TTS Long form Synthesis not working

[rcdinesh]

Summary of the Issue:

I am trying to integrate long form synthesis into my app and it keeps returning this error. 

Google Long-form API error: {
"error": {
"code": 400,
"message": "Can't write to GCS uri `gs://XXXYYY-audio-output/tts-output-1749443435083.wav`. Make sure to follow the steps at https://cloud.google.com/text-to-speech/docs/create-audio-text-long-audio-synthesis#before-you-begin. Invalid authentication from policy (go/gcs-rpc-sp): Rejected by creds_policy: Permission 'auth.creds.useNormalUserEUC' not granted to cloud-ml-tts-frontend-prod-regional-jobs@prod.google.com, because it satisfies none of the 1 rules granting that permission.; RpcSecurityPolicy http://rpcsp/p/1hEJNqELrPdL_GAiNvmvq3Bhjsd04r_gQIKuyIT27SQ ",
"status": "INVALID_ARGUMENT"
}
}

This is probably because the service agent required for the Text-to-Speech API is failing to be created automatically. ( i dont have an option to create a TTS Service agent directly) 

Troubleshooting Steps Taken:

• Confirmed our application's service account has all necessary Storage roles, including Service Usage Consumer and Service Account Token Creator.

• Attempted to force-create the service agent using gcloud beta services identity create --service=texttospeech.googleapis.com --project=long-form-synthesis. This command consistently fails with the internal error SU_INTERNAL_GENERATE_SERVICE_IDENTITY.

• Completely disabled and re-enabled the Text-to-Speech API for the project. The problem persists.

• To rule out any project-specific misconfiguration, we created a brand new, clean project (long-form-synthesis). This new project exhibits the exact same SU_INTERNAL_GENERATE_SERVICE_IDENTITY error and failure to create the service agent.

Below is the code,

import { type NextRequest, NextResponse } from "next/server"
import fs from "fs"
import path from "path"
import * as jose from "jose"

// Configuration for regional endpoint
const REGION = "us-central1" // You can change this to your preferred region

// Function to generate a JWT token for Google API authentication
async function generateGoogleJwt(credentials: any) {
const now = Math.floor(Date.now() / 1000)
const privateKey = credentials.private_key.replace(/\\n/g, "\n")

const payload = {
iss: credentials.client_email,
sub: credentials.client_email,
aud: "https://oauth2.googleapis.com/token",
iat: now,
exp: now + 3600,
scope: "https://www.googleapis.com/auth/cloud-platform",
}

const privateKeyImported = await jose.importPKCS8(privateKey, "RS256")
const token = await new jose.SignJWT(payload).setProtectedHeader({ alg: "RS256" }).sign(privateKeyImported)

return token
}

async function getAccessToken(credentials: any) {
const jwtAssertion = await generateGoogleJwt(credentials)

const tokenResponse = await fetch("https://oauth2.googleapis.com/token", {
method: "POST",
headers: {
"Content-Type": "application/x-www-form-urlencoded",
},
body: new URLSearchParams({
grant_type: "urn:ietf:params:oauth:grant-type:jwt-bearer",
assertion: jwtAssertion,
}),
})

if (!tokenResponse.ok) {
const errorText = await tokenResponse.text()
throw new Error(`Failed to get access token: ${tokenResponse.status} ${errorText}`)
}

const tokenData = await tokenResponse.json()
return tokenData.access_token
}

// ADD THIS NEW FUNCTION - API Kickstart to create service agent
async function triggerStandardSynthesis(token: string, projectId: string) {
console.log("Attempting to 'kickstart' the API with a standard synthesis call...")

const requestBody = {
input: { text: "hello" }, // A very short text
voice: { languageCode: "en-US", name: "en-US-Neural2-A" },
audioConfig: { audioEncoding: "MP3" },
}

const response = await fetch("https://texttospeech.googleapis.com/v1/text:synthesize", {
method: "POST",
headers: {
Authorization: `Bearer ${token}`,
"Content-Type": "application/json",
"x-goog-user-project": projectId, // Pass the project ID in a header
},
body: JSON.stringify(requestBody),
})

if (!response.ok) {
const errorText = await response.text()
console.error("Standard synthesis trigger failed:", errorText)
throw new Error(`Failed to kickstart API. Status: ${response.status}`)
}

const responseData = await response.json()
// We don't need the audio content, we just need the call to succeed.
if (responseData.audioContent) {
console.log("✅ SUCCESS: Standard API call successful. The service agent should now exist.")
return true
}

return false
}

// Function to start long-form synthesis using correct v1beta1 endpoint
async function startLongFormSynthesis(
text: string,
voice: any,
token: string,
audioEncoding = "LINEAR16",
projectId: string,
) {
// Create a timestamp for unique file naming
const timestamp = Date.now()
const fileExtension = audioEncoding === "MP3" ? "mp3" : audioEncoding === "LINEAR16" ? "wav" : "ogg"

