Here's some info I gathered on using Recordmydesktop (RMD) after researching how to screencast.
First off I'm using a USB microphone specifically this one by Logitech for $20.00...http://www.newegg.com/Product/Product.aspx?Item=N82E16836111601
It's nicely made with a weighted base, good looks, it will pick your voice up anywhere in the room and it's cheap. What more can you ask for.
Since it's not being used with the sound card, where most mikes are plugged in, you're going to have to tell the application, in this case RMD, where the mike is. I suppose there's a terminal command to get specific info for your computer once you plug the mike in but I don't know that. I read that you can use [device hw:1,0] and this might be universal in Linux though I'm not sure about that either but it works for me.
There is a GUI for RMD but it's simple enough using the terminal. The command I use to start a recording session is...
recordmydesktop -windowid $(xwininfo |grep "Window id:"|sed -e "s/xwininfo\:\ Window id:\ // ;s/\ .*//") -fps 15 -device hw:1,0
-windowid $(xwininfo |grep "Window id:"|sed -e "s/xwininfo\:\ Window id:\ // ;s/\ .*//")
is the window you what to record. If you what to record your whole desktop just drop this portion of the command.
-fps 15 = frames per second
-device hw:1,0 = microphone location
When first launching the command, a cross-hair will appear and you use it to select the window you want to record. Clicking on a window will start a recording session.
Some handy key combos...
Ctrl + Alt + p = pause the screencast.
Ctrl + c = ends the session. There is a slight pause before the video starts encoding. Tapping Ctrl + c a second time and you'll lose whatever is left that wasn't encoded before it finished.
The default output is an out.ogv file sitting in your /home. You can watch what you recorded by clicking on the file. Kaffeine plays them fine. For some reason VLC doesn't play the sound on my system.
Part two: Mencoder tomorrow.