ASIO Audio Interface

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ASIO is a proprietary audio interface standard which bypasses the operating system's mixing kernel, so providing low latency direct communication with audio hardware and allowing multiple audio inputs and outputs to be accessed independently.

ASIO drivers are often the only way to achieve very low latencies on consumer (Windows/Mac) operating systems, and also provide the best way to record multiple channels successfully.

Related pages:

Recording Tips

Other Digital Audio Technology

Audacity and ASIO

The ASIO  technology was developed by German company Steinberg  and is protected by a licensing agreement  which prevents redistribution of its source code.

Audacity, as an open source program licensed under the GPL , is therefore currently unable to support ASIO, despite being ASIO-capable (providing the user's sound device is similarly capable). If ASIO support was distributed in Audacity builds this would either violate Steinberg's licence agreement if the code was included, or conversely would violate 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:

  1. download the 1.3.3 source code  
  2. download and install the ASIO SDK 
  3. 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).