Speex dev - Sep 2005 - ultra wide band packet questions

Hi Jean Marc and List,

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):

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

I found one case where these numbers didn't work (for update rate 1),
where it appeared to be maybe 68 bits instead of 72- is this a variable
number?  If it is how do I check for the variation?

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...

Thanks!

Tom




______________________________________________

Tom Harper
Lead Software Engineer
SightSpeed - <http://www.sightspeed.com/>http://www.sightspeed.com/

918 Parker St, Suite A14
Berkeley, CA 94710

Email: 
<mailto:laleguire@sightspeed.com>tharper<mailto:laleguire@sightspeed.com>@sightspeed.com
Phone: 510-665-2920
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My SightSpeed Video Link: 
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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

-- 
Jean-Marc Valin <Jean-Marc.Valin@USherbrooke.ca>
Universit? de Sherbrooke
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