Recordmydesktop & MEncoder Basics

[Jaws]

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...

Code:

recordmydesktop -windowid $(xwininfo |grep "Window id:"|sed -e "s/xwininfo\:\ Window id:\ // ;s/\ .*//") -fps 15 -device hw:1,0

Where...

-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.

[Paul LeBlanc]

 Nice info Jaws.. thanks. My mic is still sitting here... not even set up... (typical me... )
 I get nervous cuz everyone laughs when I talk cuz I often sound like Sam Elliot doing those "Beef... it's whats for dinner" commercials (must be all the smokes)

[Dadster]

 Good timing, Jaws. I was fooling around with RMD monday night.  Didn't realize I was recording stuff until I noticed the 3 tabs on the tool bar. It seems I was recording everything on the desktop in triplicate. While all along I thought I couldn't get it to work.  I did try 3 times.

[Jaws]

I'm not going to pretend to know the ins and outs of MEncoder. This is an app you can experiment with using different option and see what they do. Again, there are GUI front-ends to MEncoder but using the terminal is pretty straightforward.

For instance, after successfully encoding numerous videos, I wanted to know how to connect two or more videos into one file. I noticed that the original command I started out with was not working right. The sound for the first part video was very quiet while the second part was normal. Sure enough I moved the input file options around and it played well for both segments.

This is the command I use for single file encoding...

Code:

mencoder  -ovc lavc -ofps 30 -oac mp3lame -af volnorm=1:0.5 out.ogv -o output.avi

Where...

-ovc lavc = uses the libavcodec video codecs.
-ofps 30 = output file frames per second
-oac mp3lame = encode to MP3 (using LAME).
-af volnorm=1:0.5 = increases sound volume.
out.ogv = input file
-o output.avi = output file

If you want to string together more then one video...

Code:

mencoder  -ovc lavc -ofps 30 -oac mp3lame -af volnorm=1:0.5 out.ogv out-1.ogv -o output.avi

I didn't check but I'm sure using wildcards for multiple input files in the current directory would work. Something like *.ogv -o output.avi

Some useful commands...

Code:

mencoder -oac help = available audio codec

mencoder -ovc help = available video codec

There are a ton of web sites to research with options galore, of course I hardly read any of it...

http://linuxreviews.org/man/mplayer/
http://web.njit.edu/all_topics/Prog_Lang_Docs/html/mplayer/encoding.html
http://diveintomark.org/tag/give = some background info on encoding.

Anyone wanting to add or correct something, please do.

Cheers

[conholster]

How to go about editing the captures after recording? Like speeding up some parts and stuff?

[Paul LeBlanc]

How to go about editing the captures after recording? Like speeding up some parts and stuff?

You mean to sound like Alvin & the Chipmunks? 

[lunoob]

How to go about editing the captures after recording? Like speeding up some parts and stuff?

I've found Audacity to be good for that.  It has a fairly intuitive interface, and the effects plugins are pretty cool.

[conholster]

I thought audacity was just for audio(?).

You mean to sound like Alvin & the Chipmunks? 

I meant editing the video mr. Smartpants 

[Paul LeBlanc]

 

[Sproggy]

Jaws thanks for this ... i know what to do without a GUI now woohooo

Kori

[lunoob]

I thought audacity was just for audio(?).

You mean to sound like Alvin & the Chipmunks? 

I meant editing the video mr. Smartpants 

Oh, now I get it.  I thought you meant audio too.  I haven't done speed changes with it yet, but I believe you can do a lot of that kind of stuff in Blender using a Sequence session.

[freddyp]

Oh, now I get it.  I thought you meant audio too.  I haven't done speed changes with it yet, but I believe you can do a lot of that kind of stuff in Blender using a Sequence session.

Blender, IMO is not only the best video editor for linux, it's also the only one (in linux) that I can get to work. There is a very steep learning curve when it comes to mixing and chopping video and audio, but its worth the effort.

[lunoob]

Yup.  Steep learning curve, but once you get a lot of the basics - the Select, Grab, Zoom, Object/Edit modes etc. -  it becomes really fast and easy to do amazing things. 

Here's a pretty good tutorial for getting started with Blender's Sequence Editor:

http://www.blendernation.com/tutorials/blender-3d-beginner-tutorial-the-blender-sequence-editor/

Depending on how much time you have to devote all at once, it may take days to get through it.  But it gives tons of good info. 

[conholster]

hmmm....steep learning curve....small chance of success....didnt know I could run that fast Looking into kdenlive now. Only problem is it doesnt seem to support .ogv files.

[freddyp]

ooking into kdenlive now. Only problem is it doesnt seem to support .ogv files.

I've been trying to get kdenlive running properly for a long, long time and finally just gave up, don't know if its kden, PCLOS or my computer.

Kmediagrab is a nice quick and easy way of converting those .ogv files that recordmydesktop puts out, if you get kdenlive working.

P.S. I've learned to set up kdenlive to auto save every two minutes 'cause it would crash about every two and a half.