1185 lines
No EOL
48 KiB
TeX
1185 lines
No EOL
48 KiB
TeX
\documentclass{spec}
|
|
\usepackage[pdftex]{graphicx}
|
|
\newcommand{\syntax}[1]{
|
|
|
|
\subsubsection*{Syntax}
|
|
|
|
\begin{tabbing}
|
|
|
|
\hspace{2cm}\=\\[-16pt]
|
|
|
|
#1
|
|
|
|
\end{tabbing}
|
|
|
|
}
|
|
\newcommand{\secspec}[1]{Section:\>\texttt{#1}}
|
|
\newcommand{\secspecs}[2]{Sections:\>\texttt{#1}, \texttt{#2}}
|
|
\newcommand{\HRule}{\rule{\linewidth}{0.5mm}}
|
|
|
|
|
|
\begin{document}
|
|
\title{AS5 Subtitle Format Draft}
|
|
\author{Rodrigo Braz Monteiro, Niels Martin Hansen, David Lamparter, Karl Blomster}
|
|
|
|
\begin{titlepage}
|
|
\begin{center}
|
|
|
|
\vspace*{3cm}
|
|
|
|
\HRule \\[0.5cm]
|
|
\textsc{\huge AS5 Subtitle Format}\\
|
|
\HRule \\[1.1cm]
|
|
{\large By Rodrigo Braz Monteiro, Niels Martin Hansen, David Lamparter and Karl Blomster}\\[0.3cm]
|
|
This work is licensed under a Creative Commons Attribution-Share Alike 3.0 License.\\
|
|
\vfill
|
|
|
|
\begin{minipage}{0.4\textwidth}
|
|
\begin{flushleft} \large
|
|
\includegraphics[width=0.7\textwidth]{./aegisub}
|
|
\end{flushleft}
|
|
\end{minipage}
|
|
\begin{minipage}{0.4\textwidth}
|
|
\begin{flushright} \large
|
|
\includegraphics[width=0.6\textwidth]{./asa}
|
|
\end{flushright}
|
|
\end{minipage}\\[1.5cm]
|
|
|
|
{\large \today}
|
|
|
|
\end{center}
|
|
\end{titlepage}
|
|
|
|
\setlength{\parskip}{0pt}
|
|
\tableofcontents
|
|
\newpage
|
|
\setlength{\parskip}{8pt}
|
|
|
|
|
|
\section{Abstract}
|
|
This document specifies the \emph{AS5 Subtitle Format}, developed jointly by the
|
|
Aegisub\cite{Aegisub} and asa\cite{asa} teams in order to replace the old
|
|
\emph{Sub Station Alpha}\cite{SSA} subtitle format and its extensions:
|
|
|
|
\begin{itemize}
|
|
\item Advanced Sub Station Alpha (ASS) implemented by Gabest in VSFilter\cite{VSFilter}
|
|
\item Advanced Sub Station Alpha 2 (ASS2), also implemented by Gabest in VSFilter
|
|
\item Advanced Sub Station Alpha 3 (ASS3) implemented by equinox in asa.
|
|
\end{itemize}
|
|
|
|
The goal is to create a flexible, easy to understand and powerful subtitle format
|
|
that can be used in hardsubs or multiplexed into Matroska Video\cite{mkv} files as
|
|
softsubs. The syntax is heavily influenced by the older SSA and ASS formats, which in
|
|
turn vaguely resemble the TeX typesetting language; but AS5 also has many differences
|
|
compared to these older formats and you should not expect it to behave exactly like them.
|
|
|
|
AS5 has no official meaning. The ``A'' can stand for Aegisub, asa, ASS or Advanced,
|
|
the ``S'' for Subtitles, and the 5 is a reference to the fact that it's a major
|
|
rework of the SSA4 format (from which ASS, ASS2 and ASS3 derive). The full
|
|
name of the format is ``AS5 Subtitle Format''.
|
|
|
|
|
|
\newpage
|
|
\section{AS5 Files}
|
|
\subsection{File Format}
|
|
All AS5 files are \emph{REQUIRED} to comply with the three requirements below:
|
|
|
|
\begin{itemize}
|
|
\item Be encoded with one of \emph{UTF-8}\cite{UTF-8}, \emph{UTF-16 Big Endian}
|
|
\cite{UTF-16} or \emph{UTF-16 Little Endian} Unicode Transformation Formats. UTF-8 is
|
|
preferred.
|
|
\item Not to have any character below Unicode code point U+20, except for U+09, U+0A, U+0D.
|
|
That is, it must be a plain-text file.
|
|
\item All lines must end with Windows line endings, that is, U+0D followed by U+0A.
|
|
\end{itemize}
|
|
|
|
These requirements are important so the AS5 format can be edited in most plain-text editors
|
|
across most operating systems and languages without problems. The character set of a
|
|
subtitle file can be autodetermined by its Byte-Order Mark or by the value of the first
|
|
two bytes. See below.
|
|
|
|
When used as a standalone file, the extension should be \textsc{.as5}. When multiplexed
|
|
into a Matroska container, the Codec ID used is \textsc{S\_TEXT/AS5}.
|
|
|
|
\todo{Get clearance from the Matroska team to use that Codec ID.}
|
|
|
|
|
|
\subsection{File Structure}
|
|
The file is divided in \emph{sections}, which are uniquely identified by a string inside
|
|
square brackets, in a line of its own. From that point on, every next line is considered
|
|
to be part of the last found section until another section is found. There is no end-of-section
|
|
termination mark; they always end at the start of the next one or at the end of the file.
|
|
There \must\ only be one and only one of each section; if the parser finds two lines containing
|
|
the same section header, it \must\ reject the file as invalid. \emph{Section names are case sensitive.}
|
|
|
|
Each section is divided in lines, each line representing one command or definition. Empty
|
|
lines (that is, lines only containing a line ending) \must\ be ignored by the parser.
|
|
It is recommended that programs generating AS5 files insert a blank line at the end of each
|
|
section to increase readability. There \must\ always be a blank line at the end of the file
|
|
(as every line is required to end in a line break).
|
|
|
|
Each line in a section takes the general form of \textit{Type: data1,data2,...,dataN}. An
|
|
unknown \textit{Type} \must\ be ignored by a parser. Subtitle editing programs \should\ keep
|
|
such ignored lines in the file after re-saving it. Note that the space after the colon is \emph{mandatory}.
|
|
|
|
There are two sections which are required, \emph{[AS5]} and \emph{[Events]}, the former being
|
|
the equivalent of \emph{[Script Info]} in previous formats. If either of those sections is
|
|
missing, the file is invalid and \must\ be rejected by the parser. Any other section
|
|
can be ommitted from the file, and need not be implemented by all parsers.
