Introduction
Finding that your beautifully translated subtitles have drifted out of sync with the video is a frustrating but common problem. The initial translation process itself does not change the time codes, so synchronisation loss usually points to errors in the source file or issues during the translation export and re-import process.
The core of the issue is often Frame Rate Mismatch or Encoding Corruption that was present before the translation began. By systematically correcting the source file’s timing data and ensuring clean UTF-8 encoding during the transfer, you can prevent this synchronisation disaster and maintain timing integrity across languages.
What Causes Translated Subtitles to Drift Out of Sync?
The translation tool itself does not touch the timing, meaning the sync loss originates from an existing flaw in the source file structure.
The most common culprit is an undetected frame-rate mismatch in the original subtitle file. For example, if the original subtitle file was made for a 25 frames per second (FPS) video but is used with a 23.976 FPS video, the translation will retain this progressive drift, causing perfect synchronisation at the beginning but complete out-of-sync by the end.
Another significant factor is the manual copy/Paste Error. You used an external online translator (instead of the internal Subtitle Edit tool) and manually copied the translated text back into a new file; you may have accidentally corrupted the time code format ( HH:MM:SS,MS) or deleted crucial line breaks, leading to sync chaos.
Finally, faulty format conversion can cause frame rate errors. If the original file was in a complex format (such as MicroDVD) and was converted to the SubRip Subtitle (SRT) format before translation, the time-code conversion process might have introduced subtle errors that only become apparent after translation.
How to Fix Frame Rate Drift Before Translation?
If tIf the sync progressively worsens throughout the movie, the frame rate is the underlying cause and must be corrected before you start translating. Correcting the drift requires matching the subtitle file’s speed to the video file’s actual speed. This step must be performed on the source language file before any translation is executed.
Identifying the Source and Target FPS
First, open your video file and go to Video > Show video info to confirm the video’s actual frame rate (frames per second, FPS). It will likely be 23.976, 24.000, or 25.000.
Next, open the subtitle file. Go tGo to Synchronisation> Change frame rate. “From frame rate” should match the rate the subtitle file was originally intended for, and the “To frame rate” must match your confirmed video FPS.
Applying the Frame Rate Conversion
Select the correct “To frame rate” option to match the video, then click OK. This action mathematically adjusts every timestamp in the subtitle file, correcting progressive drift before the translation process begins.
Save this newly corrected source file. Then, run the auto-translation process on this corrected version. The resulting translated file will retain perfect, drift-free synchronisation. To avoid sync errors, use internal translation tools throughout the process.
Sync errors are almost guaranteed when using an external website for translation, and manual translation goes out of sync, disrupting file integrity. You risk adding extra spaces or deleting a time-code marker. Copied text can also disturb the subtitle file’s internal structure, leading to misaligned lines and sync shifts if the Integrated Auto-Translate Feature is used.
Always use the built-in translation tool. Select all lines ( Ctrl+A) and go to Tools > Auto-translate (via Google/Nmt). The method only replaces the dialogue text within the existing time slots.
The time codes, line numbers, and formatting structure are completely protected throughout the entire process, ensuring a 100% lossless timing transfer.
Utilizing the Translation Helper Safely
If you must manually edit the translated text, use the Translation Helper ( Ctrl+Shift+T). This window locks the time code data and lets you edit only the dialogue text, preventing accidental deletion or corruption of the crucial timing markers.
How to Fix Sync Shifts After Using External Translators?
If yIf you have already translated the text externally, you likely have a file with correct text but completely broken synchronisation. The safest way to fix this is to copy the broken text onto a known-good source file, essentially stealing the correct time codes.
Stealing Time Codes via Point Sync
Open your translated subtitle file in one Subtitle Edit tab. Open the original (synced) file in another tab. Go to the Synchronisation menu. Click Point sync via other subtitles. Select the original synced file as a reference. Match the first and last lines of both files.
Click Sync. In Subtitle Edit, this will transfer the time codes from the perfectly synced source file to your newly translated text file, fixing the massive shift.
How to Check for Encoding Errors That Break Sync?
Encoding errors can corrupt line numbers, causing the parser to skip lines and leading the entire sync into chaos. If the file contains special characters (such as German or Chinese) and was converted to a simpler format (such as ANSI) at any point, character corruption can compromise the structural integrity, leading to misaligned lines upon re-import.
Enforcing UTF-8 Encoding
Before translating, ensure the source file is saved as UTF-8 (File > Encoding). After translating, save the final file as UTF-8 by selecting File > Save As > Encoding. Using this encoding prevents character corruption and preserves file structure for correct synchronisation. In the “Fix Common Errors” section of the translated file, check for any issues.
Run Tools > Fix common errors (Ctrl+Shift-F) on the translated file. Be sure to select “Fix empty lines” and “Fix missing line numbers.” If the sync has shifted due to blank lines, this tool will safely remove or repair them. Take action now to ensure your file is accurate and ready for use.
Frequently Asked Questions About Translation Sync
Why did my translation cause an out-of-sync issue?
The translation itself did not cause the sync issue. The synchronisation failure is caused either by Frame Rate Drift in the source file or by copying the translation from an external source, which corrupts the timecode structure. How do I fix the translation drift getting worse over time?
This is a Frame Rate Mismatch error. You must go to Synchronisation> Change frame rate and adjust the subtitle file’s frame rate to exactly match your video file’s frame rate. This must be done in the source language file before translation.
Can I use the “Adjust all times” tool to fix translation sync?
You should not use “Adjust all times” if the sync gets progressively worse (drift). That tool only fixes a constant shift (eg, subtitles are 5 seconds late throughout). For drifting, you must change the frame rate or use Point Sync. Is it safe to translate subtitles that are three lines long?
Yes, the translation engine can handle it. The synchronisation remains intact, but the translated line might exceed the Character Per Line (CPL) limit. must manually condense the three-line translation to ensure readability.
Should I fix the synchronisation before or after I translate?
Always fix the synchronisation before you translate. The translation process is a one-time text replacement operation that preserves the existing time codes. If the time codes are already wrong, the translated file will be wrong as well.
Why did my lines shift forward by 5 minutes after I pasted the translation?
This is a severe manual error caused by accidentally deleting or corrupting the first few time code lines when pasting the external translation. Use Point sync via other subtitle… to steal the correct timing data from your original source file.
Does the translation engine change the line breaks?
No, the translation engine typically preserves the existing line breaks (\n) in the source file. However, if the translated line is very long, Subtitle Edit might automatically insert a new line break to adhere to the CPL setting, while maintaining the original time codes.
Which is the safest way to ensure perfect synchronisation during translation?
Use the Tools > Auto-translate feature after verifying the source file’s frame rate is correct. This method locks the time codes and only replaces the text, guaranteeing no accidental synchronisation shifts.
