Subtitle Sync & Cleaner Studio
Shift timecodes with millisecond precision, adjust framerate drift (23.976 to 24/25 fps), sanitize hearing-impaired tags & HTML artifacts, and convert seamlessly between SRT, WebVTT, ASS, and plain TXT without uploading media files to any server.
Time Offset & Framerate Stretch
Sanitizer & Clean Rules
QA Telemetry & Stats
We verified that all client-side WebAssembly routines compile in isolated WebWorkers.
Technical Architecture & Browser Timecode Engine
ToolAcre utilizes native stream parsers and zero-copy WebAssembly algorithms executed entirely inside modern browser threads, assuring byte-perfect subtitle formatting.
Sub-Millisecond Regex AST Parser
High-throughput AST parser handling SubRip comma syntax (00:00:00,000), WebVTT decimal syntax (00:00:00.000), and ASS centisecond syntax without memory leaks.
Zero-Server Video Privacy & Media API
Local HTML5 video preview generates sandboxed memory pointers using URL.createObjectURL(file). Media files never hit remote networks or telemetry relays.
Drift Math & PAL/NTSC Interpolation
Exact rational arithmetic (24000/1001 ≈ 23.9760239) prevents cumulative rounding errors over 2+ hour feature films. Cues stay locked to speech waveforms.
Lossless Multi-Format Transcoder
Bidirectional conversion preserving cue alignments, ASS styling tags ({\pos(x,y)}), and WebVTT positioning headers without truncating unicode symbols or emojis.
Subtitle Synchronization & Formatting Guide
Are my subtitle files or attached reference videos uploaded to ToolAcre? expand_more
Never. ToolAcre operates on a strictly client-side architecture. Both subtitle texts (.srt, .vtt, .ass) and attached video files are held in your browser's private memory through HTML5 File and Blob APIs. There is zero server upload, zero backend database retention, and zero telemetry tracking.
How do I fix subtitles that gradually fall out of sync as the movie progresses? expand_more
Gradual desynchronization is almost always caused by a framerate mismatch rather than a fixed delay. For example, if your video was mastered at 25.000 fps (PAL) but your subtitle file was created for a 23.976 fps (NTSC Film) release, the captions will drift by about 4 seconds every 100 seconds. Select 23.976 as the Source and 25.000 as Target in our FPS Drift module to recalculate every timestamp with exact proportional scaling.
What is the structural difference between SRT and WebVTT formatting? expand_more
SubRip (.srt) uses a comma separator for milliseconds (00:01:23,456) and requires an incremental numeric index for every block. WebVTT (.vtt) is the modern web standard: it begins with the mandatory WEBVTT header, uses period decimal separators (00:01:23.456), supports optional cue settings (like line:80% align:center), and permits cues without numeric IDs.
Can I remove SDH / hearing-impaired descriptions without breaking timecodes? expand_more
Yes. The ToolAcre Sanitizer identifies bracketed audio descriptions (such as [Sirens wailing] or (Music swells)) and strips them. If a cue block contains exclusively an audio description, our engine prunes the entire empty cue and automatically re-indexes sequential cue IDs so video players render a clean stream without blinking empty captions.
Complementary Local In-Browser Utilities
Perform bulk string replacements, regex lookaheads, and clean markdown or raw text.
Cut clips, remux containers, extract MP3 audio, and re-encode H.264 video client-side.
Parse million-row delimited files, transform schema headers, and export optimized arrays.
Inspect tokens, verify signatures locally using WebCrypto API, and decode claims.