David, Congratulations! The concept, partly using differential coding seems to work better than expected. It sure is having potential for further reductions of the data rate. Artifacts could maybe reduced by applying fuzzy rules on the reconstructed values to see how probable they are. Frames with highly improbable values could than be sorted out. Keep on going!
Best regards Gerhard OE3GBB -----Ursprüngliche Nachricht----- Von: David Rowe [mailto:[email protected]] Gesendet: Montag, 07. November 2011 05:20 An: Freetel-codec2 Betreff: [Freetel-codec2] 1400 bit/s candidates Hello, I have attached some samples of Codec 2 at 1400 bit/s, with 2500 bit/s for comparison. I can hear a little more distortion in the hts2a (female) 1400 bit/s sample, but hts1a (male) sounds about the same to me. I am pretty sure I can fix up the problems in hts2a. These were generated using the c2sim simulation in the codec-dev SVN branch: $ svn co https://freetel.svn.sourceforge.net/svnroot/freetel/codec2-dev $ ./configure & make & cd src $ ./c2sim ../src/hts1a.raw --1400 -o hts1a_1400.raw I'll work on getting 1400 bit/s modes put into the library and c2enc/2dec over the next few days. Then start looking at fixing a few little quality glitches. I am hoping that releasing a 1400 bit/s version early will encourage HF digital voice experimentation. The bit allocation is: 20ms frame 1: 25 bits LSP, 2 bits voicing, 5 bits energy, 7 bits Wo (pitch), 39 bits total 20ms frame 2: 7 bit/s LSP, 2 bits voicing, 5 bits energy, 3 bits Wo (pitch), 17 bits total In frame 1 it's 13 bits scalar quantisation of LSP 1-4 differences in frequency, then 12 bit VQ for LSP 5-10. In frame 2 it's a 7 bit VQ of LSP 1-4 differences in time from frame 1. LSPs 5-10 are simply copied from frame 1. So 56 bits every 40ms or 1400 bit/s. Thanks, David ------------------------------------------------------------------------------ RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
