Codec2: 45 minutes audio for less than 1.4 MB

As I was looking for cheap communication on Brazil's Amazon region, I came up with RockBox, a very smart system that lowers the cost of "sms-like" text transmission, bringing the cost of sending an SMS to around 0,10 € which is very cheap comparing to other satellite coms.

As a matter of fact 0,10 € is for 340 bytes of data, which accounts for around 340x8 = 2,7 kb

It is cheap for sending an SMS but gets expensive when speaking about voice, which, even highly compressed gets quickly to some MB of space.

After spending some time to look at technology behind codecs for low bitrate data sampling, I found some of them:

Ogg-Vorbis, with proper parameters setted: see here for samples

OPUS, an open-source all-round codec (adapted for music, sounds, voices...) that can go as low as 6kbps sampling.

Speex, a specific voice sample which development has been stopped.

Codec2 a specific voice codec that can go down to an incredible 700bps sampling rate!

Read more on Codec2 on this very interesting post.

To use Codec2 you need a modem that can translate binary encoded information to voice and vice versa. The most used modem for codec2 is FreeDV.  See the manual of FreeDV here.

Codec2 and FreeDV are open source and currently on development (2015-2016). They are actively used for pushing the limits of Digital Modes amateur radios.

See here codec2 used by amateur satellite radio: 45min 2 way conversation on less than 1.4 MB