[opus] opus 1.2.1 regression with --enable-float-approx and --0fast

[Jean-Marc Valin]

On 02/22/2018 09:34 PM, Stepan Salenikovich wrote:
> Its unexpected because the decoder continues to output all samples
> of -32768 even when the microphone input is silence or near silence, so
> I would expect the decoded values to be at or near 0.

Oh, if the output is stuck at -32768, then it's likely some NaNs crept
in. The first thing to check is whether the problem is on the encoder
side or the decoder side (when if you use a 1.1 encoder with a 1.2
decoder and vice versa). In general, -Ofast is not IEEE-compliant when
it comes to NaN, so libopus has to work around that non-compliance.

> I will try to reproduce with opus_demo or opus-tools.

Thanks, that'll help a lot.

	Jean-Marc

> 
> 
>     Optionally, if you could bisect the git repo to see where the problem
>     started.
> 
>     Cheers,
> 
>             Jean-Marc
> 
>     On 02/22/2018 07:15 PM, Stepan Salenikovich wrote:
>     > Hi,
>     > I work on a webRTC application and recently tried updating from opus
>     > 1.1.5 to 1.2.1
>     >
>     > Afterwards I noticed occasionally weird audio glitches. I finally
>     > tracked down the issue to the opus decoder in my application
>     outputting
>     > samples with the value of -32768.
>     >
>     > This behaviour stopped when reverting to opus 1.1.5 or compiling opus
>     > 1.2.1 without configuring --enable-float-aprox and --0fast.
>     >
>     > The setup is a microphone as audio input into chrome v64 which then
>     > sends opus encoded audio to my application and my application decoding
>     > this audio stream.
>     >
>     > I could induce the glitches by breathing/blowing really loudly
>     into the
>     > microphone. I noticed that occasionally this would result in the opus
>     > decoder in my application to keep outputting a stream of -32768
>     (even if
>     > I stopped) until I talked normally for a bit.
>     >
>     > Is it possible that a regression was introduced between 1.1.5 and
>     1.2.1
>     > when configuring with --enable-float-approx and compiling
>     with --0fast?
>     >
>     > Thanks,
>     > -stepan
>     >
>     >
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> 
>