This page contains links to a number of video tutorials that show you how to use the MeqBrowser. The tutorials were all made with a linux program called xvidcap. xvidcap worked reasonably well, but did have one or two problems. Firstly, xvidcap tended to drop audio at the beginning of a broadcast, so you may notice that the video begins in the middle of a sentence. Secondly, xvidcap tended to crash when some `big' activity started, such as launching the meqserver (that's why I had to split the tutorial on starting the browser and loading a file into it, into two separate videos). Finally, xvidcap sometimes captures the screen in odd ways, especially if we're dragging a widget into the area of the screen being captured. Anyway, here you are ...
Our first tutorial (browser_one.mpeg) shows you how to start up the MeqBrowser. This tutorial is quite short because xvidcap falls over when we start up a meqserver from within the browser.After we pick ourselves up off the ground, the second tutorial (browser_two.mpeg) continues on after we have launched a meqserver. It shows you how to load a TDL script into the browser, and how the system compiles and runs a simple script. Once we have loaded and run a script, we are in a position to visualize the contents of nodes. Our third tutorial (browser_visualization.mpeg) describes some of the basic operations that can be done on a visualization node such as zooming and getting a readout of data values.
There are also tutorials that describe more specialized visualization processes. Because a MeqTrees node can have data arrays with more than two dimensions, extensions to the standard two-dimensional display described in the above tutorial were developed. This tutorial(ND_visualization.mpeg) shows you some of the capabilities for viewing data sets with more than two dimensions.
So far we have demonstrated how MeqTrees visualizes real arrays. However radio astronomers often have to work with complex-valued data such as visibility data sets, telescope gains that vary as a function of time, antenna voltage patterns etc. The following tutorial (visibilities_tutorial.mpeg) shows you how one can visualize a complex-valued data set within the MeqTrees browser. We look at a visibility data set having 32 frequency channels and a tilesize of 48. (A tilesize just gives the number of integration periods loaded and processed together in a MeqTrees domain.)
While the visualization nodes described above give you detailed information about individual nodes, it may be important that get a complete overview of the data in all nodes of a given type. This can be done with the aid of a Collections Plotter. The Collections Plotter essentially views the contents of a MeqComposer node; a MeqComposer node can be used to gather into one VellSet the contents of many children. This tutorial (collections_plotter.mpeg) demonstrates how we can use the Collections Plotter to view the contents of such a node.
If you have trouble viewing these tutorials, lower-resolution versions are available from YouTube. Click youtube_tutorials.html to see them.