Help creating screencasts on Ubuntu. keeping audio and video in sync

[heathenx]

tchomby tchomby wrote the following on 09/14/2008 08:56 PM:
> I'm creating a series of screencasts to teach object-oriented 
> programming in java to complete beginners. This is for a university, the 
> screencasts are to replace 14 one-hour lectures, so they're pretty long 
> screencasts and I have a lot to make. When I'm done I want to make them 
> all freely available.
> 
> I've been having a hellish time trying to figure out the process of 
> creating a screencast, and am at the point of desperation. I just really 
> need to get going on making the things, and stop battling with technical 
> problems. If anyone could help me it would be deeply appreciated.
> 
> So I thought I'd turn to this list for help, maybe some people could 
> walk me through the ways they do it, or explain to me why I'm having 
> problems. I'm looking for a simple approach, simple is the key, cause I 
> just need to get on with it.
> 
> What I tried to do was use gtk-recordmydesktop to record the full screen 
> (1280*1024) video and audio in one pass, then import the OGG file into 
> Kino (which uses ffmpeg to convert it to DV) and do some very simple 
> editing, editing out the bits where I cough or make mistakes, and adding 
> some text, then export it to MPEG.
> 
> The problem is that the audio and video will not stay in sync, no matter 
> what. I even installed a real-time kernel, and it didn't help. Either 
> they go out of sync in the original ogg file produced by recordmydeskop, 
> or they go out of sync after kino imports the file, or both. They get 
> further and further out of sync as time goes on, becoming completely 
> seperated after a few minutes, or sometimes they just go in and out of 
> sync at different times during the video.
> 
> What is causing this? Do I need to record a smaller area of the screen? 
> Put my screen in a smaller resolution? Install a virtual machine, run it 
> in a window smaller than the entire screen, and record that? Can this 
> one-pass approach with recordmydesktop and kino work at all?
> 
> Most screencasting on linux tutorials describe a two-pass approach, 
> first recording the video, then playing it back while recording the 
> audio, then combining the two. Does everyone do it this way? Isn't this 
> awkward, having to guess how fast to go when making the video? Are their 
> techniques you can use in a video editor, such as having the video 
> freeze while the audio continues on, to give the audio time to catch up? 
> What editors do people use and can they describe their techniques?
> 
> I know about this page:
> 
> https://wiki.ubuntu.com/ScreencastTeam/RecordingScreencasts
> 
> but it seems pretty old, xvidcap for one no longer works on ubuntu, and 
> I was hoping there was a simpler solution.
> 
> Maybe the best solution I have found is the one described here:
> 
> http://rhodesmill.org/brandon/2008/how-to-produce-a-linux-screencast/
> 
> basically, recording only a very small area of the screen using 
> recordmydesktop with on-the-fly-encoding, then using mencoder to 
> transform the ogg file into a dv file, then editing it in cinelerra, 
> then exporting. But recording only a small screen area is a limitation, 
> I would need to learn cinelerra which looks hellishly complicated (if 
> you try to open the dv file in kino it doesn't recognise it as a dv file 
> and begins converting it to dv), and from my tests I'm not confident 
> that even this approach will keep the audio and video in sync over many 
> minutes.
> 
> I'm considering giving Wink a try.
> 
> Hell, I'm even considering going to Windows and buying some proprietary 
> solution.
> 
> Any help would be greatly appreciated.
> 


I find it sometimes cumbersome working in the ogg format when trying to edit videos. Everyone has 
their own way of doing things and I'm no different. What I feel more comfortable doing is converting 
the recordmydesktop off file to an avi file that Avidemux can handle...something like "mencoder 
out.ogg -ovc lavc -oac mp3lame -o out.avi" should be sufficient. Once your editing is complete in 
Avidemux then you can save it into any number of formats, such as, ogm if you want to keep it in a 
free format. Avidemux isn't the best editor out there but it works well and it's stable.

If you are recording very long videos then you might want to consider breaking it up. Try allowing 
yourself some places where you can stop or pause recording. This may give you a break for a few 
seconds (drink of water, bathroom break) and allow for your cpu to refresh itself between 
recordings. Joining them all back together again isn't a difficult task. You can also fade out and 
back in where the videos are joined to hide some of the splicing (among other tricks).

heathenx

Kino and Cinelerra are very fine editors but not always user friendly. If Avidemux doesn't float 
your boat then perhaps Kdenlive would be easier for you to use. Just prepare yourself for saving 
often in whatever video editor that you work with. All have there flaws and you don't want to lose 
your project due to an unexpected power exit. ;)

Would love to hear that you did everything in Linux but if you must use Windows then I recommend 
Camtasia for screencasting and editing. Very nice but expensive.