On Wed, Oct 19, 2011 at 03:23:34PM +0200, Jeremy Jongepier wrote: > Soundwise, as far as I have understood as a DSP layman it could > introduce artefacts, but I wonder in how far those are audible. Guess if > you're a DSP layman you probably can't distinguish any possible > artefacts. The other point is the DSP load of JAMin, last time I used > JAMin on my quad core machine I recall the DSP load rose about 20 to > 25%. If I use separate plug-ins it's about 10%. But I have to test that > again to be sure sure. The two issues are related. The FFT based EQ in Jamin uses a form of block processing that leads to a filter that is not time-invariant, it produces AM on some frequencies. In the first release that was very obvious, you could actually hear it quite easily. Instead of changing the algorthm to a correct one (which would be quite similar) the Jamin devs chose to mitigate the effect by increasing the overlap between successive blocks. IIRC there are now 32 overlapping blocks at any time. This reduces the modulation to acceptable levels, but is also what is responsible for the high CPU load. A correct implementation of this type of EQ requires an overlap of half the FFT size, so it would require much less CPU. Ciao, -- FA _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
