[Speex-dev] Fwd: Re: Fixed Point on wideband-mode: Single Frame loss on 2000 Hz sine causes "freak off"

[Frank Lorenz]

O.k., some more info:

I just tested bandwidth widening to fix this. But I need to go to gamma values below 0.9 to become stable -- clearly too much widening, I think.

I looked inside the Levinson-Durbin algorithm next. The lines

#ifdef FIXED_POINT
      r = DIV32_16(rr+PSHR32(error,1),ADD16(error,8));
#else
      r = rr/(error+.003*ac[0]);
#endif

look interesting. While for floating point, .003*ac[0] is added to error, for fixed point, a constant value of 8 is added. When I alter this value, I get an output without "freaking out" for values 1,2,3 and 5. for 4, 6 and 7 the system is still instable.

I tired to change the line to 
 r = DIV32_16(rr+PSHR32(error,1),MULT16_16(ac[0],98));
but without success. Maybe, precision is too low...

Can you give me some hint how to proceed here?

best regards,
Frank

______________________________________________________
GRATIS für alle WEB.DE-Nutzer: Die maxdome Movie-FLAT!
Jetzt freischalten unter http://movieflat.web.de