What does it cost to convert Ogg to MP3?

$0.003 per call, paid in USDC on Base via x402.

How large can the Ogg file be?

Up to 100 MB (104,857,600 bytes), and at most 60 min (3,600 s) of media. Past a limit the call answers too_large (413).

What happens if the conversion 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.

catalogue / tools / Audio & video / Ogg to MP3

Convert Ogg to MP3

To convert Ogg to MP3, send one POST to /v1/audio-convert with the Ogg source and "to": "mp3" in the body. "mp3" is the schema default of "to", so the field may also be left out. Each call costs $0.003 in USDC on Base via x402, with no account and no API key. The source file can be up to 100 MB and 60 min (3,600 s) long.

Endpoint: POST /v1/audio-convert
Price: $0.003 per call
Service: audio-convert
Docs: /docs/audio-convert

01Limits

Limit	Value
Largest source file	100 MB (104,857,600 bytes)
Longest input	60 min (3,600 s)
Timeout	94 s
Source formats	AIFF, AVI, FLAC, MKV, MP3, MP4, Ogg, WAV
Output formats	AAC, FLAC, MP3, Opus, WAV

02Example

A real Ogg to MP3 run of audio-convert.

Request

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

{
  "url": "https://grist.tools/samples/av/pair-clip.ogg",
  "to": "mp3"
}

Response

200 OK
payment-response: <base64 settlement receipt>

{
  "source_url": "https://grist.tools/samples/av/pair-clip.ogg",
  "bytes": 12553,
  "source_container": "ogg",
  "format": "mp3",
  "bitrate_kbps": null,
  "sample_rate": null,
  "audio_bytes": 4196,
  "audio_base64": "SUQzBAAAAAAACgAAAAAAAAAAAAD/4xjEAAxoAub5QBAAh1QgCdy3AiAECgDB/D8Q..."
}

Source file: av/pair-clip.ogg, 12.3 KB (12,553 bytes). 4 s Ogg file: a 64x36 Theora video stream at 1 fps (a slate field with a small amber square moving right) and a mono 8 kHz FLAC audio track of two 500 Hz triangle beeps, both muxed by ffmpeg, plus a two-cue OGM text subtitle stream added by the generator. The recorded run returned 4.1 KB (4,196 bytes) of MP3, 33% of the source size, with the source read as the ogg container. Decoded, the MP3 in audio_base64 opens with 49 44 33 04 00 00 00 00 00 0A 00 00. Recorded with ffmpeg 8.1.2.

In the sample itself, 16 Ogg pages carry 3 logical streams: Theora 3.2.1 video of 64 by 36 pixels at 1 frame per second (serial 0), FLAC 1.0 mapping audio at 8,000 Hz with 1 channel (serial 1) and an OGM text stream (serial 2). The end-of-stream pages hold granule positions 2,250 for serial 2, 67 for serial 0 and 32,000 for serial 1. In the returned MP3: it opens with an ID3v2.4 tag with 10 bytes of body, then an MPEG 2.5 Layer III frame header at byte 20: 8 kbps, 8,000 Hz, mono.

03Format notes

Ogg as a source

An Ogg file opens with the capture pattern OggS, and the container can carry Vorbis, Opus or Theora streams. Grist sniffs that pattern and hands Ogg to three of the conversion services on these pages. Audio conversion decodes the first audio stream, leaving any Theora picture aside. A thumbnail request seeks before opening the input and decodes a single frame from the first video stream, discarding sound. Caption extraction maps a subtitle stream counted from zero among the subtitle streams and serialises it through ffmpeg. Because audio-convert writes its Opus output inside Ogg, a file produced by that service comes back as an Ogg source, not as a separate Opus format. Theora is a lossy video codec, so a frame taken from it carries compression noise into the thumbnail, unlike a clip whose video stream is itself stored losslessly.

MP3 as a target

MP3 is the default value of audio-convert's to field, encoded with the pinned libmp3lame codec. The mp3 muxer needs no seeking, so output streams straight to a pipe instead of a temporary file. bitrate_kbps applies to this lossy destination; when it is omitted, no audio bitrate argument is passed, the encoder's own default applies, and the response reports the bitrate as null. An optional sample_rate selects from the closed set, otherwise ffmpeg normally follows the source. Only the first audio stream is encoded, and video, chapters and metadata are left out, with bit-exact flags keeping the bytes reproducible for the pinned ffmpeg. Even with source metadata removed, each recorded MP3 output still begins with an ID3v2 tag written by the muxer. Inputs whose duration exceeds the service limit are refused before encoding.

04Errors

Code	HTTP
`invalid_input`	`400`
`blocked_target`	`403`
`unreachable_target`	`424`
`upstream_timeout`	`424`
`unsupported_content_type`	`415`
`too_large`	`413`
`unprocessable`	`422`
`internal`	`500`

When each is raised, and what it means for payment: /docs/audio-convert.

05Questions

What does it cost to convert Ogg to MP3?: $0.003 per call, paid in USDC on Base via x402.
How large can the Ogg file be?: Up to 100 MB (104,857,600 bytes), and at most 60 min (3,600 s) of media. Past a limit the call answers too_large (413).
What happens if the conversion 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.