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Why would you want to add subtitles ?
The main reasons would be so your 'home movie' masterpiece has 'optional' text 'explanations' or so it can be enjoyed by a deaf relative or your non-English speaking relatives abroad. Other reasons include adding guests names to a Wedding video or location information to your Holiday 'PhotoStory' video.
In each case you will want the subtitles to be 'controllable' (i.e. on/off) at the choice of the viewer.
Many packages will also offer you the option of 'burning in' or 'forced on' subtitles - 'burning in' should be used for Copyright notices since 'forced on' subtitles can be simply removed (by editing of the .vob files).
Sub-titles are 'language specific' - so if your DVD has more than one 'language' choice, you can define different sub-titles for each
How are subtitles defined on a DVD ?
As in all things 'DVD movie', subtitles are defined in an exceedingly complex and non-obvious manor.
Subtitle 'parameters' are defined inside the .VOB files (same place where the video & audio is found). The parameters define the 'position' (where on screen), the 'timing' (start, duration) and 'effects' (fade, colour, transparency) and also a 'pointer' to the place on the DVD where the 'sub-picture pack', containing the sub-title image (bit-map pixels), can be found.
Yep, that's right = 'sub-titles' are actually defined as 'mini-images' (.bmp's) and are 'overlaid' onto the main video stream by the DVD player, i.e. they are NOT TEXT at all !
Why are sub-titles such a pain ?
The problem is in the way a DVD is 'structured'. The 'main movie' is held in a series of '.vob' files that can not exceed 1Gb (1,073,741,824 bytes) each. Since most 'author' software will split the movie into exact 1gb sized .vob's, there is no 'space' for the sub-titles .. but it's very hard to 'position' sub-titles until you have 'built' the actual movie !
Adding sub-titles 'after the DVD build' thus means re-building the entire movie (as the vob file sizes have to be changed, along with all the 'pointers' to the 'chapters' and 'scenes') .. and making edits (and previewing) can be a nightmare. The 'simple' way is thus to pre-prepare your sub-title data 'blind' and have your DVD Author package add it at the same time as the main movie build - if you don't like the 'timings' result, you have to change the sub-title data and rebuild 'from scratch'.
Some DVD Author packages (such as DVDFlick, see 'Next >>') will accept 'ascii text' defined sub-titles on a 'per clip' (or 'per chapter') basis.
What are all the SubRip (.srt) and Substation Alpha (.sss / .ass) and .SUP etc. formats all about then ?
SubRip .srt is a basic 'generic' subtitle text file containing raw text, bold/italic format and start / end display time formatting only. Many PC software video players support this directly and most DVD authoring packages will 'import', 'render' and merge the control data into the .vob files for a DVD player.
Substation Alpha (.ssa) & Advanced SSA (.ass) are subtitle 'description' files that includes all the 'normal' text formatting (size, position, colour etc) that is not supported by SRT. Many subtitle editing packages work only in SSA (if they support SRT at all, you may discover you have 'saved' nothing but the basic start/end timing and raw unformatted text).
When a SSA file is 'rendered' into graphics, you get the 'image' (bit map) PLUS a .SON (DVD Maestro), .TXT (I-Author), .SST (Scenarist), .SUB (Philips IMG 2.0) or .SUB (submux) file that tells your DVD/SVCD authoring tool (such as Spruce DVD Maestro etc) how to read the bitmap files and where in the time-line of your movie .vob files control data should be placed so that each bitmap subtitle is 'called'.
SUP is another 'rendered bit map' subtitle file format.
To render .SRT into SUP, use the Freeware SRT2SUP
Can you edit the 'text' of existing subtitles ?
Yes - DVDSubEdit (Open Source) can be used to make limited changes to your subtitles once you have built them into your movie .vob files.
It is always possible to modify the subtitle 'bit map' text images (held in the sub-pack) - for example to correct spelling errors or change the fonts etc., however DVDSubEdit is unable to change (increase) the timings or sizes of the sub-title bit maps specified within the .vob files. So whilst you can 'delete' subtitle text (by 'rubbing out' the text in the bit map i.e. replacing pixels with 'transparent') or replace the text characters bitmaps, you can't add to the text bit-map area.
How can I create my subtitles ?
You can use a specialist program to generate the subtitle 'parameters' as a SRT file and then import this into your DVD authoring software (where the .SRT will be 'rendered' and added to the .vob files when the DVD is generated).
What are some of these specialist programs ?
Gaupol (Open Source).
This is a very basic .SRT file create / edit package. There is no 'interactive' mode (so you have to 'guess' the start & end times) and only basic bold/italic formatting is supported. It also has a tendency to 'forget' your edits, returning to the old text when you hit 'enter' :-)
It's only advantage over a pure text editor (such as Notepad++) is that you can 'select the main video' (but only using 'show all files' since 'show video' shows none :-) ) and it will then use VLC to 'preview' your subtitles. Of course this pre-supposes that you have already 'built' your main video (rather than have it as a series of 'chapters') and that you make no timing changes during authoring
AEGIsub (Open Source).
This is one of the more comprehensive subtitle editors available. It is NOT the most easy to use, indeed it's UI is almost as obscure as VLC's, so you would be well advised to read the manuals before attempting to use it
It uses 'DirectX' to open the video clip, so you will have no problem with your .wmv files. By default, this will 'burn in' the 'subtitles' (i.e. add text to video) or embed the subtitles as text into a video for computer playback. The 'Export' function saves a pure text file with the file name of your choice (you can choose .SRT however the contents of the file saved will be no different from .txt).
The .srt 'format' supports only 'start', 'end' time plus the raw text & 3 styles (underline (\lc), bold (\b), & italic (\i) ) & nothing else = you won't find any positioning, colour, size etc. in .srt.
By default, subtitles are saved in 'SSA' format (which preserves all the formatting and positioning).
You can use MaestroSBT to convert SSA into 'VOB SUBs'.
AEGIsub offers translation support and a US English spelling dictionary is 'built in' (you can download other language dictionaries separately)
MaestroSBT (Open Source).
A simpler package ...
Click 'Next >>' in the Navigation bar left for using DVD Author