DTS/AC3/DD+ Source Filter 1.9.1.37

These formats turn up as extracted Blu-ray and DVD audio tracks, game audio rips and disc backups.

In each case you have a bare audio file and no video container wrapped around it.

Windows does not recognise those extensions as playable, which is a registration problem rather than a decoding one.

DirectShow players such as Windows Media Player and MPC-HC rely on registered source filters to know which files they are allowed to open. Without one for .dts, .ac3 and .eac3, those players do not see the files as playable at all, no matter which decoders are installed.

DTS/AC3/DD+ Source Filter adds the missing registration. Once it is in place the extensions become valid DirectShow sources and every compatible player can open them immediately.

What It Supports

The filter covers three formats, and nothing else. DTS is the surround standard found on DVD and Blu-ray discs and in a lot of game audio.

AC3, better known as Dolby Digital, is the standard audio format on DVD video and legacy broadcast. DD+ - Dolby Digital Plus, or EAC3 - is the newer version used on Blu-ray, streaming services and modern broadcast, carrying higher bitrates and up to 7.1 channels.

The filter itself comes from the Media Player Classic codebase, originally written by Gabest, the same developer behind Media Player Classic and DirectVobSub.

It is packaged for standalone installation by the X Codec Pack project, which is where the current build and version numbering come from.

Installation and Setup

Run the installer with administrator rights and the filter registers itself. There are no configuration screens and no restart is needed.

The file it installs is DTSAC3Source.ax, placed in System32 on 64-bit Windows and SysWOW64 for the 32-bit side, so one installer covers both architectures. Open your player afterwards and any .dts, .ac3 or .eac3 file should play.

If it does not register, right-click the installer and choose Run as administrator explicitly rather than relying on the prompt. Failing that, you can register the filter by hand - our guide on registering and unregistering DLL and AX filter files covers the command and how to reverse it.

Compatible Players

Anything built on DirectShow can use it, because the filter registers with Windows rather than with one application.

• Windows Media Player - the most common reason people need this filter at all.
• MPC-HC and MPC-BE, both of which also carry their own internal version of this filter.
• Zoom Player, PotPlayer and KMPlayer.

VLC is the exception, and a useful one to know about. It carries its own internal decoder stack, ignores DirectShow filters entirely, and already plays DTS and AC3 files on its own.

If the File Opens but There Is No Sound

This is the most common follow-up problem, and it means the filter is working.

A source filter opens the file and hands the audio on. Something else has to decode it, and if no decoder in the chain understands DTS or AC3 you get a file that loads, shows a running timer and plays silence.

In MPC-HC and MPC-BE, check Options and then Internal Filters, and confirm the audio decoder for the format is enabled. On Windows Media Player there is no such panel, so the decoder has to come from elsewhere - LAV Filters is the usual answer.

Our guide on playing AC3 and DTS audio works through the silent-file case in more detail, and the Codec Finder will tell you which decoder your files actually need.

When You Need More Than Basic Playback

This filter solves the file-opening problem and stops there. If you need more, there are two routes worth knowing.

AC3 Filter is a legacy decoder with an unusually detailed settings panel - equalizer, gain, dynamic range compression and SPDIF passthrough. Version 2.6.0b from April 2013 was the final release, so nothing has been fixed in it since, but it still runs and nothing else offers that level of manual control.

LAV Filters is the modern choice for almost everything else, handling DTS-HD, TrueHD, EAC3 and a long list beyond them with hardware acceleration. For a complete DirectShow setup in one installer, K-Lite Codec Pack bundles it with MPC-HC and the rest.

If the problem is Windows itself rather than one player, the Dolby Digital Plus Decoder plugs EAC3 support in at the operating-system level. That is a different fix from this one and the two do not conflict.

For converting DTS or AC3 to another format rather than playing it, eac3to is the dedicated command-line tool.

Who Should Look Elsewhere

The tell is what happens when you double-click the file. If it opens and plays, you do not need this filter and never did.

If it opens and plays silently, the missing piece is a decoder, not this. If your player refuses to acknowledge the file exists, that is the case this fixes.

And if what you are actually chasing is the audio enhancement that shipped with your laptop, that is DTS Audio Processing, an unrelated piece of software with a confusingly similar name. Before choosing between formats at all, Is DTS Better Than AAC? covers the practical differences.

Quick questions

Download DTS/AC3/DD+ Source Filter 1.9.1.37 and see whether your files open, or tell us how you got on if you have used it before.