MMDVM

Commit Graph

Author	SHA1	Message	Date
Cort Buffington	4c7e8fbe46	Anti-alias filter before RF->network downsampling in FM mode The 24kHz->8kHz decimation in CFMDownSampler had no lowpass ahead of it, aliasing everything above 4kHz back into the audio band. Reuse the existing 300-2700Hz filter design (separate instance/state) ahead of all three addSample() call sites in FM.cpp. Also: reset() wasn't clearing the ring buffer or in-progress sample pack, so stale audio could bleed into the next transmission. And addSample() packed samples into 12 bits with no saturation, so an out-of-range value corrupted the neighbouring sample.	2026-08-11 09:57:47 -05:00
Jonathan Naylor	81518bf74c	Make AX.25, DMR, P25, NXDN and FM selectable at compile time.	2020-11-08 22:23:27 +00:00
Jonathan Naylor	14d5098018	Rename FMDownsampler to FMDownSampler.	2020-06-30 12:44:02 +01:00

Author

SHA1

Message

Date

Cort Buffington

4c7e8fbe46

Anti-alias filter before RF->network downsampling in FM mode

The 24kHz->8kHz decimation in CFMDownSampler had no lowpass ahead of
it, aliasing everything above 4kHz back into the audio band. Reuse
the existing 300-2700Hz filter design (separate instance/state) ahead
of all three addSample() call sites in FM.cpp.

Also: reset() wasn't clearing the ring buffer or in-progress sample
pack, so stale audio could bleed into the next transmission. And
addSample() packed samples into 12 bits with no saturation, so an
out-of-range value corrupted the neighbouring sample.

2026-08-11 09:57:47 -05:00

Jonathan Naylor

81518bf74c

Make AX.25, DMR, P25, NXDN and FM selectable at compile time.

2020-11-08 22:23:27 +00:00

Jonathan Naylor

14d5098018

Rename FMDownsampler to FMDownSampler.

2020-06-30 12:44:02 +01:00

3 Commits