{
  "title": "Stereo to mono downmixer",
  "human_url": "https://happytails.ai/en/media-tools/stereo-to-mono-downmixer/",
  "agent_url": "https://happytails.ai/agents/en/media-tools/stereo-to-mono-downmixer/",
  "language": "en",
  "markdown_url": "https://happytails.ai/en/media-tools/stereo-to-mono-downmixer.md",
  "content": "Stereo to mono downmixer\nMix a stereo recording down to mono with a documented formula, and see how likely the left and right channels are to cancel each other first.\nHow to use Stereo to mono downmixer\nChoose a stereo recording.\nPick a mix formula, or enter your own left and right coefficients.\nMix down and read the correlation and cancellation risk.\nDownload the mono WAV and the JSON report.\nHow can we improve this tool?\nReport a problem or share an idea.\nPlease leave out private information. Your message and the tool name go to our team via PostHog.\nUseful next steps\nAudio channel router\nMP3 to WAV\nCompress audio\nFormulas\nAverage is 0.5 times left plus 0.5 times right, which never clips. Minus 3 dB uses 0.7071 for each side, which keeps the loudness of uncorrelated material but can clip on loud centred sound. Left or right keeps one side only. Custom uses your own coefficients from -2 to 2.\nCancellation risk\nThe report gives the correlation of the two channels over the whole file. Below 0 the channels are often out of phase and parts of the sound will cancel in mono, so the risk is high. From 0 to 0.3 it is moderate, above 0.3 low. The mono fold-down change compares the mid level with the average channel level.\nBefore you export\nIf the risk is high, check the source for a channel with inverted polarity, or use the left or right formula instead of a sum.",
  "content_format": "text/plain",
  "visibility": "public",
  "links": [
    {
      "name": "Audio channel router",
      "url": "https://happytails.ai/en/media-tools/audio-channel-router/"
    },
    {
      "name": "MP3 to WAV",
      "url": "https://happytails.ai/en/media-tools/mp3-to-wav/"
    },
    {
      "name": "Compress audio",
      "url": "https://happytails.ai/en/media-tools/compress-audio/"
    }
  ],
  "tool": {
    "id": "stereo-to-mono-downmixer",
    "category": "media-tools",
    "built": true,
    "requirements": "One stereo recording up to 256 MiB and 10 minutes; custom coefficients from -2 to 2. 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: mono WAV in the source format or the format you choose, and a JSON report.",
    "implementation": {
      "fields": [
        {
          "key": "formula",
          "label": "Mix formula",
          "value": "minus-3db",
          "type": "select",
          "values": [
            "minus-3db",
            "average",
            "left",
            "right",
            "custom"
          ],
          "labels": {
            "left": "Left channel only",
            "right": "Right channel only"
          }
        },
        {
          "key": "left",
          "label": "Custom left coefficient",
          "value": "0.5",
          "type": "number",
          "min": -2,
          "max": 2,
          "step": 0.01
        },
        {
          "key": "right",
          "label": "Custom right coefficient",
          "value": "0.5",
          "type": "number",
          "min": -2,
          "max": 2,
          "step": 0.01
        },
        {
          "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. Mixes one stereo recording up to 10 minutes to mono and reports the cancellation risk.",
      "experience": {
        "automatic": false,
        "single": false,
        "inputMaxLength": 1000000,
        "inputMode": "text",
        "label": "Stereo audio file",
        "placeholder": "Choose a stereo recording",
        "help": "Left and right are mixed into one mono channel. Up to 1,000,000 characters. Review the settings before running.",
        "action": "Convert file"
      },
      "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"
    }
  },
  "markdown": "# Stereo to mono downmixer\n\n- Human page: https://happytails.ai/en/media-tools/stereo-to-mono-downmixer/\n- Markdown: https://happytails.ai/en/media-tools/stereo-to-mono-downmixer.md\n- Structured JSON: https://happytails.ai/agents/en/media-tools/stereo-to-mono-downmixer/index.json\n- Visibility: public\n\n## Tool capabilities\n\n| Property | Value |\n| --- | --- |\n| Tool ID | `stereo-to-mono-downmixer` |\n| Category | media-tools |\n| Implementation | Registered implementation. Registration alone is not a production-quality guarantee. |\n| Browser execution | Use the visible action or interactive controls. |\n| Browser processing | Browser; see tool notes for network behavior. |\n| HTTP API | Not callable through HTTP. |\n| Browser-agent interface | run_current_tool |\n\n### Implementation notes\n\nRuns locally in your browser. Mixes one stereo recording up to 10 minutes to mono and reports the cancellation risk.\n\n### Inputs and settings\n\nNo free-text input is required. Use the file inputs and/or settings below.\n\nAccepted browser files: `.wav,.mp3,.m4a,.aac,.flac,.ogg,.oga,.opus,.webm,audio/*`. Choose one file.\n\nBrowser file-input limit: 268435456 bytes in total. HTTP limits can differ.\n\n| Setting | Meaning | Control type | Default | Constraints |\n| --- | --- | --- | --- | --- |\n| `formula` | Mix formula | select | \"minus-3db\" | Allowed: minus-3db, average, left, right, custom |\n| `left` | Custom left coefficient | number | \"0.5\" | min=-2 max=2 step=0.01 |\n| `right` | Custom right coefficient | number | \"0.5\" | min=-2 max=2 step=0.01 |\n| `encoding` | WAV sample format | select | \"match\" | Allowed: match, pcm16, pcm24, float32 |\n\n### Browser-agent workflow\n\n1. Open the human page in a browser that supports WebMCP.