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

[Frank Lorenz]

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), please?

cheers,
Frank

-----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?

cheers,
Frank


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