[opus] Alleged bug in Silk codec

[Jean-Marc Valin]

Hi Marcello,

Thanks for the report. It's hard to debug this without the actual file.
Can you please post the sweep_in.raw file you used?

Cheers,

	Jean-Marc

On 11/06/14 04:46 AM, Marcello Caramma (mcaramma) wrote:
> Hi,
> 
> Apologies if this is a known issues, but I have found what I believe is
> a bug in the fixed point implementation of the Silk codec and could not
> find any mention on this in the archives.
> 
> The bug can be easily reproduced with the fixed point demo program
> (./configure —enable-fixed-point —disable-float-api && make) using the
> following command:
> 
> ./opus_demo voip 16000 1 23000 sweep_in.raw sweep_out.raw
> 
> Where sweep_in.raw is a 30 seconds full scale frequency sweep from 0 to
> 8kHz sampled at 16kHz.
> 
> The first 6 seconds of audio after transcoding sound Ok. After that
> artefacts are introduced all the way to the end of the file.
> The floating point version does not have the issue (even though the
> quality is subjectively worse roughly from the same point).
> 
> I believe I narrowed down the problem to the file burg_modified_FIX.c –
> if I make sure the input signal is scaled down to 14 bits before
> processing the coefficients of the predictor are calculated correctly
> and no artefact is introduced.
> 
> Is anyone experiencing the same problem or has a proper fix for this? (I
> can work around the bug with input scaling for now).
> 
> Thanks and best regards,
> 
> Marcello Caramma
> 
> 
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