\n2. Discover the interface exposed by that page; use its actual schema.\n3. Select files on the page first when the tool requires files.\n4. Call `run_current_tool` with valid input and settings.\n5. Inspect the returned result or error and the displayed output. Retrieve files from the displayed download links.\n\nCalls do not automatically copy or download results. Browser permissions still apply. Interface availability alone is not proof of successful execution.\n\n### Planning specification\n\nOne stereo recording up to 256 MiB and 10 minutes; custom coefficients from -2 to 2. 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: mono WAV in the source format or the format you choose, and a JSON report.\n\nThis describes intended requirements. Use the implementation notes, interface schema and observed output to determine current support.\n\n### Complete machine-readable capability record\n\n```json\n{\n  \"id\": \"stereo-to-mono-downmixer\",\n  \"category\": \"media-tools\",\n  \"built\": true,\n  \"requirements\": \"One stereo recording up to 256 MiB and 10 minutes; custom coefficients from -2 to 2. 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: mono WAV in the source format or the format you choose, and a JSON report.\",\n  \"implementation\": {\n    \"fields\": [\n      {\n        \"key\": \"formula\",\n        \"label\": \"Mix formula\",\n        \"value\": \"minus-3db\",\n        \"type\": \"select\",\n        \"values\": [\n          \"minus-3db\",\n          \"average\",\n          \"left\",\n          \"right\",\n          \"custom\"\n        ],\n        \"labels\": {\n          \"left\": \"Left channel only\",\n          \"right\": \"Right channel only\"\n        }\n      },\n      {\n        \"key\": \"left\",\n        \"label\": \"Custom left coefficient\",\n        \"value\": \"0.5\",\n        \"type\": \"number\",\n        \"min\": -2,\n        \"max\": 2,\n        \"step\": 0.01\n      },\n      {\n        \"key\": \"right\",\n        \"label\": \"Custom right coefficient\",\n        \"value\": \"0.5\",\n        \"type\": \"number\",\n        \"min\": -2,\n        \"max\": 2,\n        \"step\": 0.01\n      },\n      {\n        \"key\": \"encoding\",\n        \"label\": \"WAV sample format\",\n        \"value\": \"match\",\n        \"type\": \"select\",\n        \"values\": [\n          \"match\",\n          \"pcm16\",\n          \"pcm24\",\n          \"float32\"\n        ],\n        \"labels\": {\n          \"match\": \"Match source sample format\"\n        }\n      }\n    ],\n    \"registrationFamily\": \"audio-dsp-edit\",\n    \"presentation\": \"metrics\",\n    \"files\": true,\n    \"input\": false,\n    \"accept\": \".wav,.mp3,.m4a,.aac,.flac,.ogg,.oga,.opus,.webm,audio/*\",\n    \"maxFileBytes\": 268435456,\n    \"inputErrorCode\": \"AUDIO_DSP_EDIT_TOO_LONG\",\n    \"note\": \"Runs locally in your browser. Mixes one stereo recording up to 10 minutes to mono and reports the cancellation risk.\",\n    \"experience\": {\n      \"automatic\": false,\n      \"single\": false,\n      \"inputMaxLength\": 1000000,\n      \"inputMode\": \"text\",\n      \"label\": \"Stereo audio file\",\n      \"placeholder\": \"Choose a stereo recording\",\n      \"help\": \"Left and right are mixed into one mono channel. Up to 1,000,000 characters. Review the settings before running.\",\n      \"action\": \"Convert file\"\n    },\n    \"mode\": \"explicit\",\n    \"interactive\": false\n  },\n  \"execution\": \"Browser interface\",\n  \"api\": null,\n  \"browser_agent\": {\n    \"supported\": true,\n    \"name\": \"run_current_tool\",\n    \"discovery\": \"WebMCP on the human page in a supporting browser\",\n    \"verification\": \"See audit/API-AUDIT.md; availability is not verification\"\n  }\n}\n```\n\n## Page guide\n\nMix a stereo recording down to mono with a documented formula, and see how likely the left and right channels are to cancel each other first.\n\n### How to use Stereo to mono downmixer\n\n1. Choose a stereo recording.\n2. Pick a mix formula, or enter your own left and right coefficients.\n3. Mix down and read the correlation and cancellation risk.\n4. Download the mono WAV and the JSON report.\n\nHow can we improve this tool?\n\nReport a problem or share an idea.\n\nPlease leave out private information. Your message and the tool name go to our team via PostHog.\n\n## Useful next steps\n\n- [Audio channel router](https://happytails.ai/en/media-tools/audio-channel-router/) ([Markdown](https://happytails.ai/en/media-tools/audio-channel-router.md))\n\n- [MP3 to WAV](https://happytails.ai/en/media-tools/mp3-to-wav/) ([Markdown](https://happytails.ai/en/media-tools/mp3-to-wav.md))\n\n- [Compress audio](https://happytails.ai/en/media-tools/compress-audio/) ([Markdown](https://happytails.ai/en/media-tools/compress-audio.md))\n\n## Formulas\n\nAverage is 0.5 times left plus 0.5 times right, which never clips. Minus 3 dB uses 0.7071 for each side, which keeps the loudness of uncorrelated material but can clip on loud centred sound. Left or right keeps one side only. Custom uses your own coefficients from -2 to 2.\n\n### Cancellation risk\n\nThe report gives the correlation of the two channels over the whole file. Below 0 the channels are often out of phase and parts of the sound will cancel in mono, so the risk is high. From 0 to 0.3 it is moderate, above 0.3 low. The mono fold-down change compares the mid level with the average channel level.\n\n### Before you export\n\nIf the risk is high, check the source for a channel with inverted polarity, or use the left or right formula instead of a sum.\n"
}