OBS - Open Broadcast Studio
Open Broadcast Studio is a free and open source software for video recording and live streaming.
It enables high performance real time video/audio capturing and mixing. Create scenes made up of multiple sources including window captures, images, text, browser windows, webcams, capture cards and more.
More details on the features and the program download from https://obsproject.com/
Using OBS with Portsdown
OBS can be used as a fully flexible video source for the Portsdown DATV system. The program interfaces in to the Portsdown over a wired network connection via an ffmpeg script developed by Evariste F5OEO.
Preparing the system
As well as downloading OBS (making sure you get the right version for your system ie 64bit/32bit) and ensuring it runs on your PC, you will also need to download ffmpeg from https://ffmpeg.org/ - ffmpeg should then be installed on your PC at C:/ffmpeg. If you are using a Windows PC then you will need to change some files to ones compiled with pthreads as the w32thread compiled files will cause instability problems with your UDP stream. You can download the files from here Download. Once downloaded copy all the files in the ffmpeg-4.0.2-pthreads folder to C:/ffmpeg and over write the original files.
It is also useful to have VLC on the PC for testing, make sure you download the correct one for your system ie 64bit/32bit this will be important for later use with OBS - https://www.videolan.org/vlc/index.en-GB.html
You will need to setup the Portsdown to talk to your PC via a network cable, WiFi wont work reliably. I set the Portsdown up with a fixed IP of 10.0.0.1 by adding the text ip=10.0.0.1 to the cmdline.txt file found in the root of your SD card.
Once you have set the Portsdown up and can confirm the network is working, you need to set up OBS.
With OBS running click on the profile tab and then rename the default profile to 250Ks@3/4FEC.
Now click on the file tab and go to show the profile folder. Within that window you will see a file basic.ini, replace it with the file contained in the zip file below. File:Basic.zip
You can now duplicate this profile and rename them to suit your own choice of SR/FEC combination, I have 250Ks@3/4FEC, 333Ks@3/4FEC,500Ks@1/2FEC,500Ks@3/4FEC and 1Ms@1/2. For each profile you will need to change the muxrate, bitrate and FFVBitrate (video bitrate) values for your given choice of SR/FEC, this can be done from the settings, output (advance), recording or the ini file. Use this site http://www.satbroadcasts.com/DVB-S_Bitrate_and_Bandwidth_Calculator.html to work out your own choice of SR/FEC combinations. You will need to use the "netto ts bitrate" as this is in Mbps we need to multiply this by 1000000 to get bps for both the muxrate and bitrate, for the FFVBitrate (video bitrate) we need to multiply by 0.0006 and just round up to a whole number. So if the "netto ts bitrate" is 0.3721 x 1000000 = bitrate/muxrate = 372100 and FFVbitrate 372100 x 0.0006 = 223.26 = 223. You may need to play around a little bit with the FFVBitrate to suit your individual setup.
You can set the preview screens up to what ever takes your fancy but the FFRescaleRes should be appropriate for the SR in use so 768x576 or 352x288 are better suited to SR333/250 where as 1280x720 is better left to SR's of 500Ks and above.
Once OBS is set up you can test it's all working with VLC set to receive a network connection on udp://126.96.36.199:20000 and hitting the start recording button on OBS.
ffmpeg batch file
You now need to download the batch file below and you will need to edit it to accommodate your choice of SR/FEC's, Callsign, Ip address.
Please note the above guide is just that a guide as every set up will be different to the next so experimentation may be necessary to get it working 100%