no edit summary
OGG into MacOsX ==
Warning: this project is in study/design stage.
=== Introduction ===
The work consists of two main parts.
The first part would consist of the creation of an [http://developer.apple.com/documentation/MusicAudio/Reference/CAAudioTooboxRef/AudioFileComponent/CompositePage.html AudioFileComponent]. That component has to implement the AudioFileComponentBase AudioFileFormat and AudiofileObject classes. The example on CoreAudio/AudioFile is a good starting point. It implements a rawAudio file reader/writer. The OGG part of ogg-vorbis should go here. The streaming support go here too.
The second part is the codec support. To support Vorbis, the creation of a [http://developer.apple.com/documentation/MusicAudio/Reference/CoreAudio/audiocodec/chapter_3_section_1.html#//apple_ref/doc/uid/TP30001108-CH204 AudioCodec] is needed. The example on CoreAudio/AudioCodecs is a good starting point too. It implements an IMA4 codec. No file format is implied here. So, there should be a glue ( that I haven't discovered yet ) from the AudioFileComponent API to know that contained data is Vorbis and launches the correct AudioCodec.
Finally, for the rest of Ogg Codecs, just the second part is needed.
NOTE: This is not sufficient for full OS X support. Many if not most OS X applications (iTunes, for example) use
Quicktime APIs for playback and encoding of media files. Quicktime does not use the Core Audio components (yet). If we want to support those applications it will be necessary to also create two Quicktime Components. We would need a Movie Import component and a Movie Export component (codes 'eat ' and 'spit'). It has been suggested that some time in the future Quicktime will use Core Audio components if they exist, but it is not known when that will happen. In any case, the Quicktime components will still be necessary for Theora support and may even be necessary for multi-link Vorbis files as well.
Example code for building Quicktime components can be found [http://developer.apple.com/samplecode/ElectricImageComponent/ElectricImageComponent.html
Work in progress...
* [http://www.annodex.net/software/libfishsound/ libfishsound:] A callback-based wrapper for vorbis and speex libraries. This may be a much better match to the callback-based AudioCodec API than libvorbis.
* [[Quicktime and GDB]]: Info on debugging quicktime components with GDB.
Update ===Good news! It turns out that the eat/spit components from the [http://qtcomponents.sf.net SourceForge Quicktime Components project] were '''not''' broken by the upgrade to Quicktime 7. It's just the Sound Manager-based codec component (code 'sdec') that needs to be updated to an AudioCodec. This '''greatly''' reduces the required work, since the AudioCodec API is quite simple compared to the Quicktime component API.
See [http://lists.apple.com/archives/QuickTime-API/2005/Sep/msg00126.html this message] in the quicktime-api mailing list archives for details.