Multitrack Recording Overview


Index

If you're thinking of setting up a serious multitrack recording system running on GNU/Linux there are several pitfalls for the unwary. Development has been slow in this area so far, but with the recent involvement of big audio industry players like Harrison Consoles things are improving.


Hardware Channel Counts

There are two ways to get a high enough number of hardware channels: use an interface card with enough channels or use several cards. Use of PCI or PCIe cards is assumed here. A single card setup should work out of the box with most Linux distributions, assuming your card is supported. At the time of writing the only cards with high (as in 24+) channel count supported by Linux are the RME cards. Their MADI cards handle up to 64 digital in/outs at 48kHz (or 32 at 96kHz). If this still isn't enough, the only option is to use multiple cards.


Multiple Sound Cards

If you need very high channel counts or you can only afford low channel-count cards, you'll need more than one sound card. This is not for the faint hearted. JACK, the audio server, can only work with one interface (OK it can use different devices for capture and playback, but only one for each). It's necessary to use the ALSA pcm_multi plugin to make multiple cards appear as a single virtual device that JACK can deal with.

A problem with pcm_multi is that it doesn't necessarily work with jackd with a realtime kernel (at least on x86_64; users of other architectures should check before committing themselves). This means you might not be able to use the specialist audio distributions of Linux without changing the kernel, since they tend to use the realtime (-rt) kernel by default. In order to get good low latency performance without the -rt kernel you'll probably need to use two CPU cores.

For those who want (or have) to follow the multi-card route, here's an example describing how to set up two or more ICE1712-based cards like the M-Audio Delta 1010. Although some of the information is specific to the Delta 1010 the main steps are the same for any multi-card setup.


Recording Software

The most popular multitrack recording/editing program for professional use on Linux is Ardour. At the time of writing, the stable series is 2.8.x, although Ardour 3 has been released. There is also a Linux version of Harrison's Ardour-based Mixbus, which includes Harrison's own EQ, compressor and tape emulation in addition to the standard Ardour 2 features.

The more adventurous may be interested in Non DAW, a modular and very lightweight recording, mixing, sequencing and session management system.


Plugins

The fact that there are few commercial plugins available for Linux might be a problem for some users. The native Linux plugin architectures (used by Ardour) are LADSPA and LV2. Most Linux distributions include Steve Harris' LADSPA plugins (called swh-plugins in Debian). There are other LADSPA plugins available, but the author has found Fons Adriaensen's stereo reverb and 4-band parametric EQ (rev-plugins and fil-plugins respectively in Debian) particularly useful.

The aforementioned LADSPA plugins have a major advantage over most commercial ones in their plain, functional user interface. Most controls (as provided by host applications such as Ardour) are plain sliders with an alternative text entry field. There are no distracting graphics of control panels, and no pictures of knobs that have to be turned with a mouse to adjust settings. So far, however, few of these plugins attempt to emulate the quirks and non-linearities of "classic" analogue devices - they just do the basic job.

There is some work being done on more graphic-intensive user interfaces using LV2, which is designed as a potential replacement for LADSPA. LV2 has undergone a few changes, but current versions of Ardour now use the latest version. One popular LV2 plugin is IR (packaged as ir.lv2 in Debian), a convolution reverb.

In addition to LADSPA and LV2 there are plugin-type applications that work as standalone JACK clients, such as Fons Adriaensen's Zita range.

Those who like pretty graphics along with emulations of "classic" hardware might want to look at some of the commercial plugins from OverTone DSP (was Linux DSP).

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Last updated July 15 2014