First my story: (you can skip down to END OF STORY if you want)

Ever since I saw Mike Relm go to town with a DVDJ, I've wanted a system where I could scratch and cue video. However, I haven't wanted to spend the $2500 for a DVDJ. As I was researching, I found a number of different systems. I am not a DJ by trade, so to get a system like Traktor or Serrato with their video modules plus turntables plus hardware plus a DJ mixer, soon everything gets really expensive. But in looking around, I found the Ms.Pinky system and after a little bit, I found a USB turntable on Woot for $60. So I bought it. It was marketed as a DJ turntable, but I knew that it wasn't really serious since it had a belt drive, but it came with a slip-pad and the USB connection meant that I wouldn't need a preamp. And so I spend the $100 on the Ms.Pinky vinyl plus software license (now only $80). This worked decently, but I had a lot of trouble really getting it totally on point. The relative mode worked well, but sometimes would skip if I scratched too vigorously. The absolute mode I couldn't get to work at all. After reading a little more, I came to the conclusion that my signal from vinyl to computer just wasn't strong enough, so I would need maybe a new needle or maybe a different turntable and I didn't really want to spend the money experimenting. I think that the Ms. Pinky system is probably a very good system with the right equipment, but I don't do this professionally, so I don't want to spend the loot on a system.

Earlier, before I bought Ms.Pinky (about two years ago), I had also looked around for a cheap MIDI USB DJ controller and not found one. Well, about a month ago, I saw the ION Discover DJ controller was on sale at Bed, Bath & Beyond for $50. They sold out before I could get one, but Vann's was selling it for $70, so I decided that that was good enough and bought one. I had planned to try to use it with Ms. Pinky since you can hook up MIDI controllers to it. But it turns out that you can hook up MIDI controllers to every control except the turntable, so that was a no go. If I had Max/MSP/Jitter, I could have changed that, but that's also way expensive. So, how should I scratch? My controller came with DJ'ing software and there's also some freeware, like Mixxx, but none of this has video support. So I look around and find Pure Data and GEM.

And I see lots of questions about scratching, how to do it. And there are even some tutorials and small patches out there, but as I look at them, none of them are quite what I'm looking for. The YouTube tutorial is really problematic because it's no good at all for scratching a song. It can create a scratching sound for a small sample, but it's taking the turntable's speed and using that as the position in the sample. If you did that with a longer song, it wouldn't even sound like a scratch. And then there are some which do work right, but none of them keep track of where you are in the playback. So, whenever you start scratching, you're starting from the beginning of the song or the middle.

So, I looked at all this and I said, "Hey, I can do this. I've got my spring break coming up. Looking at how easy PD looks and how much other good (if imperfect) work other people have done, I bet that I could build a good system for audio and video scratching within a week." And, I have.


So that's what I'm presenting to you, my free audio and video scratching system in Pure Data (Pd-extended, really). I use the name DJ Lease Def, so it's the Lease Def DJ system. It's not quite perfect because it loads its samples into tables using soundfiler which means that it has a huge delay when you load a new file during which the whole thing goes silent. I am unhappy about this, but unsure how to fix it. Otherwise, it's pretty nifty. Anyway, rather than be one big patch, it relies on a system of patches which work with each other. Each of the different parts will come in several versions and you can choose which one you want to use and load up the different parts and they should work together correctly. Right now, for most of the parts there's only one version, but I'll be adding others later.

There's a more detailed instruction manual in the .zip file, but the summary is that you load:

the engine (only one version right now): loads the files, does the actual signal processing and playback

one control patch (three versions to choose from currently, two GUI versions and a MIDI version specific to the Ion Discover DJ): is used to do most of the controlling of the engine other than loading files such as scratching, fading, adjusting volume, etc.

zero or one cueing patch (one version, optional): manages the controls for jumping around to different points in songs

zero or one net patch (one version: video playback): does some sort of add-on. Will probably most commonly be used for video. The net patches have to run in a separate instance of Pd-extended and they listen for signals from the engine via local UDP packets. This is set-up this way because when the audio and video tried to run in the same instance, I would get periodic little pops, clicks, and other unsmoothnesses. The audio part renders 1000 times per second for maximum fidelity, but the video part only renders like 30 or 60 times per second. Pure Data is not quite smooth enough to handle this in a clever real-time multithreading manner to ensure that they both always get their time slices. But you put them in separate processes, it all works fine.

So, anyway, it's real scratching beginning exactly where you were in playing the song and when you stop scratching it picks up just where you left off, you can set and jump to cue points, and it does video which will follow right along with both the scratching and cuing. So I'm pretty proud of it. The downsides are that you have to separate the audio and video files, that the audio has to be uncompressed aiff or wav (and that loading a new file pauses everything for like 10 seconds), that for really smooth video when you're scratching or playing backwards you have to encode it with a codec with no inter-frame encoding such as MJPEG, which results in bigger video files (but the playback scratches perfectly as a result).

So anyway, check it out, let me know what you think. If you have any questions or feedback please share. If anyone wants to build control patches for other MIDI hardware, please do and share them with me. I'd be glad to include them in the download. The different patches communicate using send and receive with a standard set of symbols. I've included documentation about what the expected symbols and values are. Also, if anyone wants me to write patches for some piece of hardware that you have, if you can give me one, I'll be glad to do it.

Keith Irwin (DJ Lease Def)