VOX to VOC Converter

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.

VOC (Creative Voice) is a digital audio container developed by Creative Technology and introduced alongside the original Sound Blaster card in 1989. It served as the native audio format for the Sound Blaster family during the DOS era, when Creative's hardware dominated PC audio. VOC files are block-based: each file consists of typed data blocks that can carry 8-bit unsigned PCM, 4-bit and 2.6-bit Creative ADPCM, 16-bit signed PCM, as well as A-law and mu-law encoded audio. This block structure also supports silence intervals, repeat loops, and marker points, giving game developers fine-grained control over sound playback. A notable advantage was hardware-level decoding — Sound Blaster cards could play VOC data directly via DMA transfer, freeing the CPU for other tasks in an era when processor cycles were precious. The format saw extensive use in DOS games from id Software, Sierra, and LucasArts. With the rise of Windows and the WAV format, VOC gradually fell out of mainstream use, yet it remains important for retro gaming preservation and for anyone working with vintage PC audio archives.