# Audio fade editor

- Human page: https://happytails.ai/en/media-tools/audio-fade-editor/
- Markdown: https://happytails.ai/en/media-tools/audio-fade-editor.md
- Structured JSON: https://happytails.ai/agents/en/media-tools/audio-fade-editor/index.json
- Visibility: public

## Tool capabilities

| Property | Value |
| --- | --- |
| Tool ID | `audio-fade-editor` |
| Category | media-tools |
| Implementation | Registered implementation. Registration alone is not a production-quality guarantee. |
| Browser execution | Use the visible action or interactive controls. |
| Browser processing | Browser; see tool notes for network behavior. |
| HTTP API | Not callable through HTTP. |
| Browser-agent interface | run_current_tool |

### Implementation notes

Runs locally in your browser. Fades one recording up to 10 minutes and 256 MiB and leaves every sample between the fades unchanged.

### Inputs and settings

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

Accepted browser files: `.wav,.mp3,.m4a,.aac,.flac,.ogg,.oga,.opus,.webm,audio/*`. Choose one file.

Browser file-input limit: 268435456 bytes in total. HTTP limits can differ.

| Setting | Meaning | Control type | Default | Constraints |
| --- | --- | --- | --- | --- |
| `fadeIn` | Fade in (seconds) | number | "1" | min=0 max=600 step=0.01 |
| `fadeOut` | Fade out (seconds) | number | "2" | min=0 max=600 step=0.01 |
| `curve` | Fade curve | select | "equal-power" | Allowed: equal-power, linear, s-curve, logarithmic |
| `encoding` | WAV sample format | select | "match" | Allowed: match, pcm16, pcm24, float32 |

### 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

One recording up to 256 MiB and 10 minutes, with fades from 0 to 600 seconds that together fit inside it. WAV is read with every sample intact; other formats are decoded by your browser at 48 kHz. Everything is processed on your device and nothing is uploaded. Download: WAV in the source format or the format you choose, and a JSON report.

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

### Complete machine-readable capability record

```json
{
  "id": "audio-fade-editor",
  "category": "media-tools",
  "built": true,
  "requirements": "One recording up to 256 MiB and 10 minutes, with fades from 0 to 600 seconds that together fit inside it. WAV is read with every sample intact; other formats are decoded by your browser at 48 kHz. Everything is processed on your device and nothing is uploaded. Download: WAV in the source format or the format you choose, and a JSON report.",
  "implementation": {
    "fields": [
      {
        "key": "fadeIn",
        "label": "Fade in (seconds)",
        "value": "1",
        "type": "number",
        "min": 0,
        "max": 600,
        "step": 0.01
      },
      {
        "key": "fadeOut",
        "label": "Fade out (seconds)",
        "value": "2",
        "type": "number",
        "min": 0,
        "max": 600,
        "step": 0.01
      },
      {
        "key": "curve",
        "label": "Fade curve",
        "value": "equal-power",
        "type": "select",
        "values": [
          "equal-power",
          "linear",
          "s-curve",
          "logarithmic"
        ]
      },
      {
        "key": "encoding",
        "label": "WAV sample format",
        "value": "match",
        "type": "select",
        "values": [
          "match",
          "pcm16",
          "pcm24",
          "float32"
        ],
        "labels": {
          "match": "Match source sample format"
        }
      }
    ],
    "registrationFamily": "audio-dsp-edit",
    "presentation": "metrics",
    "files": true,
    "input": false,
    "accept": ".wav,.mp3,.m4a,.aac,.flac,.ogg,.oga,.opus,.webm,audio/*",
    "maxFileBytes": 268435456,
    "inputErrorCode": "AUDIO_DSP_EDIT_TOO_LONG",
    "note": "Runs locally in your browser. Fades one recording up to 10 minutes and 256 MiB and leaves every sample between the fades unchanged.",
    "experience": {
      "automatic": false,
      "single": false,
      "inputMaxLength": 1000000,
      "inputMode": "text",
      "label": "Audio file",
      "placeholder": "Choose a recording",
      "help": "The fades are applied to the start and end of this file. Up to 1,000,000 characters. Review the settings before running.",
      "action": null
    },
    "mode": "explicit",
    "interactive": false
  },
  "execution": "Browser interface",
  "api": null,
  "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

Add a fade in and a fade out to a recording, with a choice of four fade curves, while every sample between the fades stays exactly as it was.

### How to use Audio fade editor

1. Choose the recording to fade.
2. Enter the fade in and fade out lengths in seconds.
3. Pick a fade curve and the WAV sample format.
4. Apply the fades and download the WAV file and the JSON report.

How can we improve this tool?

Report a problem or share an idea.

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## Useful next steps

- [Trim audio](https://happytails.ai/en/media-tools/trim-audio/) ([Markdown](https://happytails.ai/en/media-tools/trim-audio.md))

- [Audio crossfade mixer](https://happytails.ai/en/media-tools/audio-crossfade-mixer/) ([Markdown](https://happytails.ai/en/media-tools/audio-crossfade-mixer.md))

- [Increase audio volume](https://happytails.ai/en/media-tools/increase-audio-volume/) ([Markdown](https://happytails.ai/en/media-tools/increase-audio-volume.md))

## Fade curves

Linear changes the gain at a steady rate. Equal power follows a quarter sine, which sounds even when the fade overlaps other audio. S-curve starts and ends gently. Logarithmic moves at a steady rate in decibels over 60 dB, which sounds natural for long fade outs.

### What stays unchanged

Only the samples inside the fade in and fade out are multiplied. With the sample format set to match, a 16-bit or 24-bit WAV is written in its own format, so every sample between the fades is bit for bit the same as the source.

### Lengths

Fade lengths are rounded to the nearest sample. The two fades together cannot be longer than the recording; set a fade to 0 to skip it.