I'm writing a 2 externals for PD as part of my 3rd dissertation for a computer science degree. They are both signal externals, they are part of the LPC (linear predictive coding) algorithm, 1 to analyse the signal (create the filter coefficients and filter the incoming signal to give the source signal) and 1 to resynthesize the signal (using the filter coefficients to filter the source signal).
However I've created both externals and sometimes when the items are created they behave as expected and work perfectly, but more often they do not work as intended (the explanation for the problems with each individual external are below if you wish to know more), this is without changing the C code. I've tried various techniques to try to find out why this is happening all of which preform the same when working correctly or not. So I wondered if anyone had any advise or had experienced similar problems before? I believe it could be something to do with the dsp routines? possibly getting out of sync? But I am just speculating.
the analysis part does not filter the signal properly (possibly due to the filter coefficients being wrong) but it seems to not output every block of signal (ie when shown on a graph it will randomly flash a wave then will be blank again)
the synthesis part appears not to correctly filter the input signal with the given filter coefficients possibly because the list of coefficients passed from the previous object are out of sync with incoming signal, in which case is there a way ensuring they are in sync?
I realise that the above text maybe hard to follow, but unfortunately it is hard to explain the problem, if you need more information, a better explanation etc. please don't hesitate to contact me at: a.r.hassall at gmail.com
Thank you Andrew Hassall