Text-to-Speech - Portkey Docs

Usage

We follow the OpenAI signature where you can send the input text and the voice option as a part of the API request. All the output formats mp3, opus, aac, flac, and pcm are supported. The AI Gateway also supports real time audio streaming for TTS models. Here’s an example:

OpenAI NodeJS
OpenAI Python
cURL

import fs from "fs";
import path from "path";
import OpenAI from "openai";

const openai = new OpenAI({
  apiKey: "PORTKEY_API_KEY",
  baseURL: "https://aigw.portkey.ai/v1"
});

const speechFile = path.resolve("./speech.mp3");

async function main() {
  const mp3 = await openai.audio.speech.create({
    model: "@openai/tts-1",
    voice: "alloy",
    input: "Today is a wonderful day to build something people love!",
  });
  const buffer = Buffer.from(await mp3.arrayBuffer());
  await fs.promises.writeFile(speechFile, buffer);
}

main();

from pathlib import Path
from openai import OpenAI

client = OpenAI(
    api_key="PORTKEY_API_KEY",
    base_url="https://aigw.portkey.ai/v1"
)

speech_file_path = Path(__file__).parent / "speech.mp3"

response = client.audio.speech.create(
  model="@openai/tts-1",
  voice="alloy",
  input="Today is a wonderful day to build something people love!"
)

f = open(speech_file_path, "wb")
f.write(response.content)
f.close()

curl "https://aigw.portkey.ai/v1/audio/speech" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $PORTKEY_API_KEY" \
  -d '{
    "model": "@openai/tts-1",
    "input": "Today is a wonderful day to build something people love!",
    "voice": "alloy"
  }' \
  --output speech.mp3

On completion, the request will get logged in the logs UI and show the cost and latency incurred.

SSE Streaming

OpenAI and Azure OpenAI support Server-Sent Events (SSE) streaming for the speech endpoint. Set stream_format to "sse" to receive audio data as a stream of events:

cURL

curl "https://aigw.portkey.ai/v1/audio/speech" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $PORTKEY_API_KEY" \
  -d '{
    "model": "@openai/tts-1",
    "input": "Today is a wonderful day to build something people love!",
    "voice": "alloy",
    "stream_format": "sse"
  }'

Google Vertex AI TTS

Google Vertex AI offers Gemini TTS models with advanced features like multi-speaker synthesis and style control. The AI Gateway supports two methods:

Chat Completions with speech_config - Use Gemini TTS through the chat completions endpoint
Audio Speech endpoint - OpenAI-compatible /audio/speech endpoint

Chat Completions
Audio Speech

curl https://aigw.portkey.ai/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $PORTKEY_API_KEY" \
  -d '{
    "model": "@vertex-ai/gemini-2.5-flash-tts",
    "messages": [{"role": "user", "content": "Say cheerfully: Hello!"}],
    "speech_config": {
      "voice_config": {"prebuilt_voice_config": {"voice_name": "Kore"}},
      "language_code": "en-US"
    }
  }'

curl "https://aigw.portkey.ai/v1/audio/speech" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $PORTKEY_API_KEY" \
  -d '{
    "model": "@vertex-ai/gemini-2.5-flash-tts",
    "input": "Hello! This is a test.",
    "voice": "Kore",
    "response_format": "mp3"
  }' \
  --output speech.mp3

For detailed documentation including multi-speaker synthesis, style prompts, and all available voices, see Google Vertex AI Text-to-Speech.

Last modified on September 15, 2026