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Utiloom

Audio Trim & WAV Export

Decode bounded local audio, preview a frame-aligned range, and create a structurally verified 16-bit PCM WAV with JSON evidence.

LocalNo audio retention

Reviewed July 13, 2026

Guide, examples, and validation Show

About this tool

Create a deterministic, uncompressed audio excerpt while keeping file claims, decoded properties, selection boundaries, and output verification explicit.

  • Checks maintained binary signature evidence and uses the current browser decoder as the authoritative compatibility test for a bounded local source.
  • Converts strict decimal start and end times to outward-rounded sample frames, supports local selection preview, and preflights decoded memory and PCM output size.
  • Encodes interleaved 16-bit little-endian PCM in an isolated Worker, then verifies RIFF size, format, byte rate, alignment, data length, and requested frame count before download.

How to use Audio Trim

Choose one bounded audio file, decode it in the current browser, enter strict decimal start and end seconds, preview the frame-aligned selection, then create and download the WAV only after structural verification passes.

When this tool is useful

  • Removing silence or extracting a short review excerpt without uploading audio.
  • Preparing a deterministic uncompressed clip for an editor, test fixture, or transcription handoff.

Practical tips

  • Keep the source because tags, cover art, cue data, compression, and container metadata are not copied.
  • Check the displayed decoded sample rate because the browser can resample during decode; the WAV uses that rate.
  • Use the JSON evidence to record decoded properties and exact frame boundaries.
  • Use a dedicated audio editor when fades, loudness processing, controlled resampling, compressed output, or multitrack work is required.

Examples you can test

Load an example, compare the result with the expected output, then replace it with your own input.

Trim an interview excerpt

Example input

60-second browser-decodable recording; start 12.5 s; end 27.0 s

Expected output

Frame-aligned 16-bit PCM WAV plus versioned JSON evidence

The uncompressed output may be much larger than the source, and browser codec support varies.

Validation checklist

  • Preview the selected speech and both boundaries.
  • Confirm decoded channel count and sample rate match the intended source.
  • Open the downloaded WAV in its destination player and compare duration and channels.
  • Retain the source and evidence until the output has been accepted.

Frequently asked questions

Which audio files can it open?

Compatibility follows the current browser audio decoder. A maintained signature check rejects detected non-audio data, but an audio extension or MIME claim does not guarantee decoding.

Are audio files uploaded?

No. Signature detection, decoding, preview, PCM encoding, verification, and report generation run locally in this browser.

What does verified WAV mean?

The generated file is checked for its RIFF/WAVE signature, PCM format, channels, sample rate, byte rate, frame alignment, data length, and requested frame count. It is not a perceptual quality or malware verdict.

Will the output keep the source sample rate?

Not always. The browser may decode or resample a source into the AudioContext sample rate. The tool shows that decoded rate explicitly and verifies the WAV against it.

Are source metadata and compressed encoding preserved?

No. The output is a new uncompressed 16-bit PCM WAV and does not preserve source tags, cover art, cue points, compression, or container metadata.

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