Archive for December, 2006

Recording screencasts with ffmpeg

I had Istanbul running on dapper quite happily by building the edgy source package on dapper, but I can’t get Istanbul working reliably on edgy. The audio’s fine but the video flashes horribly. Now I somehow can’t replicate my Istanbul setup on another dapper machine…

So back to the drawing board to try other options… and I took the plunge with the patched ffmpeg. Not elegant as far as starting and stopping, but the quality’s great. It does mean I end up with the result in an avi file rather than ogg, but that’s easy enough to convert.

Then I use the following to get rid of the start and end where I’m operating ffmpeg – ss is the time to crop off the start, and t is the duration I want, cropping the rest off the end:

ffmpeg -i original.avi -sameq -ss 00:00:08.005 -t 00:00:55 the_video.avi

The only issue is that the file size goes through the roof – from 1.8MB to 5.1MB – still have to figure that out without degrading the quality…

Then I can convert to high quality FLV with:

ffmpeg -sameq -i the_video.avi the_video.flv

and compressed ogg with:

ffmpeg2theora cropped.avi

Now to try the patched ffmpeg on edgy…

Istanbul recording with external USB Audio

I’ve finally got decent audio for screencasts. I’m using istanbul on Ubuntu Edgy, and the sound quality for recording through a builtin soundcard is predictably terrible, even with a Shure SM58 hooked up through several adaptors to get from XLR to 3.5mm into the mic jack…

So bring on the M-Audio Duo, a USB mic preamp that we had used previously on a Windows 2000 machine. Will it work? Even on Windows it was a black art configuring recording through this device as it had a task tray thingy that let you choose different driver options – MME, WDM, EASI and ASIO, only one of which I could actually get working.

Switch it on, connected to my laptop, and I get a notification, “New audio device connected – To configure your new audio device Duo and possibly set it as default device, open System -> Preferences -> Sound.” with a helpful “Open audio preferences” to do just that. Cool!

However, the Sound preferences weren’t very helpful. I could select “USB audio” for output – that worked – or for input – impossible to tell… Audacity had a separate configuration, and worked fine recording from this device when I configured the input to “/dev/dsp1” which appears when the Duo is connected and on.

Istanbul had no obvious way to select an input, so after much searching, I mailed Zaheer Abbas Merali, the primary Istanbul developer who mailed back this advice within half an hour:

Assuming you want to do this with alsa rather than oss. Run:
gstreamer-properties (can also get to it from Desktop, Preferences,
Multimedia Systems Selector) and set your default input plugin for
audio to custom and type: alsasrc device=hw:1.

Then Istanbul will record from the second sound device.

It worked! Now I’ve hooked up my Oktava MK319 which gets phantom power from the Duo, and the sound quality is excellent.

Update: Now if only Istanbul would record the video properly

Ubuntu-ZA gets going!


After some mailing list activity, we got our first ever IRC meeting going on 7 December with 21 people attending!

Craig Adams posted a summary of the marathon meeting – started around 20:00 (agenda points around 20:30) and seems to have run until 22:44 although I excused myself at around 21:30..

Points raised in the meeting which I find interesting:

  • Most people are intimidated when it comes to using the Wiki – that’s something we as the WikiTeam must address by giving a good introduction and clear howto’s on the mailing list.
  • is doing a better job of translating Ubuntu into our local languages than random Launchpad users. We should therefore point people to get involved with Translate rather than Launchpad. (Or is it all just merged together anyway in Launchpad?)
  • Everyone at the meeting spoke English as their first language. While we spoke about translation, none of us are likely to participate directly in it (unless we start a South African English version… “OK / Cancel” could be “Kif / Nooit” – and deleted files would go to the Rubbish Bin!)

Things I agreed to take (partial) responsibility for:

  • Wiki content and structuring – as part of the WikiTeam
  • Crossposting from the forum to the wiki and/or mailing list
  • I was tempted to put my name down for everything else – events, marketing, education… but the whole idea is to get more people involved. Nevertheless I am very interested in the LoCoTeam as a whole – seeing it gain momentum and actually do stuff!

Some additional ideas I’ve had since the meeting:

Planet Ubuntu-ZA

One of the specs discussed at UDS-MTV was how Launchpad can provide resources for LoCoTeams. While this spec was too fuzzy to get discussed sufficiently during UDS, and will probably become a series of separate Launchpad specs, one of the features mentioned was automatic creation of blog planets using Launchpad teams. This would make setting up a planet for a LoCo team trivial.

We should do this anyway. CLUG have got their, err, park, up and running… and now it can be officially said that I’m blogging!

I’ll ping Matthias who is currently providing our hosting and see what we can do…

User Map

While at UDS I spoke to Mark Van Den Borre of the Belgium LoCo Team and he showed me their user map (general locations of users willing to provide support). While this does depend on Google Maps which doesn’t have street level coverage of South Africa, there is probably enough detail for us to use since the whole idea is not to reveal your actual address…

Anyone interested? Here’s a spec and some code