What does it cost to convert AVI to Opus?

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

How large can the AVI 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 / AVI to Opus

Convert AVI to Opus

To convert AVI to Opus, send one POST to /v1/audio-convert with the AVI source and "to": "opus" in the body. Left out, "to" falls back to its default "mp3", so a Opus request has to send it. 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 AVI to Opus 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.avi",
  "to": "opus"
}

Response

200 OK
payment-response: <base64 settlement receipt>

{
  "source_url": "https://grist.tools/samples/av/pair-clip.avi",
  "bytes": 76302,
  "source_container": "avi",
  "format": "opus",
  "bitrate_kbps": null,
  "sample_rate": null,
  "audio_bytes": 33814,
  "audio_base64": "T2dnUwACAAAAAAAAAAAAAAAAAAAAAGS5xGoBE09wdXNIZWFkAQE4AUAfAAAAAABP..."
}

Source file: av/pair-clip.avi, 74.5 KB (76,302 bytes). 4 s AVI file made by ffmpeg: a 64x36 PNG video stream at 1 fps (a slate field with a small amber square moving right) and a mono 8 kHz 16-bit PCM audio track of two 500 Hz triangle beeps; no subtitle stream. The recorded run returned 33 KB (33,814 bytes) of Opus, 44% of the source size, with the source read as the avi container. Decoded, the Opus in audio_base64 opens with 4F 67 67 53 00 02 00 00 00 00 00 00 (ASCII OggS). Recorded with ffmpeg 8.1.2.

In the sample itself, the avih main header sets 1,000,000 microseconds per frame, 4 frames, 2 streams and a 64 by 36 frame; the stream headers are vids with handler MPNG, rate 1 over scale 1 and auds, rate 8,000 over scale 1, format tag 0x0001 at 8,000 Hz and 16 bits; an idx1 chunk indexes the frames at the end of the file. In the returned Opus: the first Ogg page, flagged as the beginning of the stream, has stream serial 0 and one 19-byte packet, the OpusHead: version 1, 1 channel, a pre-skip of 312 samples, an input sample rate of 8,000 Hz and channel mapping family 0.

03Format notes

AVI as a source

AVI is a RIFF container whose form type at byte eight is the four characters AVI followed by a space. Grist checks that form type, not the extension, before ffmpeg sees the file. Three of the conversion services on these pages accept it. audio-convert reads the first audio stream and ignores video; video-thumbnail seeks at the demuxer and decodes exactly one frame with audio disabled; subtitle-extract maps a subtitle stream by its zero-based index. That last route has a practical gap: ffmpeg's AVI muxer writes no text subtitle stream, only DivX XSUB bitmaps, so no real AVI with text captions could be produced for an example, and the AVI subtitle pages carry none. An AVI whose subtitle index matches nothing is refused rather than answered with an empty result. Each response reports the sniffed container as avi alongside the size of the fetched file.

Opus as a target

An Opus result is libopus-encoded audio inside an Ogg container: the ogg muxer writes it, and the recorded outputs begin with the OggS capture pattern followed by an OpusHead identification header. For that reason a returned Opus file is recognised as ogg if it is submitted again, and opus never appears as a source slug. bitrate_kbps controls the lossy encode, and an optional sample_rate may be chosen from the closed set; left out, ffmpeg normally follows the source rate. The input's duration is checked first, then the first audio stream alone is encoded, excluding video, metadata and chapters. Pinned ffmpeg and bit-exact flags make repeated calls return the same bytes. With no bitrate given the encoder's default rate applies, and for the recorded low-rate mono examples that default produced larger files than the MP3 default.

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 AVI to Opus?: $0.003 per call, paid in USDC on Base via x402.
How large can the AVI 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.