# Karaoke subtitles

- Human page: https://happytails.ai/en/subtitle-tools/karaoke-subtitles/
- Markdown: https://happytails.ai/en/subtitle-tools/karaoke-subtitles.md
- Structured JSON: https://happytails.ai/agents/en/subtitle-tools/karaoke-subtitles/index.json
- Visibility: public

## Tool capabilities

| Property | Value |
| --- | --- |
| Tool ID | `karaoke-subtitles` |
| Category | subtitle-tools |
| Implementation | Registered implementation. Registration alone is not a production-quality guarantee. |
| Browser execution | Use the visible action or interactive controls. |
| Browser processing | Server required |
| HTTP API | /api/v1/tools/karaoke-subtitles/run |
| Browser-agent interface | run_current_tool |

### Implementation notes

Local Whisper forced alignment. English, up to one minute and 5,000 transcript characters. Review word timing; singing and overlapping voices may align poorly.

### Inputs and settings

No free-text input is required. Use the file inputs and/or settings below.

Accepted browser files: `.wav,.mp3,.m4a,.flac,.mp4,.webm`. Choose one file.

Browser file-input limit: 20971520 bytes in total. HTTP limits can differ.

| Setting | Meaning | Control type | Default | Constraints |
| --- | --- | --- | --- | --- |
| `transcript` | Matching English transcript or lyrics | textarea | "" |  |

### HTTP contract

API calls process supplied data on the server. The website origin is `https://happytails.ai`. Server API hosting is not connected on the public website yet. Use your local server origin to test these requests.

```http
POST https://happytails.ai/api/v1/tools/karaoke-subtitles/run
Content-Type: application/json
```

[Detailed operation reference](https://happytails.ai/en/api/tools/karaoke-subtitles.md) · [Shared API guide](https://happytails.ai/en/api.md)

#### Limits

| Limit | Value |
| --- | --- |
| request_bytes | 31457280 |
| input_characters | 1000000 |
| files_bytes | 20971520 |
| max_files | 1 |
| timeout_seconds | 90 |

#### Complete input schema

```json
{
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "input": {
      "type": "string",
      "maxLength": 1000000,
      "default": "",
      "description": "Plain text input. File tools use files instead unless otherwise documented."
    },
    "options": {
      "type": "object",
      "additionalProperties": false,
      "properties": {
        "transcript": {
          "type": "string",
          "description": "Matching English transcript or lyrics",
          "default": ""
        }
      }
    },
    "files": {
      "type": "array",
      "maxItems": 1,
      "items": {
        "type": "object",
        "required": [
          "name",
          "base64"
        ],
        "additionalProperties": false,
        "properties": {
          "name": {
            "type": "string",
            "maxLength": 200,
            "description": "Filename only, no path."
          },
          "mime": {
            "type": "string",
            "maxLength": 150
          },
          "bytes": {
            "type": "integer",
            "minimum": 0,
            "description": "Optional decoded byte count; must match content if supplied."
          },
          "base64": {
            "type": "string",
            "contentEncoding": "base64",
            "description": "File bytes as padded base64. Use the tool-specific limits.files_bytes value for the total decoded input size."
          }
        }
      }
    }
  }
}
```

#### Complete output schema

```json
{
  "type": "object",
  "required": [
    "tool",
    "result"
  ],
  "properties": {
    "tool": {
      "type": "string"
    },
    "result": {
      "type": "object",
      "required": [
        "text",
        "files"
      ],
      "properties": {
        "text": {
          "type": [
            "string",
            "null"
          ]
        },
        "data": {
          "description": "Parsed JSON when the textual result is JSON."
        },
        "name": {
          "type": "string"
        },
        "mime": {
          "type": "string"
        },
        "files": {
          "type": "array",
          "items": {
            "type": "object",
            "required": [
              "name",
              "mime",
              "bytes",
              "base64"
            ],
            "properties": {
              "name": {
                "type": "string"
              },
              "mime": {
                "type": "string"
              },
              "bytes": {
                "type": "integer"
              },
              "base64": {
                "type": "string",
                "contentEncoding": "base64"
              }
            }
          }
        }
      }
    }
  }
}
```

#### Error and retry handling

Failures return a non-200 status and `error.code` plus `error.message`. Correct invalid input before retrying; retry server-busy responses with bounded backoff. Returned files contain Base64 data, not persistent download URLs. Decode and inspect the output before treating conversion as successful. See the shared API guide for the complete status and timeout rules.

### Browser-agent workflow

1. Open the human page in a browser that supports WebMCP.
2. Discover the interface exposed by that page; use its actual schema.
3. Select files on the page first when the tool requires files.
4. Call `run_current_tool` with valid input and settings.
5. Inspect the returned result or error and the displayed output. Retrieve files from the displayed download links.

Calls do not automatically copy or download results. Browser permissions still apply. Interface availability alone is not proof of successful execution.

### Planning specification

Generate word-highlight timings from lyrics or a transcript; preview highlighting and export ASS. Singing and accompaniment must be separately evaluated.

This describes intended requirements. Use the implementation notes, interface schema and observed output to determine current support.

