HCOM to CVU Converter

Re-encode HCOM audio as unfiltered CVU modulation

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Raw Delta Modulation

Convert HCOM to CVU — unfiltered CVSD encoding for voice systems that perform their own signal processing.

Cloud-Based

No specialized voice processing tools needed locally. The conversion runs entirely on our cloud servers.

Automatic Deletion

HCOM uploads are erased immediately. CVU output files are removed within 24 hours from our servers.

How to convert HCOM to CVU

1

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

2

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

3

Let the file convert and you can download your cvu 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
CVU is an unsigned variant of the CVS telephony audio format, differing in how delta-encoded values are represented in the binary stream. While CVS stores slope delta values as signed quantities, CVU treats them as unsigned, shifting the numerical interpretation of each sample. Both share the underlying CVSD modulation technique — 1-bit adaptive delta coding where step size varies according to recent output bit patterns — operating at comparable rates, typically 16 kbps for narrowband voice at 8 kHz. The signed-versus-unsigned distinction matters at the decoder, where correct interpretation determines proper waveform reconstruction. CVU files appear in telephony and embedded communication contexts where hardware adopted the unsigned convention. A practical advantage is straightforward interfacing with systems using unsigned arithmetic natively, avoiding sign extension in decoders. Like its signed counterpart, CVU achieves extreme bandwidth efficiency, compressing voice into compact bitstreams for constrained links. SoX supports CVU, providing a reliable path for converting these niche telephony recordings into modern formats for analysis or archival.
Developer: CCITT / ITU-T
Initial release: 1970

Frequently Asked Questions

What is CVU?

CVU is the unfiltered variant of CVSD (Continuously Variable Slope Delta) modulation. It provides raw delta-encoded audio without post-filtering.

How does CVU compare to CVSD?

CVU skips the filtering stage of CVSD. This preserves the raw delta modulation signal for systems that apply their own filtering.

Why convert HCOM to CVU?

For voice processing systems that need unfiltered delta modulation input. CVU provides the raw encoded signal for custom processing.

What tools support CVU?

SOX handles CVU files. Specialized voice processing and telecommunications equipment also works with unfiltered CVSD data.

Is the conversion private?

Uploaded HCOM files are removed after conversion. CVU results are deleted from servers within 24 hours.