Lossless compression does not work if there is no redundancy. The Quick Brown Fox has one of each symbol on the alphabet.
Jose, CO2JA Rein Couperus wrote: > > -----Ursprüngliche Nachricht----- Von: digitalradio@yahoogroups.com > > Gesendet: 13.01.07 02:36:52 An: digitalradio@yahoogroups.com > > Betreff: Re: [digitalradio] Re: Pactor versus Olivia > > > > > Rein, > > > > I am not clear on this. The B2F compression is used with Winlink > > 2000. I am not sure what it really is other than a compression > > scheme to nearly double plain text throughput and is some kind of > > adaptation to the protocols that were adopted by FBB such as B1F. > > > > Shouldn't this work with even short data packets? > > > It doesnŽt. You can try this yourself by zipping one line of `quick > brown foxesŽ, and you will see the compression factor is nil. > > Then try to zip a 10k file full of Žquick brown foxesŽ, and see that > it compresses to a factor of 1:50... > > > If you were doing some keyboarding with an ARQ mode that was > > running at 100 baud, like Pactor, (but could drop down according > > the conditions ... unlike Pactor), and even if you used a cycle of > > 2 or 3 seconds transmitting and .6 seconds open for ACK or NAK, > > wouldn't this still work reasonably well with a throughput faster > > than most can keyboard? And by using the B2F compression, and > > doubling the throughput, get further enhancements? > > > Pskmail gets good keyboarding results even when using PSK63 ARQ , > which gives you PSK31 typing speed. Rein PA0R > > > 73, > > > > Rick, KV9U > > > > > > > > Rein Couperus wrote: > > > >>> Unfortunately this won't work. BZ2 compression is based on > >>> 'redundancy' in a message. There is hardly any redundancy in > >>> short messages as used in k-to-k. > >>> > >>> The only way you can do that is by using context-based > >>> compression, like the 'context based huffman' compression in > >>> pskmail, which reaches compression factors of 1 ... 50 : 1. > >>> > >>> Rein PA0R > >>> > >>> (by the way, it is open source). > >>> > >>> > >>> > > Rick, KV9U had previously said: > > > > By the way, I have often wondered why the B2F binary compression > > system used with the Winlink 2000 system has never been used for > > nearly a 2:1 compression for improved throughput. This could be > > applied to any system, including keyboarding. > > > > 73, > > > > Rick, KV9U > Announce your digital presence via our DX Cluster telnet://cluster.dynalias.org Our other groups: http://groups.yahoo.com/group/dxlist/ http://groups.yahoo.com/group/themixwgroup http://groups.yahoo.com/group/contesting http://groups.yahoo.com/group/wnyar http://groups.yahoo.com/group/Omnibus97 Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
