On 14 January 2013 20:01, Netzblockierer <[email protected]>wrote:
> Hi,
>
> Using CRC does requre more buffering and resources...
> You may work pretty well using the standard Forward Error Correction as
> used in DVB - Standards.
>
CRC is far from ideal, and I'm only using it because I could understand it
and find code for it quicker.
If I could have found some code for FEC 6/7 (which I think is what would be
needed to fit in a 1400bps FDMDV channel) then I would have used that. If
I learn enough before anyone else does it, then I'll write it, but I think
other people are likely to beat me to it.
Using Cyclic Redundancy Check is not recommended upon streaming or
> voice-transmission. It only checks already recieved data, (That's why
> you only use SHA-512 and MD-5 in packet-transmitting/exchanging
> networks) which would result in a higher decoding latency as well as
> buffer size for decoding.
>
I'm in the middle of hacking the code in fdmdv.c to give an indication of
the quality of the received symbols as well as the symbols themselves.
This means that if the CRC check fails, we can flip the bits most likely
to be incorrect and see if it passes.
Thanks for the insights,
Dan MD1CLV
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