ASIO Audio Interface

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Introduction

ASIO is an audio interface standard using a protocol developed by Steinberg. It bypasses the operating system's mixing kernel, so provding low latency direct communication with audio hardware, and allows multiple audio inputs and outputs to be accessed independently. ASIO drivers are thus often the only way to achieve very low latencies on consumer (Windows/Mac) operating systems, and also the best way to record multiple channels successfully. Some background reading on the ASIO technology can be read here.

Audacity and ASIO

Audacity, as an open source program licensed under the GPL , is currently unable to support ASIO. This is because ASIO is a proprietary, closed source technology protected by a licensing agreement which prevents redistribution of its source code. So although Audacity is ASIO-capable (providing the user's sound device is similarly capable), ASIO support cannot be distributed in Audacity without violating either Steinberg's licence agreement (if the code was distributed), or Audacity's GPL Licence (if the code was withheld). There are persistent rumours of Steinberg opening up licensing, but without any apparent movement. Anyone who cares about this issue is invited to make their views known to Steinberg at this email address.


Non-distributable ASIO support in Audacity 1.3.3

With the 1.3.3 release of Audacity, support for ASIO under Windows is now included for individuals who are prepared to compile Audacity from source code with the optional Steinberg ASIO SDK. This support is provided strictly on the basis that it is NON-DISTRIBUTABLE i.e. you may NOT copy or distribute builds including ASIO support to any third parties. The build is strictly for your own personal (private or commercial use). For the same reasons, Audacity can NOT distribute pre-compiled versions of Audacity including ASIO support, so please don't ask!

To compile Audacity from the 1.3.3 source code including ASIO support:

  • download the 1.3.3 source code
  • download and install the ASIO SDK
  • then follow the instructions in win/compile.txt in the downloaded source code to download and build wxWidgets and Audacity.

If compiled from source code, 1.3.3 also includes optional, DISTRIBUTABLE support for Microsoft's DirectSound interface protocol. This will give support for multichannel recording on some sound devices, but not the very low latencies that are possible on ASIO. It's permissible for users to distribute Audacity with DirectSound support since no proprietary code is included (the library is merely loaded at runtime).