Feeding video to the fadecandy server via syphon actually proved to be straightforward. Here is my processing sketch if anyone needs it. This is for a 64 x 16 matrix so there is one line which may need adjusting.
If there is a better/more efficient way then let me know!
import codeanticode.syphon.*;
OPC opc;
PGraphics canvas;
SyphonClient client;
void setup()
{
size(320, 80, P3D);
println("Available Syphon servers:");
println(SyphonClient.listServers());
// Create syhpon client to receive frames
// from running server with given name:
client = new SyphonClient(this, "Avenue");
// Connect to the local instance of fcserver
opc = new OPC(this, "127.0.0.1", 7890);
// Map a 64x16 grid of LEDs to the center of the window.you may need to fiddle with this for different sized matrices
opc.ledGrid(0, 64,16, width * 1/2, height * 1/2, height/16, height/16, 0, false);
}
void draw()
{
while (!client.available()) {
//to avoid flickering if there are any dropped frames the sketch waits for the next frame (I think!)
}
background(0);
canvas = client.getGraphics(canvas);
image(canvas, 0, 0, width, height);
}