HCOM to CVS Converter

Re-encode HCOM audio as CVS delta modulation format

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Telephony Encoding

Move HCOM audio into CVS delta modulation — a format used in telephony systems and specialized voice communication equipment.

Cloud Infrastructure

No telephony tools needed locally. The conversion runs on our servers from any web browser.

Files Protected

HCOM uploads are deleted after processing. CVS outputs are erased from servers within 24 hours.

How to convert HCOM to CVS

1

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

2

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

3

Let the file convert and you can download your cvs 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
CVS is a telephony audio encoding based on Continuously Variable Slope Delta modulation, representing voice through a 1-bit delta scheme where step size adapts to track input amplitude. Developed within CCITT (now ITU-T) standards during the 1970s, CVS encodes by comparing each sample to the previous one and outputting a single bit — up or down — with slope magnitude adjusting based on recent bit patterns. This yields extremely low bit rates, typically 16 kbps at 8 kHz sampling, efficient for narrowband voice over constrained channels. CVS files store signed delta-encoded data and are commonly processed using tools like SoX. A significant advantage is bandwidth economy: the 1-bit-per-sample approach demands minimal transmission capacity, essential for military radio links and early digital telephone infrastructure. The adaptive slope mechanism also prevents overload distortion on rapidly changing signals while keeping granular noise acceptable during quiet passages. Though modern wideband codecs have superseded CVS, it retains historical importance and niche utility in legacy telephony and embedded communication devices.
Developer: CCITT / ITU-T
Initial release: 1970

Frequently Asked Questions

What is CVS?

CVS uses Continuously Variable Slope Delta modulation — a telephony encoding method that adapts compression to signal changes.

Why convert HCOM to CVS?

CVS is used in specific telephony and voice systems. Converting HCOM speech content to CVS makes it usable in those environments.

Is CVS good for speech?

Yes. CVSD-based formats like CVS are designed specifically for voice encoding in telecommunications and military radio systems.

What processes CVS files?

SOX is the primary tool for CVS files on modern systems. Specialized telephony software also handles this encoding.

How fast is this conversion?

Both formats produce very small files. The conversion finishes in seconds on our infrastructure.