Hi Adrian, Yes quite a few Ham using FreeDV use filtering and EQ to improve the speech quality, e.g. using external EQ boxes. We also have a microphone and speaker equaliser in FreeDV, plus some noise reduction. More recently, I have been working on automatic equalisation of input speech to improve vector quantisation of Codec 2 700C:
http://www.rowetel.com/?p=6860 BTW there are many Codec 2 modes, but the ones in widespread use in FreeDV modes are: FreeDV 1600: Codec 2 1300 FreeDV 700C/700D: Codec 2 700C I listened to you sample but am unsure if it was before or after your processing, Do you have A/B samples to compare? Cheers, David On 10/09/19 21:25, Adrian Musceac wrote: > > Hi David, > I think I can slightly improve the quality of playback of Codec2 > samples with some rather computationally cheap methods. This might > be of use to you for FreeDV. > Please have a listen at the sample attached, which is Codec2 at 1400 > bits/s. > Link included in case the attachment doesn't go through: > http://qradiolink.org/images/codec2_1400.wav > The trick is a little filtering, emphasis and a little audio > compression applied. > I have some pathological Codec2 samples recorded with my voice that > are really improved with this method. If you want I can send them to > you. > Noisy samples have a little problem with the compressor driving too > early and bringing out the noise, so I think I can still do some > adjusting there. > Codec2 700B is different though, I have to adjust the filters and > emphasis because I get some aliasing of higher frequencies. > > Adrian > > > It seems my previous message got stuck because of the attachment, so I'm > including just the link to the Codec2 sample. > > > > > _______________________________________________ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
