VQF to CVU Converter

Decode TwinVQ VQF into CVU mu-law online

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Format Rescue

Decode dead TwinVQ audio into functional CVU — rescue your files before VQF decoders become completely unavailable.

Online Decoding

No abandoned TwinVQ player software needed — our servers decode VQF and encode CVU through your browser.

Secure Processing

VQF uploads are erased immediately. CVU outputs are purged from servers within 24 hours.

How to convert VQF 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

VQF is the file extension for audio encoded with TwinVQ (Transform-domain Weighted Interleave Vector Quantization), a lossy compression technology developed by NTT (Nippon Telegraph and Telephone) in 1994 and later commercialized by Yamaha under the SoundVQ brand. The codec claimed a 30 to 35 percent size advantage over MP3 at equivalent perceptual quality — a 96 kbps VQF file was said to match a 128 kbps MP3 — generating considerable excitement during the late-1990s format wars. TwinVQ supports constant bitrate encoding at 80, 96, 112, 128, 160, and 192 kbps, and the underlying algorithm was incorporated into the MPEG-4 Audio standard (ISO/IEC 14496-3) as one of its defined object types. Despite strong technical merits, VQF never achieved widespread adoption: encoding was slow compared to MP3, hardware player support was scarce, and the proprietary licensing discouraged third-party development. In 2009, the FFmpeg project reverse-engineered the TwinVQ decoder, bringing playback support to VLC and other open-source players. VQF stands as a notable case study in codec history — technically ambitious yet eclipsed by MP3's ecosystem momentum and the later rise of AAC.
Initial release: 1996
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 a specialized audio format — a mu-law format for North American telephony.

Why convert VQF to CVU?

VQF is a dead format with no player support. Converting to CVU rescues your audio for specific applications that need this format.

What handles CVU?

Specialized tools, SoX, and targeted professional software support CVU audio processing and playback.

Is there quality loss?

VQF is lossy — the original quality loss is permanent. The CVU output preserves whatever quality the VQF file contained.

Is the conversion secure?

VQF uploads are deleted immediately after conversion. CVU results are removed from servers within 24 hours.