FAAD2 2.11.4 & FAAC 2.2

AAC is the format sitting inside almost every MP4, M4A and iTunes file you own, and the one YouTube and most streaming services hand you.

FAAD2 is the decoder that reads it.

FAAC is the encoder that writes it.

FAAD2 has no window of its own and FAAC ships only a very basic one, so most people meet them through some other program that quietly calls one of them.

FAAD2 handles the AAC profiles still in active use: LC (Low Complexity), Main, LTP (Long Term Prediction), LD (Low Delay), HE-AAC using Spectral Band Replication, and HE-AACv2 which adds Parametric Stereo on top. That breadth is why it survives - plenty of decoders manage LC and then stumble on the HE-AACv2 streams common in mobile and streaming audio.

If the profile names mean nothing to you yet, the guide on the differences between AAC, AAC-LC and AAC-HE is the place to start.

FAAC 2.2: Better Sound at the Same Bitrate

FAAC 2.2 arrived on 29 September 2026, and most of it is work you hear rather than switches you set. Rate control, stereo coding, the quantizer, block switching and the HE-AAC side were all reworked, all aimed at getting more quality out of the same bitrate.

The changes you will actually notice when you use it:

• MP4 is now the default output. FAAC picks the format from the file name you give it - .m4a, .mp4 or .m4b makes MP4, while .aac or .adts still makes a raw AAC stream.
• True constant bitrate. The new --cbr switch holds a -b bitrate exactly, backed by a real bit reservoir, for services and devices that insist on it.
• HE-AAC for surround. HE-AAC v1 now works on layouts up to 8 channels, so a 5.1 or 7.1 source can be squeezed small as well.
• Gapless playback. MP4 files carry iTunes-style gapless information, and HE-AAC delay is padded so players that support gapless trim the right amount at both ends.
• File names in any alphabet. Paths with Cyrillic, Greek, Chinese or accented characters now work on the command line and in the GUI, which also accepts 24-bit PCM input.
• A more useful GUI. It now uses the same encoding engine as the command line, writes MP4, and opens on 128 kbps average bitrate.

FAAD2 2.11.3 Is a Security Release

The August 2026 decoder update is not about features. It is a hardening pass, and a broad one.

It fixes a heap buffer overflow in the MP4 reader, a heap overflow in SBR channel-pair reconstruction, an off-by-one frame index check when seeking, several out-of-bounds reads and writes across the SBR and Huffman paths, and a set of integer overflows in allocation size checks. There are also null pointer dereference fixes in intra-channel and long-term prediction.

How FAAC Got Here: 2.0 and 2.1

FAAC 2.0 in July 2026 was the largest single change in the project's history, and 2.1 followed a month later to tidy up after it. Everything below is still in 2.2.

FAAC, FDK AAC, qaac or exhale

FAAC is no longer the obvious runner-up it was, but it is still not the right answer for every job.

If AAC is not obviously the right format for what you are doing, the guide Is DTS better than AAC? works through the comparison.

And Opus beats AAC outright at low bitrates for speech, streaming and game audio.

Programs That Call FAAC for You

Both tools are built to run from the command line rather than a GUI, which is why most people never touch them directly.

• X AAC Encoder wraps the FAAC binary in a Windows 10 and 11 interface, with drag-and-drop batch encoding, MP4 tagging and cover art.
• LameXP and fre:ac both call an AAC encoder when you pick AAC output.
• CDex and Exact Audio Copy do the same on the CD ripping side.
• FFMPEG Audio Encoder carries every encoder it needs inside the download, if you would rather not assemble anything.

If one of these feeds faac.exe an output name without an .aac extension and expects a raw stream back, it will now get MP4 instead. Point the program at an .aac output name, or stay on the FAAC version it was built for.

Where They Fit in a Windows Audio Chain

For everyday playback you almost certainly do not need FAAD2 as a separate install. LAV Filters, built on FFmpeg, decodes AAC, HE-AAC and everything around it inside any DirectShow player.

Where a dedicated FAAD2 wrapper still earns its place is on older setups. CoreAAC DirectShow Filter exposes the FAAD2 library as a registerable DirectShow component.

AAC ACM Codec does the same job through the Audio Compression Manager interface that VirtualDub-era applications expect.

Converting between AAC and MP3 is the other common pairing - decode with FAAD2, re-encode with the LAME MP3 Encoder, or run it the other way.

The companion piece on the best LAME settings for music, podcasts and audiobooks covers what to aim for on the MP3 side. If the terminology is still slippery, codecs versus containers untangles it.

System Requirements

FAAD2 2.11.4 and FAAC 2.2 are 64-bit builds for Windows 10 and Windows 11. The one 32-bit file on the download page is the older FAAD2 2.10.1 decoder.

Nothing needs installing. The FAAC MSYS2 UCRT64 build and FAAD2 run on a bare Windows 10 or 11 PC, while the FAAC MSVC build also needs Microsoft's Visual C++ runtime, which most PCs already have.

If the MSVC build complains that VCRUNTIME140.dll was not found, either switch to the MSYS2 UCRT64 build or install the Visual C++ Redist Runtimes.

They are small. The FAAC 2.2 MSVC build is 222 KB and the MSYS2 UCRT64 build is 333 KB, so keeping several versions side by side costs nothing.

Quick questions

The full audio encoders category lists the frontends and alternatives worth comparing before you commit to one.

Download FAAD2 2.11.4 and FAAC 2.2 and see how they handle your files, or tell us how you got on if you have used them before.