HALAC 0.5.4

HALAC was built specifically to fix this. It distributes encoding work across every available core, delivering throughput 3-5x faster than comparable codecs on the same hardware - a difference that becomes obvious the moment you start re-encoding a multi-thousand-track music library.

The speed advantage comes from a deliberate architectural choice.

Instead of the Rice Coding used by FLAC, Monkey's Audio, and most other lossless codecs, HALAC builds its compression pipeline on Asymmetric Numeral Systems (ANS).

ANS gives up roughly 1-2% of compression ratio in exchange for substantially faster processing - the right trade-off when batch-encoding archives where hours saved matter more than megabytes.

What's New in HALAC 0.5.4

The current build refines the multi-core encoder introduced in earlier 0.4.x releases and consolidates several improvements that landed across 2025:

• 32-bit float WAV support for high-resolution masters from DAWs and mastering engineers (32-bit PCM still pending).
• Extensible WAV and RF64 support for files larger than 4 GB, useful when archiving long live recordings.
• AVX2-optimised builds with significantly improved encode and decode speed on modern Intel and AMD CPUs.
• Configurable block size via the -b parameter, with internal blocksizes tuned between 128 and 8192.
• Fast Stereo mode selector and advanced polynomial estimation for cleaner handling of low-transition audio data.
• 24-bit and 16-bit, 2-channel support across any standard sample rate.

The encoder runs on Windows 10 and Windows 11.

Some users have reported that HALAC will not install on Windows 7 - if that is your environment, FLAC 1.5.0 and Monkey's Audio remain the safer choice.

Three Compression Modes

HALAC ships three presets that map to the realistic trade-offs inside a batch workflow:

• Normal - the default. Balanced compression and speed for archival passes.
• Fast - prioritises throughput when re-encoding entire album collections in one sitting.
• Ultra Fast (UFast) - maximum encode speed for time-critical jobs, with a slightly larger output file.

In the developer's own benchmarks against a 1.4 GB 32-bit float WAV set, HALAC Normal produced output around 66% the size of the source in roughly 3 seconds - while Monkey's Audio Insane took over a minute on the same files.

Compression ratios sit between FLAC level 0 and FLAC level 4 in most music genres, with a small file-size penalty traded for the big speed advantage.

Where HALAC Fits in a Lossless Audio Workflow

HALAC is a command-line tool, which means it slots into a pipeline rather than replacing one. The full archival chain on a Windows 11 machine typically looks like this:

1. Rip the source. Exact Audio Copy or CDex read your CDs to bit-perfect WAV with offset correction and AccurateRip verification.

2. Manage the album structure. CUETools keeps CUE sheets aligned through any conversion, splits single-file albums into per-track files, and verifies rips against AccurateRip and CTDB.

3. Optional preprocessing. Run lossyWAV over the WAV first if you want maximum compression. lossyWAV's noise-shaping algorithm removes inaudible bits before HALAC compresses, producing notably smaller archives at perceptual transparency.

4. Encode with HALAC. Pipe the WAV through halac_encode.exe input.wav out.halac from PowerShell or a batch script. For automated jobs, the CLI accepts wildcards and integrates cleanly into scripted workflows.

5. Play it back. Player support is the area where HALAC trails established formats. The HALAC source ships a player API for developers, but for everyday playback most users either decode back to WAV first or pair HALAC with players that accept custom DirectShow filters - foobar2000, MPC-BE, and VLC Media Player all support custom plugin chains.

6. Convert to portable copies. When you need MP3 or AAC for a phone or car stereo, decode the HALAC archive back to WAV and feed it to LameXP, winLAME, MediaHuman Audio Converter, or the foobar2000 Free Encoder Pack.

For browser-based or portable MP3 conversion without server uploads, X Audio Converter handles the job locally with the LAME MP3 Encoder under the hood.

How HALAC Compares to Established Lossless Codecs

FLAC remains the universal default - every hardware player, streaming protocol, and operating system handles it natively. FLAC 1.5 added multithreaded encoding, narrowing the gap, but HALAC still wins on raw throughput.

Monkey's Audio compresses around 1-2% smaller than FLAC, which is meaningful for huge archives, but its encoder is significantly slower and decode is heavier on the CPU during playback.

WavPack offers something neither FLAC nor HALAC does - hybrid compression, where you get a smaller lossy file plus a separate correction file that restores bit-perfect lossless on demand. If you need that flexibility, WavPack is the right pick.

OptimFROG holds the compression-ratio crown but is notoriously slow and has limited hardware support. HALAC is essentially OptimFROG's opposite - prioritising speed where OptimFROG prioritises ratio.

The honest summary: choose HALAC when encoding speed is the bottleneck - batch jobs over thousands of files, multi-core machines that would otherwise sit idle, or production workflows where waiting on the encoder costs real time. Choose FLAC when device compatibility, streaming, or universal player support matter more than throughput.

CLI vs GUI - Should That Stop You?

HALAC has no graphical front-end. If the command line feels intimidating, the GUI vs CLI comparison guide walks through the trade-offs in plain language.

In practice, encoding with HALAC takes one line of syntax that you can paste into a .bat file once and forget about.

For users who are happier with a window and buttons, X FLAC Encoder over standard FLAC is a smoother starting point and produces files every device on earth can play.

Companion Tool: HALIC for Images

The same developer maintains HALIC, a lossless image compressor that applies the same ANS-based, multi-core philosophy to PNG-style image archiving.

The combined story is covered in detail in the HALAC and HALIC guide - useful reading if you're already running HALAC and curious whether the image counterpart is worth installing.

Our Verdict

HALAC 0.5.4 is not the right choice for casual users who just want to rip a CD - that's still FLAC territory. But for technical users sitting on a multi-core CPU and a serious WAV archive, it does something no mainstream lossless codec does: it actually uses the hardware you paid for.

Three to five times faster encoding adds up quickly across a thousand-track library, and the small compression-ratio penalty is rarely worth fighting for.

Browse the full Audio Codecs category for alternatives and complementary tools.