Tag: audio

Ruby GUI Toolkit Talk: Notes and Audio

On March 27th I gave a talk at the St. Louis Ruby User Group about Ruby GUI Toolkits. As with my last few talks, there were no slides, but rather a handout. The original handout fit tightly on a single, two-sided printed page; I’ve expanded the materials slightly and pasted them here.

I also recorded audio of the talk with my Olympus WS-100 digital voice recorder, then used Audacity to clean it up; Audacity’s “Remove Noise” feature worked surprisingly well. The recording lasts 1 hour 23 minutes, is 49 MB in size: RubyGUIToolkitTalk.mp3

A transcript of the talk is also available.

In the audio I mention screen shots and demos; you can find those at the respective toolkits’ web sites (linked below). I also briefly discuss and demo some code from a 2005 talk about Swing.

The handout contents follow below.

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I have seen the future, and it runs OSX

iPhone: Wow

It’s a phone. It’s a PDA. It’s an iPod. It’s a widescreen video iPod. It has zero physical buttons, rather the whole front is a multi-touch-screen. I’ll leave the rest of the raving to the many other sites doing a great job of that.

The real innovation of this new device is the OS. Apple has an answer to PalmOS and Windows Mobile (CE): run their real desktop/server OSX, with Unix inside, on the phone. Today’s handhelds have much more computing power and storage than desktop PCs of a decade ago, and there are enormous benefits to running a real, common OS on such a device. I’d been saying since I bought my first Palm (a Handspring, actually) than within a decade the handheld OS’s would go away.

Apple has gone first. How soon will Microsoft follow? Will Palm and RIM make to the new era at all?

(Update: Yes, the title of this post is slightly in jest. I’m serious about real OSs in handheld devices, and the iPhone looks fantastic, but Apple is very unlikely to dominate the phone market in the way the iPod dominates the tiny-media-player market.)

Java Scripting Talk – Code, Notes, and Audio

Last night (9 Nov 2006) at the St. Louis Java User Group, I gave a talk on “Scripting Your Java Application”. As I mentioned, there were no slides, but rather a handout, the text of which is pasted below. You can download the handout (a tight, one page PDF), the code, audio of the talk (WMA), and audio of the talk (MP3, larger). The audio was recorded with my Olympus WS100 Digital Voice Recorder, so the quality is bearable but not great.

Update: As an experiment, I also had CastingWords prepare a transcript of the talk. It’s somewhat tedious to read (I didn’t edit it at all), but it is available as Google fodder rather than trapped only in audio.
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“Looping” an audio file with Sox, Lame and mkfifo

Today I needed a very long (3 hour) MP3 audio file to use for an experiment; a test file with some music on it. My first thought was to start a MP3 audio recorder, turn on the radio, and leave for 3 hours.

But impatience is among the three great virtues of a programmer, so I turned to Google instead, seeking command line tools for audio manipulation. It turns out that sox and lame will do the job. I installed the tools – here is the Debian / Ubuntu invocation:

apt-get install sox lame

then grabbed an MP3 file of a piece of music (Peter T. Noonan, album “Cafe at Arles”, track 9 “Life’s Old Road”, if you are curious) and repeated it a few times:

sox music.mp3 foo.wav repeat 3

lame foo.wav longmusic.mp3

This worked well, the first time… but consumed a lot of disk space. To get to 3 hours I would need enough disk space for a 3 hour uncompressed WAV file. Unfortunately Sox does not support MP3 output, and I didn’t want to compress to a format it does support, then uncompress and recompress again. So I used a Unix/Linux FIFO pipe instead of a file, with Sox running in the background to fill the pipe with data for Lame:

mkfifo foo.mp3

sox music.mp3 foo.wav repeat 10 &

lame foo.wav longmusic.mp3

a little while later, longmusic.mp3 is a very long MP3 file… but not long enough, because sox fails when the “virtual” WAV file it is writing reaches 2 Gb in size, just as it fails with a real WAV file at that size. That was about 1 hour and 41 minutes – not long enough; so I ended up looking elsewhere:

The Ugly Hack

It turns out that Lame will tolerate an MP3 which consists of several appended MP3 files as its input. It complains but keeps processing when encountering the extra headers in the middle of such a file. So this solution with cat, a pipe, and Lame, worked:

cat 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 1.mp3 | lame – longmusic.mp3

A little while later, I had a 3 hour long, valid MP3 file.

Make a DVD with ffmpeg

For a project we have going at Oasis Digital, we have explored various libraries for creating video DVDs from computer-generated content until program/script control. There are quite a few ways to do this; one that is appealing for a command-line junkie is the combination of ffmpeg, dvdauthor, and mkisofs. It took considerable research to figure out what commands to string together for a simple scenario:

  • you have some video in AVI format (for example, an MJPEG AVI from a DV video camera)
  • you have some background music in mp3 format
  • you want a simple one-title one-chapter DVD with that video and audio

There are plenty of sites with long and complex sets of commands to accomplish these things. But for this simplest case, the essential commands are:

ffmpeg -y -i video.avi -i audio.mp3 -target ntsc-dvd -aspect 4:3 dvd.mpg

mkdir DVD

dvdauthor -x file.xml # there is a way to avoid the file by putting a few more options here

mkisofs -dvd-video -o dvd.iso DVD

Of course, there is considerable other work involved in wiring up a full solution, but that is more project specific. I hope these example commands shorten the research time for the next fellow who needs to do this core processing.

Slider Control for Touch-Screen Applications

An improved version of this post is cross-posted on the Oasis Digital blog.

At Oasis Digital we are working on an application that will run on a touch-screen computer, and which will be used to (among other things) control an audio amplification system. There are some design considerations for touch-screen applications which are rather stark once you use the touch-screen for a few minutes:

  • A finger is rather less precise than a mouse pointer – hitting small targets is hard
  • Drag/drop operations (or grab-adjust operations) sometimes don’t start quite where you aimed
  • Your finger blocks the point on the screen where you are pressing
  • The concept of keyboard “focus” is moot on applications with no keyboard

To accomodate the first two of these, I’ve built a prototype/example of a slider control to use for audio adjustment in such an application. It has these key features:

  1. It does not matter if you click on the “handle” or on the rest of the bar – because with touch screen you won’t be able to reliably do one vs. the other.
  2. The adjustment is not immediate; there is a limit of the speed of the adjustment to produce smoother audio control. The slider handle will move down very quickly, but will move up slowly. This avoids the possibility of an accidental touch pushing the audio amplification in to feedback.

The prototype/example looks like the screenshot here:

Touchscreen Slider

… but ignore the static image, it doesn’t tell the story. To see it in action, take a look at the screencast (currently in a WMV file, easily viewable only on Windows) or download the example program and play with it. The source is also on github.

This example runs on Delphi 2007 (rather old… but I had it handy on the PC at hand), an enhanced version of it in us used in a production application for a touch-screen audio control system. My secondary goal was to use it as a target to create an AJAX control with the same behavior. Anyone want to write that?