|
|
|
|
Finally, there is a special type of undefined group, \emph{[Private:PROGNAME]}, which
|
|
\must\ be \emph{ENTIRELY} preserved by other programs when re-saving it. This is used to
|
|
store program-specific data. For example, Aegisub would create a group called
|
|
\emph{[Private:Aegisub]} to store its data inside. This type of group is identified
|
|
by the fact that it starts with \emph{``[Private:''}.
|
|
|
|
Additionally, private data may also be stored in any other section by using commented-out
|
|
lines: any line where the first character is a semicolon (\textit{;} - U+3B) is considered a
|
|
"comment line" and \must\ be ignored by the parser; they also \must\ be preserved by an editing program
|
|
when resaving. It is suggested that an editing program \should\ check whether commented lines are
|
|
actually valid AS5 lines, and if they are, display them to the user in some way as "disabled" lines.
|
|
Note that commented out lines \mustnot\ influence subtitle rendering in any way.
|
|
|
|
The sections \may\ be written in any order, with the exception of the \emph{[AS5]} section which
|
|
\must\ always be the first section.
|
|
|
|
In general, malformed lines in AS5 (such as unrecognized lines, lines with missing fields, fields
|
|
with invalid data for its type (for example, malformed timestamps) or unrecognized section headers)
|
|
are not considered fatal syntax errors. If nothing else is explicitly specified, the renderer \must\
|
|
ignore such lines completely, and the parser \should\ emit a warning describing the syntax error. The
|
|
spirit of this rule to be forgiving; something that doesn't make the entire file unuseable or dangerously
|
|
ambigous should not be a fatal syntax error. It is usually better to render the valid parts of the file
|
|
correctly and tell the user about the problematic lines by the way of warning messages. Under certain
|
|
circumstances it may be desirable to suppress warning messages; a well-behaved parser \should\ include
|
|
an option to do so, but in general it is probably more useful to let the user know about the problem
|
|
instead of just silently failing to render the line.
|
|
|
|
\subsubsection{[AS5]}
|
|
This \must\ be the first section in every AS5 file. If the very first line of the file is not
|
|
[AS5], the file \must\ be rejected by the parser as invalid. Note, however, that the first
|
|
line is allowed to contain a Byte-Order Mark (BOM), which is the character U+FEFF encoded in
|
|
the encoding used for the rest of the script\cite{Unicode BOM}. The first four bytes will therefore be:
|
|
|
|
\begin{itemize}
|
|
\item 0xEF 0xBB 0xBF 0x5B - UTF-8 (with BOM)
|
|
\item 0x5B 0x41 0x53 0x53 - UTF-8 (without BOM)
|
|
\item 0xFF 0xFE 0x5B 0x00 - UTF-16 LE (with BOM)
|
|
\item 0x5B 0x00 0x41 0x00 - UTF-16 LE (without BOM)
|
|
\item 0xFE 0xFF 0x00 0x5B - UTF-16 BE (with BOM)
|
|
\item 0x00 0x5B 0x00 0x41 - UTF-16 BE (without BOM)
|
|
\end{itemize}
|
|
|
|
It is possible, therefore, to determine the encoding of the file by checking its first two bytes.
|
|
|
|
This section is used to declare several script properties that affect its parsing and rendering.
|
|
All properties are stored in the format \textit{Name: data}, with one property per line.
|
|
|
|
This section \must\ always declare the following properties (a file that is missing one of them is not valid):
|
|
|
|
\begin{itemize}
|
|
\item ScriptType: Should always be set to \textit{AS5}, for this particular version of the specification.
|
|
An unrecognized ScriptType value is considered a fatal syntax error, and \must\ cause the parser to
|
|
reject the entire file as invalid.
|
|
\item Resolution: Should contain the script resolution in \textit{WxH} format. For example, for a 640x480
|
|
script, this should say \textit{``Resolution: 640x480''}. Note that this does not need to correspond to the
|
|
video resolution, however, subtitles \must\ be rendered on such a coordinate space. That is, in a
|
|
640x480 script, \textbackslash{pos(320,240)} always represents the center of the script, no matter the
|
|
resolution of the video it's being drawn on. Also, in a 100x100 script, a radius 50 circle centered on
|
|
the center will always take half of the height and half of the width of the video, even if that means
|
|
being distorted if drawn on a video with a non-1:1 aspect ratio (for example, a 640x480 video).
|
|
An unrecognized or malformed Resolution value is considered a fatal syntax error, and \must\ cause the parser
|
|
to reject the entire file as invalid.
|
|
\end{itemize}
|
|
|
|
The following items \may\ also be used; they are not required, but are recommended. They all have default values:
|
|
|
|
\begin{itemize}
|
|
\item Generator: The name of the program that generated this script, e.g. \textit{``Generator: Aegisub''}.
|
|
Default value is empty. This should be ignored by the renderer, but might be useful for inter-editing-program
|
|
interaction.
|
|
\item Wrapping: The line wrapping style. This can be ``Manual'', in which case only \textbackslash{n} can
|
|
break lines or ``Automatic'', in which the renderer chooses how to break them. If this is not set, or if the
|
|
value set is not recognized, the renderer \must\ default to ``Automatic''.
|
|
Even if it is set to Automatic, \textbackslash{n} will still insert a forced line break.
|
|
On the other hand, if set to manual, the line can NEVER be broken at anywhere other than forced line breaks,
|
|
even if it means that the line will become unreadable because it goes outside the display area.
|
|
This property is not case sensitive.
|
|
\item Extensions: A comma-separated list of all extensions being used in this file. At the moment, there are
|
|
no extensions available. Renderers should read this to enable any extensions that they might support.
|
|
Editing programs \must\ keep this field intact, unless the user chooses otherwise. Scripts WILL break
|
|
if the list of extensions is suddenly lost.
|
|
\item Credits: Credits for the people who worked on this subtitle file. Purely for informational purposes and
|
|
\should\ be ignored by the renderer. Subtitling programs \should\ be able to display these credits to the user.
|
|
\item Title: The title of this script. Purely for informational purposes and \should\ be ignored by the renderer.
|
|
Subtitling programs \should\ be able to display this title to the user.
|
|
\end{itemize}
|
|
|
|
Unlike in the previous incarnations of the format, storing private properties here is strongly discouraged,
|
|
which means that this section \shouldnot\ contain any properties not listed here. It \may\, just like any other
|
|
section, contain commented-out lines prefixed with a semicolon (;) which of course may contain anything, but it
|
|
is strongly recommended that any application-specific or otherwise private data \should\ be stored in the
|
|
\textit{[Private:PROGNAME]} section instead, as mentioned above, or if it is line-specific data, in the User field.
