July 2010 Archives

As you might know by now, I started an informal podcast in Croatian about Free and Open Source software called Razgovori o slobodnom softveru. This blog post will try to summarize my experiences and serve as information for podcast guests on how to get the best possible audio quality.

Every podcast currently starts as google wave. While this isn't ideal, it does work for now. I would love some other service which would allow me to see information color-coded by users. Those notes are later used to write blog post with all links and information about episode.

First, let's get Skype out of way. Only reason why we aren't using free software for audio conversation is simple fact that everybody has Skype and there is great skype-call-recorder which allows us to get uncompressed audio recording with local audio on one channel and remove one on another which enables easy matching of audio levels for local and remote speakers.

While we are at audio levels, let me share a little secret: right after recording audio from Skype, I use Levelator to adjust audio levels. There is Linux version of it, but it doesn't seem to work for me on recent Debian. But, effect is so valuable to good quality podcast that I just use Windows version under wine.

As far as guest audio is concerned I have found following notes really important for my guests:

• use any microphone other than one on your laptop. Built in microphones catch typing sounds and all huss and buzz from machine itself. Even cheapest possible microphone will generate better results, just compare Ivan's audio from episode 0 (audio via built-in laptop microphone) versus episode 1 (which is cheap plastic external microphone)
• if you have headset with microphone, use it. Adjust your microphone level to be above your nose. That will prevent recording of air that you breath.
• When you need to take a pause while speaking, just do it! I edit whole podcast to remove bloopers and breading anyway, but it helps if you repeat last word of full sentence when you start over so it will fit in context (and intonation) of previous material.

If at all possible, it's great if guests can record local audio (only microphone sound, not full mix from conversation) so you can replace Skype's remote channel with better quality audio.

Much more useful information can be found in Skype for interviews by Doug Kaye and Paul Figgiani (guys behind Conversations Network which also implemented Levelator mentioned above), so if you need to record on Windows or Mac take a look there.

For editing audio I use audacity which is great audio editor, but I still have to learn all keyboard shortcuts because using mouse to edit audio is too slow and cumbersome if you want real flow of montage (and I did video montage back in 1990 on local TV station, so I know unnecessary mouse clicks when I see them). It would be nice if labels moved when I do cut of audio, because editing of audio leaves labels at old positions which isn't useful since audio moved. To give you some idea of how much effort is involved in editing audio (mostly removing silences, bloopers and breading): for last 35 minute podcast, it took 420 edits to get it into final state. And most of single day. It's about the same as creating good presentation: I often need 6 times more than presentation length to create it. For audio editing, you can count on 10-15 times ratio for editing.

Finally, I hop over to some creative commons audio site (to be honest, it was first one in google search for CC music), pick one of top tracks and extract intro and outro music from it to put it at beginning of podcast and end. Finally, audio introduction and web address information for end are recorded and put on top of music.

I have two screens, and 9 virtual dekstops on my machines. Which sometimes makes it tricy to remember on which virtual desktop is xterm connected to klin. Fortunatly, I have that information in window title, so something as simple as:

xdotool search --name klin windowactivate

Will do the right thing. However, my mouse pointer is not always over xterm on local machine, so keyboard shortcut in awesome window manager for this simple xdotool usage would be helpful. So, here it is:

-- XXX dpavlin: search windows and active them
awful.key({ modkey }, "F12",
  function () 
    awful.prompt.run({ prompt = "window: " },
      mypromptbox[mouse.screen].widget,
      function (find)
        awful.util.spawn("xdotool search --name "..find.." windowactivate", false)
      end)
  end),

I would love to be able to insert this snippet somehow dynamically instead of editing rc.lua by hand, so suggestions are welcomed.

So you have a car. And you are a geek. You know kind of I don't really know or care how cars work. And then you got graph like this from your car:

If you take a look at OBD2, you might think that it's only useful to your car mechanic. But, as you can clearly see above, any technology which can draw graphs and uses computers is interesting to me.

You can take two different paths to getting sensor data from your car using open source software. Freediag is project which support dumb (basically level converters between your car OBD2 connector and RS232 or USB) cables. This approach requires very funky boud rates on serial port and lot of knowledge inside software, but offers future-prof route because you can hack software.
So I decided to buy one of those cables (available locally in Zagreb) and ended up with VW cable which did dump some data, but freediag didn't really helped in decoding them.

So, in next step, I opted for one of ELM327 based devices (which decode car protocol within microcontroller) and moved to OBD GPS Logger for data collection. This did work, and result is graph included in this post. In the process, I figured out why you can disconnect both cables (to car and to usb) from micro-controller in metal box: it's the only way to reset it, sigh!

However, now I have a few observations about state of free software for OBD2: I wasn't able to found any software which would introspect all my sensors and log them. This is quite strange since you can inquire car about supported sensors, so that will probably be next thing for me to do. If you have more information, please let me know.