[Asterisk-Users] Re: G729 vs. gsm

[Tony Mountifield]

In article <200505281615.01031.akohlsmith-asterisk at benshaw.com>,
Andrew Kohlsmith <akohlsmith-asterisk at benshaw.com> wrote:
> You can convert between ulaw and alaw 10000 times and it'll sound exactly the 
> same as the original 8000Hz 16-bit sample because... well... it is.

Just to pick a nit, the above can't be right. G.711 is a logarithmic
recoding of 16 bits into 8. So each 8-bit value can be reached from
a whole lot of different 16-bit values. The information as to which
16-bit value it came from is lost, so you can't get back to the
original values, just to approximations of them.

Also, I believe the 16-bit range is chopped up in slightly different
places for aLaw than for uLaw, which could mean a slight loss of
information going back and forth repeatedly between the two.

Cheers
Tony
-- 
Tony Mountifield
Work: tony at softins.co.uk - http://www.softins.co.uk
Play: tony at mountifield.org - http://tony.mountifield.org