The Timeline Masterclass: How to Sync Subtitles to Video Frames
The AI gets most of the timing right on the first pass. But every video has moments where a subtitle appears a beat too early, lingers too long, or is missing entirely. The timeline is where you fix all of that. This guide walks you through every timing control in the Stra.ai subtitle editor so you can get every line synced perfectly before export.
How the timeline works
The timeline runs along the bottom of the editor and shows the full audio waveform of your video. Each subtitle segment appears as a small block sitting directly on top of the waveform, labeled with its translated text and its duration in seconds.
Clicking anywhere on the timeline moves the playhead to that position and jumps the video preview to that exact moment. This is the fastest way to navigate to a specific part of your video without scrubbing through the work area.
To move left and right along the timeline, hold Shift and scroll with your mouse wheel.
To zoom in or out, use the zoom controls on the right side of the timeline. Zoom in when you need frame-level precision. Zoom out when you want to see the full video at once.
Selecting a segment
Click any subtitle block on the timeline to select it. The block highlights in yellow and the corresponding row in the work area highlights at the same time. Both the timeline and the work area stay in sync, so you can work from either side depending on what is easier at that moment.
Adjusting timing by dragging
To move a subtitle segment to a different position on the timeline, click and drag the block left or right. Drop it where you want the subtitle to appear.
To change how long a segment stays on screen, drag the left or right edge of the block. Dragging the right edge forward makes the subtitle linger longer. Dragging it back shortens the display time. This works exactly like trimming a clip in any video editor.
Use the video preview while you drag to confirm the subtitle is appearing and disappearing at the right moment relative to the speech.
Adding a missing subtitle segment
If the AI missed a line of dialogue, you can add it manually in three steps.
First, click on the timeline at the point where the missing dialogue begins. The playhead will move to that position.
Second, use the zoom controls to zoom in on the waveform until you can clearly see the shape of the speech you want to capture.
Third, click the plus button in the toolbar. A new blank segment appears at the playhead position, highlighted in yellow, and a new empty row appears in the work area at the same time.
You can now drag the new block along the timeline to align it exactly with the audio, and stretch its edges to match the length of the dialogue. Type your translation directly into the empty row in the work area.
Re-transcribing a segment from the timeline
If a segment exists on the timeline but the transcription is wrong, you can ask the AI to listen to that audio again without reprocessing the whole project.
Click the three-dot menu in the upper corner of the segment block on the timeline. Select Re-transcribe this segment. The block will show a Re-listening status while the AI processes that section of audio. After a few moments it will update the transcription and generate a new translation automatically.
What happens when segments overlap
If two subtitle blocks overlap on the timeline, Stra.ai gives display priority to the block that comes next in sequence. The earlier block will be cut off rather than both showing at the same time. This prevents double subtitles from appearing on screen.
If you notice an overlap, fix it by shortening the earlier segment or moving it back so there is a clean gap between the two blocks.
What to do next
You can now control exactly when every subtitle appears and disappears. The next step is refining the text itself and styling the output before export.
To edit translation text and style, go to Subtitle Work Area: Pro-Tips for Editing
To export your finished subtitles, go to Finalizing Your Subs: How to Export SRT and Burned-in Captions
To go back to the editor overview, go to AI Subtitles Overview: Navigating the Subtitle Interface
Continue here: Subtitle Work Area: Pro-Tips for Editing