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             The Xiph.org Foundation's libtheora 1.1
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*** What is Theora?

Theora is Xiph.Org's first publicly released video codec, intended
for use within the Foundation's Ogg multimedia streaming system.
Theora is derived directly from On2's VP3 codec, adds new features
while allow it a longer useful lifetime as an competitive codec.

The 1.0 release decoder supported all the new features, but the
encoder is nearly identical to the VP3 code.

The 1.1 release features a completely rewritten encoder, offering
better performance and compression, and making more complete use
of the format's feature set. Files produced by both encoders can
be decoded by either release.

*** Where is Theora?

Theora's main site is www.theora.org.  Theora and related libraries
can be gotten from www.theora.org or the main Xiph.Org site at
www.xiph.org.  Development source is kept in an open subversion
repository, see http://theora.org/svn/ for instructions.

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Getting started with the code
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*** What do I need to build the source?

Requirements summary:

  For libtheora:

      libogg 1.1 or newer.

  For example encoder:

      as above,

      libvorbis and libvorbisenc 1.0.1 or newer.

  For creating a source distribution package:

      as above,

      Doxygen to build the API documentation,
      pdflatex and fig2dev to build the format specification
        (transfig package in Ubuntu).

  For the player only:

      as above,

      SDL (Simple Direct media Layer) libraries and headers,
      OSS audio driver and development headers.

The provided build system is the GNU automake/autoconf system, and
the main library, libtheora, should already build smoothly on any
system.  Failure of libtheora to build on a GNU-enabled system is
considered a bug; please report problems to theora-dev@xiph.org.

Windows build support is included in the win32 directory.

Project files for Apple XCode are included in the macosx directory.

There is also an experimental scons build.

*** How do I use the sample encoder?

The sample encoder takes raw video in YUV4MPEG2 format, as used by
lavtools, mjpeg-tools and other packages. The encoder expects audio,
if any, in a separate wave WAV file. Try 'encoder_example -h' for a
complete list of options.

An easy way to get raw video and audio files is to use MPlayer as an
export utility.  The options " -ao pcm -vo yuv4mpeg " will export a
wav file named audiodump.wav and a YUV video file in the correct
format for encoder_example as stream.yuv.  Be careful when exporting
video alone; MPlayer may drop frames to 'keep up' with the audio
timer.  The example encoder can't properly synchronize input audio and
video file that aren't in sync to begin with.

The encoder will also take video or audio on stdin if '-' is specified
as the input file name.

There is also a 'png2theora' example which accepts a set of image
files in that format.

*** How do I use the sample player?

The sample player takes an Ogg file on standard in; the file may be
audio alone, video alone or video with audio.

*** What other tools are available?

The programs in the examples directory are intended as tutorial source
for developers using the library. As such they sacrifice features and
robustness in the interests of comprehension and should not be
considered serious applications.

If you're wanting to just use theora, consider the programs linked
from http://www.theora.org/. There is playback support in a number
of common free players, and plugins for major media frameworks.
Jan Gerber's ffmpeg2theora is an excellent encoding front end.

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Troubleshooting the build process
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*** Compile error, such as:

encoder_internal.h:664: parse error before `ogg_uint16_t'

This means you have version of libogg prior to 1.1. A *complete* new Ogg
install, libs and headers is needed.

Also be sure that there aren't multiple copies of Ogg installed in
/usr and /usr/local; an older one might be first on the search path
for libs and headers.

*** Link error, such as:

undefined reference to `oggpackB_stream'

See above; you need libogg 1.1 or later.

*** Link error, such as:

undefined reference to `vorbis_granule_time'

You need libvorbis and libvorbisenc from the 1.0.1 release or later.

*** Link error, such as:

/usr/lib/libSDL.a(SDL_esdaudio.lo): In function `ESD_OpenAudio':
SDL_esdaudio.lo(.text+0x25d): undefined reference to `esd_play_stream'

Be sure to use an SDL that's built to work with OSS.  If you use an
SDL that is also built with ESD and/or ALSA support, it will try to
suck in all those extra libraries at link time too.  That will only
work if the extra libraries are also installed.

*** Link warning, such as:

libtool: link: warning: library `/usr/lib/libogg.la' was moved.
libtool: link: warning: library `/usr/lib/libogg.la' was moved.

Re-run theora/autogen.sh after an Ogg or Vorbis rebuild/reinstall

# theora fork for VTK

This branch contains changes required to embed theora into VTK. This
includes changes made primarily to the build system to allow it to be embedded
into another source tree as well as a header to facilitate mangling of the
symbols to avoid conflicts with other copies of the library within a single
process.

  * Ignore whitespace errors for VTK's commit checks.
  * Integrate the CMake build with VTK's module system.
  * Export symbols using `declspec` and `__attribute__`.
  * Mangle all exported symbols to have a `vtktheora_` prefix.