
Codec2: GNU low-bitrate speech codec (2400 bits/second) - IgorPartola
http://www.rowetel.com/blog/?page_id=452
======
mctavjb9
Low bit rate codecs with acceptable quality will be a boon for VoIP over
satellite. Satellite Internet service is both bandwidth-limited and hideously
expensive-- Inmarsat Fleet Broadband for cargo ships, for instance, typically
costs $6/MB. The idea would be to set up local phone networks that employ one
of the GSM codecs or mu-law (allowing the use of plain vanilla handsets) and
then transcode the voice to a more efficient codec like this one
upstream/downstream of the satellite connection to the PSTN.

Incidentally, David Rowe is one of the pioneers of the Mesh Potato.

~~~
IgorPartola
Thanks for the Mesh Potato mention. I haven't seen this project before but am
very interested in stuff like this. My question is: what would happen if we
overnight got an entire country wired? What kind of social, political and
economic consequences would that have? I'm not thinking of the US, which
already has a decent infrastructure, even if we want it to be
better/faster/more neutral. I am thinking of African countries, a market
largely underexposed to the internet. I suppose I can picture a startup trying
to do this. Just think how many more Facebook users there could be...

~~~
mctavjb9
Here are some suggestions for further reading: <http://www.villagetelco.org>

Steve Song's blog (Telecommunications Fellow at the Shuttleworth Foundation):
<http://manypossibilities.net/>

<http://openmobile.futuretext.com/>

There was an article in Linux Journal last December that includes more
technical details on the Mesh Potato.

~~~
IgorPartola
Thank you very much.

------
hvs
I can finally dig out my old U.S. Robotics 2400 baud modem and start doing
some low-bandwidth voice communication!

Seriously, though, the samples are very impressive. I was surprised at the
quality.

------
woodson
The samples sound quite good, suspiciously good even. I'll give it a try on
speech samples from other languages and speakers (this often makes quite a
difference).

~~~
nitrogen
I've always wondered if some human languages work better with speech codecs
than others, ever since I saw someone having a cell phone conversation in an
Asian language without appearing confused or asking for clarification (based
on facial expression, body language, and conversation pacing). My experience
speaking English on cell phones is one of constantly repeating myself.

------
AndrewHampton
I don't know much about voice encoding, but I'm really curious as to why all
the example files are the same size (46.9 KB). Could someone explain why this
is an advancement if the file sizes remain the same?

I suspect it has something to do with all of them using wav as the container,
but would love to hear from someone more knowledgeable.

~~~
woodson
The example files are produced by encoding and then decoding the original. In
PCM 16bit raw format they will end up having the same uncompressed size. The
encoded bitstream files will be a lot smaller.

For example: hts1a

original: 48000 bytes

encoded: 1050 bytes

Edit: Note that this is only the size of the bitstream written to disk. I
didn't look into the actual format.

~~~
AndrewHampton
Ah, that explains it. I didn't see that in the article.

------
nitrogen
I can hear the 50Hz modulation caused by the 20ms frames in the Codec2
samples. It's particularly problematic on the sibilants from the female
sample. Codec2 seems to have a wider frequency response, but MELP is more
intelligible.

That said, it sounds like a great version 0.1, and look forward to hearing
what comes in the future.

------
seltzered
I'm still trying to understand the processing involved, but it could be
interesting if one could use it to effectively do voip calls over EDGE using
this - may require having an external dsp dongle though.

