Richard Shockey [richard(_at_)shockey(_dot_)us] wrote:
I can see the motivation to pay big bucks for video codecs. Using
Mpeg4 can reduce your bandwidth costs and save real money. I can see
why there was a big incentive to save money on audio codecs in the
1990s.
At this point an audio codec is going to have to save a huge amount ot
bandwidth to be worth the hassle, let alone the cost of using
encumbered technology.
Its not about the bandwidth. Its about the quality of the voice in
occasionally lossy networks landline or mobile.
"full quality" mono audio takes around 44.1/16bit linear, you can argue that a
little higher or lower is required for full transparency in some conditions or
another, but 44.1k/16 is what CDDA provides. It's a good number and commonly
available on hardware today.
As uncompressed thats 705kbit/sec before you get into packetization overhead.
Thats per-communication channel, each way. A good perceptual lossy codec can
get you down to under 100kbit/sec while preserving transparency for most
material, with most listeners, most of the time.
Networks have improved a lot. It actually is viable to send uncompressed CDDA
across many wide-area networks today, at least in small amounts, but I think
we're a long way from when compression doesn't have considerable advantages,
even for audio. I think it would be fair to say that networks have become fast
enough other considerations such as error robustness, perceived-transparency,
computational cost, latency, licensing considerations, etc. are now often more
important than the absolute minimization of bandwidth. but savings on the order
of 8-12 : 1 are not something which can be ignored.
8-12:1 is still a material difference in capacity and cost. Audio is cheaper
now relative to the network, but that just means we can do more of it: More
quality, more capacity.
Moreover, every bit wasted on uncompressed audio could instead be spent on
additional redundancy. In a bandwidth plentiful model I'd much rather run a
128kbit/sec/ch codec sending each packet three times than a 705kbit/sec
lossless stream.
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