Hi Tomas, I suspect you are right regarding the noise, I've done this myself along with some audio compression and I was happy with the results. Eliminating or smoothing high-pitch artefacts due to bit errors would also be nice.
Adrian On 19 April 2024 11:29:46 UTC, "Tomas Härdin" <g...@haerdin.se> wrote: >Hi > >Following Bruce's email I took a look at >https://github.com/drowe67/codec2/blob/main/doc/codec2.pdf to see how >the speech synthesis in codec2 actually works. This because I suspect >that NN synth (LPCnet?) is doing something similar to what CELT (one >half of Opus) does, namely filling off-peak parts of the spectrum with >noise. > >Filling the spectrum with noise makes the output sound a lot less >robot-y, and robot-y sound is known in the CELT world to be due to >collapsing all energy into a single spectral bin per Bark band which, >looking at equation (10), is *precisely what the codec2 synth does*! >Or, sort of. For low F0 there may be multiple peaks in some bands. > >One way to make the output less robot-y could be to convolve Ŝw with a >suitable function that smooths out the peaks. In CELT this is done via >clever use of rotations if I remember correctly. A floor of comfort >noise might also be a good idea. > >Oh and on the topic of errors in the paper, there's a spelling mistake >on page 2: anlaysed. > >/Tomas > > >_______________________________________________ >Freetel-codec2 mailing list >Freetel-codec2@lists.sourceforge.net >https://lists.sourceforge.net/lists/listinfo/freetel-codec2
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