Listen to Active Call

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Authentication

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Path Parameters

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Prerequisites

• Live listen must be enabled in organization preferences (live_listen_enabled: true)
• Call must be in active status (not completed)
• Call must belong to the authenticated organization

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Response

curl -X POST "https://api.bland.ai/v1/calls/call_123456/listen" \
  -H "Authorization: YOUR_API_KEY"

{
  "status": "success",
  "data": {
    "url": "wss://api.bland.ai/ws/listen/call_123456"
  },
  "errors": null
}

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WebSocket Connection

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Connection Details

• URL: Use the url returned in the response
• Protocol: WebSocket (WSS)
• Binary Type: arraybuffer
• Authentication: Handled via the URL token

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Audio Data Format

• Format: PCM Int16 (16-bit signed integers)
• Sample Rate: 16,000 Hz
• Channels: Mono (1 channel)
• Byte Order: Little-endian
• Data: Combined audio from all call participants

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WebSocket Implementation Example

// Connect to WebSocket
const socket = new WebSocket(websocketUrl);
socket.binaryType = 'arraybuffer';

socket.onmessage = (event) => {
  // Convert ArrayBuffer to Int16Array
  const dataView = new DataView(event.data);
  const int16Array = new Int16Array(dataView.byteLength / 2);
  
  for (let i = 0; i < int16Array.length; i++) {
    int16Array[i] = dataView.getInt16(i * 2, true); // Little-endian
  }
  
  // Process audio data (convert to Float32 for Web Audio API)
  const float32Array = new Float32Array(int16Array.length);
  for (let i = 0; i < int16Array.length; i++) {
    float32Array[i] = int16Array[i] / 32768; // Normalize to [-1, 1]
  }
  
  // Use audio data for playback
};

socket.onclose = () => {
  console.log('Live listen session ended');
};

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Error Codes

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Notes

• WebSocket connection automatically closes when the call ends
• Multiple concurrent listeners can subscribe to the same call
• Audio stream includes all participants in the call (combined)
• The WebSocket URL can be used by multiple connections simultaneously