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              The Xiph.org Foundation's libtheora 1.2

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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 featured a completely rewritten encoder, offering

 better performance and compression, and making more complete use

 of the format's feature set.

 The 1.2 release features significant additional improvements in

 compression and performance. Files produced by newer encoders can

 be decoded by earlier releases.

 *** 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.

       (libvorbis 1.3.1 or newer for 5.1 audio)

   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 a more limited 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