I’m trying to build realtime speach to text transcription in node.js using AWS transcribe. I’m sure that the audio is transferred from react to node.js through socket.io and I have cross verified by creating writeStream and appending the audio chunks and the audio is playing from that file. But the AWS transcribe service results empty response.

Tech stack:

• React.js
• Node.js
• Socket.io
• @aws-sdk/client-transcribe-streaming

Code:

const express = require("express");
const http = require("http");
const { Server } = require("socket.io");
const {
  TranscribeStreamingClient,
  StartStreamTranscriptionCommand,
} = require("@aws-sdk/client-transcribe-streaming");
const cors = require("cors");

const app = express();
app.use(cors()); // Enable CORS for all origins

const server = http.createServer(app);
const io = new Server(server, {
  cors: {
    origin: "*", // Allow all origins (or specify your frontend's URL)
    methods: ["GET", "POST"],
    allowedHeaders: ["Content-Type"],
    credentials: true,
  },
});

const transcribeClient = new TranscribeStreamingClient({
  region: "us-west-2",
});

io.on("connection", (socket) => {
  console.log("Client connected");

  let audioQueue = [];

  socket.on("audio", (chunk) => {
    audioQueue.push(new Uint8Array(chunk));
  });

  const audioStream = async function* () {
    while (true) {
      if (audioQueue.length > 0) {
        yield { AudioEvent: { AudioChunk: audioQueue.shift() } };
      } else {
        await new Promise((resolve) => setTimeout(resolve, 100)); // Wait for more data
      }
    }
  };

  const command = new StartStreamTranscriptionCommand({
    LanguageCode: "en-US",
    MediaSampleRateHertz: 16000,
    MediaEncoding: "pcm",
    AudioStream: audioStream(),
  });

  const startTranscription = async () => {
    try {
      const response = await transcribeClient.send(command);
      console.log(response.$metadata)
      for await (const event of response.TranscriptResultStream) {
        console.log(event)
        if (event.TranscriptEvent) {
          const transcriptResults = event.TranscriptEvent.Transcript.Results;
          transcriptResults.forEach((result) => {
            if (result.Alternatives.length > 0) {
              const transcriptText = result.Alternatives[0].Transcript;
              socket.emit("transcript", transcriptText);
            }
          });
        }
      }
    } catch (error) {
      console.error("Error streaming transcription:", error);
      socket.emit("error", error.message);
    }
  };

  startTranscription();

  socket.on("disconnect", () => {
    console.log("Client disconnected");
  });
});

server.listen(4000, () => {
  console.log("Server is running on port 4000");
});

Output:

Server is running on port 4000
Client connected
{
  httpStatusCode: 200,
  requestId: 'dfbe7ba4-2340-48bf-8d68-d220cd13be2d',
  extendedRequestId: undefined,
  cfId: undefined,
  attempts: 1,
  totalRetryDelay: 0
}
{ TranscriptEvent: { Transcript: { Results: [] } } }

Can you help me to solve this issue.

Is there any different approach to achieve my goal.