Extend Audio

Extend audio (sync)

Extend an existing audio clip at the end. Pass the audio prefix and the desired total output duration. Credits are charged only for the generated extension portion (total_duration − input_duration). The prefix must be at least 3 seconds long; duration_ms must exceed the prefix by at least 1s. Maximum new audio is 57 seconds. With loop: true the prefix is never shortened, so prefix + new audio must stay within 60 seconds and the extension must be at least 1s — appending the maximum then requires a prefix at the 3s minimum.

post/v2/extend-audio/v1.6/sync

Request

  • Base URL: https://api.mirelo.ai
  • URL: https://api.mirelo.ai/v2/extend-audio/v1.6/sync
  • Auth: HTTP bearer

Headers

Idempotency-Keystring

Stable key for one logical sync request, for retrying after an ambiguous response such as a transport timeout. Reuse it only with the identical body. While the original request is in progress, after it completed, or with a different body, the retry returns 409 idempotency_conflict instead of starting another billable request. A failed attempt may run again with the same key. A completed request's key is remembered for 24 to 48 hours after the original request completes, depending on when the daily sweep runs. A 409 retry does not extend this window; reusing the key after it is forgotten starts and bills a new request.

Request body

OR

Example request

{
  "prompt": "heavy rain continues to intensify",
  "seed": 42,
  "output_format": "mp3"
}

Response

Extended audio URLs

modelstring nullable

Public release that produced this result. Null when unknown or when multiple releases contributed; not a runtime fingerprint or reproducibility guarantee.

result_urlsstring[] required

Array of URLs to the generated output files (audio, or video with SFX mixed in when output is "video"). Signed by the inference service at upload time and valid for one hour from then — not from when you read them. Prefer download_urls.

download_urlsstring[]

Short download links on mirelo.ai, index-aligned with result_urls when present. Each is a 302 to a URL signed at the moment you follow it, so the link stays valid for as long as the generation is retained instead of expiring on the job's clock. Short enough for clients that reject long URLs, and accepted anywhere this API takes an input URL. Repeated follows are expected and supported; a link followed hard enough to be throttled answers 429 with Retry-After rather than looking like a dead file. Optional — always fall back to result_urls. Every SFX endpoint emits it, extend and inpaint included; the music endpoints record no generation and so never carry one. Minting is best-effort on top of that, so even a response carrying generation_id may omit it.

generation_idstring

Server-side generation record id, present when the generation was persisted. Retain it to later reference the generation (e.g. attach feedback). Absent when persistence was skipped or failed — never blocks the result.

Changes

No recorded changes to this operation across all 1 revision of this API.