Klone V2 Flash

Voice Clone · Fast

Klone V2 Flash is our faster voice-cloning model. It is a drop-in option on the same one-shot endpoint as Klone V2 Pro: add model=klone_v2_flash to the request and everything else stays the same.

Overview

Key characteristics

Synchronous: the audio comes back inline in the HTTP response. No job ID and no polling.
12 languages: Bengali, English, Gujarati, Hindi, Kannada, Malayalam, Marathi, Odia, Punjabi, Tamil, Telugu, Urdu.
Up to 5,000 characters per request. The server splits and merges long text.
Billed at 1 credit per 8 characters, times the voice multiplier.
Does not use speed, duration, instruct or num_step.

Request

API endpoint

Base URL: https://api.fonada.ai
Endpoint: /v1/voice-clone/chunks
Method: POST
Content-Type: multipart/form-data (always, even with no file upload)
Authorization: Bearer YOUR_FONADA_API_KEY

curl

curl -X POST "https://api.fonada.ai/v1/voice-clone/chunks" \
  -H "Authorization: Bearer YOUR_FONADA_API_KEY" \
  -F "model=klone_v2_flash" \
  -F "share_id=YOUR_SHARE_ID" \
  -F "text=यह एक छोटा सा फ़्लैश वॉइस क्लोन टेस्ट है।" \
  -F "language=hi" \
  -F "output_audio_codec=mp3" \
  -o voice.mp3

JavaScript (fetch)

const form = new FormData()
form.append('model', 'klone_v2_flash')
form.append('share_id', 'YOUR_SHARE_ID')
form.append('text', 'यह एक छोटा सा फ़्लैश वॉइस क्लोन टेस्ट है।')
form.append('language', 'hi')
form.append('output_audio_codec', 'mp3') // optional, default wav

// Do not set Content-Type yourself - the browser adds the multipart boundary.
const res = await fetch('https://api.fonada.ai/v1/voice-clone/chunks', {
  method: 'POST',
  headers: { Authorization: `Bearer ${API_KEY}` },
  body: form,
})

if (!res.ok) {
  const err = await res.json() // { detail: { error, message, details? } }
  if (err?.detail?.error === 'rate_limit_exceeded') {
    const wait = err.detail.details?.retry_after_seconds ?? 5
    // wait `wait` seconds, then retry
  }
  throw new Error(err?.detail?.message || 'voice clone failed')
}

const url = URL.createObjectURL(await res.blob())
audioElement.src = url

The body of a successful response is the raw audio. Read it as a Blob or ArrayBuffer, not JSON. Response headers: Content-Type, Content-Disposition, X-Output-Codec, X-Upstream-Time-Ms, X-Processing-Time-Ms. No credit or model headers are returned.

Parameters (multipart form)

Field	Required	Description
text	yes	Text to synthesize. Non-empty, at most 5,000 characters.
language	yes (default hi)	ISO code or display name. See Languages.
model	yes for Flash	Must be `klone_v2_flash`.
output_audio_codec	no (wav)	See Output formats.
share_id	one of 3	Catalog voice ID. Works on all tiers. `audio`, `audio_url` and `audio_text` are ignored when it is set.
audio	one of 3	Reference upload (WAV/MP3/M4A/FLAC/OGG/WebM), max 10 MB and 30 s. Enterprise only.
audio_url	one of 3	Public HTTPS URL of a reference clip. Enterprise only.
audio_text	no	Transcript of the reference audio. Omit it to auto-transcribe. Ignored with `share_id`.

Send exactly one of share_id, audio or audio_url. Zero returns 400 missing_audio_source; more than one returns 400 ambiguous_audio_source. Do not send speed, duration, instruct or num_step with Flash.

Languages

Pass an ISO code or a display name (case-insensitive). Anything else returns 400 invalid_language.

