On 2/02/2012 9:10 AM, Steve Strobel wrote: > I think it is impressive how natural-sounding codec2 is even at > 1400bps. I am considering a potential application that would be > practical only if the bandwidth was a small fraction of even that. It > wouldn't be important that the audio sound natural, but it would need > to be intelligible. I would like to try reducing the number of bits > used for each field in an effort to see how much the bandwidth could > be reduced and still provide speech that could be understood. I > suppose in the extreme case, the pitch field could be eliminated > altogether, resulting in monotone output. Some of the other fields > could surely also be reduced somewhat. > > If any of you that have worked with codec2 could give me a suggestion > about where to focus my efforts, that would be great. Any wild > guesses about how far the bandwidth could be reduced and still produce > intelligible speech? (I realize that intelligibility is highly > subjective). Thanks. > > Steve > > Hi Steve,
As a former broadcaster, and one interested in the eventual outcome of this codec for hf comms avoiding selective fade, static and multipath effects, I have an interest in audio quality and communications more generally. I hope you don't mind if I give just a personal opinion here. I have seen the so-called "sub noise level" WSJT tx coding systems being so reduced in bandwidth that a "QSO" is possible "in name only". Call-signs can be exchanged with rudimentary "RST" reports, but anything like a normal discussion is impossible. This is useful for measuring path loss, but frankly it's not much use for anything else - except the nominal breaking of DX records, just within the limits of legal requirement. It's interesting, but it doesn't really "turn me on" as an operator. If this was all that there was to ham radio, I would have departed from the activity decades ago. The "naturalness" of a codec conveys a lot of the personality, inflection and subtext/meaning of a person's delivery on radio. It also conveys contextual information about a person's ethnic, national, racial and cultural background. I would suggest that if one was considering the paring-down of speech transmission to removing any of its "naturalness", one would be better to have good speech recognition software at the tx end, and to transmit the speech as PSK31 or some similar code, printing out the speech as text at the "far end". Or one could simply use speech synthesis software to audibly reproduce ANY form of transmitted text. It gets to the point where one really has to pose the question: "what is the purpose of ham radio"? Surely it isn't the progressive narrowing of bandwidth to the point where individuality, personality and humanity is completely eliminated. Neither should it be a progressive battle for smaller bandwidth and marginally better DX, if that is at the expense of those human characteristics that comprise inter-personal communications of any depth or real interaction. I worry that the ENTIRE POINT of the hobby is beding marginalised here. I sometimes operate an amplitude modulated transmitter on 160 metres, not because it is 'heritage equipment', but because the quality of the reproduced audio is considerably above that of most other so-called "comms quality" systems. And I'm representative of the interests of a sizeable and growing sub-set of hams who also have these audio quality interests - because the quality of not only the voice, but the whole auditory environment of the 'studio' can be conveyed thereby. Mere intelligibility is not the sole consideration of ham radio communication, or of ANY inter-personal communication. Hoping that this produces some discussion supervening mere technical considerations, With best wishes for a productive outcome with codec2, Chris Long VK3AML, Melbourne, Australia. ==================================== ------------------------------------------------------------------------------ Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
