Codec 2 PAPR, Phase and VQ Experiments

[drowe67]

This PR supports R&D aimed at improving Codec 2 speech quality (WP2000 in ARDC plan). It's not intended for merge, rather to support R&D. The development is conducted using a combination of C, Octave and bash scripts. The R&D is documented in a LaTeX report in codec2/doc/ratek_resampler.

Topics include:

1. ratek resampling.
2. The effect of PAPR on speech quality.
3. The drop in speech quality when coarsely quantised amplitudes are used to synthesise phase spectra.
4. Two new post filters.
5. Vector quantisation of rate K vectors.
6. Microphone equalisation.
7. Pitch errors and background noise problems
8. Energy Normalisation.
9. Mean versus energy quantisation.
10. SSB style compression of Hilbert Clipping of synthesised speech.
11. Candidates for new 700 and 1200 bits/s modes.
12. High Pass filtering of input speech.