|
|
|
|
|
|
\subsubsection{[Events]}
|
|
|
|
The most important section, [Events], lists all the actual subtitle lines in the file. The syntax has
|
|
been radically simplified from previous incarnations of the format, and now consist of only five fields.
|
|
Each line is represented as:
|
|
|
|
\begin{verbatim}
|
|
Line: start,end,style,user,content
|
|
\end{verbatim}
|
|
|
|
Where:
|
|
|
|
\begin{itemize}
|
|
\item Start: The start time of the line. See below for the timestamp format. A line is only displayed if
|
|
the timestamp of the current frame is \emph{greater than or equal} to the start time. That is, start
|
|
time is \emph{inclusive}.
|
|
\item End: The end time of the line. It follows the same format as the start time. The line is only
|
|
displayed if the timestamp of the current frame is \emph{lesser than} the end time. That is, end time is
|
|
\emph{exclusive}. In particular, it means that a line whose start time is equal to its end time will
|
|
never be displayed. If the end time is earlier than the start time, the renderer \should\ issue a warning,
|
|
but this is not considered a fatal syntax error and it \should\ render the remaining lines regardless of the issue.
|
|
If the end time is earlier than the start time, it should for rendering purposes be considered to be equal to
|
|
the start time, and editing programs \may\ automatically reset the end time to be equal to the start time.
|
|
\item Style: The name of the default style used for this line. See the [Style] section below. If left blank,
|
|
the script's global default style \must\ be used. If there is no default style defined, or if an unknown
|
|
style name is specified, the renderer \must\ fallback to its own defaults (see below), and \should\ issue a warning.
|
|
\item User: This field is used by the program to store program-specific data in each line. Renderers
|
|
\should\ ignore this (but \may\ use it for application-specific extension features). This field \should\
|
|
be left empty if it's not used. Note that whatever data is stored here \mustnot\ contain any commas!
|
|
|
|
It is suggested that text in the User field is encoded with the following scheme: The characters
|
|
0x00 to 0x1F (control codes), 0x23 (number sign), 0x2C (comma), 0x3A (colon) and 0x7C (pipe)
|
|
are replaced with a number sign (0x23) followed by the hexadecimal code for the character, for example
|
|
a comma is replaced with ``\#2C''. This scheme allows the field to contain several sub-fields separated
|
|
with pipe characters, optionally using a ``Name:Value'' format.
|
|
\item Content: The actual text of the line. This contains actual text and override tags. See the section
|
|
on override tags for more information.
|
|
\end{itemize}
|
|
|
|
The timestamp format is h...h:mm:ss[.s...], that is, it begins with an integer of arbitrary length
|
|
(up to a maximum of 4 digits) representing the number of hours, followed by a one-digit or two-digit integer
|
|
representing minutes, and a floating point number representing seconds. Leading zeroes \may\ be ommitted.
|
|
Localization is irrelevant: a period (``.'') is always used to separate the decimal point. This way,
|
|
0:21:42.5 and 0000:21:42.5000 are equivalent, and both represent 0 hours, 21 minutes, 42 seconds and 500 miliseconds.
|
|
|
|
Spaces between each field \must\ be ignored by the parser. Any spaces at the beginning of the
|
|
content line \should\ be stripped by any editing program. A hard space (see the overrides section) or empty
|
|
override block should be used if space at the start of a line is truly desirable. That is, the two
|
|
following lines are syntactically identical:
|
|
|
|
\begin{verbatim}
|
|
Line: 0:2:31.57 , 0:02:34.22 , , , Hello world of {\b1}AS5{\b0}!
|
|
Line: 0:02:31.570,00:02:34.22,,,Hello world of {\b1}AS5{\b0}!
|
|
\end{verbatim}
|
|
|
|
|
|
\subsubsection{[Styles]}
|
|
|
|
This is equivalent to the \emph{[V4 Styles]} (and subsequent variations) from the Sub Station Alpha format.
|
|
Like \emph{[Events]}, it has been greatly simplified when compared to the previous formats, and now
|
|
each entry contains only three fields. They are declared as:
|
|
|
|
\begin{verbatim}
|
|
Style: name,parent,overrides
|
|
\end{verbatim}
|
|
|
|
Where:
|
|
|
|
\begin{itemize}
|
|
\item Name: The name of this style. Style names are not case-sensitive, but \must\ be unique. A
|
|
script with conflicting style names \must\ be rejected by the parser. If the style name is ``Default'', it
|
|
will be used for all lines that omit the style name. If there is no ``Default'' line, the renderer
|
|
default is used.
|
|
\item Parent: The style from which the current style derives from. See below for more information.
|
|
Leaving this field blank means that the style derives from the renderer's default style.
|
|
\item Overrides: A list of override tags to define this style. See below.
|
|
\end{itemize}
|
|
|
|
Styles work in a very different way from the way they did on previous formats (with the notable exception
|
|
of ASS3, which actually implements this very same style based on this format, as ``StyleEx'').
|
|
Instead of setting multiple parameters across many commas, you simply specify override tags. When a line
|
|
uses a style, it's as if the overrides of the style were inserted right before the start of the line
|
|
contents, with one exception: certain tags without parameters revert to the style default. For example,
|
|
\textbackslash 1c will revert the primary colour to the one specified in style. Such use of tags is invalid
|
|
in the style definition, and \must\ be ignored if found in them; the parser \may\ choose to emit a warning.
|
|
|
|
Also, a style can inherit from another style, and define new overrides which are then appended to those
|
|
of the parent style. The parent style \must\ have been declared \emph{BEFORE} the style trying to use
|
|
it as a parent. If the parent doesn't exist or wasn't declared yet, the parser must refuse to parse the
|
|
script. This is important because otherwise you could get a ``inheritance loop'', where styles derive from
|
|
each other in a cycle.
|
|
|
|
For example, see the following \emph{[Styles]} group:
|
|
|
|
\begin{verbatim}
|
|
[Styles]
|
|
Style: Default,,\fn(Arial)\fs20
|
|
Style: Speech,,\fn(Respublica)\fs24\bord2\shad2\4a#80\2c#000000
|
|
Style: Actor1,Speech,\1c#B9C5E3
|
|
Style: Actor2,Speech,\1c#FFB3CF
|
|
Style: UglinessItself,Default,\fn(Comic Sans MS)
|
|
\end{verbatim}
|
|
|
|
In the above fragment, the first style defines the Default style that will be used on all lines that
|
|
don't set any style and the second style defines a base speech style that will be used for all actors
|
|
(note that it doesn't inherit from Default, even though Default overrode the renderer's default, that
|
|
one is still used for style definitions.)
