Category Archives: Technical

i for one welcome our new google video overlords

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Google had been notably quiet since acquiring video codec developer On2 Technologies, but today it revealed what it’s been up to: On2′s VP8 codec is now open-source, with a Theora-style irrevocable royalty-free grant for anyone to use the patents that Google now owns that cover it. Google’s calling the initiative WebM, which combines the VP8 video with Vorbis audio in a Matroska container.

The software’s a bit rough right now, but it really does work. Google has already started re-encoding Youtube’s videos, and after grabbing a WebM-enabled Firefox nightly build (the WebM site has to Firefox, Chrome, and Opera builds, and instructions for Youtube) I was able to check out the joys of HTML5 Youtube for the first time. As for encoding, there’s a reference encoder and a set of patches for FFmpeg; using the latter, I was able to build a WebM-enabled FFmpeg, encode a video, and play it back within Firefox.

Maybe Google’s just doing this as a lever against H.264 — MPEG LA might be less likely to go jacking up its prices if there’s a serious competitor in the market — but I get the impression it they really want to see WebM take off. There’s a big emphasis on hardware support, with simultaneous announcements from TI, Broadcom, Qualcomm, ARM, AMD, NVIDIA, and others, and Google will of course be bringing support to Android. With Adobe pledging to support it in Flash, giving support for IE and Safari, WebM is going to work just about everywhere apart from iPhone OS.

What remains to be seen is whether or not there are potential patent challenges here, from MPEG LA or other parties. Google obviously doesn’t think so, and it has a long list of partners that also seem willing to take that bet, so time will tell if MPEG LA makes good on its threats.

testing ubuntu lucid

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Ubuntu 10.04, aka Lucid Lynx, is just a couple of days away, so I’ve been testing it on my laptop to see just how it’s coming along. I rely too much on both my laptop and my desktop to mess with new OSs before they’ve been released (or even just after they’ve been released), but I do keep a little 4GB partition spare on my laptop, so that I can install and test new releases without messing up my primary install.

So far, it’s looking really good. The new visual theme is great to look at, and while it still insists on moving the close/minimise/maximise widgets in window title bars, it at least puts the close button in most accessible place, in the far left. It also has “teh snappy” — Firefox 3.6 on 10.04 snaps tabs around just as quickly as Chrome did on 9.10. I’m not sure what’s going on here, but I suspect it’s an Intel video driver update at play.

In terms of music-making, 10.04 gets two big improvements: JACK is now in the “main” repository, which means that a bunch of apps that didn’t ship with JACK support in earlier versions now can (and do), and LV2 support is much more widespread, with major apps like Ardour supporting LV2 out-of-the-box, and more LV2 plug-ins (such as the Invada pack) available as standard packages. The JACK package now automatically sets itself up to get realtime priority access, removing a manual configuration step that’s often a stumbling block for users new to Linux audio.

linux synth tutorial: part 6

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Another long one! In part 6, I jump from Xsynth to Specimen, a simple sampler, which is ideal for when you want to take a simple sound and quickly transform it in to a playable instrument. Specimen does much more than just playing samples, though — it can sculpt and shape them with envelopes, filters, and LFOs, just like you’d find in Xsynth.

Hi-res Ogg Theora version is here, or watch the Youtube version after the jump!

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linux synth tutorial: part 5

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In part 5 of my Linux soft synth tutorial, I look at the concept of modulation — changing synth parameters over time. We saw an example of this in part 4, where we used an envelope to control the volume of a sound over time; modulation extends this to other parameters, such as the pitch of the oscillators and the filter cutoff. Modulation can use envelopes to change parameters over the length of the sound — in fact, there’s a second envelope in Xsynth-DSSI just for modulation — or the low frequency oscillator, or LFO, to perform repeating rhythmic changes.

Modulation can produce effects ranging from subtle vibrato through to sweeping soundscapes and alien sound effects. Either way, it’s a powerful way to breathe life and movement in to what might otherwise be a dull sound.

High-res Ogg Theora version is here, or watch the Youtube version after the jump!

