Converting & Joining Subtitles

Contents

  1. 1 Introduction
    1. 1.1 Required Software:
  2. 2 Converting Subtitles
    1. 2.1 OCR:
    2. 2.2 Start VobSub:
    3. 2.3 Open your Subtitles:
    4. 2.4 Examine Images:
    5. 2.5 Select Destination:
    6. 2.6 OCR:
    7. 2.7 Completion:
  3. 3 How to Join Subtitles:
    1. 3.1 Using VobSub Joiner:
    2. 3.2 Load Your Source Files:
    3. 3.3 Input 2 Start Time:

Introduction


Almost all the latest DVD's comes with one or multiple subtitles and sometimes when we rip the DVD we want to extract the subtitles also. One of the main reason for extracting subtitles is to hard code it with the video or if some of the scenes have very fast conversation.

For this reason we sometimes need to have text based subtitles because most new DVD players support SRT subtitle format. SRT is easy to join and split.

VobSub's IDX and SUB subtitle format has also beocme very popular do in large part to its flexibility and nearly universal compatibility with media players. But there are still times when you need something different, especially when the filesize of SUB and IDX are big. Fortunately VobSub also includes a tool capable of converting subtitles to text-based formats like SRT or SSA.

Like other parts of your video files you may need to join multiple subtitle files together to form one. It may be that you have subtitles from a multiple CD rip, or even that your subtitles have been edited to remove something from the middle. Whatever the reason for joining, it's actually a simple and straight forward operation which can be performed quite easily.

Required Software:

VobSub

Converting Subtitles


OCR:

The key to converting from image based subtitles to text based is a process called Optical Character Recognition, or OCR. This basically allows your computer to "read" the text and output the results. Due to limitations of both OCR and the images used for subtitles you'll need to help VobSub out during the OCR process. Fortunately this is fairly easy and doesn't take any special skill other than reading.

Start VobSub:

For converting subtitles the program we'll need to use is called SubResync. Despite the name, it actually does much more than fixing sync problems, although it can do a good job with that as well.


Open your Subtitles:

The first thing you'll need to do is load your subtitles into SubResync. Click the Open button and browse for your subtitle file. You'll also need to make sure to have the correct framerate specified. For most NTSC video from film sources this will be 23.976fps. For actual NTSC video (from a video camera rather than film) it will be 29.97. PAL always uses 25fps. It's important that you get this right since it can cause sync problems later otherwise.

Examine Images:

Once the subtitle file is opened you'll see a list of timecodes representing when the subtitles will be displayed. If you click on a timecode in the left column you'll see the image that will be converted to text through OCR. It's a good idea to look through some of the subtitles before continuing to the next step. This may help you make adjustments before OCR is even performed to help SubResync do a better job the first time. This will mean more accurate results, and usually fewer things for you to fix.

Select Destination:

Next you'll need to select the name and destination folder for your new subtitle file. Click the Save As button and browse for the folder where you want the output to be saved. Make sure the format is set to SRT.

You'll also have an option to Clear image->letters database, which resets any OCR information previously set. If you find that the characters in your output file aren't being recognized accurately you can run the process a second time with this option checked. The slider at the bottom is for determining spacing between letters. If the letters are extremely close you may get better results from moving it to the left. If they're further apart moving it to the right may improve results.

OCR:

Once you click the Save button SubResync will perform OCR and show you any places it's not sure about. Simply type in the character shown in the box and click the Add button. Typically there will be more questions toward the beginning of the file, and fewer as SubResync "learns" how characters look.
In many cases you'll be shown multiple characters to identify. Pay close attention to what characters are included in the selection. This will not only make the process go faster, but also improve the results.

Completion:

Once the OCR proces finishes you'll be left with a brand new SRT subtitle file, which you can use in any program that supports the format.

How to Join Subtitles:

We'll be using the VobSub Joiner for this guide. Simply select it from the Start menu entry to run it.

Using VobSub Joiner:


As you can see VobSub Joiner is extremely simple. Two input files are loaded, and a timecode is entered for the second one to start at. Only two files can be joined at a time, so if you have more than that you'll need to repeat this procedure until they're all merged. Unlike many of the operations possible with VobSub, joining only supports IDX and SUB (VobSub) subtitles.

Load Your Source Files:


To load an input file simply click the ... button next to either Input 1 or Input 2.

Input 2 Start Time:


You'll need to know the exact length of the first subtitle stream is. How you find it will depend on the type of file. If it's an AVI file you can load it in VirtualDub and select File Information from the file menu. Enter that value here, but increment the last number by one. For example, if the length of the first video file is 1:10:37:15 you would enter 1:10:37:16

Once everything is loaded and the start time for the second subtitle file is set you can use the Go button to create your new (joined) subtitle files.

The End.
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