How much does a waveform-data call cost?

$0.003 per call, paid in USDC on Base via x402, with no account and no API key.

What does waveform-data return?

A JSON object with 8 top-level fields: source_url, bytes, container, sample_rate, sample_count, duration_seconds, peak_count and peaks. The example on this page is a real call over av/waveform-beeps.wav.

What happens when a waveform-data call fails?

The tool answers with a typed JSON error from the errors table. Payment is settled only after the tool has produced its result; a call that fails inside the tool is never settled. A 503 upstream_unavailable can follow a settled call; the x402 payments guide covers it, 429, 402 and an uncertain 500.

catalogue / tools / Audio & video / Waveform Data API

Waveform Data API

Reduces an audio file to a fixed number of normalised waveform peaks for drawing, without shipping samples.

Endpoint: POST /v1/waveform-data
Price: $0.003 per call
Family: Audio & video
Docs: /docs/waveform-data

01When to use it

Decoding audio to peaks needs ffmpeg AND a hardened fetch: an agent that pulls the URL itself walks past every SSRF control, and carrying an ffmpeg per call is not something an agent does inline.

When not to use it

The input is over 100 MB (104,857,600 bytes): waveform-data answers too_large (413).
The destination needs more than 90 s to answer: the call ends with upstream_timeout (424).
The destination is on a private or local network: the network guard refuses it with blocked_target (403).

02Parameters

Field	Type	Required	Description
url	string	yes	Absolute http(s) URL of an audio or video file, up to 2048 characters, in a recognised container (MP4/MOV, Matroska/WebM, AVI, Ogg, WAV, FLAC, AIFF or MP3); its first audio stream is decoded to mono.
peaks	integer	no	Number of buckets to return, 1 to 4000, default 200; each is the largest absolute sample in an equal slice of the track, scaled to 0..1 against 16-bit full scale. Default: 200.
sample_rate	integer	no	Decode rate in Hz, one of 4000, 8000, 11025, 16000, 22050 or 44100, default 8000; it sets sample_count and how finely each bucket is scanned. Default: 8000.

03Limits

Limit	Value
Size cap	100 MB (104,857,600 bytes)
Timeout	90 s

04Example

The published example of waveform-data, verbatim: the request body and the response it returns.

Request

POST /v1/waveform-data
content-type: application/json
payment-signature: <base64 x402 payload>

{
  "url": "https://grist.tools/samples/av/waveform-beeps.wav",
  "peaks": 20,
  "sample_rate": 8000
}

Response

200 OK
payment-response: <base64 settlement receipt>

{
  "source_url": "https://grist.tools/samples/av/waveform-beeps.wav",
  "bytes": 32044,
  "container": "wav",
  "sample_rate": 8000,
  "sample_count": 16000,
  "duration_seconds": 2,
  "peak_count": 20,
  "peaks": [
    0.25,
    0.25,
    0.25,
    0.25,
    0,
    0,
    0,
    0.5,
    0.5,
    0.5,
    0.5,
    0,
    0,
    0,
    0.8999,
    0.8999,
    0.8999,
    0.8999,
    0,
    0
  ]
}

Sample file: av/waveform-beeps.wav. Two-second mono 16-bit PCM WAV at 8 kHz: three 0.4 s 500 Hz triangle-wave beeps at rising level separated by silence, generated from integer arithmetic.

In the sample itself: The RIFF header counts 32,036 bytes after itself, and the fmt chunk, in its own field order, declares audio format 1 (integer PCM), 1 channel, 8,000 Hz, 16,000 bytes per second, a block align of 2 bytes and 16 bits per sample. The data chunk right after it holds 32,000 bytes of samples, 2 s at that rate.

