In David's recent blog post on LilacSat-1 (http://www.rowetel.com/?p=5671) he posited:
Note to self #2 – add some noise reduction inside of Codec 2 to make it more robust to different input signal conditions. Now, I'm a bit of an old UNIX beard, which means I like my tools to do one thing and do them well. Codec2 does a great job of coding voice signals, so it stands to reason that we can create a separate tool/module/pathway/pony to give it better signal to work with. I notice when building the codec2 source that it depends on libspeexdsp. I'm not sure what we're doing with that, but I do note that this library has a denoising filter. A simple test filter program is shown in its repository: https://github.com/xiph/speexdsp/blob/master/libspeexdsp/testdenoise.c I was able to compile that up on my Ubuntu machine with libspeexdsp-dev already installed with a simple: gcc testdenoise.c -o testdenoise -lspeexdsp From there I took a voice sample I grabbed off the local repeater using my scanner and ran it through the processor: ./testdenoise < sample.raw > sample-denoised.raw And then on to encoding testing: ./c2demo sample-denoised.raw sample-denoised-c2.raw The sample I had didn't suffer too terribly from the background noise, but it was nice to have it completely gone in the final output. Would be interesting to see if other folk have better luck with this, perhaps twiddling the knobs a bit from the defaults. 73 de Kevin N8VNR ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
