Hello Peter, Wow, great work!
> Codec2 in the 1400bps mode operates on audio in chunks of 40ms. > However, the modem implementation uses powers-of-2 (a reasonable thing > to do with FFTs), which results in a symbol period of 12ms. I've been working on a "wideband Codec2" that uses the FFT at a power of two by choosing a sample rate of 12.8 kHz, leading to an FFT over 512 elements. The wonderful thing about Codec2 is that it is fully agnostic to sample frequency, so you would end up sending the same frames, although possibly with harmonics that won't be played at the other end -- unless they also use your soundcard implementation. A shorter symbol period would mean a change of protocol; going widebind means that you can make a local choice. I've done only rough tests with this codec, but it would seem to work. Let me know if you would like a copy. I still need to sample children's voices to see if they run over 600 Hz. What I have done is sample an opera-singing lady (which is not fair, the codec isn't designed for that) and she ends up sounding like a toad (no phantom of the opera needed here) because her 1 kHz voice is not sought for, and other frequencies are recognised as the apparent base tone. If people on the list want to see the code, or hear the toad, I can put it online. The lady is so far off after Codec2 is done with her that this is not copyright infringement ;-) David: all this derivative work... must be a sign that you're on to something very good :-) Cheers, -Rick ------------------------------------------------------------------------------ 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 [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
