On 24/02/2015 16:32, FranK Turner-Smith G3VKI wrote:
"AndyW" wrote in message

Bandwidth reduction for one.
If you can encode and compress speech sufficiently then you can use
less bandwidth in transmission.

That's the bit I have trouble getting my head around. Back in the 1970s
and 1980s digital transmissions used a much greater bandwidth than their
analogue equivalents. Sampling at 2.2 x max frequency x number of bits
plus housekeeping bits etc. etc.

But then you add compression on top. As technology increases and the
ability to process data quickly advances you can real-time encode and
decode data at a frightening rate. Back when I started playing about
with digital sound we had enough speed to run-length encode in real
time, now with dedicated number cruncher chips you can carry out very
complex lossless sound compression in real time and for lo-fi sound you
can use lossy compression and have a lot of the band left over for a
time-slice share.
One of my final dissertation for university was on digital compression
techniques (lossy and lossless) and I get a bit geeky about it all :-)
Surprised I still remember it all....


Andy