// Use the specified bucket: gs://XXXYYY-audio-output
const outputGcsUri = `gs://XXXYYY-audio-output/tts-output-${timestamp}.${fileExtension}`

console.log(`Using output GCS URI: ${outputGcsUri}`)

const requestBody = {
input: { text },
voice: {
languageCode: "en-US",
name: "en-US-Standard-A",
ssmlGender: "FEMALE",
},
audioConfig: {
audioEncoding: audioEncoding,
},
outputGcsUri: outputGcsUri,
}

// Correct URL format with v1beta1 and full project path
const url = `https://${REGION}-texttospeech.googleapis.com/v1beta1/projects/${projectId}/locations/${REGION}:synthesizeLongAudio`

console.log("Starting long-form synthesis with default voice (en-US-Standard-A)")
console.log(`Using correct v1beta1 endpoint: ${url}`)

const response = await fetch(url, {
method: "POST",
headers: {
Authorization: `Bearer ${token}`,
"Content-Type": "application/json",
},
body: JSON.stringify(requestBody),
})

if (!response.ok) {
const errorText = await response.text()
console.error("Google Long-form API error:", errorText)

// Try to parse as JSON first, if that fails, return the raw text
let errorDetails
try {
const errorJson = JSON.parse(errorText)
errorDetails = JSON.stringify(errorJson, null, 2)
} catch {
errorDetails = errorText
}

throw new Error(`Google Long-form API Error (${response.status}) from ${REGION}: ${errorDetails}`)
}

const responseData = await response.json()
return responseData.name // This is the operation name
}

export async function POST(request: NextRequest) {
console.log("Long-form text-to-speech API route called")

try {
const body = await request.json()
const { text, voice, audioEncoding = "LINEAR16" } = body

if (!text) {
return NextResponse.json({ error: "Text is required" }, { status: 400 })
}

// Check if credentials file exists
const credentialsPath = path.join(process.cwd(), "long-form-credentials.json")
if (!fs.existsSync(credentialsPath)) {
return NextResponse.json({ error: "Long-form credentials file not found" }, { status: 500 })
}

// Read credentials file
const fileContent = fs.readFileSync(credentialsPath, "utf8")
const credentials = JSON.parse(fileContent)

if (!credentials.private_key || !credentials.client_email || !credentials.project_id) {
throw new Error("Credentials file is missing required fields (private_key, client_email, project_id)")
}

// Generate access token for authentication
const token = await getAccessToken(credentials)
console.log("Access token generated successfully for long-form synthesis")

// ====================================================================
// TEMPORARY CODE TO KICKSTART THE API - ADD THIS BLOCK
// Make sure your new project ID is available
const projectId = credentials.project_id
if (!projectId) throw new Error("Project ID is missing from credentials!")

await triggerStandardSynthesis(token, projectId)
// ====================================================================

// Start long-form synthesis with correct project ID
const operationName = await startLongFormSynthesis(text, voice, token, audioEncoding, credentials.project_id)
console.log("Long-form synthesis started with operation:", operationName)

return NextResponse.json({
success: true,
operationName: operationName,
region: REGION,
projectId: credentials.project_id,
message: "Long-form synthesis started successfully",
})
} catch (error) {
console.error("Error in long-form text-to-speech:", error)

return NextResponse.json(
{
error: "Failed to start long-form synthesis",
details: error instanceof Error ? error.message : "Unknown error",
},
{ status: 500 },
)
}
}

[marckevin]

Hi @rcdinesh,

Welcome to Google Cloud Community!

Here are several suggestions that may help resolve the issue:

• Double-check if there are any policy or Organization Policy constraints preventing the creation of the service agent. The error you encountered possibly suggests that a policy is blocking this action.
• As already part of your troubleshooting steps taken, ensure all the necessary storage roles include Storage Object Creator and Storage Object Viewer on the output GCS bucket.
• As a best practice, double check consistency in your code and ensure there are no typographical errors as this might result to invalid argument.

Per checking on Google Cloud Service Health report for Text-to-Speech and Google Cloud Storage, there have been no major service outages listed in the past few weeks. Just to add, Google Cloud Text-to-Speech: Create long-form audio is currently in Preview, which means it is still under development, and may not yet offer the expected quality, and might have limited support. Preview features often come with certain limitations and might not provide the full range of quality or functionality available in the final product. It may have bugs or unexpected behaviors. However, you can expect the quality to improve as the feature matures.

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