|
|
|
|
The third and fourth styles are based on the second, and simply assign different colours to it. They
|
|
will both have all properties of Speech, and only differ in primary colour. Finally, the last example
|
|
shows how to derive from the overriden default. In this case, font size would be 20 points, regardless
|
|
of renderer's default.
|
|
|
|
The two Actor styles could have been defined without a parent style as follows:
|
|
|
|
\begin{verbatim}
|
|
[Styles]
|
|
Style: Actor1,,\fn(Respublica)\fs24\bord2\shad2\4a#80\2c#000000\1c#B9C5E3
|
|
Style: Actor2,,\fn(Respublica)\fs24\bord2\shad2\4a#80\2c#000000\1c#FFB3CF
|
|
\end{verbatim}
|
|
|
|
Since all that deriving a style from another does is append the new tags to the end of the previous,
|
|
this way of declaring styles is identical to the one above, but is more verbose.
|
|
|
|
\todo{This is bad, we need to fix it with specified defaults to get consistent rendering}
|
|
If no Default style is defined, the renderer \must\ choose its own defaults to render the text with.
|
|
The defaults \must\ also be used any for any properties not specified in a given style (in other words,
|
|
styles with no parent inherit from the renderer defaults). To ensure consistent rendering while still
|
|
avoiding having to explicitly define every single property, some of these defaults are mandatory and
|
|
specified below; some others have recommended values, also specified below, but a well-featured renderer
|
|
\may\ allow the user to change these defaults at will.
|
|
|
|
The following default overrides are mandatory and \must\ be set as following:
|
|
\begin{itemize}
|
|
\item \textbackslash i(0)
|
|
\item \textbackslash b(0)
|
|
\item \textbackslash u(0)
|
|
\item \textbackslash s(0)
|
|
\item \textbackslash fe(Unicode)
|
|
\item \textbackslash bordstyle(0)
|
|
\item \textbackslash fscx(100)
|
|
\item \textbackslash fscy(100)
|
|
\item \textbackslash fsp() - undefined (font default)
|
|
\item \textbackslash fsvp() - undefined (font default)
|
|
\item \textbackslash 1a(\#00)
|
|
\item \textbackslash 2a(\#00)
|
|
\item \textbackslash 3a(\#00)
|
|
\item \textbackslash 4a(\#80)
|
|
\item \textbackslash left(12)
|
|
\item \textbackslash right(12)
|
|
\item \textbackslash top(12)
|
|
\item \textbackslash bottom(12)
|
|
\item \textbackslash ax(50)
|
|
\item \textbackslash ay(100)
|
|
\item \textbackslash nx(50)
|
|
\item \textbackslash ny(100)
|
|
\item \textbackslash rel(0)
|
|
\item \textbackslash vertical(0)
|
|
\item \textbackslash q(1)
|
|
\item \textbackslash pos() - undefined (defined by alignment, margins and script resolution)
|
|
\item \textbackslash org() - undefined (defined by alignment, margins and script resolution)
|
|
\item \textbackslash bls(0)
|
|
\item \textbackslash frx(0)
|
|
\item \textbackslash fry(0)
|
|
\item \textbackslash frz(0)
|
|
\item \textbackslash fax(0)
|
|
\item \textbackslash fay(0)
|
|
\item \textbackslash fad(0,0)
|
|
\item \textbackslash distort() - undefined (none)
|
|
\item \textbackslash baseline() - undefined (none)
|
|
\item \textbackslash blpos(0)
|
|
\item \textbackslash vc() - undefined (none)
|
|
\item \textbackslash blend(normal)
|
|
\item \textbackslash clip() - undefined (none)
|
|
\item \textbackslash iclip() - undefined (none)
|
|
\item \textbackslash \$blur(0)
|
|
\end{itemize}
|
|
|
|
\subsubsection{[Resources]}
|
|
|
|
The new \emph{[Resources]} section can be used to store information on external file resources,
|
|
such as images and fonts. The general syntax is:
|
|
|
|
\begin{verbatim}
|
|
Resource: type,name,path
|
|
\end{verbatim}
|
|
|
|
Where:
|
|
|
|
\begin{itemize}
|
|
\item Type: Must be either ``font'' or ``image''. Any other types \must\ be ignored by the parser.
|
|
\item Name: An unique name identifying this resource. For fonts, it must correspond to the font
|
|
name, e.g., ``Verdana''. For images, it's the name that the file will be reffered as in the rest
|
|
of the script. If there is already a resource with this same name, the parser \must\ abort the
|
|
parsing.
|
|
\item Path: The location of the file relative to the subtitles. This \must\ be a relative path
|
|
for external .as5 files, or a container-specific string for AS5 multiplexed into a container.
|
|
The relative path \must\ use forward slashes and be case-sensitive, in order to avoid UNIX
|
|
compatibility issues.
|
|
\end{itemize}
|
|
|
|
|
|
\newpage
|
|
\section{Style Overrides}
|
|
|
|
\subsection{General Information on Override Tags}
|
|
As with previous formats, AS5 uses override tags to set the style for lines. Also, it uses those
|
|
same tags to set style definitions themselves (see above). Although many tags were imported from
|
|
\emph{Advanced Sub Station Alpha}, do not assume that they behave exactly the same. Some had their
|
|
behavior changed or properly defined. Also, AS5 defines many new tags in addition to the old ones.
|
|
|
|
All tags must be inserted between a pair of curly brackets (\emph{\{\}}), except on style definitions.
|
|
A pair can contain any number of override tags inside it. They should be listed one after the other,
|
|
with no spaces or any other kind of separator between them. Tags then affect all text that follows
|
|
it, unless re-overriden or reset by the \emph{\textbackslash r} tag. For example:
|
|
|
|
\begin{verbatim}
|
|
{\fn(Verdana)\fs26\c#FFA040}Welcome to {\b1}AS5{\b0}!
|
|
\end{verbatim}
|
|
|
|
In the above example, the first override block affects the entire text, but only ``AS5'' is bolded.
|
|
|
|
Some tags begin with a \$ in their names. This means that there are actually five variations
|
|
of this specific tag, the tag with \$ replaced with a number from \emph{1} to \emph{4} (inclusive)
|
|
or without it altogether - in that case, the tag is assumed to mean the \emph{1} variation. Those
|
|
numbers represent the four different colours available on any given line (see below). If no number
|
|
is specified, the tag will affect all 4 colours. The 4 colurs are:
|
|
|
|
\begin{itemize}
|
|
\item 1 - Primary colour, used for the main face of the text.
|
|
\item 2 - Secondary colour, used on karaoke. See the karaoke tags for more information.
|
|
\item 3 - Border colour. This is the colour of the border that outlines the text. See the \textbackslash
|
|
bord tag for more information.
|
|
\item 4 - Shadow colour. This is the colour of the shadow dropped by the text. See the \textbackslash
|
|
shad tag for more information.
