[Speex-dev] Fwd: Re: Fixed Point on wideband-mode: Single Frame loss on 2000 Hz sine causes "freak off"
Jean-Marc.Valin at USherbrooke.ca
Tue Feb 2 07:10:02 PST 2010
Basically, if you have coefficients [a, b, c, d], then it means that your filter
is: 1 + a*z^-1 + b*z^-2 + c*z^-3 + d*z^-4
In fixed-point mode, the scaling factor is 8192 (i.e. Q13).
Quoting Frank Lorenz <Frank_wtal at web.de>:
> Hi Jean-Marc,
> I'm currently trying to analyze the LPC synthesis filter. For this, can you
> please tell me the exact format of the LPC coeffs (in variable interp_qlpc),
> -----Ursprüngliche Nachricht-----
> Von: "Frank Lorenz" <Frank_wtal at web.de>
> Gesendet: 02.02.10 11:00:16
> An: jean-marc.valin at usherbrooke.ca
> CC: speex-dev at xiph.org
> Betreff: Re: [Speex-dev]Fwd: Re: Fixed Point on wideband-mode: Single Frame
> loss on 2000 Hz sine causes "freak off"
> Jean-Marc Valin <Jean-Marc.Valin at USherbrooke.ca> hat am 1. Februar 2010 um
> 17:29 geschrieben:
> > Can you look at the residual signal? i.e. what it looks like after the
> pitch is
> > removed. Any significant difference there? Also, the pitch gain can be
> > informative.
> I catched the "orignal" residual (st->exc from line 400 inside nb_celp.c)
> plus the "synthesized" one (exc on line 880 inside nb_celp.c) both for fixed
> and floating point.
> There is a significant difference in the residual signal -- the fixed point
> signal shows some kind of "glitches" (see attachments) while the floating
> point version looks more or less smooth. But it is interesting that the huge
> overdrive you can observe in the re-synthesized output signal isn't present
> in the synthesized residual. This leads to an instable LPC synthesis filter,
> or am I wrong?
> GRATIS für alle WEB.DE-Nutzer: Die maxdome Movie-FLAT!
> Jetzt freischalten unter http://movieflat.web.de
> Speex-dev mailing list
> Speex-dev at xiph.org
More information about the Speex-dev