BATC Forum

I am testing using Portsdown/RPi-3/DATV-Express set-up. I am having a problem with Pi-cam/MPEG2 transmissions not being stable (4 second LOCK with video...then drop…and then repeat) on my SatLink analyzer (although video is fine on MiniTiouner) and seeing a SatLink pop-up error message saying “HDTV not support”. My initial suspicion is that either a DATV-Express configuration file has an improper setting or the FFMPEG set-up is improper? So I used the WinSCP software to snoop-around looking at the files on the RPi-3.

1) I can NOT find a configuration file that would normally be called “datvexpress.cfg”. I did find a “datvexpress.txt” file, but that file was very incomplete (just a subset of settings) and did not represent recent configuration changes that I had made. Is there a configuration file for the DATV-Express board that I can inspect??

2) I am hoping to find a configuration file on the RPi-3 that represents the settings for FFMPEG for my set-up. I suspect that the TS may be improperly formed and is resulting in the “HDTV not support” error pop-up on SatLink analyzer? Is there such a file on RPi-3 that I can look at??

I appreciate any assistance…de Ken W6HHC

Hi Ken

There is no datvexpress.cfg file. I suspect this is only used in the Windows DATV Express software. All the settings for DATV Express in the Portsdown software are derived from the file /home/pi/rpidatv/scripts/rpidatvconfig.txt. This file is read by the bash script /home/pi/rpidatv/scripts/a.sh which is called by the Console Menu or the Touchscreen when transmit is selected.

Most of the derivation and sending of commands to the DATV Express server software happens here https://github.com/BritishAmateurTelevi ... /a.sh#L168 in lines 168-264. The commands are sent to a pipe at /tmp/expctrl which is monitored by the DATV Express server software.

Bitrate and other parameters are calculated here: https://github.com/BritishAmateurTelevi ... /a.sh#L249 in lines 249-299.

The ffmpeg parameters that you are looking for are defined in the statements here https://github.com/BritishAmateurTelevi ... /a.sh#L390 at lines 392-401 (no audio) or lines 404-413 (with a USB microphone).

Please confirm using the Windows DATV Express software (with vMix?) that your SatLink analyzer handles 720x576 video at 25 fps without error messages so that we can discount a problem with the analyser.

If you can find settings that work better with the Portsdown ffmpeg configuration I would be pleased to include them in the next build. You can amend the a.sh file to include hard-coded ffmpeg parameters for testing if required. Just save a copy of the original file first so that you can get back to where you started!

Note that ffmpeg is only used in CAMMPEG-2 mode (to produce MPEG-2). All other modes use a (compiled C++) program called avc2ts to feed the picture into the hardware H264 encoder and encode the output as an H264 transport stream.

Dave

Thanks Dave G8GKQ,

Let me begin to digest all of the good info you have provided.

73...de Ken W6HHC

Hi Dave G8GKQ,

I decided to first eliminate the SatLink analyzer as the possible source of the MPEG2 instability problems I was having receiving Portsdown/RPi-3/DATV-Express with Pi-cam/MPEG2 transmissions. So I went to a strictly DATV-Express set-up on Windows10 using a web-cam and H.262 protocol..

To my surprise the SatLink was reporting the exact same error message...“HDTV not support”. Since I never remembered seeing that error message before, I then remembered my earlier SatLink tests with Portsdown or MiniTioune had involved H.264 testing. SatLink must evidently require the user to SCAN the signal I am interested in before I can really watch the video on the analyzer...since, I then used SatLink to rescan the DATV-Express transmission in MPEG-2 that I was now testing and the “HDTV not support” error message had DISAPPEARED and the SatLink was displaying a VERY STABLE video.

I now suspect that when I do a scan with SatLink...the SatLink remembers some settings. If I receive a changed transmission on the same frequency (for example: MPEG-2 instead of H.264) SatLink still uses some settings saved from the last SCAN.

I have now returned to the Portsdown set-up with CAMMPEG-2 as video SOURCE and both the SatLink and MiniTioune have stable video displayed. No wonder the MiniTiouner has become my favorite receiver...MiniTiouner requires NO SCANS.

Thank you for suggesting the SatLink as a possible source of the error I was seeing.

73...de Ken W6HHC