BATC Forum

Hello to the group.

I am just starting to get a signal up to QO-100, but as this is really about the streaming (recording) software, I hope this is the best place.

I have tried to follow the recent article in CQ-TV 265 regards 'OBS and the Portsdown'. Now I am not using the Portsdown system but rather a headless Linux PC running GNU radio driving a Hackrf one. But it still needs to receive a UDP stream on a port so I believe things are very similar.

I have tried to set up the OBS system as per the article, with it 'recording to a UDP stream on 230.0.0.11:20000 and have also tried to copy the essence of the batch file in to a shell script to take the stream from OBS and then forward to gnu radio changing the meta data as it goes. I see lots repeated TS errors between the OBS and gnu radio from the shell script doing the conversion.

I am wondering a few things, is there a way to see the bit rate actually output from OBS as I think it may still have the 32Kbits per sec audio on top of the muxrate?

Are there any LINUX guru's that can help as the last line of a shell script with &biterate=329610 means I can not stop the shell script and have to go into processes (task manager) to stop it.

Lastly, within OBS output why can one not have the metadata set in the output stream, ( call sign etc) but have to set it in another process?

I am presently just going to be using ffmpeg with mpeg2 streams to determine the received signal into the satellite at a couple of low SR's. Then hope to be able to sit down and work out what SR and FEC rates will be viable for me to use.

Sorry for the long post many of these things I struggle with and hope someone can help.

Adrian

Hi Adrian,

Not sure if the following will help much as it doesn't answer the questions exactly, it uses Python not a shell script, and I'm running OBS on the same Linux computer as the Lime is attached to but here it is!

In Linux I use a Python script, localcalc.py, influenced by the earlier batch files to take command line supplied options and an input to ffmpeg and output to limesdr_dvb. I usually use this with OBS saving to a local FIFO named pipe file so the script defaults to that, it takes RTMP or other supplied input to ffmpeg though so can be taken in over the network. It also sends a MQTT message to turn the amplifier on/off with a delay and uses the OBS websocket plugin to turn OBS recording on/off.

There's also another script netcalc.py that outputs to UDP but I've not used it in a bit so it's a bit behind the localcalc script usability wise but it is maybe easier to understand what's going on.

OBS doesn't provide direct access to the ffmpeg command and doesn't support adding metadata unfortunately. I have seen there is a ffmpeg direct access plugin now that might work but it is Windows only, again unfortunately!

John

Thank you John, not saying I will understand it all but I will have a look through the files and see how much I can follow.

At present I am just using a couple of scrips one to select which gnu file to run in python and one to use ffmpeg for mpeg2video and aac audio, it selects one of two cameras or test card and what SR rate to be used. It is all very basic as uplink frequencies, SR's and such are all fixed within the scripts. My brain is not used for programming

OK on the OBS and access to ffmpeg, I try to stay away from windows if I can.

Thanks again.

Adrian

Hi Adrian,

I have NGINX plus ffmpeg running on a Pi which is in turn streaming to the Portsdown. I stream RTMP from a Linux PC to the NGINX server using OBS, if the OBS Streaming Output Bitrate is set to high, you do get 'TS is invalid' messages from ffmpeg.

Phil
M0PIT

Thanks Phil;

I need to find some way of working things out. as said I do not have a Portsdown, DATV, express or use a raspberry PI. My entry into this has been slim as one may say, I had a Hackrf one I use Linux and run gnu radio which has files for DSB-S" and with some minor changes got it to work sending a picture across the room just from the Hackrf.

I used a radio hams guide using ffmpeg to do a simple stream to the PC running gnu radio and did things for 1ms and 2 ms as separate scripts as basic mpeg2.

But I think I need to concentrate on lower SR rates that requires the use of h264 and h265. and for the life of me can not get successful streams yet. it will take me time, lots of trying and reading I think.