|
|
\end{itemize}
|
|
|
|
So, for example, you would use \textbackslash 1c to set the primary colour, or \textbackslash 3c to set
|
|
the colour of the border. \textbackslash \$c, however, does not exist in itself.
|
|
|
|
When a tag requires a floating point parameter, the decimal part \must\ be specified using a period (.);
|
|
never a comma. When a tag requires a colour parameter, it is given in HTML hexadecimal code, which is
|
|
\# followed by a 6-digit hexadecimal string, where the first two digits represent the red component,
|
|
the next two the green component, and the last two the blue component (\#RRGGBB). Sub Station Alpha
|
|
style (Visual Basic hexadecimal) is not supported.
|
|
|
|
In the tag specification in this document, optional parameters are denoted by being enclosed by square
|
|
brackets (``[]''), and may be ommitted. For example, \emph{\textbackslash baseline(curve1[,curve2])}
|
|
means that the second parameter is entirely optional. It's also possible that the entire parameter set
|
|
is enclosed in square brackets, e.g. \emph{\textbackslash vc[(c1,c2,c3,c4)]}.
|
|
|
|
The parameters of a tag \must\ be enclosed within parantheses, with exception for tags with only one numerical
|
|
parameter, for which the parantheses \may\ be omitted.
|
|
|
|
All tags \must\ start with a backslash (\textbackslash ). If an override block (a pair of curly brackets)
|
|
or any tag starts with anything else than a backslash, it is considered a syntax error and the parser \must\
|
|
ignore the block or tag and \should\ emit a warning (see the section "Invalid or Malformed Tags and Syntax Errors"
|
|
below). Thus it is not possible, as it was in earlier formats, to hide inline comments inside normal override blocks.
|
|
There is, however a special kind of comment block that can be used for this. Any curly opening brace that is
|
|
immediately followed by an exclamation mark (!) starts a comment block (ending with a matching closing curly brace),
|
|
the contents of which \must\ be ignored by the parser and the renderer.
|
|
For example:
|
|
|
|
\begin{verbatim}
|
|
{\fn(Verdana)\fs26\c#FFA040}Welcome to {\b1}AS5{\b0}!{!It's a nifty format, isn't it?}
|
|
\end{verbatim}
|
|
|
|
|
|
\subsection{Invalid or Malformed Tags and Syntax Errors}
|
|
Any override tag (excluding the special character escape) that meets any of the following conditions:
|
|
\begin{itemize}
|
|
\item - is not specified in this document (that is, tags not present in the standard or just simply
|
|
misspelled variants of existing tags)
|
|
\item - does not start with a backslash
|
|
\item - is found outside an override block (that is, not within curly braces)
|
|
\item - is missing parantheses where they should be present, or is missing a matching opening/closing paranthesis
|
|
\item - has arguments not matching those expected by the parser
|
|
\end{itemize}
|
|
is considered \emph{invalid} or \emph{malformed}. Invalid or malformed tags are syntax errors, and the renderer
|
|
\must\ ignore them. The parser \should\ also emit warnings about these errors, although it should be noted that
|
|
under certain circumstances it may be desirable to suppress warnings. The parser \should\ include an option to do so.
|
|
|
|
Any curly brace (start/end of an override block) which is missing its matching pair is also a syntax error; the
|
|
resulting line \must\ be drawn as if it was just plain text without the override block. Naturally, the parser
|
|
\should\ warn about this.
|
|
|
|
\todo{Finish this}
|
|
|
|
|
|
\subsection{Vector Path Format}
|
|
\todo{Write me}
|
|
|
|
|
|
\todo{Write detailed descriptions for all the override tags}
|
|
|
|
\subsection{Special Character Escapes}
|
|
The following tags are not considered override tags, but rather escape codes for special characters. They
|
|
\mustnot\ be inside an override block, but only in the middle of the text (i.e. not between \{ and \}).
|
|
|
|
|
|
\subsubsection{\textbackslash n}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
Line 1\nLine 2
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Inserts a forced line break.
|
|
|
|
\todo{Should the presence of a forced line break in a line disable automatic line breaking for that line?}
|
|
|
|
\subsubsection{\textbackslash h}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
Word1\hWord2
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Inserts a ``hard'' space. This is equivalent to Unicode character U+00A0 No-Break Space, but script authors
|
|
are recommended to use \textbackslash h over U+00A0 since U+00A0 can visually easily be mistaken for a regular
|
|
space character.
|
|
|
|
\subsubsection{\textbackslash \{, \textbackslash \}}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
Text \textbackslash \{inside curly braces\textbackslash \}
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Insert respectively literal \{ and \} into the rendered output.
|
|
|
|
\subsubsection{\textbackslash \textbackslash}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
A \textbackslash \textbackslash\ (backslash)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Insert a literal \textbackslash\ into the rendered output.
|
|
|
|
|
|
\subsection{Basic Typography Tags}
|
|
|
|
\subsubsection{\textbackslash i}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\i(1)
|
|
\i(0)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Enable (parameter 1) or disable (parameter 0) italics font style. If the selected font face does not
|
|
have a native italics variation, a simulated italics style \must\ be used. If the selected font face
|
|
does not have a non-italics variation, the italics vatiation \must\ be used even when \textbackslash i(0)
|
|
is specified.
|
|
|
|
\subsubsection{\textbackslash b}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\b(1)
|
|
\b(0)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Enable (parameter 1) or disable (parameter 0) boldface font style. If the selected font face does not
|
|
have a native boldface variation, a simulated boldface \must\ be used. If the selected font face
|
|
does not have a non-boldface variation, the boldface variation \must\ be used even when \textbackslash b(1)
|
|
is specified.
|
|
|
|
AS5 does not support specifying a specific font weight with \textbackslash b and any other parameter
|
|
than 0 or 1 (zero or one) is an error. To specify a specific weight version of a font that has more
|
|
than two weight variations, the textual name of the weight variation must be specified with the
|
|
\textbackslash fn override.
|
|
|
|
\subsubsection{\textbackslash u}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\u(1)
|
|
\u(0)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Add an underline decoration to the text (parameter 1) or not (parameter 0.) The underline is a straight
|
|
line parallel to the text baseline, placed slightly below the baseline.
|
|
|
|
\subsubsection{\textbackslash s}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\s(1)
|
|
\s(0)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Add a strikeout decoration to the text (parameter 1) or not (parameter 0.) The strikeout is a straight
|
|
line parallel to the text baseline, which strikes through the letters.
