HEVC to SPH Converter

Get NIST Sphere audio from HEVC video quickly

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

Corpus Standard

SPH is the format for major speech corpora — extracting from HEVC creates research-ready audio data.

Fast Extraction

Audio extraction skips video processing — your HEVC-to-SPH conversion finishes in seconds, not minutes.

Secure Files

HEVC uploads are erased immediately after conversion. SPH outputs are deleted within 24 hours.

How to convert HEVC to SPH

1

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

2

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

3

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

About formats

HEVC (High Efficiency Video Coding), also designated as H.265 and MPEG-H Part 2, is a video compression standard developed jointly by the ITU-T Video Coding Experts Group and the ISO/IEC Moving Picture Experts Group. Approved in January 2013, HEVC was designed as the successor to H.264/AVC with the primary goal of doubling the compression efficiency — achieving equivalent visual quality at roughly half the bit rate. The standard accomplishes this through larger coding tree units of up to 64x64 pixels, more sophisticated motion prediction with 35 directional intra modes, advanced sample adaptive offset filtering, and parallel processing tools including tiles and wavefront parallel processing. HEVC supports resolutions from 320x240 up to 8192x4320 (8K UHD), making it future-proof for emerging display technologies. The codec is widely adopted in broadcasting, where it enables efficient delivery of 4K and HDR content over bandwidth-constrained channels, as well as in video conferencing and surveillance applications. Apple adopted HEVC as the default recording format for iOS devices beginning with iOS 11, dramatically expanding its consumer reach. Despite technical superiority over H.264, a complex and fragmented patent licensing landscape has driven interest in royalty-free alternatives like AV1, though HEVC remains deeply embedded in broadcast infrastructure and consumer electronics worldwide.
Initial release: January 25, 2013
SPH is the file extension for audio stored in the NIST SPHERE (SPeech HEader REsources) format, a standard created by the U.S. National Institute of Standards and Technology around 1990. Built for speech research, SPH files carry a 1024-byte ASCII header packed with metadata — database identifiers, channel counts, sample rates, byte ordering, and compression type — making every recording self-describing. The underlying audio is typically 16-bit linear PCM sampled at 16 kHz, though other configurations are permitted. Researchers at NIST, DARPA, and universities worldwide rely on SPH for distributing speech corpora such as TIMIT, Switchboard, and the LDC collections that underpin modern automatic speech recognition systems. A key advantage is that the human-readable header lets scripts parse recording metadata without binary decoding. The format's strict standardization also eliminates ambiguity when sharing datasets across institutions and platforms. Because SPH files store uncompressed PCM, they preserve full audio fidelity — critical when training acoustic models where even small artifacts can skew results.
Initial release: 1990

Frequently Asked Questions

Why convert HEVC to SPH?

SPH is the standard for speech research corpora like TIMIT and Switchboard.

How do I open SPH files?

NIST tools, Kaldi, HTK, and SoX.

Is only the audio extracted?

Yes — the video portion of the HEVC file is discarded. Only the audio track is saved as SPH.

Can I convert multiple files?

Upload several HEVC videos at once and extract SPH audio from each simultaneously in a single batch.

Are my uploads secure?

HEVC files are deleted immediately after conversion. SPH outputs are removed from our servers within 24 hours.