23-07-2017, 09:42 PM
Codec2 benefit:
1) Very low bit rate or data rate.
2) Open Source, we can implement it at NO COST.
Not the $50 (or so) for the codec in P25, D-Star, Fusion and DMR.
This means we are not limited to any proprietary hardware.
Compatibility:
It was never meant to be compatible. AMBE as used in P25, DMR etc. require 9600BPS data rate.
Codec2 is experimental with bit rates down at 1400 bits/sec and now lately 700 bits/sec.
How it works:
Our human voice starts with our vocal cords then our mouth, tongue, lips and nose shapes. And
added wind noise.
Analyse this, send as digital data, recreate. Do this with the minimum data rate still maintaining intelligibility.
At 700bits/sec this can work well in our SSB 2.7KHz bandwidth at signal-to-noise ratios at the point where we humans
have difficulty.
If you've experienced P25 or DMR, the clarity can be much better (though it has an "accent") than regular noisy FM.
The services use digital as it can be encrypted. - Very important.
Our Emergency teams assisting them also need communications secrecy.
We are not allowed encryption. A codec is not encryption but you'd better be a good programmer if
we change say the bit order.
Alan VK2ZIW
1) Very low bit rate or data rate.
2) Open Source, we can implement it at NO COST.
Not the $50 (or so) for the codec in P25, D-Star, Fusion and DMR.
This means we are not limited to any proprietary hardware.
Compatibility:
It was never meant to be compatible. AMBE as used in P25, DMR etc. require 9600BPS data rate.
Codec2 is experimental with bit rates down at 1400 bits/sec and now lately 700 bits/sec.
How it works:
Our human voice starts with our vocal cords then our mouth, tongue, lips and nose shapes. And
added wind noise.
Analyse this, send as digital data, recreate. Do this with the minimum data rate still maintaining intelligibility.
At 700bits/sec this can work well in our SSB 2.7KHz bandwidth at signal-to-noise ratios at the point where we humans
have difficulty.
If you've experienced P25 or DMR, the clarity can be much better (though it has an "accent") than regular noisy FM.
The services use digital as it can be encrypted. - Very important.
Our Emergency teams assisting them also need communications secrecy.
We are not allowed encryption. A codec is not encryption but you'd better be a good programmer if
we change say the bit order.
Alan VK2ZIW