TTA to NIST Converter

Encode True Audio as NIST evaluation format online

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Evaluation Data

NIST is the standard for speech benchmarks — lossless TTA gives high-quality audio for evaluation datasets.

Clean Recordings

Lossless TTA ensures speech data enters NIST format without compression artifacts from prior encoding.

Online Encoding

No NIST toolkit needed — our servers convert TTA to NIST format entirely through your browser.

How to convert TTA to NIST

1

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

2

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

3

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

About formats

TTA (True Audio) is a real-time lossless audio compression codec developed by Aleksander Djourik, with its origins tracing back to the early 2000s. The format reconstructs the original PCM stream bit-for-bit upon decoding, guaranteeing that no sonic detail is lost during storage or transfer. TTA handles standard CD-quality audio as well as high-resolution content up to 32-bit integer samples, making it suitable for everyday listening and professional archiving alike. Processing speed is one of TTA's defining strengths — the codec achieves fast encoding and decoding without heavy CPU demands, keeping it lightweight even on older hardware. The file structure supports ID3v1, ID3v2, and APEv2 metadata tags, so track information and album art travel with the audio. Hardware support appeared in several portable players, giving TTA a practical edge over some competing lossless formats. The open-source reference implementation ships under the GNU GPL, encouraging community adoption and third-party integrations. While newer codecs like FLAC have captured a larger share of the lossless audio landscape, TTA continues to serve users who value its simplicity and transparent compression.
Developer: Aleksander Djourik
Initial release: 2003
NIST SPHERE (SPeech HEader REsources) is a specialized audio file format created by the National Institute of Standards and Technology for speech research, particularly projects funded by DARPA. The format wraps raw audio samples with a structured ASCII header encoding metadata such as sample rate, channel count, encoding type, speaker demographics, and transcription annotations — making it ideal for distributing speech corpora. NIST files typically store uncompressed PCM or mu-law audio at telephone-quality sample rates (8 kHz or 16 kHz), though the container is flexible enough to hold various encodings. A key advantage is the rich self-documenting header that lets researchers embed detailed corpus metadata directly in the file, eliminating sidecar files. SPHERE has also become the de facto standard for major speech databases like TIMIT, Switchboard, and the Fisher corpus, ensuring broad recognition across academic and government labs. The open specification and availability of command-line tools (sphere, h_strip, w_decode) make it straightforward to convert, inspect, and process these files programmatically in speech processing pipelines.
Initial release: 1990

Frequently Asked Questions

What is NIST?

NIST is the audio specification from the National Institute of Standards and Technology for speech evaluation benchmarks.

Why convert TTA to NIST?

Speech recognition benchmarks require NIST-formatted audio. Lossless TTA provides clean recordings for evaluation.

What reads NIST?

Kaldi, HTK, NIST tools, and speech recognition frameworks process NIST audio for model training.

Is NIST different from SPH?

They share the same NIST Sphere header specification — some tools treat them interchangeably.

Is the conversion private?

TTA uploads are deleted immediately. NIST outputs are removed within 24 hours.