Response field	Type	In the example
source_url	string	"https://grist.tools/samples/av/waveform-beeps.wav"
bytes	number	32044
container	string	"wav"
sample_rate	number	8000
sample_count	number	16000
duration_seconds	number	2
peak_count	number	20
peaks	array	20 items

05Call it from code

JavaScript

// waveform-data: $0.003 per call, paid in USD Coin on eip155:8453 via x402
// Install: npm install @x402/fetch@2 @x402/evm@2 viem@2
// Save as client.mjs (ES module, Node 18+), export EVM_PRIVATE_KEY with the paying wallet's key in your shell, then run: node client.mjs
// The wrapper reads the 402 (payment-required), signs and retries with payment-signature.
import { wrapFetchWithPayment, x402Client, decodePaymentResponseHeader } from '@x402/fetch'
import { ExactEvmScheme } from '@x402/evm/exact/client'
import { privateKeyToAccount } from 'viem/accounts'

const account = privateKeyToAccount(process.env.EVM_PRIVATE_KEY)
const client = new x402Client().register('eip155:8453', new ExactEvmScheme(account))
const fetchWithPayment = wrapFetchWithPayment(fetch, client)

const body = {
  "url": "https://grist.tools/samples/av/waveform-beeps.wav",
  "peaks": 20,
  "sample_rate": 8000
}

const res = await fetchWithPayment('https://grist.tools/v1/waveform-data', {
  method: 'POST',
  headers: { 'content-type': 'application/json' },
  body: JSON.stringify(body),
})
console.log(res.status, await res.json())
const settle = res.headers.get('payment-response')
if (settle) console.log(decodePaymentResponseHeader(settle).transaction)

Python

# waveform-data: $0.003 per call, paid in USD Coin on eip155:8453 via x402
# Install: pip install "x402[requests,evm]>=2.24,<3"
# The session reads the 402 (payment-required), signs and retries with payment-signature.
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http import decode_payment_response_header
from x402.http.clients.requests import x402_requests
from x402.mechanisms.evm.exact import register_exact_evm_client
from x402.mechanisms.evm.signers import EthAccountSigner

account = Account.from_key(os.environ["EVM_PRIVATE_KEY"])
client = x402ClientSync()
register_exact_evm_client(client, EthAccountSigner(account), networks="eip155:8453")
session = x402_requests(client)

payload = {
    "url": "https://grist.tools/samples/av/waveform-beeps.wav",
    "peaks": 20,
    "sample_rate": 8000
}

res = session.post("https://grist.tools/v1/waveform-data", json=payload)
print(res.status_code, res.json())
settle = res.headers.get("payment-response")
if settle:
    print(decode_payment_response_header(settle).transaction)

curl

# waveform-data: $0.003 per call, paid in USD Coin on eip155:8453 via x402
# 1. Unpaid call: HTTP 402, the requirements in the payment-required header (base64 JSON) and in the body.
curl -i -X POST 'https://grist.tools/v1/waveform-data' -H 'content-type: application/json' -d '{"url":"https://grist.tools/samples/av/waveform-beeps.wav","peaks":20,"sample_rate":8000}'

# 2. Same call with the signed payment (an EIP-3009 authorization, EIP-712 signed: it cannot be
#    typed by hand). x-payment is accepted as the v1 alternative. HTTP 200 carries payment-response.
curl -i -X POST 'https://grist.tools/v1/waveform-data' -H 'content-type: application/json' -H 'payment-signature: <base64 x402 payload>' -d '{"url":"https://grist.tools/samples/av/waveform-beeps.wav","peaks":20,"sample_rate":8000}'

06Errors

Code	HTTP	For this service
invalid_input	400	The body does not match the schema; its fields are url, peaks and sample_rate.
blocked_target	403
unreachable_target	424
upstream_timeout	424
unsupported_content_type	415
too_large	413
unprocessable	422
internal	500

Input that is rejected before the tool runs (malformed JSON, schema mismatch, body over the size limit) is never charged.

When each code is raised, and what it means for payment: /docs/waveform-data.

07Questions

How much does a waveform-data call cost?: $0.003 per call, paid in USDC on Base via x402, with no account and no API key.
What does waveform-data return?: A JSON object with 8 top-level fields: source_url, bytes, container, sample_rate, sample_count, duration_seconds, peak_count and peaks. The example on this page is a real call over av/waveform-beeps.wav.
What happens when a waveform-data call fails?: The tool answers with a typed JSON error from the errors table. Payment is settled only after the tool has produced its result; a call that fails inside the tool is never settled. A 503 upstream_unavailable can follow a settled call; the x402 payments guide covers it, 429, 402 and an uncertain 500.

08Related

Audio & video guide