[Speex-dev] ultra wide band packet questions

Jean-Marc Valin Jean-Marc.Valin at USherbrooke.ca
Sat Sep 24 03:25:32 PDT 2005

Hi (sorry for the long delay),

> So I have started finally fiddling around with Ultra-wideband mode.
> It appears to be very similar in operation to Wide mode, except that
> when peering into the packet structure it looks like (and these are
> kind of questions as much as statements here):

If you're using ultra-wideband, be aware that it can sometimes sound
worse than wideband (depends on the input and who's listening). 

> 1. update rate 0 is not used  in UWB- only 1-4?

It's not an update rate, it's a submode.

> 2. The total bits used for each UWB update rate seem to be as follows:
> 0:36 bits (a guess)
> 1:72 bits
> 2:148 bits
> 3:224 bits
> 4:384 bits

Only submode 0 is valid for UWB, i.e. an SBR-like high-band.

> Which leads to my follow up- it was hard for me to determine why in 
> some cases UWB was 36 bits per packet more and other cases only 
> 32 than WB mode.  I couldn't find anything in the code that could
> easily 
> account for the difference.  The only thing I could find didn't
> account for 
> all 32/36 bits.  Any pointers appreciated...

Maybe this just has to do with the rounding of bytes (e.g. if there's
only 4 bits used in the last byte).


Jean-Marc Valin <Jean-Marc.Valin at USherbrooke.ca>
Université de Sherbrooke
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