Convolver 3.9 released on http://convolver.sf.net

Convolver is an open source high performance Windows application for applying long FIR filters to multi-channel digital audio in the form of

a real time DSP audio plug-in (DMO) for Windows Media Player. The install package also contains

two DirectX/DirectShow filter versions — ConvolverWrapper or the equivalent ConvolverFilter — for Adobe Audition and real time applications such as Zoom Player Pro, TheaterTek 2.2, Windows Media Player Classic, J.River Media Center (when used with the DirectX host plug-in), or Console. See the setup walkthrough for ZoomPlayer after reading this page for further details. In many cases the DMO (Convolver DSP plug-in will also work). Finally, there are a number of

command line applications for testing performance, and convolving files offline, for example

Convolver will take a set of impulse response (FIR filter) files and convolve them with sound paths mixed from the input channels, mixing the results into a set of specified output channels.

Applications

Why would you want to do this? There are several main applications:

With a suitable impulse response generated by a tool such as DRC you will be able to play sound corrected for your room response. For more details, see Ed Wildgoose's Duff Room Correction site.

You can also use Convolver for bass management, cross-overs, cross-talk cancellation, equalization and other purposes that require the source signal to be filtered and redirected to different output channels.

You can also use Convolver as an effects filter (reverb) in Adobe Audition, or other sound or music application that accepts DX filters.

Features

Performance is excellent, possibly the best available under Windows, and subject continual improvement. A stereo 65536-tap filter, the largest that makes sense when applied to a 44.1kHz source, executes at 40 times real time, representing a 3% cpu hit, on a 3.4GHz Pentium 4. Even on a 300MHz Pentium II, the reported cpu hit is about 30% when convolving with such a filter. So your old machine can be put to good use. Mixing channels results in some slowdown (six 65536-tap filters will consume less than 10% cpu on a 3.4GHz Pentium 4).

Arbitrary-length convolutions for unusual applications (1 million tap limit imposed only as a sanity check)

Multi-channel input and output, 8, 16, 20, 24 and 32-bit PCM and 32 and 64-bit IEEE Float

Mixing, scaling and delay of both input and output channels (eg, for "true stereo" convolution, or cross-talk cancellation)

Dither and noise shape of 8, 16, 20 and 24-bit output

Wide range of filter file formats accepted (Microsoft WAV, SGI/Apple AIFF/AIFC, Sun AU/Snd, Raw (headerless 32-bit IEEE float), Paris Audio File (PAF)
Commodore IFF/SVX, Sphere/NIST WAV, IRCAM SF, Creative VOC, SoundForge W64, GNU Octave MAT4/5, Portable Voice Format, Fasttracker 2 XI, HMM Tool Kit HTK)
Sample encodings supported include unsigned and signed 8, 16, 24 and 32 bit PCM, IEEE 32 and 64 floating point, U-LAW, A-LAW, IMA ADPCM, MS ADPCM, GSM 6.10, G721/723 ADPCM, 12/16/24 bit DWVWk, OK Dialogic ADPCM, and 8/16 DPCM. Wavpack files are not currently supported.

Windows Media Player plug-in (DMO) and DirectShow filter interfaces

Several filters can be loaded at once. The first to match the playback format (channels, sample rate) is automatically selected.