Subtitle Frame Rate Converter
Scale subtitle timecodes between video frame rates. Fix the 4% NTSC/PAL speedup, match 24fps cinema subtitles to 25fps video, and more.
Drag & drop your subtitle file here
Drag and drop subtitle files here or click to browse
Key Features
Engineered for video editors and localization teams. Helps enforce common subtitle timing rules and formatting.
Subtitle Frame Rate Converter Live Execution Demo
In-Memory Processing
File parsing, mutations, and time shifts for standard tools run in browser memory without sending subtitle files to our servers.
Millisecond Precision
Millisecond-accurate timecode parsing and arithmetic prevent synchronization drift across desktop and web players.
Fault-Tolerant Engine
Automatic multi-encoding detection and syntax sanitization gracefully handle malformed cues and unexpected linebreaks.
Common Use Cases
Real-world scenarios across video post-production, course transcription, and global localization.
NTSC to PAL Conversion
Film is captured at 23.976 fps but European PAL releases play at 25 fps, a 4.04% speedup. Scaling timecodes by 25/23.976 fixes the drift.
Cinema to TV
Movie subtitles authored at 24 fps need a 25/24 ratio to stay in sync on a 25 fps broadcast master.
Broadcast Captioning
Move captions between 29.97 and 30 fps deliverables for North American broadcast without re-timing each cue by hand.
High Frame Rate Video
Convert standard 24/25 fps subtitles to 48/50/60 fps HFR masters while keeping every cue aligned.
Interlaced to Progressive
Repurpose 59.94/60 fps interlaced captions for 29.97/30 fps progressive web delivery.
SRT FPS Repair
Rescale SRT cue timing when a 23.976, 24, or 29.97 fps subtitle track is played against a different video master.
How It Works
Streamlined end-to-end processing pipeline engineered for speed and precision.
Upload & Import
Select your subtitle file.
Format Analysis
Pick the original video frame rate the subtitles were timed for.
Configuration
Pick the target frame rate of the video you want to play them with.
Processing
Choose the output format (SRT, VTT, or ASS).
Verify & Export
Click Convert and download the rescaled subtitle file.
Why Choose AllSubConverter?
Client-Side Privacy
Standard tools run in your browser so standard files are not uploaded to our servers.
Fast Local Parsing
Optimized processing engine parses and converts files directly in your browser.
Generous Batches
Up to 50 MB per file, 200 files or 1 GB total per batch.
Universal Compatibility
Runs in modern browsers across Windows, macOS, Linux, iOS, and Android.
More Subtitle Tools
Frequently Asked Questions
It multiplies every cue start and end time by the ratio targetFps / sourceFps. For 23.976 to 25 that ratio is about 1.0427, which shortens each cue by roughly 4% and exactly cancels the NTSC-to-PAL speedup.
Sync adds a fixed offset or a two-point linear shift. Frame rate conversion multiplies the timecodes, so the correction grows with time. That is exactly what a frame-rate mismatch needs.
Input: SRT, VTT, ASS, SSA, LRC, SBV, TTML, SCC, STL, SMI. Output: SRT, VTT, or ASS.
The speed adjuster scales timing by an arbitrary playback-speed factor you choose (for example 1.25x). The frame rate converter instead computes the ratio from two named frame rates, so you get the exact mathematical correction for a frame-rate mismatch.
Gradual drift that gets worse toward the end of the video is the classic symptom of a frame-rate mismatch. Converting from the source to the target frame rate removes the drift across the whole file.
Yes. Everything runs client-side. No subtitle data is ever sent to a server.
Related Articles
Convert YouTube JSON3 Subtitles to SRT, VTT, or LRC | AllSubConverter
Download YouTube captions as JSON3 and convert them to SRT, VTT, or LRC. Step-by-step guide covering yt-dlp, the JSON3 format, and free online conversion.
Add Pinyin & Furigana to Subtitles | AllSubConverter
Learn how to add pinyin to Chinese subtitles and furigana to Japanese subtitles. AI-powered reading aids for language learners, karaoke, and study materials.