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Aug 6, 2026
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Bass Audio Source is a free, open-source DirectShow filter built on the BASS audio library. It lets players like MPC-HC and MPC-BE open audio formats Windows does not handle on its own, including FLAC, APE, WavPack, DSD, OptimFROG, Musepack and MIDI. Version 0.3.3.260 adds Matroska and WebM audio support plus cover art in M4A and APE files.
Bass Audio Source is a DirectShow filter, which means it does not play anything on its own - it teaches the player you already use how to open audio formats Windows ignores.
If MPC-HC or MPC-BE stares blankly at an APE, WavPack or DSD file, this is the piece that fixes it.
It is free and open source, with the full source published on GitHub, and it arrives as a small ZIP rather than an installer.
What Bass Audio Source Actually Does - in Plain Terms
Windows media players do not decode audio themselves. They hand each file to whichever DirectShow filter claims it, and if no filter claims the format, the player shows an error or plays silence.
Bass Audio Source is the filter that claims the awkward ones. It wraps the BASS audio library, a long-running toolkit from un4seen, and exposes everything BASS can decode to any DirectShow player on your PC.
The practical effect is that you keep the player you like and simply widen what it can open. Media Player Classic and its descendants are the usual hosts, and nothing else about your setup changes.
Which Audio Formats It Adds
The 0.3.3.260 release ships the BASS core plus fifteen decoder components. Between them they cover the following.
| Format | Typical file extensions |
|---|---|
| MP3, MP2, MP1, WAV, AIFF, Ogg Vorbis | .mp3, .mp2, .wav, .aiff, .ogg |
| AAC and ALAC | .aac, .m4a, .mp4 |
| FLAC | .flac |
| Monkey's Audio | .ape, .apl |
| WavPack | .wv |
| OptimFROG | .ofr, .ofs |
| Musepack | .mpc, .mp+, .mpp |
| TTA | .tta |
| Opus and Speex | .opus, .spx |
| WMA | .wma |
| DSD | .dsf, .dff |
| MIDI, needs a SoundFont | .mid, .midi, .rmi, .kar |
| Matroska and WebM audio, off by default | .mka, .webm |
It also handles internet radio streams in these formats, and a bundled BASSZXTUNE archive adds chiptune playback if you want it. If you are not sure which format is stopping a file from playing, our Codec Finder will narrow it down.
Installing It - Five Steps
Match the bitness to your player, not to Windows. A 64-bit copy of Windows running a 32-bit build of MPC-HC needs the 32-bit filter. Getting this backwards is the most common reason people think the filter did not install.
- Download the ZIP that matches your player: BassAudioSource.zip for a 32-bit player, BassAudioSource64.zip for a 64-bit one.
- Unpack it into its own permanent folder. The filter runs from wherever you put it, so do not use a temporary folder you plan to delete.
- Run Install_BassAudioSource_32.cmd or Install_BassAudioSource_64.cmd as administrator.
- In your player, add BassAudioSource.ax or BassAudioSource64.ax to the external filters list and set it to "Prefer". Leaving it on the default merit means it will mostly be ignored.
- Open an audio file and check the player is using the new filter.
The external filters screen sits in your player's options, under External Filters in both MPC-HC and MPC-BE. The process is close enough to our guide on setting up the MP4 splitter that it works as a walkthrough if you have not done this before.
To remove it later, run Uninstall_BassAudioSource_32.cmd or Uninstall_BassAudioSource_64.cmd as administrator, then delete the folder. Menus differ between players, so check your player's documentation if the external filters list is not where you expect.
Two Settings Worth Knowing About
Matroska and WebM audio ship switched off. Support for .mka and .webm audio is new in 0.3.3.260 and disabled by default, so you have to enable it in the filter settings before those files will open.
MIDI is the other one. Bass Audio Source can play .mid, .midi, .rmi and .kar files, but MIDI carries no sound of its own, so it needs a SoundFont to tell it what the instruments sound like.
Drop a .sf2 or .sfz SoundFont file into the Bass Audio Source folder and select it in the filter's settings panel. Without one, MIDI files will open and play nothing at all.
What Changed in Bass Audio Source 0.3.3.260
This release landed on 6 August 2026, two years to the day after 0.3.1.192, and it is the first public update since. The headline changes are these.
- Matroska and WebM audio files are now supported, disabled by default in the settings.
- Embedded cover art now reads from M4A and APE files, and FLAC files with multiple embedded images are handled properly.
- Registering the filter from a folder with non-English characters in its path no longer fails.
- MOV video files are ignored more reliably, so the filter stops grabbing things it should leave alone.
The bundled BASS components were refreshed as well: bass.dll 2.4.18.3, bass_aac.dll 2.4.7.2, bassmidi.dll 2.4.16, basswebm.dll 2.4.2, bassdsd.dll 2.4.2, bassopus.dll 2.4.3.3, bassape.dll 2.4.1 and bassflac.dll 2.4.6.1.
Where It Came From
Bass Audio Source is built on the code of the DC-Bass Source Filter, which has not been actively developed for years. It exists to keep that idea working on modern DirectShow players.
There was also a DC-Bass Source Mod, a community continuation of the original. That one is discontinued too, and its home page has since gone offline, so treat both as historical curiosities rather than live options.
Who Should Look Elsewhere
The tell is simple: if the phrase "external filters list" makes you want to close the tab, this is not the tool for you. Bass Audio Source assumes you are comfortable editing your player's filter configuration by hand.
Most people are better served by something that installs and works. LAV Filters covers the common lossless and lossy formats with no manual wiring, and the K-Lite Codec Pack bundles a player and a full decoder set in one go.
Our codec packs page lists the rest, and the wider audio codecs section covers single-purpose decoders.
For narrower jobs there are better fits. AC3 Filter handles AC3 and DTS with per-channel control, and the MPEG Layer-3 Decoder restores MP3 playback in older applications.
If you would rather not install anything, converting the file is often quicker. Our online audio converter turns an awkward format into something any player opens, and LAME MP3 Encoder handles bulk conversion on your PC.
Quick questions
Is Bass Audio Source free?
Yes. It is free and open source, and the full source code is published on GitHub. There is no paid version and no trial period.
Do I need the 32-bit or the 64-bit version?
Whichever matches your media player, not your copy of Windows. Plenty of people run a 32-bit player on 64-bit Windows, and in that case you need the 32-bit filter.
Why will my MKA or WebM audio file not play?
Because that support is switched off out of the box. Open the filter settings and enable Matroska and WebM audio, which arrived in version 0.3.3.260.
Do I still need this if I already have LAV Filters or K-Lite?
Usually not for everyday files. It earns its place when you have formats those do not cover well, such as OptimFROG, Musepack, TTA or DSD, or when you want the BASS library's handling of internet radio streams.
How do I play MIDI files with it?
Copy a SoundFont file with a .sf2 or .sfz extension into the Bass Audio Source folder, then select it in the filter settings. MIDI files contain instructions rather than sound, so without a SoundFont there is nothing to play.
Which players does it work with?
Any Windows player with DirectShow support and an external filters list. MPC-HC and MPC-BE are the usual picks, and you can browse other DirectShow players if neither suits you.
Download Bass Audio Source 0.3.3.260 and see how it handles your files, or tell us how you got on if you have used it before.
