How to synchronize subtitles by Jean-Paul Lehmann

Why do I need it ?

Well, watching a movie where the subtitles are 5 seconds late is a pain in the ass! (As well as desynchronized sound)
If you recreate subtitles from a DVD or a .TS file (Recorded from a TV TNT station) it it quite simple to synchronize the titles with the movie. Just shift everything up or back, and all is right. (I will tell you later how to do this)

But if you got your file from the web, you may have serious problems :
Except this last point, the method bellow allows correction in a minimum of time. If there are SOME cuts, it is possible to correct the file too. But I found at last two or three movies where there were many cuts, and the tempo of the titles was changing between them. This was a desperate case.

Main tools used:

There are two plus a help.
  1. A program to edit/modify the subtitles. One that works very well for me is a freeware 'Subtitle tool': Subtitle Tool
  2. It allows editing, changing start/stop times, changing speed, moving blocs, conversion, cutting, adding, also checking the validity of the file.

    This show the 'Change Speed' function used later.

  3. A player that allows for image by image moves.
  4. I use mostly 'Tmpgenc DVD Author 3' (download here). Version 3 is obsolete, this is version 4. It is a commercial tool. I like it because it allows to create DVD's with a lot of freedom, and to watch image by image the movie you want to create and cut.
    A plus is that it allows changing the Subtitles files (.srt) on the fly, so changes are immediately seen. Also, while it is a DVD generator, it can work with many input video formats like mp4 HD (strangely, you must rename it .mpg in order to accept it).
    A big minus (beside its price) is that it requires a monthly validation on the web. That's a killer, alas, so I will never buy another version from them.

    Some viewers, like VLC, Smplayer, Nero allow to see the subtitle and to move into the file, but most of the time you need to restart it to change the subtitle file, and moving to a specific image may be hard.

    This shows the sub-title page, while editing a file. You can set the format, import a .srt sub file, or create/change directly subtitles here. Another view that show the same image is used to move into the file, image by image, chapters, specific time... (Note that exportation is in own format .subtitles, that can be converted to .srt by small VB routines)

    I also use EXCEL (I will give the formulas), to compute time differences in hour:minutes:seconds,hundreds into plain seconds and calculate the coefficient for speed changes. (A simple calculator can do it too)

How to synchronize subtitles.

I will only gives the steps for a normal simple job, convert a title file from the web to adjust it to the movie you have.
  1. Simplest case
  2. Your file is created from the same copy (extracted from it). Usually, the only problem will be that the first title start before or after the right time.

    You just start the movie player, and the Subtitle tool.
    Load the file (usually the simpler form is .srt) in both programs.
    Use the 'check consistency' tool, and edit any serious problem (overlapping, too short times…)

    With the player, find when the first title shows, and when the corresponding sound dialog is heard. (You must have an idea of the audio language to do it!, but the voice may be a guide too)
    Just enter both times into the Excel sheet, and you get the necessary forward/backward time to insert into the 'time shift' page. In the 'subtitle tool program', enter the time, click 'do it', save the file, and reload the video to check if it is all right.

    You will also have to check the latest subtitles to confirm that they are right there too, as some errors can prevent loading the whole file in the player.

  3. File from the web
  4. You have got the video and the subtitles from different sources. Chances are that the speeds are different too. I will not explain how to manage a case with cut in the video.
    The first step is like the preceding case. You just set everything so the FIRST subtitle is synchronized with its image.
    Then, you find the times for the LAST (or an easily recognizable one near the end).

    Enter all the times into the Excel sheet:
    start 1st sub
    start 1st dialog
    start last sub
    start last dialog
    (if you don't have Excel, use the formulas given bellow)

    You will normally obtain 0 for the first difference, and a result for the last, with a coefficient showing how much the time should be slowed or accelerated. (Keep a copy of the file first before changing it!)

    When the result is obtained, like '0.9985623', go to the Subtitle tool 'Time shift' page, and move BACKWARD so the first subtitle will be at time 00:00!
    Then, go to the 'change speed' page, and enter the coefficient found, and 'do it'. Be carefull to use all of the 7 decimal digits, or it will not work correctly.
    Go back to the 'Time shift' page, and apply the same time used before, but now FORWARD.
    Check to see if the last subtitle is really now at the time it should be. If not, verify the entries, load back the original file, and start over with a slightly different coefficient. Save it ! And check twice to see if all is right now.

    That's it... Now you are an expert in synchronizing subtitles! :)

    Samples: A sample .srt file, Foreign correspondent

    The Excel sheet to compute times: VidCalc.xls

    For assistance please E-mail me with a significant subject:

    January 28, 2015