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Lizely

Reverse Audio

Reverse every decoded audio sample locally and download the result as an explicitly labeled PCM16 WAV file.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Choose a supported audio file up to 50 MB and optionally preview the original in the browser.
  2. 2.Select Reverse audio and wait while every decoded channel sample is reversed locally.
  3. 3.Preview the result, verify its duration and audio properties, then download the PCM16 WAV.

About Reverse Audio

Reverse Audio plays a recording from its end back to its beginning by reversing the decoded samples in every channel. Choose a supported audio file, select Reverse audio, preview the result, and download a new WAV. The browser retains the original sample rate and channel count when those values fit the stated limits. A stereo input stays stereo: the left channel is reversed independently, the right channel is reversed independently, and the two channels are interleaved again in the correct WAV frame order. No samples are deliberately skipped, shortened, or capped inside an accepted file.

The operation happens in the current browser tab. The original file receives a temporary local object URL for the built-in preview, and the finished WAV receives a separate temporary download URL. Selecting another file, running the operation again, or leaving the page releases obsolete URLs. The Web Audio context used for decoding is also closed after the operation or when work is replaced. The file bytes, decoded samples, filename, and result are not uploaded to Lizely. This local workflow can be useful for sound-design experiments, reverse speech, transition effects, sample inspection, and checking the end of a recording from a different perspective.

Input acceptance and successful decoding are separate checks. The file picker accepts common MP3, WAV, M4A, AAC, Ogg, and WebM audio MIME types, but actual codec support depends on the visitor's browser and operating system. A container can also contain a codec that a particular browser cannot decode. When Web Audio rejects the data, the tool reports a decode error rather than claiming that every file with a familiar extension must work. It does not install FFmpeg, call a conversion server, or silently substitute a different remote workflow.

Limits are explicit. The compressed input must be no larger than 50 MB. Decoded audio must be five minutes or shorter, contain one to eight channels, use a sample rate from 8,000 to 192,000 Hz, and contain no more than 30 million channel samples in total. The channel-sample budget is the number of frames multiplied by the number of channels; it protects the tab from unexpectedly large decoded arrays even when a compressed source file looks small. A file that exceeds any limit receives a specific message and is not partially processed. Changing files or retrying also clears the previous download first, so an old success cannot be mistaken for a new result after an error.

The download is always a newly encoded PCM16 WAV. It is not the original MP3, M4A, AAC, Ogg, WebM, or compressed WAV stream played backward, and the interface does not imply that the original codec or bitrate is retained. Each browser-decoded floating-point sample is clipped to the range from -1 to 1, mapped to signed 16-bit PCM, and written little-endian. Negative full scale maps to -32768 and positive full scale maps to 32767. WAV may therefore be much larger than a compressed source, and reducing floating-point samples to 16-bit can change numerical precision.

The result is a fresh audio file, so original metadata is not promised. Album art, tags, chapters, loop markers, encoder settings, compressed bitrate, and container-specific fields are not copied. The tool reverses decoded audible sample data rather than editing or preserving the source container. It also does not normalize loudness, remove silence, change pitch intentionally, stretch time, or repair clipping. Reversing samples preserves the decoded duration, sample rate, and channel count, but it moves every event to the corresponding position measured backward from the end.

The core transformation and encoder are shared by production and isolated tests. Reversal tests cover odd and even frame counts, multiple channels, and confirmation that source arrays are not mutated. PCM tests cover values below -1, above 1, negative and positive half scale, endpoints, and non-finite input. WAV golden tests inspect the RIFF, WAVE, fmt, and data fields, byte rate, block alignment, little-endian PCM bytes, and stereo interleaving. These checks catch common failures such as reversing channel order instead of time, dropping the center sample of an odd-length clip, or writing an invalid header.

For a reliable workflow, keep the source file, listen to the original preview, create the reversed WAV, and listen to the beginning and end of the result. Confirm the duration, channel count, sample rate, and file size displayed by the tool. Open the download in the editor or player where it will be used, because browser preview success does not guarantee that every older device supports the same WAV channel layout or high sample rate. Use an audio editor when you also need fades, trimming, codec selection, metadata preservation, or mastering controls.

Methodology & sources

The browser validates the input MIME type and 50 MB byte limit, reads the file into an ArrayBuffer, and decodes it with Web Audio. Decoded audio is rejected rather than truncated if it exceeds five minutes, eight channels, 30 million channel samples, or the 8,000–192,000 Hz sample-rate range. Production calls the same reverseChannels function exercised by odd, even, and multichannel tests, then calls the same encodePcm16Wav function whose RIFF header, PCM clamp values, little-endian bytes, and stereo interleaving are covered by golden assertions. The output is a newly encoded PCM16 WAV; job and mounted-state guards prevent stale asynchronous work from replacing newer results.

Frequently asked questions

Does the result keep the original MP3 or M4A encoding?
No. The result is always a newly encoded PCM16 WAV. Original codec, bitrate, tags, artwork, and container metadata are not promised.
Are audio files uploaded?
No. File reading, Web Audio decoding, sample reversal, WAV encoding, and preview creation happen locally in the current browser tab.
Why might a listed format fail to decode?
Codec support varies by browser and operating system, and a familiar container can hold an unsupported codec. The tool reports a decode error when the current browser cannot read the file.
Does stereo audio remain stereo?
Yes. Each accepted channel is reversed independently and then written back in interleaved WAV frame order with the decoded channel count and sample rate.

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