Join dubbed voiceover lines into one gapless file for a cent on Sume

Concatenate them. Sume timeline audio joins 1 to 20 ordered parts into one file for $0.01 flat. The join happens in the sample domain, so there is no re-synthesis and no silence at the seams, and you get back a durable media.sume.com URL plus the offsets where each part landed.

Concat, step by step

• operation: concat with parts[]. Each part is a url, with optional source_in and duration to take a slice.
• All URLs must already be this workspace's media.sume.com audio. Import first.
• Parts must share one channel layout, or you get audio_parts_channel_mismatch.
• Default mode is async. mode sync waits up to 30 seconds for a 200.
• Output is up to 1800 seconds.

Use the segment offsets

The result carries segments[] with index, start and duration_seconds for each part. Those are the offsets to re-base your video start times against, so a dubbed line lands under the shot it belongs to. If a join is needed only inside one render, put it in the render's audio.parts instead and skip this job.

Split the other way

To cut many ranges out of a talking-head MP4, run audio detach once ($0.01), then split here with up to 20 ranges, $0.01. Ranges may overlap, and an omitted end means the rest of the file. A 20-line script costs $0.02 to detach and split.

Keep wav when you join again

The docs advise wav when the file will be joined again or drives lip-sync; mp3 re-adds priming padding at every edge.

Concat request

curl -X POST https://api.sume.com/v1/timeline-1.0/audio \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: join-1" \
  -d '{"operation":"concat","parts":[{"url":"https://media.sume.com/artifacts/artf_demo/line1.wav"},{"url":"https://media.sume.com/artifacts/artf_demo/line2.wav"}]}'