Seed Speech 2.0 API
by ByteDance41 voices with tone set in plain language
- 41 voices
- 10 languages
- Text to Speech
Call it with the model name bytedance/seed-speech-2.0/text-to-speech on POST /jobs/createTask, from 11 credits per 1,000 characters ($0.11). New accounts get 30 free credits to try it in the Playground first.
bytedance/seed-speech-2.0/text-to-speechPOST https://api.popnow.ai/api/v1/jobs/createTask# 1. Create the task. Keep the Idempotency-Key if you retry after a network error.
export IDEMPOTENCY_KEY="$(uuidgen)"
curl -X POST https://api.popnow.ai/api/v1/jobs/createTask \
-H "Authorization: Bearer $POPNOW_API_KEY" \
-H "Content-Type: application/json" \
-H "Idempotency-Key: $IDEMPOTENCY_KEY" \
-d '{
"model": "bytedance/seed-speech-2.0/text-to-speech",
"input": {
"text": "Welcome back. Your files finished rendering a minute ago and are ready to download.",
"voice_id": "stokie_en",
"output_format": "mp3"
}
}'
# 2. Copy data.taskId from the response, then poll until state is succeeded, failed, canceled or expired.
TASK_ID="TASK_ID_FROM_RESPONSE"
curl "https://api.popnow.ai/api/v1/jobs/recordInfo?taskId=$TASK_ID" \
-H "Authorization: Bearer $POPNOW_API_KEY"// Node 18+ (or any runtime with fetch). Keep the API key on your server.
const BASE = "https://api.popnow.ai/api/v1";
const headers = { Authorization: `Bearer ${process.env.POPNOW_API_KEY}` };
const sleep = (ms) => new Promise((r) => setTimeout(r, ms));
async function call(path, init = {}) {
const res = await fetch(BASE + path, { ...init, headers: { ...headers, ...init.headers } });
const body = await res.json();
if (body.code !== 200) throw new Error(`${body.code} ${body.msg}`);
return body.data;
}
const { taskId } = await call("/jobs/createTask", {
method: "POST",
headers: { "Content-Type": "application/json", "Idempotency-Key": crypto.randomUUID() },
body: JSON.stringify({
"model": "bytedance/seed-speech-2.0/text-to-speech",
"input": {
"text": "Welcome back. Your files finished rendering a minute ago and are ready to download.",
"voice_id": "stokie_en",
"output_format": "mp3"
}
}),
});
// Poll with backoff. A finished task may still be copying files: wait while an asset is pending.
let task;
for (let delay = 2000; ; delay = Math.min(delay * 1.5, 15000)) {
await sleep(delay);
task = await call(`/jobs/recordInfo?taskId=${taskId}`);
const copying = (task.output?.assets ?? []).some((a) => a.pending && !a.unavailable);
if (["succeeded", "failed", "canceled", "expired"].includes(task.state) && !copying) break;
}
if (task.state !== "succeeded") throw new Error(`${task.state}: ${task.errorMessage ?? "no detail"}`);
// Each asset has a signed url (no API key needed) that expires at expiresAt: save the file.
for (const asset of task.output.assets) console.log(asset.url);import os, time, uuid, requests
BASE = "https://api.popnow.ai/api/v1"
HEADERS = {"Authorization": f"Bearer {os.environ['POPNOW_API_KEY']}"}
def call(method, path, **kwargs):
body = requests.request(method, BASE + path, headers={**HEADERS, **kwargs.pop("headers", {})}, timeout=30, **kwargs).json()
if body["code"] != 200:
raise RuntimeError(f'{body["code"]} {body["msg"]}')
return body["data"]
task_id = call(
"POST",
"/jobs/createTask",
headers={"Idempotency-Key": str(uuid.uuid4())}, # reuse it if you retry
json={
"model": "bytedance/seed-speech-2.0/text-to-speech",
"input": {
"text": "Welcome back. Your files finished rendering a minute ago and are ready to download.",
"voice_id": "stokie_en",
"output_format": "mp3"
}
},
)["taskId"]
# Poll with backoff. A finished task may still be copying files: wait while an asset is pending.
delay = 2.0
while True:
time.sleep(delay)
task = call("GET", "/jobs/recordInfo", params={"taskId": task_id})
assets = (task.get("output") or {}).get("assets") or []
copying = any(a.get("pending") and not a.get("unavailable") for a in assets)
if task["state"] in ("succeeded", "failed", "canceled", "expired") and not copying:
break
delay = min(delay * 1.5, 15.0)
if task["state"] != "succeeded":
raise RuntimeError(f'{task["state"]}: {task.get("errorMessage", "no detail")}')
# Each asset has a signed url (no API key needed) that expires at expiresAt: save the file.
for asset in assets:
print(asset["url"])The input is built from the schema below, so it passes validation as written. Change the prompt and links to your own.
