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. > > > > > > > > > >
