A Browser-First Workflow for Video Subtitles, Audio, and Export

Short-form video work often jumps between several tools: extract the audio, transcribe speech, translate the transcript, and finally burn subtitles into the video. For footage under two minutes, much of that computation can run directly in a modern browser.

Video Describer AI follows a browser-first approach. The original file is used locally for preview, frame sampling, audio extraction, speech recognition, and subtitled-video export. A network request is made only for steps that genuinely require a cloud AI service.

What runs locally in the browser?

Video inspection and limit checks

After you choose a video, the browser reads its file size, duration, and resolution. The current workspace accepts videos up to 50 MB and two minutes. Validating before analysis avoids uploading a file only to discover that it cannot be processed.

Audio extraction

Save Audio uses FFmpeg WebAssembly files hosted with the application. Conversion runs in the current browser tab and downloads an MP3 directly, without sending the entire video to the server first.

The FFmpeg runtime must load on first use and can then be reused. High-resolution footage may still require significant memory, so closing other demanding tabs can improve stability.

Subtitle generation with Whisper Tiny

Subtitle generation converts the video's audio track into 16 kHz mono audio and passes it to a Whisper Tiny model running in the browser. You can select the spoken language before starting or leave the setting on automatic detection.

The first model load depends on device performance and browser caching. Once transcription finishes, cues appear on a timeline linked to video playback. The active cue highlights as the video plays, and selecting a cue seeks the video to the matching time.

SRT, VTT, or a subtitled video?

Video Describer AI provides three practical output paths:

• SRT works with most editors and video platforms and is best for continued editing.
• VTT is designed for web video players and browser-based projects.
• Subtitled video renders the active subtitle track into an exported video that does not depend on a separate subtitle file during playback.

Choose SRT when you still need to revise text, typography, or placement. Export a subtitled video when you need a self-contained result that displays captions immediately.

Why does subtitle translation use a cloud service?

Speech recognition can run with a specialized compact model, while reliable multilingual translation generally benefits from a larger language model. The current translation workflow sends subtitle text and the target language to the configured Fal service; it does not upload the original video for translation.

Translated cues keep the original timestamps, so they can be reviewed, downloaded, or used for subtitled-video export. Review the source transcript first so recognition mistakes do not propagate into the translation.

What is stored in Recent Analyses?

After transcription, Recent Analyses stores the video metadata, recognition language, subtitle text, and cue timings under the “Subtitles” type. The original video, extracted audio, and temporary model input held in browser memory are not stored in that history item.

History items can be permanently deleted one at a time or cleared together. Opening a subtitle record shows its complete timeline in a separate dialog without replacing the active workspace above.

Practical ways to improve subtitle accuracy

1. Use footage with clear speech and lower background music when possible.
2. Select the known language instead of always relying on automatic detection.
3. Manually verify names, brands, numbers, and technical terms.
4. Correct the source transcript before translation.
5. Play the full result once before exporting a subtitled video to verify timing and line breaks.

Browser processing will not run at the same speed on every device, but it reduces unnecessary transfer of original footage and keeps the most common short-video tasks in one workspace.