2026-09-30

ffmpeg -vn -ac 1 -ar 16000 as audio detach API fields

Audio detach rejects raw ffmpeg fields such as af, filter, cmd and codec. Map -ac, -ar and -ss/-to to channels, sample_rate and range; mp3 is 128 kbps.

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Audio detach compiles ffmpeg on the server, so sending af, filter, ffmpeg, cmd or codec fails with ffmpeg_fields_rejected. The four things people set on the command line have fields: channels, sample_rate, range and format.

Which flag maps to which field?

The mapping below follows the Audio detach docs; the flag column is the usual ffmpeg meaning.

ffmpeg options and audio detach fields, from the Sume docs read 2026-09-30.
ffmpeg idea	Detach field
Drop the video (`-vn`)	Implicit: the result is a new audio artifact
Mono (`-ac 1`)	`channels: "mono"` (default `source`)
Sample rate (`-ar 16000`)	`sample_rate`: 16000, 44100 or 48000; omit to inherit
Start and end (`-ss`, `-to`)	`range: { start, end? }` in seconds
128 kbps mp3	`format: "mp3"` (default is wav, `pcm_s16le`)

What is the speech-to-text shape?

The docs call 16000 plus channels: "mono" the STT shape.

curl -X POST https://api.sume.com/v1/audio-detach \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: detach-stt-001" \
  -d '{
    "video_url": "https://media.sume.com/artifacts/artf_demo/talk.mp4",
    "format": "wav",
    "channels": "mono",
    "sample_rate": 16000
  }'

What about filters like volume or fades?

Not on this surface: detach accepts no filtergraph. For level and fades in a finished video use Timeline 1.0 fields such as audio.gain_db, output.fade_in_seconds and soundtrack.duck_db.

How does the job run?

Audio detach defaults to mode: "async". Pass mode: "sync" to wait up to 30 seconds for a 200 finished job, or you get 202 and poll GET /v1/jobs/:id/status and GET /v1/jobs/:id/result. There is no GET /v1/audio-detach/:id. Idempotency-Key is required. The result is kind: audio_detach with audio_url, duration_seconds, format, channels and sample_rate; sample_rate is null when you omitted it and the source rate was inherited. A warnings list may appear on the result.

Detach is not clip inspection. For probing, stills or transcripts use video inspect; for a new MP4 cut use video trim, described in the Audio detach docs.

Sources

Audio detach