LAPLACE Cap's subtitle generation is built on the Soniox async transcription API. It transcribes an uploaded audio or video file — or a remote URL — offline, producing a subtitle file with timestamps
Unlike real-time STT, this feature targets post-production on recordings — a fast way to produce subtitle material for editing once a stream ends
Features
- Upload a local file (audio or video), or enter a remote URL directly
- Speaker diarization separates multiple speakers automatically and marks each one with a speaker label
- Very long files are chunked automatically, so the duration limit of a single API request does not apply
- Optionally configure S3-compatible storage: the audio file goes to object storage first and reaches Soniox as a URL, which suits very large files
- Finished transcripts export as standard SRT or plain-text TXT
Usage
Prerequisites
- Enter your Soniox API key on the General settings page
- To handle large files in URL mode, also configure S3-compatible storage under General
Submit a Transcription Job
- Switch to the Generate Subtitles tab
- Choose an input method:
- Local File: click the upload area, or drag in an audio or video file
- Remote URL: enter a publicly accessible link to an audio or video file
- Configure the options you need:
| Option | Description |
|---|---|
| Language Hints | Names the languages likely to appear in the file, improving recognition accuracy |
| Speaker Diarization | Separates multiple speakers automatically when enabled |
| Domain / Topic / Terms | Context information, used the same way as in real-time STT |
- Click Start Transcription to submit the job, and wait for it to finish
Export Subtitles
- The result appears on the page once transcription finishes
- Click Export SRT or Export TXT to download the subtitle file
- Import the subtitle file directly into the LAPLACE Cap media editor for further editing
S3 Storage Configuration
When a file is large — usually over a few hundred MB — route it through S3-compatible storage:
- On the General settings page, fill in S3 Endpoint, Access Key ID, Secret Access Key, Bucket name, and the public access URL
- Once configured, LAPLACE Cap uploads each file to S3 and submits the resulting public URL to Soniox for transcription
S3 settings are stored only in your local browser, never uploaded to LAPLACE servers
Notes
- Subtitle generation uses Soniox's Async models, which bill through a different endpoint than real-time STT; Soniox's official pricing is authoritative
- Chunked transcription splits long audio into segments submitted in parallel, which is faster, but a few words can be clipped at chunk boundaries — proofread in the media editor before exporting
Last updated on September 19, 2026