Speex dev - Jan 2010 - FW: Re: Fwd: Re: Fixed Point on wideband-mode: Single Frame loss on 2000 Hz sine causes "freak off"

Did not send this to speex-dev mailing list by error...

-----Urspr?ngliche Nachricht-----
Von: "Frank Lorenz" <Frank_wtal at web.de>
Gesendet: 14.01.10 14:03:22
An: Jean-Marc Valin <jean-marc.valin at usherbrooke.ca>
Betreff: Re: [Speex-dev] Fwd: Re: Fixed Point on wideband-mode: Single Frame
loss on 2000 Hz sine causes "freak off"
Hi Jean-Marc,

The codec mostly does not recover, it stays instable. I have attached a
screenshot of the 2 waveforms of the output for quailty 7, complexity 2: The
upper one is for a 2000 Hz, -15 dB input, the other one for 2200 Hz input. You
see the frame loss 2 seconds after start, and approx. 1.5 seconds later this
"freak out" starts. In this picuture, 2200 Hz looks worse, but in
fact, I can stabilize the 2200 Hz output by setting complexity to >= 4.
In our real time system, we had the situation that the codec did only recover
after we reduced the input signal to very small level.

One thing to note is the very different "fade in time" after the frame
loss for the two frequencies. I do not get the point what happens here...

I will test for smaller values of cumul_gain (already tested a few vaules
without success, but perhaps I missed a good one...)

best regards,
Frank


Jean-Marc Valin <jean-marc.valin at usherbrooke.ca> hat am 14. Januar 2010
um 13:15 geschrieben:
> What happens if you change that line:
>
> if (cumul_gain > 262144)
>
> to use a smaller value? What value works OK (if any)?
>
> One more thing, when things go wrong, do they eventually go back to
> normal or does the codec never recover? It's unavoidable that the audio
> goes bad for a short period of time because of the long-term predictor.
>
>         Jean-Marc
> 

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