What are "Xiph frameworks"? Do I need to install them?
A (Mac OS X) framework is a conveniently packaged software library. Xiph frameworks is a set of Xiph libraries containing the actual coding/decoding functionality used by XiphQT.
Yes, the Xiph frameworks need to be installed on your system but no, you no longer need to worry about installing them manually. Starting with XiphQT version 0.1.2 the installation package for OS X contains the necessary frameworks' files and will be able to install them automatically, or upgrade a previously installed version, if necessary.
After installation on OS X 10.3.9 I can open .ogg files but there is no sound...?
If an application, e.g. QuickTime Player, can open an .ogg file without errors but then simply produces just silence you may need to restart your computer.
Some of the XiphQT components are implemented as system components and not QuickTime components. While "Tiger" seems to be able to detect those components automatically - "Panther", apparently, can only detect those newly installed components on system start.
It's good, but... how do I uninstall this "XiphQT" thing?
To manually uninstall XiphQT packages on OS X:
Or you can have a look here for a more automated approach.
How do I make XiphQT work with iTunes on 64 bit Mac OS X?
Apple doesn't publish a 64 bit API for Quicktime, so the current XiphQT components are 32 bit. Recent Mac OS X on recent MacBooks defaults to running iTunes in 64 bit mode. There's an extra install step necessary to use XiphQT on 64 bit machines:
iTunes stopped playing .ogg files after an upgrade
After an iTunes or Mac OS X upgrade, the iTunes install on a 64 bit machine might have reverted to running in 64 bit mode. The current XiphQT components are 32 bit; use the instructions above ("How do I make XiphQT work with iTunes on 64 bit Mac OS X?") to verify that iTunes is running in 32 bit mode.
Track names (numbers, dates, ...) of .ogg files are missing, or displayed incorrectly, in iTunes - can you fix it?
Having the ability to play Ogg Vorbis files in iTunes was one of the main driving forces behind the qtcomponents project and also behind XiphQT development. However, iTunes is a proprietary software which does not provide a way to expand directly it's audio formats handling functionality by third-party developers. Given the iTunes support for QuickTime formats and architecture, writing a QuickTime extension (a component) has an effect of indirectly extending iTunes functionality. Unfortunately, iTunes support for QuickTime formats and extension mechanisms seems to be very selective - it is not even clear what exactly is supported as there is no single page of documentation about it.
Having said that, the XiphQT development efforts go into ensuring compatibility with QuickTime architecture and as complete (and proper) support for QuickTime extension mechanisms as possible. But the way applications, such as iTunes, choose to use, or not to use, QuickTime architecture is beyond our control.
Regarding the .ogg files meta-data missing in iTunes - to my knowledge, there is no way to fix this from the XiphQT source code point of view. However, there exist some AppleScript scripts that can help you with track's meta-data in iTunes (for example, see this ticket or this thread).
By the way, if you are curious or sceptical about the above paragraphs - here is a simple practical experiment:
Did you get all the meta-data imported correctly? Or - does the file behave exactly like the other formats (mp3, m4a), in all aspects?
Equaliser/visualisation/crossfade doesn't work in iTunes with .ogg files - how come?
In short? No idea, honestly! This is how iTunes treats all the "foreign" file formats, XiphQT-supported amongst them, in its mysterious internals.
Please see the first question in this section for a longer explanation.
iTunes doesn't use airTunes speakers when playing .ogg files - is XiphQT's audio output device fixed to the main audio output only?
XiphQT doesn't even come near any audio output device. Basically all it does is it gets a handful of compressed audio data bits and decompresses them, when asked to do so, returning a (slightly bigger) handful of decompressed, raw audio sample bits to whomever asked XiphQT to perform that decompression task.
For some reason iTunes doesn't treat all the audio compression formats equally. Please see the first question in this section for a longer explanation.
Does XiphQT allow one to listen to ogg network streams in iTunes?
Not as such. While XiphQT support for network ogg streams has lately (v.0.1.3) improved significantly (and you can try it in QuickTime Player), iTunes has its own routines for working with network audio streams and broadcasts. However, those routines see every network stream as an 'MPEG audio stream'. Obviously, this can not work with streams which are not MPEG audio streams. Such as ogg streams, for example.
iTunes doesn't open (ignores) some .ogg files, but the same files play just fine in other applications (not QuickTime Player, though). What can I do?
You can check if the filenames of those files are longer than 63 characters. If they are, shortening the filenames may solve the problem.
This is an acknowledged limitation of the recent QuickTime releases.