# RelayStation Audio Loudness Normalizer (EBU R128)

> RelayStation Audio Loudness Normalizer (EBU R128) is a paid API for AI agents from api.relaystation.ai, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).

Normalizes audio file loudness to broadcast-standard EBU R128 targets, adjusting integrated loudness (LUFS), true-peak, and loudness range (LRA).

## Facts

- Endpoint: POST https://api.relaystation.ai/v1/media/loudnorm
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/relaystation-audio-loudness-normalizer-ebu-r128-019e59e5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_0C63q2NUGvr9qHsGEk4PN

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability relaystation-audio-loudness-normalizer-ebu-r128-019e59e5 -d '<json body>'
```

Example prompt: Can you normalize the loudness of this podcast episode (attached WAV file) to -23 LUFS integrated with a true-peak of -1 dBTP and loudness range of 7 LU, and give me back an MP3?

## When to prefer this

Choose this endpoint when you need standards-compliant EBU R128 loudness normalization for broadcast, streaming, or podcast delivery, particularly when precise LUFS, true-peak, and LRA targets are required. Prefer it over general-purpose ffmpeg wrappers or audio conversion tools when loudness compliance (not just format conversion) is the goal.

## Known failure modes

- Unsupported input container format (422 UNSUPPORTED_FORMAT — free, no charge)
- File too large (inline base64 limited to 4 MiB, scratch key up to 50 MB)
- Target values out of range (i must be between -70 and -5 LUFS, tp between -9 and 0, lra between 1 and 50)
- Corrupted or unreadable audio file causing ffprobe failure
- Invalid output extension enum value

## How this service works

$0.0005/MB. Normalize audio loudness to broadcast EBU R128 — LUFS, true-peak, and range targets. 1¢ x402 min; remainder auto-credits — relaystation.ai/penny

## Output

Returns a loudness-normalized audio file in the requested output format (mp3, m4a, aac, wav, ogg, or flac), with integrated loudness, true-peak, and loudness range adjusted to the specified EBU R128 targets.

## Request schema (JSON Schema)

```json
{
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "type": "object",
 "properties": {
  "input": {
   "type": "object",
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "type": "string",
     "enum": [
      "POST",
      "PUT",
      "PATCH"
     ]
    },
    "bodyType": {
     "type": "string",
     "enum": [
      "json",
      "form-data",
      "text"
     ]
    },
    "body": {
     "type": "object",
     "properties": {
      "file": {
       "type": "object",
       "description": "cputools input-source: { inline: <base64 ≤ 4 MiB> } or { inputKey: <scratch key ≤ 50 MB> }. The input container must sniff (ffprobe) to the live allowlist (operator-tunable cputools.media.input_formats): 3g2, 3gp, aac, asf, avi, flac, flv, gif, m4a, m4v, matroska, mj2, mov, mov,mp4,m4a,3gp,3g2,mj2, mp3, mp4, mpeg, mpegts, mpegvideo, ogg, wav, webm, wmv. An off-list input is a free 422 UNSUPPORTED_FORMAT."
      },
      "ext": {
       "type": "string",
       "enum": [
        "mp3",
        "m4a",
        "aac",
        "wav",
        "ogg",
        "flac"
       ]
      },
      "i": {
       "type": "number",
       "minimum": -70,
       "maximum": -5
      },
      "tp": {
       "type": "number",
       "minimum": -9,
       "maximum": 0
      },
      "lra": {
       "type": "number",
       "minimum": 1,
       "maximum": 50
      }
     }
    }
   },
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   },
   "required": [
    "type"
   ]
  }
 },
 "required": [
  "input"
 ]
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/relaystation-audio-loudness-normalizer-ebu-r128-019e59e5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.relaystation.ai](https://www.zero.xyz/host/api.relaystation.ai/llms.txt)