AC3Filter - it is a DirectShow filter for AC3 decoding to play .AVI with AC3 audio tracks and MPEG2 (DVD). Distributed absolutely for free (FREEWARE, OpenSource).

Features:

* Full AC3 standard compliance.
* S/P DIF passthrough support.
* Decode MPEG2 PES streams.
* Multichannel output support.
* LFE support.
* Dynamic Range Compression (DRC) support.
* Overflow control and automatic gain control.
* Gain levels control.
* Bitstream information (channel format, bitrate, sample rate, coupling freq and maximun freq).
* Input/output levels.
* Matrix mixer with direct control of mixing matrix.
* Stereo to multichannel mixing.
* DolbySurround/ProLogic/ProLogicII downmixing.
* Delays for each channel.
* Equalizer.

What's New in version 1.62b:

* Precise PCM passthrough
* Fixed: Noise on LPCM 20/24bit tracks
* Fixed: Delay settings did not work after restart.
* German translation updated (thanks to Philipp Wode)
* Japan translation added (thanks to tnetsixenon)