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linux synth tutorial: part 4

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In part 4 of my Linux soft synth tutorial, I look at Xsynth-DSSI’s amplifier section, and particularly the “envelope”, which defines how the volume of your sound changes over time. By tweaking the envelope, you can make your sounds fade in and out softly, hit hard and then slowly fade like a piano, or come on strong and then disappear just as quickly, like a xylophone.

High-res Ogg Theora version is here, or watch the Youtube version after the jump!

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linux synth tutorial: part 3

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In part 3 of my Linux soft synth tutorial, I look at the next major component of the traditional analogue synth — the filter. The filter… uhh… filters the sound from the oscillators, typically cutting away at the high frequencies; the effects range from the subtle to the drastic, especially once you start tweaking that “resonance” parameter. In fact, analog synthesis is sometimes called “subtractive synthesis”, due to the way the filter cuts away parts of the sound.

High-res Ogg Theora version is here, or watch the Youtube version after the jump!

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linux synth tutorial: part 2

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In part 2 of my Linux soft synth tutorial, I look at the oscillators in Xsynth-DSSI, the different kinds of sounds they can produce, and some of the ways they can be combined to create more interesting sounds. The oscillators create the raw synth sound, before it’s shaped by the filter and amplifier, so it’s more responsible than any other part of the synth for the general timbre of your sound.

Again, if you’re on Chrome or Firefox, or you just want to download it for later viewing, you can grab a high-res Ogg Theora version here, or watch the Youtube version after the jump!

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sketchbook: supercollider? i just met her!

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It took some doing, but I got SuperCollider running a sequenced filter cutoff pattern effect. It actually does a little more than just changing the filter cutoff — it also gates the incoming sound, to get more of a synth arpeggio effect. Here’s a sample, running a cello sound (a soundfont played by Qsynth), with a stereo delay added for good measure:


mp3 | vorbis | 44 seconds

You can check out the code after the jump: Continue reading →

how hard can step-sequencing a filter be?

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Yesterday I had a suggestion to add a “woody” sound, like a bowed string instrument, to my “daybreak” track, and while I don’t think I’ll be editing that track now, it did inspire me to grab some instrument samples and see what I could do with them. One effect I wanted to try was running sound through a filter that has it’s cutoff frequency controlled by a step sequencer, which gives the sound a bit of a rhythmic, glitchy feel. Short of buying an Evolver, was there a way I could do this under Linux?

I tried a few approaches, and did actually get this working in a couple of ways, but none exactly to my liking yet:

  • JACK Rack can control plugin parameters using MIDI, so I set it up with a Calf Filter, configured the cutoff for MIDI control, and created a sequence of parameter changes in Qtractor. This was quick to set up, and it kinda worked, but the timing wasn’t stable — I’m not sure if JACK Rack’s MIDI support is meant to be used this way.
  • The next idea was to use a modular synth. I tried AlsaModularSynth, but I’m not sure that its step sequencer is generic enough to use for modulation, instead of playing notes — I had it all hooked up but just couldn’t get it working. Ingen looked a bit more promising, but it’s still very alpha, and crashed too often for me to be bothered dealing with.
  • Following that line of thought, I fired up Pure Data (“Pd” to its friends) and tried to get to grips with it. Pd is one of the many programmatic audio/music synthesis environments available for Linux, and I’ve been looking for an excuse to check one out; this seemed to fit the bill pretty well. Pd is a bit like a modular synth, but much lower-level — it doesn’t have a step-sequencer, but I was able to build one! I got a working setup, but the resonant bandpass filter I used didn’t sound ideal to me, and I had hassles trying to pull in a better one, either as a Pd add-on or through LADSPA. I could’ve actually built a better filter, but that wasn’t something I was interested in doing today.
  • Moving on from Pd, I had another crack with SuperCollider, another synthesis environment. Unlike Pd, which is graphical, SuperCollider is based around writing code, which should mean that it’s more to my liking. I can get sound out of it, and it has some good filters, but the sequencing stuff is gonna take a bit of work to get my brain around.