[Mixxx-devel] SoundSource plugins branch merged into trunk, details on M4A plugin

[Albert S. <al...@mi...>]

Hi guys,

I've just merged the sadness_ssplugin branch into trunk. A significant
amount of work was done in this branch in order to refactor our
SoundSource classes so that the SoundSourceM4A class could be compiled
as a dynamic library and loaded at runtime.

If you compile Mixxx from source, the M4A plugin is built by default.
The source code is located in the "plugins/soundsourcem4a" directory
in our source tree. Please do a "sudo scons install" after compiling
in order to install the plugin system-wide. The install path is
"[prefix]/lib/mixxx/plugins/soundsource/".

In the "plugins/build" directory, there is a script for building a
.deb package containing the M4A plugin. There is also an Inno Setup
project file that generates a Windows installer,  and an OS X
Installer project file build a .pkg installer.

Due to legal uncertainty, we will not be distributing the M4A playback
plugin ourselves. M4A playback will not work out-of-the-box in Mixxx.
>From a user experience perspective, we know this is less than ideal,
especially considering the popularity of the iTunes Music Store, which
distributes M4As. The M4A plugin is a temporary solution - It's very
important for us to write a SoundSource class that uses an AAC decoder
that's provided by the operating system, be it through the Quicktime
API, DirectShow, or a wrapper like Phonon. Doing so will eliminate the
distribution problems we face with the M4A plugin because the AAC
decoder would not have to be distributed.

Attached is a screenshot of what the Library preferences pane looks
like now. The "Available Online..." button opens up a web browser to
our Mixxx Add-ons Wiki page.

Lastly, I want to acknowledge that the build system is a bit of a mess
for this. I forked our SConscript in the soundsourcem4a directory, but
it's overkill. The SoundSource plugins are tied to Qt because I didn't
want to rewrite all those classes without Qt, so the SConscript in
that directory does detection for a bunch of libraries. The build is
hierarchical - our root SConstruct does call the SConscript in the
plugins directory, and the list of DLLs that are created does get
passed into our usual SConscript. However, the Configure environment
should be shared between these two SConscripts. If that was done, I
suspect 99% of the soundsourcem4a/SConscript file would be
eliminated....

Thanks,
Albert

P.S. I finally got rid of that defs_audiofiles.h that I disliked so
much. :) The supported audio filetypes are enumerated at runtime after
all the plugins are loaded, and SoundSourceProxy has static functions
that replace the hardcoded constants previously provided by
defs_audiofiles.h.