This should reduce (but not completely eliminate) gradual audio desyncs in dumps. This also allows for accurate sample rates for the GameCube.
Completely eliminating gradual audio desyncs will require resampling to an integer sample rate, as nothing seems to support a non-integer sample rate.
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
In particular, I wanted to do change this in
AudioInterface::Init so that dumped GC audio doesn't need
to have a file split (changing from 32000 Hz to 32029 Hz)
when the emulated software initializes the AI registers.
I've also made the same change to DI's DTK code.
Normalizes variable names to conform to our coding conventions.
Previously we were signifying some variables as externally linked
globals, which wasn't the case.
The main problem was that the volume of the mixer wasn't savestated.
The volume is typically 0 at the beginning of a game, so loading a
savestate at the beginning of a game would lead to silent DTK audio.
I also added savestating to StreamADPCM.cpp.
The GameCube's sample rate is slightly different due to a hardware bug.
The exact numbers are (54000000 / 1124) for GameCube and (54000000 / 1125)
on Wii. I also modified 32KHz mode. This fixes audio desyncs in several
GameCube games and severe issues in Sonic Mega Collection.
The primary motivation here is to make sure we submit samples from the
CPU thread. This makes sure the timing of related interrupts accurate,
and generally keeps the different kinds of audio synchronized. This will also
allow improvements to audio dumping functionality.
The new code is also more concise because it gets rid of some duplicated
audio mixing code.
