Yes it is
Steinar Aanesland wrote: > Is this the IVOX system:? > > http://downloads.pf.itd.nrl.navy.mil/ivox/ > > LA5VNA Steinar > > > > > W2XJ skrev: > >> >>Very low bitrate algorithms exist now. There are a few that operate from >>200 bps to 600 bps. The Navy has software called IVOX that gets in this >>range. So you could transmit 16 QAM and hit the 100 HZ goal. The bigger >>problem would be getting it to survive propagation and survive receiver >>filtering. One would probably need to use a very narrow band OFDM >>scheme. It would be an interesting but do-able experiment. If it worked >>well, it would be a very worthwhile mode. >> >>Patrick Lindecker wrote: >> >>>Hello Cesco, >>> >>>For information, I have tried to see if it was possible to transmit >> >>a speech through a 500 Hz channel using a digital transmission. I have >>decomposed the audio spectrum (but not through a FFT, but by >>intercorrelation to choose the carriers I wanted) in several carriers >>and associate to each carrier a level. >> >>>Then I have tried to decrease the number of carriers N, the number >> >>of levels L and increase to the maximum the duration of >>intercorrelation T (the duration of an element of a speech), up to to >>find a "just comprehensible speech". It's a compression of the >>information, up to the maximum possible. Above this limit, the speech >>can't be understood. >> >>>After that, I do the reverse operation (equivalent to a FFT-1) and >> >>have not much that listening to the result. >> >>>At each 1/T it was necessary to send NxL elements of information, >> >>which gives the final rate. >> >>>This way is disappointed because you need much more information that >> >>you can transmit through a 500 Hz channel (for example: 23 carriers, >>128 levels and T=40 ms). With 23 carriers, 8 levels and T=40 ms (which >>can be send through a 500 Hz channel), it is very difficult to >>understand a (French) speech. >> >>>73 >>>Patrick >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>>----- Original Message ----- >>>From: cesco12342000 >>>To: digitalradio@yahoogroups.com >> >><mailto:digitalradio%40yahoogroups.com> >> >>>Sent: Friday, November 16, 2007 4:26 PM >>>Subject: [digitalradio] Re: digital voice within 100 Hz bandwidth >>> >>> >>>I would be plased to have a complete list of the phonemes and >> >>corresponding >> >>>audio files from different speakers. I fear 44 phonemes will not be >> >>enough >> >>>to do a context-free analisis. >>> >>>The data rate will be closer to 200pbs i think, since you will have to >>>transfer a magnitude component along with the phoneme index, and maybe >>>also a pitch component. Think of the pitch raise in a question, this >>>feature is important for understanding. >>> >>>The main problem will be the fft to phoneme table correlation i >> >>think ... >> >>>but to work on this there must be a phoneme table first. >>> >>> >>> >>> >> >> > > > >