|
|
|
|
\subsubsection{\textbackslash fn}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\fn(fontname1,fontname2,...,fontnameN)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
List of preferred fonts in descending order of preference
|
|
|
|
\todo{What about fonts that have commas or parentheses in their names?}
|
|
|
|
\subsubsection{\textbackslash fe}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\fe(fontencoding)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set font encoding in some ISO code
|
|
|
|
\todo{What does this affect? Apart from possibly selecting national variations of some characters
|
|
and possibly fixing things in Windows.}
|
|
|
|
\subsubsection{\textbackslash fs}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\fs(size)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set font height in pixels. The font nominal character width is also set by \textbackslash fs to the default
|
|
of the font face.
|
|
|
|
The parameter can also be interpreted as a typographic point value, when
|
|
the script resolution is assumed to be 72 dpi and the size of a typographic point is defined as
|
|
$1/72$ inch.
|
|
|
|
\todo{Can this be defined more clearly?}
|
|
|
|
A negative font size must be considered an error and \must\ be ignored.
|
|
|
|
\subsubsection{\textbackslash bord}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\bord(bordersize)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set the width of the text outline. The outline width \mustnot\ be negative.
|
|
|
|
The text outline can be defined by a morphological dilation operation using the rasterised text
|
|
and a circular element with the radius specified by the \textbackslash bord tag. The outline is the
|
|
original rasterised text subtracted from the result of the dilation operation. Ie.:
|
|
\[O = (T \oplus E_{bord}) - T\]
|
|
Where $O$ is the image of the outline, $T$ is the image of the text,$E_{bord}$ is the image of the
|
|
circular element with radius $bord$ and $\oplus$ is the morphological dilation operation.
|
|
|
|
The border can also be calculated from the vector outlines of the text.
|
|
|
|
\todo{Define border by vector operations?}
|
|
|
|
\todo{Is the outline calculated before or after applying other transformations? Ie. does X/Y axis
|
|
rotations affect it?}
|
|
|
|
\subsubsection{\textbackslash shad}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\shad(shadowsize)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set shadow depth in script resolution pixels. The shadow depth \mustnot\ be negative.
|
|
|
|
\todo{Or define what a negative shadow depth should mean instead?}
|
|
|
|
The shadow can be defined as a shadow image offset from the text and outline images. The shadow image
|
|
\must\ be rendered visually ``further away'' than the text and outline images, ie. ``behind'' them.
|
|
|
|
The shadow image is the sum of the text and outline images, rendered entirely in the fourth color.
|
|
|
|
The shadow image offset from the text and outline images is $shadowsize$ script resolution pixels in
|
|
both X and Y direction.
|
|
|
|
After offsetting the shadow image, the text and outline images are subtracted from it at its new position.
|
|
|
|
\subsubsection{\textbackslash bordstyle}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\bordstyle(0)
|
|
\bordstyle(1)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set border style; 0 means normal, 1 means solid bounding box.
|
|
|
|
When border style is 1 the outline image defined by the \textbackslash bord override \mustnot\ be used
|
|
and instead an opaque box of the border color must be drawn behind the text.
|
|
|
|
\todo{Define that box further}
|
|
|
|
\subsection{Font Scaling Tags}
|
|
|
|
\subsubsection{\textbackslash fsc, \textbackslash fscx, \textbackslash fscy}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\fsc(scale)
|
|
\fscx(xscale)
|
|
\fscy(yscale)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set font X/Y scaling in percent.
|
|
|
|
\todo{Implementation for this should probably go in a section that deals with transformation pipeline.}
|
|
|
|
\subsubsection{\textbackslash fsp}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\fsp(fontspacing)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set additional spacing between characters in pixels. When the spacing is non-zero, an additional
|
|
number of script pixels equal to the parameter given to \textbackslash fsp are skipped after rendering
|
|
each glyph in the text. When the spacing is non-zero, any ligatures defined by the font face
|
|
\mustnot\ be used.
|
|
|
|
\todo{Does non-zero spacing have further implications? How about complex scripts?}
|
|
\todo{What about negative spacing?}
|
|
|
|
\subsubsection{\textbackslash fsvp}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\fsp(verticalspacing)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set font spacing between vertical baselines in pixels. This is an additional number of script pixels
|
|
to skip after each rendered line of text.
|
|
|
|
\todo{Any further implications on text rendering? What about negative values?}
|
|
|
|
\subsection{Colouring Tags}
|
|
|
|
\subsubsection{\textbackslash \$c}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\$c(colour)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set font colouring in hexadecimal RGB.
|
|
|
|
\subsubsection{\textbackslash \$a}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\$a(alpha)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set font alpha channel (transparency) in hexadecimal RGB.
|
|
|
|
\subsection{Positioning and Rotation Tags}
|
|
|
|
\subsubsection{\textbackslash left, \textbackslash right, \textbackslash top, \textbackslash bottom}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\left(distance)
|
|
\right(distance)
|
|
\top(distance)
|
|
\bottom(distance)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Margins are the distance between the subtitle text and the edge of the frame. They are used for
|
|
improved aesthetics, readability, and to avoid issues with overscan. Unless manually overriden
|
|
by another tag (such as \textbackslash pos), the text should always be contained inside the box
|
|
defined by the script area minus the four borders, as long as automatic line breaking mode is
|
|
set (see the section on [AS5]).
|
|
|
|
All distance values are specified in script coordinates. The default value for all borders is 12.
|
|
Margin tags can only be present once per line, and will affect all of it, not just the following
|
|
block. Margin tags cannot be animated.
|
|
|
|
\textbf{Implementation:}
|
|
The default positioning of the pivot point of the subtitles box is also determined by the margins.
|
|
On left-align, the \emph{x} of pivot is set to the left margin; on right-align, to $w - r$,
|
|
and on middle-align, to $\frac{w + r - l}{2}$, where \emph{w} is the script width, \emph{r} is
|
|
the value of the right margin and \emph{l} is the value of the left margin, that is, it is put
|
|
halfway between the edges defined by the margins. The rules are analogous to the \emph{y} coordinate.
|
|
|
|
See the alignment tags for more information regarding screen alignment.
|
|
|
|
\subsubsection{\textbackslash an, \textbackslash ax, \textbackslash ay, \textbackslash nx, \textbackslash ny}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\an(numpadalignment)
|
|
\ax(xalignment)
|
|
\ay(yalignment)
|
|
\nx(xinneralignment)
|
|
\ny(yinneralignment)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set alignment in various ways
|
|
|
|
\todo{How about an alignment mode where the position set controls the text baseline position instead
|
|
of an edge of the text bounding box?}
|
|
|
|
\subsubsection{\textbackslash rel}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\rel(0)
|
|
\rel(1)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Script resolution relative to video area (0) or not (1)
|
|
|
|
\todo{Is this really a good tag name?}
|
|
|
|
\subsubsection{\textbackslash vertical}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\vertical(0)
|
|
\vertical(1)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Makes text vertical. This in particular affects the use of some glyph variations in CJK scripts.