Price
| Option | Credits per 1,000 characters | ≈ USD |
|---|---|---|
| Standard | 10.8 | $0.11 |
1 credit = $0.01 · Every option and its price: GET /models/bytedance/seed-speech-2.0/text-to-speech
Each task is rounded up to whole credits, so one run at the lowest tier costs 11 credits per 1,000 characters ($0.11).
Limits
- Text length (characters)
- 5,000
- Voices
- 41
- Languages
- 10
Parameters
These fields come from the same schema we check every request against. Fields that are not listed are rejected.
textstringRequiredThe words to be spoken, exactly as written. Billed per 1,000 characters.
voice_idstringOptionalPick from the available voices.
instructionsstringOptionalHow to read the text: tone, emotion, pace or volume. Not spoken and not billed.
speednumberOptionalSpeaking pace.
pitchintegerOptionalPitch shift in semitones; 0 keeps the voice's own pitch.
volumenumberOptionalLoudness multiplier; 1 is the normal level.
languagestringOptionalThe language of the speech.
output_formatstringOptionalFile type of the result.
sample_rateintegerOptionalSample rate in Hz. The model uses 24000 when omitted.
Raw JSON Schema
{
"type": "object",
"required": [
"text"
],
"properties": {
"text": {
"type": "string",
"maxLength": 5000,
"minLength": 1,
"description": "The words to be spoken, exactly as written. Billed per 1,000 characters."
},
"pitch": {
"type": "integer",
"default": 0,
"maximum": 12,
"minimum": -12,
"description": "Pitch shift in semitones; 0 keeps the voice's own pitch."
},
"speed": {
"type": "number",
"default": 1,
"maximum": 2,
"minimum": 0.5,
"description": "Speaking rate; 1 is the voice's normal pace."
},
"volume": {
"type": "number",
"default": 1,
"maximum": 2,
"minimum": 0.5,
"description": "Loudness multiplier; 1 is the normal level."
},
"language": {
"enum": [
"zh",
"en",
"ja",
"es-mx",
"id",
"pt-br",
"ko",
"it",
"de",
"fr"
],
"type": "string",
"description": "Forces the reading language. Leave empty to detect it from the text."
},
"voice_id": {
"enum": [
"vivi_mixed_en_zh_ja_es_id",
"mindy_en_es_id_pt_zh",
"stokie_en",
"dacey_en",
"tim_en",
"kian_en_zh",
"cedric_en_zh",
"sophie_en_zh",
"jean_en_zh",
"magnus_en_zh",
"mabel_en_zh",
"nadia_en_zh",
"opal_en_zh",
"pearl_en_zh",
"quentin_en_zh",
"vienna_mixed_en_zh",
"alina_mixed_en_zh",
"corinne_mixed_en_zh",
"esther_mixed_en_zh",
"freya_mixed_en_zh",
"gigi_mixed_en_zh",
"holly_mixed_en_zh",
"lyla_mixed_en_zh",
"daisy_mixed_en_zh",
"tracy_es_zh",
"jess_ja_es_id_pt_en_zh",
"pinky_es_ko_mixed_en_zh",
"sweety_ja_es",
"sandy_es_mixed_en_zh",
"sven_de",
"minimi_ja",
"usseau_fr",
"felipe_es",
"han_id",
"martins_pt",
"enzo_it",
"shane_ko",
"bonnie_zh",
"felix_zh",
"celeste_zh",
"monkey_king_zh"
],
"type": "string",
"default": "stokie_en",
"description": "Preset voice. The suffix shows the languages it is built for."
