On Wed, 2012-05-23 at 23:22 +0200, Kristoff Bonne wrote: > Hi, > > > I am currently working with Peter on defining the format for a VHF > modem. > > There are some things where I would like to get the help of the > knowledge of the list. It deals with the syncronisation pattern put in > front of the stream. >
> > Question: > Does anybody see a reason to support bitrates other then the four > available in option 2? > Since this is a spec, why not? I think the basic idea of a sampling rate of 48000 is good, but why not allow 96000 and 192000 as well, allowing extension of the spec? After al, hw is available. 48000 should of course be the "basic standard", since that is supported by all hw. Once in software, tweaking for other (higher or lower ) speeds becomes natural. > P.S. I like the idea of a 1800 bps stream. This would be roughly > equivalent of a non-protected codec2-stream running at 1400 bps plus > some overhead for syncronisation. > Me too!! > > 2/ > Modulation systems: > > So, the question is simple: > Is there a reason to forsee C4FM/4FSK on a codec2 VHF format? Yes, if the spec can include (most) hw / radios that exist, it will surelybe more successful, since people will adapt and modify what they get their hands on. Time will then tell what will be the most successful implementations and "profiles" used. > Does anybody see a reason to add C4FM in this version of the specs? > (appart from "I want everthing"). > I think so, we are mostly discussing software implementations of the codec2, fdmdv protocols, initially on a "PC" but soon on a MCU. Being careful and anticipate evolution, will allow this to become "a family of digital modes" rather than a "dstar competitor". > > > One final remark: Understood, 4800 is fine! One comment to the polarity discussion: Would it not be a good idea to SPEC that bit encoding is differential, i.e. no change = 0, change = 1 (ore somesuch) , which will eliminate all polarity issues? Was that not part of the bit encoding of AX25, for exact that reason? My 2 cents worth... SM6FBD ------------------------------------------------------------------------------ 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 Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