### Complete machine-readable capability record

```json
{
  "id": "karaoke-subtitles",
  "category": "subtitle-tools",
  "built": true,
  "requirements": "Generate word-highlight timings from lyrics or a transcript; preview highlighting and export ASS. Singing and accompaniment must be separately evaluated.",
  "implementation": {
    "fields": [
      {
        "key": "transcript",
        "label": "Matching English transcript or lyrics",
        "type": "textarea",
        "value": ""
      }
    ],
    "files": true,
    "accept": ".wav,.mp3,.m4a,.flac,.mp4,.webm",
    "multiple": false,
    "input": false,
    "processing": "Server required",
    "native": true,
    "extra": true,
    "maxFileBytes": 20971520,
    "note": "Local Whisper forced alignment. English, up to one minute and 5,000 transcript characters. Review word timing; singing and overlapping voices may align poorly.",
    "experience": {
      "automatic": false,
      "single": false,
      "label": "Your text",
      "placeholder": "Type or paste your input…",
      "help": "Up to 1,000,000 characters. Review the settings before running.",
      "action": null
    },
    "mode": "explicit",
    "interactive": false
  },
  "execution": "POST /api/v1/tools/karaoke-subtitles/run",
  "api": {
    "id": "karaoke-subtitles",
    "name": "Karaoke subtitles",
    "category": "subtitle-tools",
    "description": "Create word-timed karaoke subtitles from matching speech and text.",
    "notes": "Local Whisper forced alignment. English, up to one minute and 5,000 transcript characters. Review word timing; singing and overlapping voices may align poorly.",
    "human_path": "/en/subtitle-tools/karaoke-subtitles/",
    "method": "POST",
    "endpoint": "/api/v1/tools/karaoke-subtitles/run",
    "schema_url": "/api/v1/tools/karaoke-subtitles",
    "input_schema": {
      "type": "object",
      "additionalProperties": false,
      "properties": {
        "input": {
          "type": "string",
          "maxLength": 1000000,
          "default": "",
          "description": "Plain text input. File tools use files instead unless otherwise documented."
        },
        "options": {
          "type": "object",
          "additionalProperties": false,
          "properties": {
            "transcript": {
              "type": "string",
              "description": "Matching English transcript or lyrics",
              "default": ""
            }
          }
        },
        "files": {
          "type": "array",
          "maxItems": 1,
          "items": {
            "type": "object",
            "required": [
              "name",
              "base64"
            ],
            "additionalProperties": false,
            "properties": {
              "name": {
                "type": "string",
                "maxLength": 200,
                "description": "Filename only, no path."
              },
              "mime": {
                "type": "string",
                "maxLength": 150
              },
              "bytes": {
                "type": "integer",
                "minimum": 0,
                "description": "Optional decoded byte count; must match content if supplied."
              },
              "base64": {
                "type": "string",
                "contentEncoding": "base64",
                "description": "File bytes as padded base64. Use the tool-specific limits.files_bytes value for the total decoded input size."
              }
            }
          }
        }
      }
    },
    "output_schema": {
      "type": "object",
      "required": [
        "tool",
        "result"
      ],
      "properties": {
        "tool": {
          "type": "string"
        },
        "result": {
          "type": "object",
          "required": [
            "text",
            "files"
          ],
          "properties": {
            "text": {
              "type": [
                "string",
                "null"
              ]
            },
            "data": {
              "description": "Parsed JSON when the textual result is JSON."
            },
            "name": {
              "type": "string"
            },
            "mime": {
              "type": "string"
            },
            "files": {
              "type": "array",
              "items": {
                "type": "object",
                "required": [
                  "name",
                  "mime",
                  "bytes",
                  "base64"
                ],
                "properties": {
                  "name": {
                    "type": "string"
                  },
                  "mime": {
                    "type": "string"
                  },
                  "bytes": {
                    "type": "integer"
                  },
                  "base64": {
                    "type": "string",
                    "contentEncoding": "base64"
                  }
                }
              }
            }
          }
        }
      }
    },
    "processing": "Server; self-hosted native engine, no external conversion service",
    "limits": {
      "request_bytes": 31457280,
      "input_characters": 1000000,
      "files_bytes": 20971520,
      "max_files": 1,
      "timeout_seconds": 90
    }
  },
  "agent_processing": "Server; self-hosted native engine, no external conversion service",
  "browser_agent": {
    "supported": true,
    "name": "run_current_tool",
    "discovery": "WebMCP on the human page in a supporting browser",
    "verification": "See audit/API-AUDIT.md; availability is not verification"
  }
}
```

## Page guide

Create word-timed karaoke subtitles from matching speech and text.

## Useful next steps

- [Subtitle alignment](https://happytails.ai/en/subtitle-tools/subtitle-alignment/): Align a matching English transcript to recorded speech. ([Markdown](https://happytails.ai/en/subtitle-tools/subtitle-alignment.md))

## How to use Karaoke subtitles

1. Choose a file in WAV, MP3, M4A, FLAC, MP4 or WEBM.
2. Review the settings, then choose Run Karaoke subtitles.
3. Review the result, then use Copy result or a download link when available.

## What to expect

Create word-timed karaoke subtitles from matching speech and text. Local Whisper forced alignment. English, up to one minute and 5,000 transcript characters. Review word timing; singing and overlapping voices may align poorly.