Audio Duck

Immutable Catalog Entry

This descriptor comes from the active versioned Portal catalog.

WRITEffmpeg.audio_duck

• Contract tier: agent_ready
• Risk: write
• Catalog version: 2026-07-12.3
• Descriptor hash: 36256558e349900b345a75ea6cac2caf9ec1372cd0f0d2986d2404977e14ad73

Use this to mix voice over music while automatically reducing music during speech. It queues a new audio asset using bounded compressor controls.

Request Body

{
  "jsonrpc": "2.0",
  "id": "ffmpeg-audio-duck-example",
  "method": "tools/call",
  "params": {
    "name": "ffmpeg.audio_duck",
    "arguments": {
      "voice_asset_id": "voice_asset_id_123",
      "music_asset_id": "music_asset_id_123",
      "ratio": "",
      "bitrate": "",
      "priority": "",
      "attack_ms": "",
      "threshold": "",
      "music_gain": "",
      "release_ms": "",
      "output_format": "output_format_example"
    }
  }
}

Arguments Schema

{
  "type": "object",
  "required": [
    "voice_asset_id",
    "music_asset_id"
  ],
  "properties": {
    "ratio": {
      "anyOf": [
        {
          "type": "number"
        },
        {
          "type": "null"
        }
      ],
      "description": "Compressor ratio used for voice-driven music ducking."
    },
    "bitrate": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Optional FFmpeg bitrate string accepted by the bounded operation."
    },
    "priority": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "description": "Optional queue priority configured by the server, such as urgent or batch."
    },
    "attack_ms": {
      "anyOf": [
        {
          "type": "integer"
        },
        {
          "type": "null"
        }
      ],
      "description": "Ducking compressor attack time in milliseconds."
    },
    "threshold": {
      "anyOf": [
        {
          "type": "number"
        },
        {
          "type": "null"
        }
      ],
      "description": "Signal threshold used to trigger ducking."
    },
    "music_gain": {
      "anyOf": [
        {
          "type": "number"
        },
        {
          "type": "null"
        }
      ],
      "description": "Background-music gain multiplier within server limits."
    },
    "release_ms": {
      "anyOf": [
        {
          "type": "integer"
        },
        {
          "type": "null"
        }
      ],
      "description": "Ducking compressor release time in milliseconds."
    },
    "output_format": {
      "type": "string",
      "default": "m4a",
      "description": "Requested supported container or codec family for the new audio asset."
    },
    "music_asset_id": {
      "type": "string",
      "description": "Stable ID of the staged background music asset."
    },
    "voice_asset_id": {
      "type": "string",
      "description": "Stable ID of the staged voice or dialogue audio asset."
    }
  },
  "additionalProperties": false
}

Output Schema

{
  "type": "object",
  "required": [
    "job_id",
    "cache_hit"
  ],
  "properties": {
    "job_id": {
      "type": "string",
      "description": "Stable ID used with the job readback tools."
    },
    "cache_hit": {
      "type": "boolean",
      "description": "Whether a matching completed result was reused."
    },
    "output_asset_ids": {
      "type": "array",
      "items": {
        "type": "string"
      },
      "description": "Completed output asset IDs when immediately available from cache."
    }
  },
  "additionalProperties": false
}

Code Examples

cURL

curl -X POST 'https://portal.madpanda3d.com/api/mcp' \
  -H 'Authorization: Bearer mad_live_***' \
  -H 'Content-Type: application/json' \
  -d '{
  "jsonrpc": "2.0",
  "id": "ffmpeg-audio-duck-example",
  "method": "tools/call",
  "params": {
    "name": "ffmpeg.audio_duck",
    "arguments": {
      "voice_asset_id": "voice_asset_id_123",
      "music_asset_id": "music_asset_id_123",
      "ratio": "",
      "bitrate": "",
      "priority": "",
      "attack_ms": "",
      "threshold": "",
      "music_gain": "",
      "release_ms": "",
      "output_format": "output_format_example"
    }
  }
}'

Node.js

const response = await fetch('https://portal.madpanda3d.com/api/mcp', {
  method: 'POST',
  headers: {
    Authorization: 'Bearer mad_live_***',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
  "jsonrpc": "2.0",
  "id": "ffmpeg-audio-duck-example",
  "method": "tools/call",
  "params": {
    "name": "ffmpeg.audio_duck",
    "arguments": {
      "voice_asset_id": "voice_asset_id_123",
      "music_asset_id": "music_asset_id_123",
      "ratio": "",
      "bitrate": "",
      "priority": "",
      "attack_ms": "",
      "threshold": "",
      "music_gain": "",
      "release_ms": "",
      "output_format": "output_format_example"
    }
  }
}),
});
const data = await response.json();
console.log(data);

Python

import requests

url = 'https://portal.madpanda3d.com/api/mcp'
headers = {
    'Authorization': 'Bearer mad_live_***',
    'Content-Type': 'application/json',
}
payload = {
  "jsonrpc": "2.0",
  "id": "ffmpeg-audio-duck-example",
  "method": "tools/call",
  "params": {
    "name": "ffmpeg.audio_duck",
    "arguments": {
      "voice_asset_id": "voice_asset_id_123",
      "music_asset_id": "music_asset_id_123",
      "ratio": "",
      "bitrate": "",
      "priority": "",
      "attack_ms": "",
      "threshold": "",
      "music_gain": "",
      "release_ms": "",
      "output_format": "output_format_example"
    }
  }
}
response = requests.post(url, headers=headers, json=payload, timeout=60)
print(response.json())

Example Responses

200 Success

{
  "ok": true,
  "message": "Tool ffmpeg.audio_duck executed successfully.",
  "note": "Response shape varies by MCP tool. Inspect live responses for exact fields."
}

502 Upstream Error

{
  "ok": false,
  "classification": "upstream_http_error",
  "message": "Upstream MCP returned a non-success status."
}