David for resampling... so you want to go from 8000 to 7500 Hz ?
I've always picked my modems to be integer divisors of 48k . makes life easy. However, if we are stuck with 7500... 1) SRC using 120kHz as the common sample rate (polyphase resampler interpolator/decimator) cleanest, highest MIPS usage, easiest to understand. 2) Farrow interpolator. Best if passband is a small fraction of the sample rate. Most used for fractional sample rate conversion for mismatched clocks. A counter is used counting samples in and out, the fraction determined, and the resampling FIR coefficients are calculated on the fly. given a big chunk of the Nyquist BW is used, perhaps upsample to 16k , convert to 15k, and then crash-downsample/undersample to 7500 (cheap). -- I can do this. --- On 3/08/2015 9:20 AM, David Rowe wrote: > Further to this thread (started on the digitalvoice list) James has > provided a patch to implement his suggested changes to the FreeDV API, > which is now checked into codec2-dev. > > So wonderful for me to have some one step up and contribute some code. > > Thanks James! > > Now I need to go to work on the FreeDV GUI program to support these changes. > > Down the track I'd like to see the FreeDV API accept a 8000 Hz sample > rate for the 700 mode (its currently 7500Hz). I have some ideas on how > to do this if anyone would like to work on the C code. But right now my > focus is on tuning the FreeDV 700 mode. > > On that subject I'm getting some great reports from people working > across the Atlantic on FreeDV 700 on as little as 5W - thanks Gerhard, > Walter, and Mel! The new modem is really working well on the HF fading > channel, and we have several examples of 80% DV copy when SSB was > unusable. I feel the speech codec needs some work, but we will get there. > > Exciting times for HF DV! > > - David > > ------------------------------------------------------------------------------ > _______________________________________________ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > -- - Glen English RF Communications and Electronics Engineer CORTEX RF & Pacific Media Technologies Pty Ltd ABN 40 075 532 008 PO Box 5231 Lyneham ACT 2602, Australia. au mobile : +61 (0)418 975077 ------------------------------------------------------------------------------ _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
