A millisecond offset moves every subtitle cue in a file earlier or later by the same amount. It changes only timing. The wording, the cue order, the duration of each cue, and the playback speed of the video all stay the same. That makes an offset the right fix when subtitles are consistently early or late from the first line to the last. It is the wrong fix when subtitles start in sync and slide further out as the program runs.
How SRT stores the timing you are changing
An SRT file is a plain-text subtitle sidecar. It sits beside the video file and is not part of the picture, which is why a player can load the same subtitles against different versions of a program. Each cue is a block with three parts: a sequence number, a timing line, and one or more lines of text, followed by a blank line.
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00:01:16,195 --> 00:01:18,400
The train leaves at six.
The timing line holds a start time, the arrow -->, and an end time. Each time is written as HH:MM:SS,mmm: hours, minutes, and seconds in two digits each, then a comma, then milliseconds in three digits. Official Prime Video Tech Docs, in its page “SRT file content information and troubleshooting” (last updated August 5, 2024), describes the same convention: two-digit time units everywhere except milliseconds. That guidance applies to Prime Video’s submission context, so treat it as the platform’s rule rather than a rule for every player.
SRT has no formal standard. The Library of Congress format description notes that it is widely used without being formally standardized, which is why parsers and players can disagree at the edges, such as how they handle malformed timestamps, extra blank lines, or styling tags.
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What a fixed millisecond offset does
A signed offset is added to every cue’s start and end time. A positive value moves cues later; a negative value moves them earlier. Subtitle Edit documents signed millisecond values such as -1500 and +1500, and it also accepts an hh:mm:ss:ms form for its offset parameter. Because the shift is applied uniformly, the gap between cues and the length of each cue are unchanged.
The arithmetic below shows the effect on two cues. It is a worked calculation of the documented operation, not a test of a particular file.
| Original cue | Offset | Result |
|---|---|---|
| 00:01:16,195 –> 00:01:18,400 | -1500 ms (1.5 s earlier) | 00:01:14,695 –> 00:01:16,900 |
| 00:00:03,000 –> 00:00:05,250 | +1500 ms (1.5 s later) | 00:00:04,500 –> 00:00:06,750 |
A negative offset can push an early cue below zero. Check the first few cues after any negative shift, because a cue that would start before 00:00:00,000 needs a decision: trim it, move it, or accept the tool’s handling, and then confirm that choice in the player.
Decide whether the problem is an offset at all
Before you apply a correction, find out whether the error is constant or grows. Pick one line of dialogue near the start and one near the end, and note how far the subtitle is from the spoken word at each point.
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- If the gap is near zero at the start and grows toward the end, the file has drift. A single shift will fix one part and break another, so the correction has to scale the timings rather than move them.
To estimate the scale, divide the extra delay by the elapsed time. For example, a cue that is 2 seconds late at the 10-minute mark and in sync at the start has drifted about 2 ÷ 600 ≈ 0.33 percent. That figure points toward a frame-rate or speed mismatch between the subtitle file and the video, which Subtitle Edit handles as separate operations from the offset.
| Symptom | Operation to consider | What to verify |
|---|---|---|
| Every cue is about equally early or late | Fixed signed offset | Check the first, middle, and last cues; confirm the sign and size of the shift. |
| Timing is right at the start and grows worse later | Frame-rate or speed correction | Compare the gap at the beginning and end; do not expect a single offset to fix it. |
| The target application needs another subtitle format | Format conversion | Check timing, text, and styling in the target player. |
| Many files need the same fix | Batch or command-line processing | Keep originals and inspect a representative sample of outputs. |
This mapping is editorial guidance based on how Subtitle Edit separates shifting timings, frame-rate conversion, and speed adjustment into distinct functions. It describes which operation fits which symptom, not a diagnosis of any specific file.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Apply the correction and convert the format
Convert the file only after you know the timing is right, so a format change does not hide a timing error.
- Save an untouched copy of the original subtitle file in a separate folder, with a name that says it is the original.
- Open the file in Subtitle Edit. For a fixed shift, use the Adjust All Times function, enter the signed offset, and apply it to all lines.
- Play the video with the adjusted file and check a line near the start, one near the middle, and one near the end.
- Save the file in SRT format using the save-as workflow, and keep the new file under a name that differs from the original.
- For a batch of files, use Subtitle Edit’s documented command-line converter with the same offset value, then inspect a sample of the outputs rather than trusting every file.
- Open the converted file in a plain-text editor and confirm the timing lines follow the
HH:MM:SS,mmm --> HH:MM:SS,mmmpattern and the first and last cues look right. - Play the converted file in the player you intend to use, at the same three points as before.
Format conversion changes how the file is written. Formats that carry styling or positioning instructions can lose those details when saved as plain SRT, and SRT players do not all render formatting tags the same way. If a line shows raw tags or appears in the wrong place, the problem is usually the player’s styling support, not the timing.
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Troubleshooting checklist
- Subtitles are early everywhere: the offset needs to be positive so the cues move later. Confirm the sign before applying it again.
- Subtitles are correct at the start and wrong later: stop applying offsets and check for a frame-rate or speed mismatch.
- The player ignores the file: confirm the file is saved as plain text in an encoding the player supports, and check whether the player expects the subtitle file to share the video’s filename. Behaviour varies by player, so check its documentation.
- Raw tags appear on screen: the player does not support those styling tags. Remove them from a copy of the file or use a format the player handles.
- A cue disappears after a negative shift: it probably started before zero. Trim or move it, then recheck the first lines of the file.
Subtitle Edit’s documentation is the primary reference for the operations named here. Software labels and interfaces can change between versions, so if a menu item differs from the one above, check the version you have installed.
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