Code	Language
bn	Bengali
en	English
gu	Gujarati
hi	Hindi
kn	Kannada
ml	Malayalam
mr	Marathi
or	Odia
pa	Punjabi
ta	Tamil
te	Telugu
ur	Urdu

Output formats

output_audio_codec	Content-Type	Extension	Encoding
wav (default)	audio/wav	.wav	PCM WAV
mp3	audio/mpeg	.mp3	MP3
opus	audio/ogg	.opus	Opus in Ogg
pcm (linear16)	audio/pcm	.pcm	Raw headerless 16-bit PCM
mulaw (ulaw)	audio/basic	.ulaw	μ-law (telephony)
alaw	audio/x-alaw-basic	.alaw	A-law (telephony)

For web playback, mp3 or opus give the smallest payload, and wav gives the lowest latency. pcm, mulaw and alaw are headerless raw streams, so your player needs to be told the format. An unsupported value returns 400 invalid_output_audio_codec.

Billing

credits = max(round(characters / chars_per_credit × multiplier, 2), 0.01)

Flash: 1 credit per 8 characters by default (the per-user voice_cloning_flash_deduction_value). Pro uses 2.
Multiplier with share_id: the catalog voice's credit multiplier.
Multiplier with audio / audio_url: ×1.
Example: 20 characters on a 7× voice is 17.5 credits on Flash, versus 70 on Pro.
Credits are charged before the upstream call and refunded automatically if it fails.
An unknown share_id returns 404 and is not charged.

Rate limits

10 requests per minute per user by default.
A global concurrency cap returns the same error with rate_period: "concurrent" and retry_after_seconds: 5.
Flash handles roughly 1.5 to 2 requests per second in total. Under heavy load, latency grows instead of erroring.
The wait time is only in the body. There is no Retry-After header.

429 response body

{
  "detail": {
    "error": "rate_limit_exceeded",
    "message": "Rate limit exceeded. You can make 10 requests per minute.",
    "details": {
      "rate_limit": 10,
      "current_usage": 10,
      "remaining": 0,
      "retry_after_seconds": 37,
      "rate_period": "minute"
    }
  }
}

Errors

All errors are JSON: {"detail": {"error": "<code>", "message": "<text>"}}

HTTP	error	Cause
400	empty_text	text is empty or whitespace
400	text_too_long	text is longer than 5,000 characters (limit_chars and received_chars in the body); nothing is charged
400	invalid_language	language is not in the supported list (response includes supported_languages)
400	missing_audio_source	No reference source supplied
400	ambiguous_audio_source	More than one of share_id / audio / audio_url supplied
400	empty_audio / audio_decode_failed / audio_too_long	Reference upload is empty, not valid audio, or longer than 30 s
413	audio_too_large	Reference upload larger than 10 MB
403	enterprise_only	audio / audio_url on a non-enterprise tier
403	invalid_api_key / inactive_api_key	Bad or disabled API key
404	voice_not_found	share_id is not in the catalog
429	rate_limit_exceeded	More than 10 requests/minute per user, or too many requests in flight (see Rate limits)
429	credits_exhausted	Insufficient credits / credit limit reached
500	encoding_failed	Server-side transcode to the requested codec failed
502	upstream_error / upstream_unreachable / upstream_empty	Upstream cloner failed or returned no audio. Credits are refunded automatically

Python SDK

Set model="klone_v2_flash" on TTSClient.generate_audio(). Flash does not send speed or duration. As with Pro, mp3 and opus are limited to 450 characters in the SDK. See the Klone V2 Pro SDK section for installation and authentication.

Python

from fonadalabs.tts.client import TTSClient

client = TTSClient(api_key="YOUR_FONADA_API_KEY")

audio_bytes = client.generate_audio(
    text="Hello from flash cloning.",
    language="Hindi",
    model="klone_v2_flash",
    share_id="YOUR_SHARE_ID",
    output_file="flash.wav",
)

FAQ

Both use POST /v1/voice-clone/chunks with the same reference sources, response headers, errors and billing formula. Flash is faster, supports 12 languages, takes the whole text in one request (the server splits and merges it), and ignores speed, duration, instruct and num_step. Only the characters-per-credit value differs: 8 for Flash, 2 for Pro.

Next: Fonada V1

Klone V2 Flash

Overview

Key characteristics

Request

API endpoint

Parameters (multipart form)

Languages

Output formats

Billing

Rate limits

Errors

Python SDK

FAQ

What is the difference between Flash and Pro?

How is Flash billed?

How long can the text be?

What if I get a 429?

Am I charged if the client disconnects?

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