
Codec 2 700C - BuuQu9hu
http://www.rowetel.com/?p=5373
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Zenst
Given Adobe demonstrated technology to convert text into somebodies voice
based upon a few samples and make that person sound like they can say whatever
you want to type. Are we not eventually going to use that approach for the
optimum voice compression and just send text which is converted into voice.
Given most phone conversations are with people already spoken to then that
would certainly be a solution for low-bandwidth voice comms, or at least an
approach more viable today than previously.

But low bandwidth voice comm research is useful on many levels, one aspect is
that it tends to push latency down and in some area's that gets more and more
important.

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BuuQu9hu
Got a link to that research? Sounds like doing key verification over the phone
just became a bad idea.

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Zenst
[https://www.youtube.com/watch?v=rJksour9Ifw](https://www.youtube.com/watch?v=rJksour9Ifw)

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JoeDaDude
Very cool achievement! IIUC, the author was targeting a digital replacement
for analog SSB voice comms.

I don't expect to see widespread adoption in other areas though, such as
cellular phones and similar. To my ears, I doubt the codec will compete with
common voice intelligibility metrics, such as Diagnostic Rhyme Test [1] or
PESQ [2].

However, it may be an improvement over SSB voice intelligibility!

[1]
[http://www.dynastat.com/Speech%20Intelligibility.htm](http://www.dynastat.com/Speech%20Intelligibility.htm)

[2] [https://en.wikipedia.org/wiki/PESQ](https://en.wikipedia.org/wiki/PESQ)

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derf_
Keep in mind that 700 b/s is an _extremely_ low bitrate.

I worked on Opus, which bottoms out at around 6000 b/s. A typical IP+UDP+RTP
packet has 40 bytes of headers, which with 40 ms frames is 8000 b/s of
overhead. Cell networks will use header compression to reduce that, but even
so. 8000 b/s is almost eleven and a half 700C codec2 streams.

codec2 is just in another league. It's seriously impressive work.

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nitrogen
I think the old Crichton novel, Congo, mentioned using a very low bitrate
codec over a digital satellite link. So maybe something already exists off the
shelf that one could try over amateur radio.

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jdietrich
AFAIK there aren't any commercial codecs with such low bit rates, as there
simply isn't the demand. The minimum bit rate of GSM-AMR is 4.75kbps. Some
military codecs designed for use over HF are in the same ballpark as Codec2 -
STANAG 4479 operates at 800bps. There is some academic research on voice
codecs below 500bps.

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nullc
Fun fact: export of very low bitrate (<2400 bps) codecs has been restricted
under the same munitions restrictions as crypto (And also when open source
presumably subject to the same court outcomes in the US).

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axman6
Gotta talk to those subs somehow, those ultra long wavelength Comms aren't
exactly high bandwidth. (I'm just making this up but it feels plausible, at
least a few decades ago)

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EvanAnderson
Hugged to death. Cached version:
[http://webcache.googleusercontent.com/search?q=cache:http://...](http://webcache.googleusercontent.com/search?q=cache:http://www.rowetel.com/%3Fp%3D5373&num=1&prmd=ivn&strip=1&vwsrc=0)

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johansch
It sounds a bit like 80s-style speech synthesis:

[https://www.youtube.com/watch?v=sV3pYZZ2jEw](https://www.youtube.com/watch?v=sV3pYZZ2jEw)

(This example is the Dr. Sbaitso demo that shipped with Sound Blaster 1.0/1.5
or so and onwards.)

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fsiefken
It'd be awesome if this could be coded and decoded in javascript in realtime
so you could do extremely low bandwidth podcasts (1,3 megabyte per half an
hour) and play them in a browser or send them by e-mail. With HCCB color
coding (Microsoft Tag) you could back that up on an A4 and send it by mail!

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Someone
It is even better; the ‘b’ is ‘bits’, not ‘bytes’.

700 bits/sec = 700 * 60 * 60 / 8 bytes/hour = 315,000 bytes/hour, or slightly
under 308 kilobytes per hour/154 kilobytes for that 30 minute podcast.

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fsiefken
Wow, yes! And someone is actually offering codec2 audio files:
[https://lowbitnet.wordpress.com/audio-
books/](https://lowbitnet.wordpress.com/audio-books/)

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sofaofthedamned
The website is at 700b/sec too, it seems...