|
|
|
|
\todo{Does vertical imply that the baseline is vertical, ie.
|
|
\verb/{\vertical1\fscx0}this is vertical text/ is indeed shown top-down?}
|
|
|
|
\subsubsection{\textbackslash q}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\q(0)
|
|
\q(1)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set wrap style to manual (0) or automatic (1)
|
|
|
|
\subsubsection{\textbackslash pos}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\pos(x,y)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set line position to x,y in script coordinates.
|
|
|
|
Can be animated with \textbackslash t.
|
|
|
|
\subsubsection{\textbackslash org}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\org(x,y)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set origin to x,y in script coordinates.
|
|
|
|
Can be animated with \textbackslash t.
|
|
|
|
\subsubsection{\textbackslash bls}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\bls[#]
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
This sets the baseline shift, that is, the vertical spacing between each character and the baseline
|
|
in which it is supposed to be sitting on. The default value is 0, and the parameter is given in
|
|
script coordinates.
|
|
|
|
This tag can be animated with \textbackslash t, and can be reverted to style default by ommitting
|
|
its parameter.
|
|
|
|
\subsubsection{\textbackslash frx, \textbackslash fry, \textbackslash frz}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\frx(xrotation)
|
|
\fry(yrotation)
|
|
\frz(zrotation)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set font rotation around x/y/z axis in degrees.
|
|
|
|
\todo{Define the axes}
|
|
|
|
\subsubsection{\textbackslash fax, \textbackslash fay}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\fax(xshearing)
|
|
\fay(yshearing)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Set shearing in x and y axis. 0 means no shearing takes place. Negative values allowed.
|
|
The parameters are multipliers in a shearing matrix.
|
|
|
|
\subsection{Animation Tags}
|
|
|
|
\subsubsection{\textbackslash fad}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\fad(t1,t2)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Fading text
|
|
|
|
\subsubsection{\textbackslash t}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\t([t1,t2,]tags)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Animate tags between t1 and t2
|
|
|
|
\subsection{Shape Transformation Tags}
|
|
These are tags characterized by the fact that they distort the shape of the text itself. They
|
|
were designed to enhance the flexibility of the format while dealing with unusually-shaped
|
|
imagery.
|
|
|
|
\subsubsection{\textbackslash distort}
|
|
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\distort(x1,y1,x2,y2,x3,y3)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
The distort tag allows you to apply an arbitrary distortion to the block that follows it.
|
|
It takes three coordinate pairs that, along with the origin (at the current baseline position)
|
|
specify a quadrilateral.
|
|
|
|
$P_0$ is the origin, $P_1 = (x1,y1)$ is the corner at the end of the baseline for the affected text,
|
|
$P_2 = (x2,y2)$ is the point above that, and $P_3 = (x3,y3)$ is the point above $P_0$. That is, they
|
|
are listed clockwise from origin ($P_0$).
|
|
|
|
The following picture illustrates how this tag works:\\
|
|
\begin{center}
|
|
\includegraphics[width=0.7\textwidth]{./distort}
|
|
\end{center}
|
|
|
|
If the parameter list is ommitted, the distort reverts to the style's default (none by default).
|
|
This tag can be animated with \textbackslash t.
|
|
|
|
\textbf{Implementation:}
|
|
This tag cannot be reduced to an affine transformation, so it cannot be expressed in Matrix form.
|
|
In order to transform a given (x,y) coordinate pair to it:
|
|
|
|
\begin{enumerate}
|
|
\item Normalize the (x,y) coordinates to a (u,v) system, so that $P_0$ = (0,0) and $P_2$ = (1,1).
|
|
This can be done by dividing x by the block's baseline length (bl) and y by the block height (h).
|
|
The affine 3D transformation matrix for this operation is:\\
|
|
\begin{center}
|
|
$\displaystyle \begin{bmatrix}
|
|
\frac{1}{bl} & 0 & 0 & -\frac{P_{0x}}{bl} \\
|
|
0 & \frac{1}{h} & 0 & -\frac{P_{0y}}{h} \\
|
|
0 & 0 & 1 & 0 \\
|
|
0 & 0 & 0 & 1
|
|
\end{bmatrix}$
|
|
\end{center}
|
|
%\vspace{10pt}
|
|
That is, $\displaystyle u = \frac{P_x - P_{0x}}{bl}; v = \frac{P_y - P_{0y}}{h}$.
|
|
\item Apply the following formula: $P = P_0 + (P_1-P_0) u + (P_3-P_0) v + (P_0+P_2-P_1-P_3) u v$.\\
|
|
This can be interpreted as simple vector operations, that is, apply that once using the x coordinates
|
|
and another using the y coordinates. Since the four points are constant, the coeficients can be
|
|
precalculated, resulting in a very fast transformation.\\
|
|
\end{enumerate}
|
|
|
|
\subsubsection{\textbackslash baseline}
|
|
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\baseline(path1[,path2])
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Similarly to \textbackslash distort, this tag distorts the text, however, it does so by curving the
|
|
baseline into a vector path, so you can write curved text. Alternatively, you can specify a second
|
|
path to work as the ``ceiling'' of the text. The format of both path parameters is the standard
|
|
vector path format (see above).
|
|
|
|
\textbf{Implementation:}
|
|
Implementation of this tag can be summarized by the conversion of a generic $P_n = (x,y)$ point into
|
|
$P'_n = (x',y')$. Let $c1(t)$ and $c2(t)$ be the parametric equations of the two paths specified.
|
|
The conversion can then be done in the following manner:
|
|
|
|
\begin{enumerate}
|
|
\item Find the parameter \emph{t} along the baseline path that corresponds to the x position of
|
|
the point being converted. This can be done with a function that calculates the length from the
|
|
beginning of the path until an arbitrary point $P_t = c1(t)$ along it.
|
|
\item Calculate the base point along path1: $P_0 = c1(t)$
|
|
\item Calculate \emph{u} so that $u = \frac{y-y_0}{h}$, where $y_0$ is the y coordinate of the original
|
|
baseline and \emph{h} is the height of the block box.
|
|
\end{enumerate}
|
|
|
|
Now, for the single curve version:
|
|
|
|
\begin{enumerate}
|
|
\item Find the tangent vector of path1 at point $c1(t)$ and find the \emph{V} unit vector that is
|
|
perpendicular to the curve at that point, by rotating the tangent vector by -90 degrees along the Z axis.
