MP4 to VOX Converter

Extract Dialogic ADPCM audio from MP4 video online

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IVR Standard Format

VOX is the backbone of Interactive Voice Response. Converting MP4 audio to VOX creates prompts ready for telephony and call center systems.

Ultra-Compact Voice

Dialogic ADPCM compresses voice audio aggressively from your MP4 — ideal for telephony hardware with limited storage.

Cloud-Based Extraction

No Dialogic tools required on your machine. Our servers handle the MP4 to VOX conversion and encoding entirely.

How to convert MP4 to VOX

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

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

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

About formats

MP4 (MPEG-4 Part 14) is the most widely used multimedia container format in the world, standardized by the Moving Picture Experts Group as part of the MPEG-4 specification in 2003. Built on the ISO base media file format (MPEG-4 Part 12), which itself drew from the Apple QuickTime container, MP4 uses a hierarchical atom/box structure that can encapsulate virtually any type of media data. The container most commonly packages H.264 or H.265 video with AAC audio, though it also supports a wide range of alternative codecs including AV1, VP9, MPEG-4 Visual, AC-3, and ALAC. The design supports advanced features such as streaming hints for progressive download and adaptive streaming, chapter markers, multiple audio and subtitle tracks, metadata tags, and embedded thumbnail images. A standardized structure and broad codec support have made MP4 the default choice for online video platforms, mobile devices, digital cameras, and operating system media libraries. HTML5 video with H.264 in MP4 is supported by every major web browser, establishing the combination as the universal baseline for web video delivery. Efficient packaging overhead, combined with the compression capabilities of modern codecs it carries, enables high-quality video distribution at practical file sizes across bandwidth-constrained networks and storage-limited devices.

Developer: Moving Picture Experts Group

Initial release: 2003

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.

Developer: Dialogic Corporation

Initial release: 1983

Frequently Asked Questions

Why convert MP4 to VOX?

VOX uses Dialogic ADPCM encoding — the standard for IVR (Interactive Voice Response) systems, call centers, and automated telephony platforms.

What opens VOX files?

Dialogic telephony software, SoX, and Audacity handle VOX files. IVR and PBX systems process this format natively for voice prompts.

Is VOX for telephony only?

Primarily yes — VOX is designed for telephone systems. Its 4-bit ADPCM encoding is optimized for voice at telephone-grade quality.

Can I convert multiple files?

Upload a batch of MP4 videos and extract each audio track to VOX format simultaneously. Perfect for building IVR prompt libraries.

How compact is VOX?

VOX ADPCM compresses audio to about 4:1 versus raw PCM — producing very small files ideal for storage-constrained telephony hardware.

Does VOX include a header?

VOX files are typically headerless raw ADPCM data. The telephony system must know the sample rate to decode playback correctly.

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MP4 to VOX Quality Rating

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