Add text to speech with an integration

Connect the Azure Speech integration and Func gets ctx.tts.azure.speak(): turn text into audio for article narration, podcasts, audiobooks or spoken prompts. The subscription key stays on the server and never appears in your code.

Connect Azure Speech

First create a Speech service resource in the Azure portal:

1. Open Create Speech service and pick a subscription, resource group and region. The free F0 tier is enough to try it.
2. Once created, go to Keys and Endpoint and copy KEY 1.
3. Note the Location/Region, something like eastus, eastasia, southeastasia.

Then open Backend → Integrations in the editor and pick Azure Speech:

Saving asks Azure for the voice list for real, so a wrong key or region fails right there.

speak: synthesise audio

The common case is just the text:

export function read(input, ctx) {
  const audio = ctx.tts.azure.speak(input.text)
  return { audioBase64: audio.audioBase64, mimeType: audio.mimeType }
}

Pass an object to control voice, rate and delivery:

export function read(input, ctx) {
  const audio = ctx.tts.azure.speak({
    text: input.text,
    voice: 'en-US-JennyNeural',
    rate: '+10%',
    pitch: '-2st',
    style: 'cheerful',
    styleDegree: 1.5,
    format: 'audio-24khz-48kbitrate-mono-mp3',
    upload: true,
  })
  return { url: audio.fileUrl }
}

The result:

upload: true is usually what you want

Without upload the audio comes back into your code as base64. A minute of speech is roughly 500KB, close to 700KB once base64 encoded, which costs Func memory and then costs bandwidth again on the way to the browser.

With upload: true the audio goes straight into your project's own file space on the server and you get back a permanent URL:

const audio = ctx.tts.azure.speak({ text: paragraph, upload: true })
ctx.db.insert('chapters', { text: paragraph, audioUrl: audio.fileUrl })

Skip upload for one-off prompts you play immediately and never store.

Why only plain text, never SSML

The Azure API takes SSML. The platform builds it for you and escapes your text on the way in. You cannot write SSML tags yourself.

If you genuinely need to author whole SSML documents, the capability does not pass them through today. Configure your own key as an environment variable and call the API with fetch.

Audio formats

Blank means mp3, which covers almost everything. Common values:

Common voices

The full list is in Azure Speech language and voice support. Not every voice supports style.

Several channels: via(tag)

A project can hold several configurations, one per language for instance, or a trial tier and a paid tier. Tag each one and pick it with via():

ctx.tts.azure.via('zh').speak({ text: '你好' })
ctx.tts.azure.via('en').speak({ text: 'hello' })

Without via() the configuration tagged default is used.

Caching and deduplication are yours

The platform does not cache: the same sentence twice costs twice. Keep your own table mapping a text hash to a URL.

export function speakCached(input, ctx) {
  const key = input.text.trim()
  const hit = ctx.db.query('tts_cache', { where: { text: key }, limit: 1 })
  if (hit.list.length > 0) return { url: hit.list[0].url }

  const audio = ctx.tts.azure.speak({ text: key, upload: true })
  ctx.db.insert('tts_cache', { text: key, url: audio.fileUrl })
  return { url: audio.fileUrl }
}

It is not built in because only you know what counts as the same sentence. Does a different voice count? A different rate? Building that judgement into the platform would only produce a version you disagree with.

Reading the errors

Azure's own errors (out of quota, unknown voice, key and region mismatch) keep their message but come back as 400 or 502. An upstream 401 is never passed through as-is.

What this does not do

See also: More integrations, OpenAI models, Func backend capabilities.