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Text subtitles can be embedded in an Ogg stream alongside a Theora video.
* Overview
* Subtitles related options
* Converting non-UTF-8 files to UTF-8
* Examples
* Playing subtitles
* Overview
Subtitles are read from SubRip (.srt) format files and converted to
Kate streams. Those SubRip files must be encoded in UTF-8 (7 bit ASCII
is a subset of UTF-8 so is valid input as well). See below for more
information on converting SubRip files with other encodings to UTF-8.
ffmpeg2theora can convert files to UTF-8 transparently if build with
a C library that supports iconv.
Subtitles support requires libkate, available from:
http://code.google.com/p/libkate
A subtitles input file is given with the --subtitles option.
The language of subtitles in a file is given by the --subtitles-language
option. See below for a list of subtitles related options. At the most
simple, supplying a single input file:
./ffmpeg2theora -o output.ogv --subtitles input.srt input.avi
Any number of subtitles streams can be multiplexed, presumably with
different languages and/or categories. See below for examples of this.
Additionally, text subtitles from the input stream may also be used.
Use --nosubtitles if those are not to be converted.
* Subtitles related options
--subtitles <file>
Loads subtitles from a file, which must be an UTF-8 encoded SubRip
(.srt) file
--subtitles-language <language>
Sets the language of the relevant subtitles stream. Language must be
a language tag according to RFC 3066 (usually a two letter language
code, optionally followed by a dash (or underscore) and a region code.
Examples include en, it, ja, en_GB, de_DE, etc.
If unspecified, the default is to not set a language. It is however
strongly encouraged to set the language.
--subtitles-category <category>
Sets the category of the relevant subtitles stream. Category must be
a free text string describing the type of the subtitles streams. This
is meant to be parsable automatically, so should be ASCII only, and
preferably among a list of predefined well known categories, such as
subtitles, commentary, transcript, lyrics.
If unspecified, the default is subtitles.
--subtitles-encoding <encoding>
Sets the encoding of the relevant input file. Allowed encodings are
UTF-8, UTF8, iso-8859-1, and latin1. The first two are synonymous and
yield no conversion. The latter two are synonymous and convert from
iso-8859-1 to UTF-8.
If the input file is in another encoding, a separate step is needed
to convert the input file to UTF-8. See below for more information on
converting other encoding to UTF-8.
If unspecified, the default is UTF-8.
--subtitles-ignore-non-utf8
Any invalid sequence in UTF-8 text will be ignored. This may be useful
when using an UTF-8 file with stray non UTF-8 characters. This is not
a substitute for converting a non UTF-8 file to UTF-8, however, as the
non UTF-8 sequence will be missing from the output stream.
--nosubtitles
Subtitle streams from the input file will not be converted. Subtitles
from any supplied --subtitles option will still be used.
--subtitle-types <types>
By default, only text based subtitles found in the input file are
included in the output file. This option allows selecting which types
are to be included: none, all, text, or spu (spu being the type of
image-based subtitles found on DVDs).
* Converting non-UTF-8 files to UTF-8
If ffmpeg2theora wasn't build with iconv support, only UTF-8 and latin1
input text is supported.
If you have SubRip files in another format than UTF-8, you can use the
iconv or recode programs to convert them to UTF-8 so ffmpeg2theora can
read them.
* iconv
If you have a file called subtitles.srt which is not in UTF-8,
you can convert it to UTF-8 with the command:
iconv -t utf-8 -f ENCODING subtitles.srt > subtitles.utf8.srt
Substitute ENCODING with the actual encoding of the input file.
For instance, if your input file is in Shift-JIS encoding, replace
ENCODING with SHIFT-JIS. If your input file is in big endian UCS2
encoding, replace ENCODING with UCS-2BE.
This will create a new file called subtitles.utf8.srt, which will
be the equivalent of the input file, but in UTF-8 format, so it
can be used as input to ffmpeg2theora.
To view a list of all the encodings iconv can convert to UTF-8,
see the output of `iconv -l'.
* recode
If you have a file called subtitles.srt which is not in UTF-8,
you can convert it to UTF-8 with the command:
recode ENCODING..UTF-8 < subtitles.srt > subtitles.utf8.srt
Substitute ENCODING with the actual encoding of the input file.
For instance, if your input file is in Shift-JIS encoding, replace
ENCODING with SHIFT-JIS. If your input file is in BIG5 encoding,
replace ENCODING with BIG5.
This will create a new file called subtitles.utf8.srt, which will
be the equivalent of the input file, but in UTF-8 format, so it
can be used as input to ffmpeg2theora.
To view a list of all the encodings recode can convert to UTF-8,
see the output of `recode -l'.
* Examples
Add a single English subtitles stream:
./ffmpeg2theora --subtitles-language en --subtitles input.srt input.avi
Add German and Italian commentary:
./ffmpeg2theora --subtitles comm.german.srt --subtitles-language de \
--subtitles-category commentary \
--subtitles comm.italian.srt --subtitles-language it \
--subtitles-category commentary \
input.avi
Add English subtitles and commentary:
./ffmpeg2theora --subtitles subs.srt --subtitles-language en \
--subtitles-category subtitles \
--subtitles commentary.srt --subtitles-language en \
--subtitles-category commentary \
input.avi
* Playing subtitles
At the moment, only VLC has playback support for Kate streams. However, the
libkate distribution includes patches for other players and media frameworks
(MPlayer, GStreamer, liboggplay).
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