Auto Captions for Silent Films 2026
Step-by-step process for adding timed captions to a 1927 silent film using Flixly Auto Captions. Covers upload, timing adjustments, and export of SRT plus burned-in MP4 in under 20 minutes.
TL;DR
Upload your silent film clip to the Auto Captions tool, select Gemini 3.1 Flash TTS for timing, generate 87 blocks in four minutes, adjust overlaps on the timeline, then export SRT and MP4. The workflow finishes a 12-minute 1080p file in 19 minutes with 92 synced lines.
You hold a 12-minute 1080p scan of a 1927 silent short with intertitles already burned in and need English captions synced for a festival upload by midnight.
Upload the source clip
Open the dashboard and head to the Auto Captions page. Drag the 1.2 GB MP4 file into the drop zone. The system detects 24 fps and 1920x1080 resolution automatically. A progress bar shows 100 percent upload in 47 seconds.
Pick generation settings
Select English as the target language. Choose the 3-second minimum display time per caption line. Toggle on speaker labels even though the film has no dialogue. Pick Gemini 3.1 Flash TTS as the timing model because it processes 720 frames per minute on average.
Available style presets
- Classic intertitle font at 48 pt
- Modern sans at 36 pt with 10 percent background opacity
- Subtle bottom-third placement at 42 pt
Run the first pass
Hit generate. The job consumes 180 credits and finishes in 4 minutes 12 seconds. The output shows 87 caption blocks with start and end timestamps accurate to 40 ms.
Review timings on the timeline
Scrub through at 0:00-0:18 where the first intertitle appears. Adjust the end time from 0:17.8 to 0:19.2 to match the on-screen text fade. Repeat for the 12 instances where burned-in titles overlap generated captions.
Add descriptive lines for visual action
Insert five new lines describing key actions such as "Train pulls into station" at 3:44. Link each new line to the exact frame reference. Export a side-by-side preview at 720p to confirm readability on mobile.
Export the final file
Download the SRT file and the burned-in MP4 version. Both files retain the original 24 fps and embed the captions as soft subs. Total project time from upload to export lands at 19 minutes.
The finished 12-minute file now carries 92 synced caption lines ready for the festival platform. Repeat the same sequence on your next reel by returning to Auto Captions.
Verify output quality
Play the exported MP4 in VLC with subtitles forced on. Check that every line clears the screen before the next action starts. Confirm no caption exceeds 42 characters per line on the 1080p version.
Integrate with other Flixly tools
If you later add a voice-over track, route the SRT timestamps into Text to Speech for consistent pacing. The same timing data works with Lip Sync Video when you decide to animate mouth movements on a restored print.
Compare caption density
| Segment | Original intertitles | Generated captions | Average length (chars) |
|---|---|---|---|
| 0-3 min | 11 | 19 | 31 |
| 3-6 min | 14 | 24 | 28 |
| 6-9 min | 9 | 21 | 34 |
| 9-12 min | 13 | 28 | 29 |
The table shows the generator added 45 extra descriptive lines while keeping average length under 35 characters.
Handle edge cases
For scenes with rapid cuts every 8 frames, raise the minimum display time to 4 seconds. The system splits longer lines automatically. When a single intertitle runs 11 seconds, the preview splits it into two blocks at the natural sentence break.
Store the project
Save the workspace so the next team member can reopen the same 12-minute timeline without re-uploading the source. The SRT file remains editable in any standard subtitle tool if further tweaks are required outside Flixly.
Frequently Asked Questions
What are auto captions for silent videos?▾
Auto captions for silent videos use AI to generate text descriptions synced to visuals, like actions or scenes, without audio input. Flixly's tool analyzes frames for 98% accurate timestamps. This makes old films accessible and engaging for modern viewers.
How does Flixly sync text to video?▾
Flixly syncs text to video by processing motion and key frames in seconds. Upload your clip, select silent mode, and it aligns captions precisely. Exports include customizable fonts and positions for professional results.
Best AI captioning for films 2026?▾
In 2026, Flixly's Auto Captions tops for films with visual AI from Seedance 2.0. It handles 10-minute clips at low cost. Competitors lag in silent accuracy and speed.
Are auto captions accessibility video tools?▾
Yes, auto captions are key accessibility video tools, meeting WCAG guidelines for deaf users. They boost engagement by 12% on average. Flixly ensures multilingual support for global compliance.
Cost of auto captions silent video addition?▾
Flixly charges 5 credits per 30 seconds for auto captions silent video addition. Free tier offers 100 credits monthly. Pro plans start at $9/month for unlimited.
Can I caption old silent films with AI?▾
AI easily captions old silent films by detecting actions frame-by-frame. Upload to Flixly, choose vintage style, and get synced text in 90 seconds. Perfect for restorations like Metropolis.
Flixly vs Runway for video captions?▾
Flixly outperforms Runway in silent caption accuracy (98% vs 92%) and speed. It supports longer videos and more languages at lower cost. Use Flixly for film projects.
