Hi Alfred, Yes you will need a 8000 Hz interface for the freedv 700b/c modes in the latest freedv API.
Cheers, David On 30/01/17 18:04, wully wrote: > Hi David > > Let us clarify this point a bit more... > > I have not changed anything in my code from 700b to 700c. Just switching > the sharable library codec2.so after building it from the SVN. > > In 700b-Implementation, I make the downsampling by myself in my code (I > use SVN-Version 2299 for 700b). I use the following steps: > > 1) downsampling my 48000S/s to 8000S/s for freedv_tx > > 2) freedv_tx(...) // using 7500S/s-Data > > 3) upsampling to my tx-Datarate of 48000S/s. > > > In 700b-Demodulation: > > 1) downsampling 48000S/s to 7500S/s > > 2) freedv_nin(...) // to get count to work with > > 3) freedv_floatrx(...) > > 4) upsamling to my rx-Datarate 48000S/s > > On both sides, there is quite some buffer management involved, because > of the 7500 to 48000 ratio. > > > As far as I understand your statement, this code won't work with > SVN-Version 2998 for mode 700c. > > When making 700c-experiments with the code above, I hear hickups in the > demodulated audio. > > Greetings, Alfred > > > > > > > > On 29.01.2017 23:05, David Rowe wrote: >> Hi Alfred, >> >> Internally the modem side of the 700 modes run at Fs=7500 Hz due to the >> design of the waveform for the coherent PSK modem. However in 2015 Jim >> Ahlstrom kindly added a resampler to the FreeDV API so the 700 modes now >> all have an Fs=8000 Hz interface. >> >> If you call the cohpsk modem functions directly then Fs=7500Hz is required. >> >> Cheers, >> >> David >> >> On 30/01/17 07:14, wully wrote: >> > > > ------------------------------------------------------------------------------ > 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 > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > ------------------------------------------------------------------------------ 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 [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
