VOX to FSSD Converter

Convert Dialogic VOX telephony audio to FSSD

Drop files here. 1 GB maximum file size or Sign Up
to
Facebook Amazon Microsoft Tesla Nestle Walmart L'Oreal

Telephony to Classic Mac

Bridge Dialogic IVR audio and early Macintosh sound — two legacy ecosystems connected.

Browser Conversion

No SoX or Mac emulator needed. Convert VOX to FSSD in the browser.

Private Processing

VOX uploads are deleted immediately. FSSD outputs purged within 24 hours.

How to convert VOX to FSSD

1

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

2

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

3

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

About formats

VOX is a headerless audio format built around Dialogic ADPCM encoding, widely adopted in telephony, interactive voice response (IVR) systems, and voice mail platforms since the 1980s. Each audio sample is compressed into 4 bits using an algorithm developed by Oki Electric and implemented in hardware on Dialogic Corporation's telephony interface cards. VOX files typically use a sampling rate of 6000 or 8000 Hz, producing extremely compact recordings optimized for speech intelligibility rather than musical fidelity. Because the format carries no header, playback software must know the sample rate and encoding parameters in advance — a trade-off that reduces overhead but demands careful file management. The primary advantage of VOX is storage efficiency: a one-minute voice recording at 8 kHz occupies roughly 240 KB, making it practical for systems storing thousands of prompts. Dialogic ADPCM conforms to the ITU-T G.726 standard, ensuring interoperability across telephony equipment from different vendors. Even as modern call centers migrate to IP-based systems with codecs like Opus), vast libraries of VOX recordings persist in legacy IVR deployments and compliance archives worldwide.
Initial release: 1983
FSSD is a raw audio format that originated in the classic Macintosh ecosystem, where Farallon Computing's MacRecorder hardware (1988) stored digitized sound as unsigned 8-bit PCM in resource fork entries tagged with the 'FSSD' type code. In modern audio processing tools such as SoX, FSSD is treated as an alias for the u8 (unsigned 8-bit) raw format — headerless files containing a flat stream of single-byte amplitude samples, where each value from 0 to 255 represents an audio level with 128 as the center point. Because there is no header, playback parameters like sample rate and channel count must be provided externally. The original MacRecorder typically captured at rates up to 22 kHz in mono, though any sample rate is valid when interpreting the raw data. FSSD and its compressed companion format HCOM (which adds Huffman compression to the same underlying data) were the standard audio formats for early Mac multimedia: HyperCard stacks, educational CD-ROMs, and system alert sounds of the late 1980s and early 1990s relied heavily on this encoding. One advantage of the raw FSSD format is trivial parseability — with no container overhead, the audio data begins at byte zero and can be read by any tool capable of processing unsigned 8-bit PCM. The format's historical significance also makes it practically relevant for digital archivists: converting FSSD recordings to modern containers like WAV preserves the original audio content losslessly, since the raw samples only need a header prepended, not any form of transcoding.
Developer: Farallon Computing
Initial release: 1988

Frequently Asked Questions

Why convert VOX to FSSD?

FSSD is a legacy Macintosh audio format. Converting VOX serves vintage Mac projects and audio preservation.

What can open FSSD files?

SoX and classic Mac emulators (Mini vMac, Basilisk II) handle FSSD.

Is FSSD modern?

No — FSSD is purely legacy. It appears in vintage Mac computing and digital preservation.

Is quality preserved?

The decoded VOX audio transfers into FSSD without additional loss.

Can modern Macs use FSSD?

Modern macOS does not support FSSD natively. Use SoX or a classic Mac emulator.