BRP-PACU is a dual channel FFT audio analysis tool. It is designed to be used with an omnidirectional calibrated microphone to configure any sound system with an appropriate equalization and delay. It compares the output of the system to the input of the system to obtain the transfer function

Transfer function

A transfer function is a mathematical representation, in terms of spatial or temporal frequency, of the relation between the input and output of a linear time-invariant system. With optical imaging devices, for example, it is the Fourier transform of the point spread function i.e...

 of the system. These data allow one to perform final equalization using just the input/output of the DSP

Digital signal processor

A digital signal processor is a specialized microprocessor with an architecture optimized for the fast operational needs of digital signal processing.-Typical characteristics:...

 or any other device used for Equalization

Equalization

Equalization, is the process of adjusting the balance between frequency components within an electronic signal. The most well known use of equalization is in sound recording and reproduction but there are many other applications in electronics and telecommunications. The circuit or equipment used...

.

Theoretical basis

This software program uses a Transfer Function Measurement method to compare the output of a (unprocessed) loud-speaker system and room combination to the input signal which is usually filtered pseudorandom noise. Because the sound has a propagation time from the exit point of the transducer to the measurement device, a delay must be inserted in the reference signal to compensate. This delay is automatically found by the software to aid in practical system measurement.

Supported platforms

Currently the only supported platforms are Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

 and Mac OS X

Mac OS X

Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...

  because it relies on POSIX Threads

POSIX Threads

POSIX Threads, usually referred to as Pthreads, is a POSIX standard for threads. The standard, POSIX.1c, Threads extensions , defines an API for creating and manipulating threads....

. It also is written using floating point processing, making most embedded Linux device support difficult.

Features

• Four capture buffers, with auto-save (in case of crash) and save-as ability
• Averages buffers to a separate buffer and flips it for analysis
• Automatic delay calculation
• Impulse response capturing
• Uses JACK
  JACK Audio Connection Kit
  JACK is a professional sound server daemon that provides real-time, low latency connections for both audio and MIDI data between applications that implement its API...
  
   to route and manage audio paths
• Pink Noise
  Pink noise
  Pink noise or 1/ƒ noise is a signal or process with a frequency spectrum such that the power spectral density is inversely proportional to the frequency. In pink noise, each octave carries an equal amount of noise power...
  
   generation tool to eliminate need for an external Pink Noise source

Licensing and availability

The software is licensed under the GPL

GNU General Public License

The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....

 Version 2. It is available from sourceforge

SourceForge

SourceForge Enterprise Edition is a collaborative revision control and software development management system. It provides a front-end to a range of software development lifecycle services and integrates with a number of free software / open source software applications .While originally itself...

 as C

C (programming language)

C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....

 code.

Future development

• Ubuntu
  Ubuntu (operating system)
  Ubuntu is a computer operating system based on the Debian Linux distribution and distributed as free and open source software. It is named after the Southern African philosophy of Ubuntu...
  
   and Debian
  Debian
  Debian is a computer operating system composed of software packages released as free and open source software primarily under the GNU General Public License along with other free software licenses. Debian GNU/Linux, which includes the GNU OS tools and Linux kernel, is a popular and influential...
  
   packages
• A Virtual Machine
  Virtual machine
  A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
  
   for usage under other Operating Systems such as Microsoft Windows
  Microsoft Windows
  Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
  
  
• The ability to create and load User Interface options
• Phase response for transfer function