frames of 
latency) but i still got a mysterious latency that is added to the theory.

All the latency values given are approximative (maybe a few frames of 
difference) because my eyes was tired of watching supper zoomed in 
sounds. :)

to  get those result i take tow computer, divide the micro cable in two 
one for PC1 input 1, one for PC2 input 2, then i take the output 1 of 
PC1 to the input 2 of PC2.
PC1 is for sound processing, and PC2 is for measurment

MIC --o---> (in1)PC1 (out1)
      |                 |
      o---> (in1)PC2    |
            (in2)<------o


PS: use fixed font with to read this message