Documentation:Modules/dvbsub

Module: dvbsub
Type	Subtitles
First VLC version	0.8.0
Last VLC version	-
Operating system(s)	all
Description	DVB subtitles decoder/encoder
Shortcut(s)	-

There are notes in the source code:

/*****************************************************************************
 * Preamble
 *
 * FIXME:
 * DVB subtitles coded as strings of characters are not handled correctly.
 * The character codes in the string should actually be indexes referring to a
 * character table identified in the subtitle descriptor.
 *
 * The spec is quite vague in this area, but what is meant is perhaps that it
 * refers to the character index in the codepage belonging to the language
 * specified in the subtitle descriptor. Potentially it's designed for widechar
 * (but not for UTF-*) codepages.
 *****************************************************************************/

and

/*****************************************************************************
 * Notes on DDS (Display Definition Segment)
 * -----------------------------------------
 * DDS (Display Definition Segment) tells the decoder how the subtitle image
 * relates to the video image.
 * For SD, the subtitle image is always considered to be for display at
 * 720x576 (although it's assumed that for NTSC, this is 720x480, this
 * is not documented well) Also, for SD, the subtitle image is drawn 'on
 * the glass' (i.e. after video scaling, letterbox, etc.)
 * For 'HD' (subs marked type 0x14/0x24 in PSI), a DDS must be present,
 * and the subs area is drawn onto the video area (scales if necessary).
 * The DDS tells the decoder what resolution the subtitle images were
 * intended for, and hence how to scale the subtitle images for a
 * particular video size
 * i.e. if HD video is presented as letterbox, the subs will be in the
 * same place on the video as if the video was presented on an HD set
 * indeed, if the HD video was pillarboxed by the decoder, the subs may
 * be cut off as well as the video. The intent here is that the subs can
 * be placed accurately on the video - something which was missed in the
 * original spec.
 *
 * A DDS may also specify a window - this is where the subs images are moved so that the (0,0)
 * origin of decode is offset.
 ********************************************************************************************/

Options

• dvbsub-position <integer> { 0, 1, 2, 4, 8, 5, 6, 9, 10 } : Subpicture position^(key)
• dvbsub-x <integer> : X coordinate of the rendered subtitle default value: -1
• dvbsub-y <integer> : Y coordinate of the rendered subtitle default value: -1

Encoder

• sout-dvbsub-x <integer> : X coordinate of the encoded subtitle default value: -1
• sout-dvbsub-y <integer> : Y coordinate of the encoded subtitle default value: -1

Appendix

For the option --dvbsub-position:

Integer alignment mapping

Integer	Alignment	Comment
0	Center
1	Left
2	Right
4	Top
8	Bottom
5	Top-Left	4 + 1
6	Top-Right	4 + 2
9	Bottom-Left	8 + 1
10	Bottom-Right	8 + 2
3	n/a	contradictory
7	n/a	contradictory

Source code

• modules/codec/dvbsub.c

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