Repair gradual subtitle drift with two anchors
SRT anchor sync is for subtitles that do not need a simple global offset. The first line may be close, the middle may be slightly late, and the end may be far out of sync. This usually happens when the subtitle came from a video version with a different frame rate, a slightly different export duration, or edits that changed the timeline gradually.
Instead of adding the same number of seconds to every cue, this tool asks for two known-good points. Pick a cue near the beginning and a cue later in the file, then enter the correct video time for each cue. The tool compares those anchor times with the original SRT times and recalculates the rest of the file by stretching or compressing the timing curve.
How to choose anchor points
Good anchors should be easy to identify in the video. Choose a clear spoken phrase, a scene change with a visible line, or a subtitle that starts exactly on a recognizable word. Avoid ambiguous background speech, music-only captions, or very short cues that are hard to place precisely.
The first anchor should usually be near the start of the useful section, and the second anchor should be later in the same continuous version of the video. If the file has a major edit in the middle, split the problem into sections and run anchor sync separately. A single pair of anchors works best for smooth drift, not for missing scenes.
Why anchor sync is different from time shift
A normal time shift moves every subtitle by the same offset. That is perfect when all cues are exactly one second late, but it cannot fix drift where the error grows over time. Anchor sync changes the scale of the timeline so the first anchor and the second anchor both land on their correct positions.
This makes the tool useful for frame-rate mismatch, PAL to NTSC timing differences, edited lecture exports, translated subtitles copied from a slightly different source, and long interviews where small timing errors accumulate. It is a lightweight alternative to opening a full subtitle editor when the drift is mostly linear.
Validate the synced SRT before delivery
After anchor sync, preview the anchor cues first. Then check at least one cue before the first anchor, one between the anchors, and one after the second anchor. If the middle is still wrong, your source may have multiple edits or non-linear drift, and the file should be corrected in smaller sections.
Keep the original subtitle file and record the two anchor values you used. If another reviewer needs to reproduce the fix, the cue numbers and correct seconds are enough to explain the timing decision. This is especially helpful for localization teams that need repeatable subtitle QA notes.