},
"sample_rate": {
"enum": [
8000,
16000,
22050,
24000,
32000,
44100,
48000
],
"type": "integer",
"description": "Sample rate in Hz. The model uses 24000 when omitted."
},
"instructions": {
"type": "string",
"maxLength": 1000,
"description": "How to read the text: tone, emotion, pace or volume. Not spoken and not billed."
},
"output_format": {
"enum": [
"mp3",
"opus"
],
"type": "string",
"default": "mp3",
"description": "File format of the result; opus is an Ogg Opus file."
}
},
"additionalProperties": false
}Responses, polling and callbacks
Every model works the same way: create a task, then poll it or wait for a callback.
Price it first
curl -X POST https://api.popnow.ai/api/v1/jobs/quote \
-H "Authorization: Bearer $POPNOW_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "bytedance/seed-speech-2.0/text-to-speech",
"input": {
"text": "Welcome back. Your files finished rendering a minute ago and are ready to download.",
"voice_id": "stokie_en",
"output_format": "mp3"
}
}'Same body as createTask. It returns the expected and the highest possible charge, and runs nothing.
Accepted
HTTP/1.1 202 Accepted
{
"code": 200,
"msg": "success",
"data": {
"taskId": "task_01k3m8x9q2z4v7n5p6r8s0t1w3",
"state": "queued"
},
"request_id": "req_example_create"
}HTTP 202 means the task was accepted and the credits are held, not charged yet. The final charge never goes above the hold.
Check status
curl "https://api.popnow.ai/api/v1/jobs/recordInfo?taskId=$TASK_ID" \
-H "Authorization: Bearer $POPNOW_API_KEY"Poll every few seconds with backoff and stop once state is succeeded, failed, canceled or expired.
Finished task
{
"code": 200,
"msg": "success",
"data": {
"taskId": "task_01k3m8x9q2z4v7n5p6r8s0t1w3",
"model": "bytedance/seed-speech-2.0/text-to-speech",
"state": "succeeded",
"output": {
"assets": [
{
"url": "https://cdn.popnow.ai/tasks/task_01k3m8x9q2z4v7n5p6r8s0t1w3/output.mp3?signature=FROM_RESPONSE",
"expiresAt": "2026-10-17T12:20:00Z",
"mime": "audio/mpeg",
"durationSeconds": 30
}
]
},
"settled": true
},
"request_id": "req_example_record"
}Download from url before expiresAt. Need a fresh link later? Ask POST /common/download-url.
Verify a callback
import { createHash, createHmac, timingSafeEqual } from "node:crypto";
import express from "express";
const app = express();
// express.raw keeps the exact bytes that were signed; express.json would not match.
app.post("/hooks/popnow", express.raw({ type: "application/json" }), (req, res) => {
const timestamp = req.header("X-Webhook-Timestamp");
const signature = req.header("X-Webhook-Signature") ?? "";
const body = JSON.parse(req.body.toString("utf8"));
const taskId = body.data?.taskId ?? body.task_id;
const digest = createHash("sha256").update(req.body).digest("hex");
const expected = createHmac("sha256", process.env.POPNOW_WEBHOOK_SECRET)
.update(`${taskId}.${timestamp}.${digest}`)
.digest("base64");
const ok = expected.length === signature.length && timingSafeEqual(Buffer.from(expected), Buffer.from(signature));
// Check the signature first, then reject anything older than five minutes.
if (!ok || Math.abs(Date.now() / 1000 - Number(timestamp)) > 300) return res.status(401).end();
res.status(200).end(); // answer fast, then fetch the task and store its files
});With callBackUrl set, we post the finished task to you. Check the signature against the raw body before you trust it.
Send a local file
curl -X POST https://api.popnow.ai/api/v1/common/upload-url \
-H "Authorization: Bearer $POPNOW_API_KEY" \
-H "Content-Type: application/json" \
-d '{"contentType": "image/png", "bytes": 482113}'
# PUT the file bytes to data.uploadUrl with every header in data.headers, then commit it:
curl -X POST https://api.popnow.ai/api/v1/files/$FILE_ID/commit \
-H "Authorization: Bearer $POPNOW_API_KEY"
# The commit returns a popnow://f/... reference. Put it in any image, video or
# audio field of the task input instead of a public https URL.Public https links work as they are. Local files go through upload-url and commit first.