|
|
This should give you a vector pointing ``up'', towards where the letters go. This can be summarized as:\\
|
|
$\displaystyle V = ( \lim_{h \to 0} (c1_y(t)-c1_y(t+h)) , \lim _{h\to0} (c1_x(t)-c1_x(t+h)))\\
|
|
V = \frac{V}{\left \| V \right \|}\\$
|
|
\todo Is that correct?
|
|
\item Multiply \emph{u} by the vector to find the offset from $P_0$, that is, $P'_n = P_0 + u V$.
|
|
\end{enumerate}
|
|
|
|
And for the two-curve version:
|
|
|
|
\begin{enumerate}
|
|
\item Calculate the ceiling point along path2: $P_1 = c2(t)$
|
|
\item Get \emph{P} with the parametric equation of the line defined by $(P_0,P_1)$: $P = (1-u) P_0 + u P_1$.
|
|
\end{enumerate}
|
|
|
|
\subsubsection{\textbackslash blpos}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\blpos#
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
This sets the position of the text relative to the baseline start. This tag can be animated.
|
|
\todo{Write proper specs for this.}
|
|
|
|
\subsection{Rastering Tags}
|
|
These tags affect how the subtitles are rasterized, that is, they affect things such as
|
|
colour, blurring, etc.
|
|
|
|
\subsubsection{\textbackslash \$vc}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\$vc(colour1,colour2,colour3,colour4)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Sets the primary colour to blend with each of the four vertices of draw polygon.
|
|
The primary use for this is to make smooth gradients easily, which are often required
|
|
for proper blending with the background. Note that you can also set alpha using this tag.
|
|
|
|
\subsubsection{\textbackslash \$blend}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\$blend(mode)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Sets the blending mode for the colour specified. Acceptable values are "normal", "add" and "multiply".
|
|
|
|
\subsubsection{\textbackslash clip}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\clip(x1,y1,x2,x2)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Clips so only text inside the rectangle formed by x1,y1,x2,y2 will be drawn
|
|
|
|
\subsubsection{\textbackslash iclip}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\iclip(x1,y1,x2,x2)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
The inverse of \textbackslash clip, i.e. clips so only text outside the rectangle formed
|
|
by x1,y1,x2,y2 will be drawn.
|
|
|
|
\subsubsection{\textbackslash \$blur}
|
|
\textbf{Usage:}
|
|
\begin{verbatim}
|
|
\$blur(???)
|
|
\end{verbatim}
|
|
|
|
\textbf{Description:}
|
|
Blurs stuff. Animatable.
|
|
|
|
\todo{Gaussian kernel or a number of applications of box blur?}
|
|
|
|
\subsection{Advanced Typography Tags}
|
|
These are more advanced tags, which might prove to be fairly complex to implement. They include
|
|
things such as ruby text support (also known as furigana, when used with Japanese Kanji.)
|
|
|
|
\todo{Write me}
|
|
|
|
|
|
\newpage
|
|
\section{Renderer Behaviour Specification}
|
|
\todo{Write this section}
|
|
|
|
|
|
\newpage
|
|
\section{Container Multiplexing Specification}
|
|
|
|
\subsection{Matroska}
|
|
Storage of AS5 files in Matroska files is similar to how similar formats are stored.\cite{mkv ssa}
|
|
The Codec ID used is \textsc{S\_TEXT/AS5}
|
|
|
|
First, the entire file is converted to UTF-8 (if it isn't already UTF-8). Then, all sections other
|
|
than \emph{[Events]} and \emph{[Resources]} are stored on the \emph{CodecPrivate} element. For the
|
|
\emph{[Resources]} section, each line is parsed and files are converted to Matroska file attachments.
|
|
\todo{Specify this more clearly.}
|
|
|
|
Finally, each line in the \emph{[Events]} section is read and stored each in a block. The \emph{start}
|
|
and \emph{end} fields are parsed (see the specifications on the section describing [Events]) and set
|
|
as the \emph{TimeStamp} and \emph{BlockDuration} elements. The line itself is then stored in the
|
|
following format:
|
|
|
|
\begin{verbatim}
|
|
Line: readOrder,style,userData,contents
|
|
\end{verbatim}
|
|
|
|
Where \emph{readOrder} is the number that the line had on the file. This is necessary so the file
|
|
can be demultiplexed back in its original order, since lines will be stored in chronological order
|
|
while inside the Matroska file. The remaining fields should just be copied from the original line.
|
|
|
|
|
|
\newpage
|
|
\addcontentsline{toc}{section}{References}
|
|
\begin{thebibliography}{1}
|
|
|
|
\bibitem{Aegisub} Rodrigo Braz Monteiro, Niels Martin Hansen, David Lamparter et al., Aegisub. Application, 2005-2007.\\
|
|
\url{http://www.aegisub.net/}
|
|
|
|
\bibitem{asa} David Lamparter, asa. Application, 2004-2007.\\
|
|
\url{http://asa.diac24.net/}
|
|
|
|
\bibitem{SSA} Kotus, Sub Station Alpha. Website, 1997-2003.\\
|
|
\url{http://web.archive.org/web/*/http://www.eswat.demon.co.uk/substation.html}
|
|
|
|
\bibitem{ASS} \#Anime-Fansubs, Advanced Sub Station Alpha.\\
|
|
\url{http://www.anime-fansubs.org}\\
|
|
\url{http://moodub.free.fr/video/ass-specs.doc}
|
|
|
|
\bibitem{VSFilter} Gabest, VSFilter. Application, 2003-2007.\\
|
|
\url{http://sourceforge.net/projects/guliverkli/}
|
|
|
|
\bibitem{ASS3} David Lamparter, Advanced Sub Station Alpha 3. Website, 2007.\\
|
|
\url{http://asa.diac24.net/ass3.pdf}
|
|
|
|
\bibitem{mkv} The Matroska project. Website.\\
|
|
\url{http://www.matroska.org/}
|
|
|
|
\bibitem{UTF-8} The Internet Society, RFC 3629, ``UTF-8, a transformation format of ISO 10646''. Website, 2003.\\
|
|
\url{http://tools.ietf.org/html/rfc3629}
|
|
|
|
\bibitem{UTF-16} The Internet Society, RFC 2781, ``UTF-16, an encoding of ISO 10646''. Website, 2000.\\
|
|
\url{http://tools.ietf.org/html/rfc2781}
|
|
|
|
\bibitem{Unicode BOM} Unicode, Inc, The Unicode Standard, Chapter 13. PDF, 1991-2000.\\
|
|
\url{http://www.unicode.org/unicode/uni2book/ch13.pdf}
|
|
|
|
\bibitem{mkv ssa} The Matroska project, specification for SSA/ASS subtitle formats. Website.\\
|
|
\url{http://www.matroska.org/technical/specs/subtitles/ssa.html}
|
|
|
|
\end{thebibliography}
|
|
|
|
\end{document} |