Tuesday, 17 February 2015


Live transmission using vMix

Transmitter graph
Windows Server Application
This picture shows DATV-Express transmitting a 4 MSymbol/sec signal all running
on Windows 8. The video mixing software is the free version of vMix  which is adding
a caption to the picture. The output is then sent via a directShow capture filter to a
filter graph which does the sound and vision encoding, it is then sent to DATV-Express
via UDP. The rather washed out picture is then being received on a Satlink receiver. It
is only washed out because of the difference in light between the two display screens
was too much for my still camera.
This example was done to show what is possible with a bit of imagination and is not
supported by the DATV-Express group.

The video capture in the picture above used a Logitech C920 webcamera.
vMix is capable of supporting many other devices and formats. The only other
input format I have tried so far is Firewire but that adds a 1/2 second delay. I am
looking at adding HDMI capture. 

The free version of vMix only supports 2 SD input capture devices but is useful for
the budget conscious Ham.


  1. Hi Charles. Looking like you are making good progress on "the dark side". Are you planning to release the windows server code at some time (on an unsupported basis)
    Have downloaded vmix - now to get the 920 webcam to work with it :-) 73. Ian

  2. Yes I will make the code available. There is just a limit to what it is physically possible for me to support. I am still fighting demons in the FPGA code. vMix seems like a really nice piece of software. I would watch the tutorial on YouTube (saves reading the manual)

    1. ha ha when all else fails read the instruction book - am more a soldering iron person than a software one Even boxed up the datv express over the weekend that has been sitting in its padded bag for ages. Can offer proof reading or photography skills if that is any use.

    2. Very nice, HDMI sounds good, as you know not software guy, last thing I did was VB in 1984, not real programming, like Ian, more soldering iron guy..