opus - Feb 2015 - Questions regarding OPUS_APPLICATION_AUDIO vs OPUS_BANDWIDTH_NARROWBAND

I have an audio device whose 'driver' gives me Opus encoded frames using
OPUS_APPLICATION_AUDIO and max bandwidth set to OPUS_BANDWIDTH_NARROWBAND.
How does Opus encoder decide the center point of the 4K bandpass filter?
Is it done frame by frame?

-- 
Tony
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Can you explain what you mean by "center point"?

	Jean-Marc

On 24/02/15 11:30 AM, Tony wrote:
> I have an audio device whose 'driver' gives me Opus encoded frames
> using  OPUS_APPLICATION_AUDIO and max bandwidth set to
> OPUS_BANDWIDTH_NARROWBAND.  How does Opus encoder decide the center
> point of the 4K bandpass filter?  Is it done frame by frame?
> 
> -- 
> Tony
> 
> 
> _______________________________________________
> opus mailing list
> opus at xiph.org
> http://lists.xiph.org/mailman/listinfo/opus
>

Ooops!  I didn't reply-all...

When I look at the opus_defines.h, OPUS_BANDWIDTH_NARROWBAND, is defined as
'< 4 kHz bandpass'.  I assume 'bandpass' in this case refers
to a 'bandpass
filter'.

http://en.wikipedia.org/wiki/Band-pass_filter

Looking at the briefly looking at the Opus RFC, I __think__ the
'bandpass'
is applied per frame.  Which means the 'center' of the bandpass filter
could change frame to frame.  Maybe I'm wrong and I need to slapped in the
face with fish, but that's what it looks like it happening.


On Tue, Feb 24, 2015 at 11:59 AM, Jean-Marc Valin <jmvalin at jmvalin.ca>
wrote:
> Can you explain what you mean by "center point"?
>
>         Jean-Marc
>
> On 24/02/15 11:30 AM, Tony wrote:
> > I have an audio device whose 'driver' gives me Opus encoded
frames
> > using  OPUS_APPLICATION_AUDIO and max bandwidth set to
> > OPUS_BANDWIDTH_NARROWBAND.  How does Opus encoder decide the center
> > point of the 4K bandpass filter?  Is it done frame by frame?
> >
> > --
> > Tony
> >
> >
> > _______________________________________________
> > opus mailing list
> > opus at xiph.org
> > http://lists.xiph.org/mailman/listinfo/opus
> >
>


-- 
Tony
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