MP4 to SPH Converter

Extract speech audio from MP4 in SPHERE SPH format

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Speech Research Standard

SPH is the format for NIST and LDC corpora. Converting MP4 audio to SPH integrates your data into speech research pipelines.

Research-Ready Output

Configure encoding and sample rate for your SPH output. Match the format requirements of your speech recognition toolkit.

Cloud Processing

The extraction runs on our servers — no SPHERE tools or research software needed on your local machine.

How to convert MP4 to SPH

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

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

Let the file convert and you can download your sph 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

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.

Developer: National Institute of Standards and Technology

Initial release: 1990

Frequently Asked Questions

Why convert MP4 to SPH?

SPH (SPHERE) is the standard format for speech research corpora — used by NIST, LDC, and linguistic research institutions for annotated speech data.

What opens SPH files?

NIST SPHERE tools, SoX, Kaldi, and HTK speech recognition toolkits handle SPH files natively for training and analysis.

Is SPH used in AI research?

SPH is widely used in speech recognition research. Training corpora from LDC and NIST are commonly distributed in SPHERE format.

Can I batch convert?

Upload multiple MP4 files at once. Each audio track is extracted to a separate SPH file and processed in parallel.

What encoding does SPH use?

SPH supports PCM and compressed encodings with metadata headers — designed for annotated speech data in research applications.

Does SPH preserve metadata?

SPHERE files include rich header metadata for speaker information, recording conditions, and corpus annotations.

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Specific converters

MP3 to SPH

WAV to SPH

MP4 to SPH

ASF to SPH

FLAC to SPH

M4A to SPH

OGG to SPH

SWF to SPH

WVE to SPH

3G2 to SPH

3GP to SPH

AAF to SPH

AV1 to SPH

AVCHD to SPH

AVI to SPH

CAVS to SPH

DIVX to SPH

DV to SPH

F4V to SPH

FLV to SPH

HEVC to SPH

M2TS to SPH

M2V to SPH

M4V to SPH

MJPEG to SPH

MKV to SPH

MOD to SPH

MOV to SPH

MPEG to SPH

MPEG-2 to SPH

MP4 to SPH Quality Rating

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