RFI: Feasibility of adding RTL_TCP | SoapyExporter protocol ?

[hvegh]

Just a question:
The driver for this question is:
It would be awesome if we could combine the visualization and tuning capabilities of sdrpp with rtl_433 decoding...

As far as I know this cannot be done directly at the moment, and I would like to consult your opinion on these possible options:

1. Add a RTL_TCP protocol to the network_sink module and push the IQ/stereo base-band stream
   Might be relatively easy to implement in existing code, maybe this is just prefixing the IQ stream with the appropriate Dongle Info Header and pushing the IQ as an int8 stream.
   This solution is very specific for RTL compatible softwares and is a bit of a hack in my opinion as it misuses the VFO for base-band transmission, and only allows for 8 bit resolution..

2. Add networking to the recorder
   And stream the baseband as UDP, TCP, RTL_TCP to the network, might be quite useful to have in general.

3. Adding a SoapySDR sink.
   This might be the most useful option as it is the most generic, should also work for rtl_433.

4. Enhance rtl_433 with a VFO UDP source
   That might be a solution but does not enhance the capabilities op sdrpp

What do you think?

[AlexandreRouma]

use the IQ Exporter module

[hvegh]

I tried the IQ exporter:

./rtl_433 -v -d rtl_tcp -s 250000
rtl_433 version 25.02-4-gda289d37 branch master at 202503111533 inputs file rtl_tcp RTL-SDR SoapySDR with TLS
[Protocols] Registered 238 out of 275 device decoding protocols [ 1-4 8 10-12 15-17 19-23 25-26 29-36 38-47 49-60 63 67-71 73-85 87-100 102-105 108-116 119-122 124-128 130-149 151-161 163-168 170-175 177-197 199 201-215 217-232 234-241 243-244 246-247 249-259 261-269
[Input] The internals of input handling changed, read about and report problems on PR #1978
[SDR] rtl_tcp input from localhost port 1234
connect: Connection refused
[rtltcp_open] Bad rtl_tcp header magic ""

I think its missing the appropriate Dongle Info Header header.

If there is no direct solution that I might have overlooked, I might be able to send in some patches.
But there are several options, what would be the best route to support this in sdr++?

Does it make sense to extend the IQ exporter with SoapyRemote | RTL_TCP protocol or, or create a seperate SoapyExporter module?

[hvegh]

I tested the IQ VFO with netcat, I see only an empty stream? (The active VFO is the rtl_433_sink / IQ Exporter)

nc localhost 1234 | head -c 10000000 | hexdump -C
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00989680

[hvegh]

switch (_this->sampType) {
        case SAMPLE_TYPE_INT8:
            volk_32f_s32f_convert_8i((int8_t*)_this->buffer, (float*)data, 128.0f, count*2);
            size = sizeof(int8_t)*2;
            break;

Aha ok, I get it, could be because signal is below 48 DB, so it is below the threshold..
Is there is a way to add a scale/gain or AGC option to the exporter in order to preserve some resolution?