Other Concepts and Features
While the output format is indeed a conversion option, currently it's not located in the conversion dialog but in the control panel of the main window. The main reason for this is to keep those options in the control panel which directly affect the bitmap in the target panel.
There are four output modes available:
- SUB/IDX: also known as VobSub, a DVD subtitle format
- SUP/IFO: a DVD subtitle format defined by the author of IFOEdit
- SUP(BD): a Blu-Ray PGS stream demultiplexed from a M2TS by tools like EAC3TO or tsMuxeR.
- XML/PNG: the Sony BDN subtitle format consisting of an XML file containing the times etc. and palettized bitmaps in PNG format.
Depending on the selected output format, the bitmap displayed in the target panel will be updated (4 color palette in DVD modes vs. 256 color palette in BD modes).
BDSup2Sub supports only default output resolutions:
- NTSC: 720x480
Command line options ntsc, 480 - PAL: 720x576
Command line options: pal, 576 - HD 720: 1280x720
Command line options: 720p and 720 - HD 1440: 1440x1080
Command line option: 1440x1080 - FULL HD: 1920x1080
Command line options: 1080p and 1080
In BD-SUP, VobSub and SUP/IFO streams, individual subtitles can be marked as "forced" which tells the player to display them even if subtitles are switched off. This means that forced subtitles and normal subtitles can be stored in the same stream. If forced subtitle frames are detected in an imported stream (and only then), you can choose to export only the forced subtitles to SUB/IDX or SUP by checking the according checkbox in the export dialog (or by using the "/forced" parameter on the command line).
When reading a BD-SUP, BDSup2Sub tries to read the source frame rate from the stream. Keep in mind that it might be wrong or inaccurate! For HD-DVD SUPs, there is no frame rate information, so always 24p is assumed. However the source frame rate is only important if you change the frame rate during export. In this case, it's used together with the target frame rate to calculate the factor used to manipulate the time stamps. Note that to convert a movie from NTSC (3:2 pulldown) to PAL, you would still need to select 24p as source and not NTSC or 30p because the source timing is natively 24p and this is the only thing that matters for the conversion.
The target frame rate is always important, as it's always used to synchronize the start/end times with the frame rate. For best results, always select the correct target frame rate. Note that the default setting only depends on the resolution (PAL -> 25p, NTSC -> 30p, HD -> 24p).
You can select a scaling filter in the according combo box in the main view. The fastest algorithm is Bilinear, the slowest modes are Lanczos3 and Mitchell. For SUP/XML export with a 256 color palette, Mitchell or Lanczos3 are usually the best choice. For VobSub (or SUP/IFO) with only 4 colors, this is harder to predict. Just play around with the filters, alpha threshold and luminance thresholds to find the best quality.
BDSup2Sub allows to scale captions in X and Y direction independently of the screen resolution. This feature can be used to e.g. enlarge the captions to make them more readable or to shrink them a little bit to make them fit into the cinemascope bars. Simply enter any value between 0.5 and 2.0 for scaling in X and Y direction. Indeed, for conversion from BD to DVD it's often a good idea to scale the subtitles by a factor of e.g. 1.2 to make them more readable. To compensate for the slightly increased size, you may want to move the captions with the "move all" feature then.
Some streams contains single subtitles which are too short to read. It's possible to let BDSup2Sub automatically fix these subtitles. There's [command line option](Command-line Interface) ("--minimum-time") as well as an option in the [conversion dialog](Conversion Dialog). Every time that a caption is shorter than the given time (in milliseconds), BDSup2Sub will try to increase the display time to the given time. Note however that this is not possible if the next subtitle starts before that. In this case, the end time of the subtitle in question will be set to the start time of the following frame.
For some reason (probably due to a buggy authoring tool), there are quite a few BD subtitle streams which contain duplicated subtitle frames. I.e. the very same frame is repeated two, three or even more times with no or very short gaps between it. BDSup2Sub automatically tries to fix this issue, yet sometimes this behavior might not be wanted. Therefore it's possible to configure this feature via the command line option "/tmerge:". The default value is 200ms, which means that two identical subtitles with a gap smaller or equal to 200ms will be merged to one subtitle. Setting the time to 0ms ("/tmerge:0") effectively disables the feature.
Some subtitle streams contain information about the language of the stream. E.g. SUB/IDX, SUP/IFO and XML do, SUP BD and SUP HD don't. For those formats that don't support language information, BDSup2Sub tries to guess the correct language from the file name. If a file name for a BD-SUP or SUP-HD input stream contains a valid English language name (e.g. "german" or "french"), this will be used as default. Note that this can fail if the file name contains language names for other reason (e.g. movie titles like "Greek Wedding" or "Johnny English"). Therefore, there's always the possibility to edit the language in the [export dialog](Export Dialog). Then again, the language info is only needed if the export format supports it. If you export to BD-SUP, there's no need to define it and the option in the export dialog is grayed out.
