It does not seem to handle the fact that Qt events may not follow the pace of the hardware as the sample rate increases. In particular the SampleSourceFifo and the way it is handled in DSPDeviceSinkEngine looks weird to me now. I am not sure this can fix this particular problem but having a second look years after it was initially designed makes me perplexed. I could not reproduce the case even at 20 MS/s on the HackRF (on Ubuntu 18.04) and any combination of interpolation however the way the FIFOs are handled on the Tx side deserves some careful inspection. The most interesting phenomenon is the "popping" or "cracking" noise (very prominent in the last case) because it can be symptomatic of a FIFO issue. It is more than 40dB down from the carrier so I would not consider this. The second test shows noise picked up from the microphone or line. I have tested this on two different computers, my desktop PC with an Intel Core i7-4770 on Windows 10 and my laptop with an Intel Core i5-8250U on Windows 10 and Ubuntu 18.04 (dual boot, not using VM) with the same results. I can get rid of this noise as well, but after the procedure, a popping sound is present even when no audio is provided on the input: audioinput_afterdifferentnoise.zip Sometimes, the noise appears differently, with a crackling sound: audioinput_differentnoise.zip Unfortunately, after this there are still some crackling and popping sounds: 200hz_audioinput.zip
I can get rid of the noise if I change some modulator settings to different values, and then back to the values that I want to use.
Here is a 200Hz tone provided via Audio input, with the noise: 200hz_audioinput_withnoise.zip This is how it sounds and looks with no sound provided to the input: audioinput_noise.zip This noise is visible on SDRangel waterfall so I guess it is created before the data is sent to the HackRF. When I enable Audio input, no matter what the input device is (here using VB-Cable), a noise of unknown origin can appear. (Audio is recorded with RTL-SDR connected to HackRF output, provided in zip files because github doesn't support audio attachments)įor comparison, this is a 200hz tone from SDRangel's own generator - here everything is good: 200hz_sdrangel.zip I have encountered some issues with transmitting using Audio input, these issues seem to appear only when Audio input is enabled.
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