HCOM to SOU Converter

Transcode Macintosh HCOM into SOU raw audio format

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Headerless Audio

Strip away the HCOM container and Huffman compression — get pure 8-bit PCM in SOU format for raw audio processing.

Server Processing

The encoding runs on our cloud. No audio tools or command-line utilities needed on your local device.

Private and Secure

Uploaded HCOM files are erased immediately. SOU results are cleaned from servers within 24 hours.

How to convert HCOM to SOU

1

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

2

Choose sou or any other format you need as a result (more than 200 formats supported)

3

Let the file convert and you can download your sou file right afterwards

About formats

HCOM is a Huffman-coded audio format from the early Macintosh era, designed to shrink digitized sound for distribution on floppy disks and bulletin board systems when storage was precious and modems were slow. The encoder takes 8-bit unsigned PCM input, computes a frequency table of sample-delta values, and builds an optimal Huffman tree that replaces common deltas with short bit sequences. Compression ratios of 2:1 or better were typical for speech recordings, a meaningful saving when a 3.5-inch floppy held only 800 KB. Files were distributed as Macintosh resource forks and played through utilities like SoundApp and the BinHex ecosystem that defined Mac software exchange in the late 1980s. The format supported sample rates up to 22.255 kHz, matching the output capabilities of original Macintosh sound hardware. Tools such as SoX retain HCOM decoding support, ensuring that archived recordings remain accessible decades later. HCOM holds three practical advantages for preservation work: lossless compression that recovers the original samples exactly, a self-contained Huffman table embedded in each file for dependency-free decoding, and historical prevalence across thousands of vintage Mac sound archives.
Developer: Apple Computer
Initial release: 1985
SOU is a raw audio format designation that functions as an alias for unsigned 8-bit PCM data (u8) in the SoX audio processing framework. Files with the .sou extension contain headerless, uncompressed audio samples stored as unsigned 8-bit integers — each byte represents a single amplitude value from 0 to 255, with 128 as the silence midpoint. Because there is no header, playback parameters such as sample rate and channel count must be specified externally. The default assumption is typically mono at 8000 Hz, though the data can represent any rate the recording hardware supported. The u8 encoding that SOU aliases is one of the simplest possible digital audio representations, predating structured audio containers like WAV and AIFF. Raw unsigned PCM was commonly produced by early sound cards and digitizers in the late 1980s and early 1990s, when storage constraints and limited processing power made headerless formats a practical choice. One advantage is absolute simplicity: SOU files can be read by any program capable of basic file I/O, with no parsing of container structures or metadata decoding required — useful for embedded systems, hardware diagnostics, and educational contexts where audio fundamentals are being explored. The format's minimal overhead also means that conversion to any modern container is lossless and instantaneous, since the raw PCM samples can be wrapped in a WAV or AIFF header without any transcoding.
Developer: SoX Contributors
Initial release: 1991

Frequently Asked Questions

What is SOU?

SOU is an 8-bit unsigned integer PCM raw audio format. It stores audio data without headers — similar to FSSD but used in different contexts.

Why convert HCOM to SOU?

SOU provides raw, unadorned audio data suitable for custom applications, embedded systems, and retro computing platforms.

Is SOU the same as FSSD?

Both store 8-bit unsigned PCM raw audio. They are functionally identical but may be expected by different software or hardware.

What processes SOU files?

SOX and raw audio import tools in Audacity handle SOU. Specify the correct sample rate when importing raw audio data.

Is the process private?

HCOM uploads are removed after conversion. SOU outputs are deleted from servers within 24 hours automatically.