Hello Alfred, The use of 16 bit shorts was just due to convention.
The fdmdv modem (and codec 2) uses floats underneath, converting to shorts at the last moment in the API. We could perhaps create freedv_api functions that have float interfaces. The demodulator isn't level sensitive so should work down to very small amplitude input samples. Cheers, David On 17/10/14 18:10, wully wrote: > Hi all > > In the last few days, I made an number of successfull QSOs with freeDV. > It starts geting "standard use"! I am very happy about it working so > good even under somewhat difficult conditions on 40m band. > > But I have seen a point: When using the function freedv_rx(...) I have > to give the samples in short format. > Since the TRX works over a wide range, lets say between -40dBm and > -100dBm, one has to apply a reasonable conversion of the samples to give > a good dynamic range in short format. The rx-data from HPSDR are > 24bit-Numbers, which then are converted to float or double, so, that the > filters can be applied seemlessly. Before going to freedv_rx(...), I > filter and downconvert the samples to 8kHz. Then I apply a "AGC" to get > the samples in reasonable short range. > > Why is the short format chosen in rx? Would float give more dynamic > range to the demodulation? Or, why not? > > best regards, Alfred, hb9epu > > > > > > ------------------------------------------------------------------------------ > Comprehensive Server Monitoring with Site24x7. > Monitor 10 servers for $9/Month. > Get alerted through email, SMS, voice calls or mobile push notifications. > Take corrective actions from your mobile device. > http://p.sf.net/sfu/Zoho > _______________________________________________ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > ------------------------------------------------------------------------------ Comprehensive Server Monitoring with Site24x7. Monitor 10 servers for $9/Month. Get alerted through email, SMS, voice calls or mobile push notifications. Take corrective actions from your mobile device. http://p.sf.net/sfu/Zoho _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
