HI Steve,
On 05-09-12 19:56, Steve Strobel wrote: >> With reading more about FEC systems and coding for the header of c2-gmsk >> modem; I have also been thinking about other (better) FEC systems for >> the voice-part of the stream. > It seems to me that it would be best to match the size of the FEC to > the size of the voice payload for a frame (48 bits or whatever) rather > than correcting four groups of 12 bits. In other words, if there is > such a thing as (48,24)BCH, I would expect it to work better than > doing (12,6) four times. > > Consider that a (48,24) FEC could correct for a certain number of bit > errors no matter where they occurred in the frame. If those bit > errors (after de-interleaving) were evenly distributed in each of the > four (12,6) FEC blocks, they would also be correctable. But if they > were not evenly distributed, the (12,6)*4 version would fail to work > as well as the (48,24) version. > In other words, I think error correction should be done on the largest > blocks possible without increasing latency. Well, I will of course interleaving. Depending on option-bits in the stream-header, it will be using blocks of 1 (i.e. only inside the frame) or 2, 4 or 16 frames. The latter modes will greatly increase latency, but is designed only be used for -say- 10 meter DXing; to deal with fading. Now, concerning FEC. I haven't had time to look at BCH in detail but do you suggest that (64,32)BCH is simply 5 times (12,6)BCH or am I missing something. (I mention 64,32 BCH as the frame-size of 1400 bps codec2 is 56 bits / 50 ms). > Steve 73 Kristoff - ON1ARF ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
