workaround audio bug since Magia Record 3.0.1
author: segfault-bilibili

Since Magia Record 3.0.1, there appears to be a bug affecting minor fraction of players.

Such bug makes the game audio (including BGM, sound effects etc) sound strange:
(1) the pitch sounds to be lower than normal;
(2) the time sounds to be "stretched" longer/slower than normal.

There's currently an experimental modification to workaround this bug.
To distinguish from other EX versions without this experimental modification,
APK files which contain this mod have "-audiofix" suffix in its file name, like:
"magireco-3.0.2-EX-audiofix.apk".

The root cause of this bug is still unclear. It should be some kind of sample rate mismatch.

It's observed that the audio is "stretched" exactly 8.84% longer than it should be,
which matches exactly with 48 / 44.1 = 108.84%;
plus the currently observed fact that only environments with a 44.1kHz system audio output
sample rate seem to have this problem;
it's guessed that deceiving the game to make it think the system audio output sample rate
was 48kHz (instead of actual 44.1kHz) might make this problem go away - and luckily, it does,
at least in our limited tests.

However, it's still confusing why such trick seems to work.

自从魔法纪录3.0.1版开始，出现了一个影响少数玩家的bug。

这个bug会让音频（包括背景音乐、音效等等）听起来很奇怪：
(1) 音调听起来比正常低；
(2) 时间听起来也被拉长/变慢了。

目前有一个实验性的小修改来绕过这个bug。
为了与不带这个修改的其他EX版区分，进行过这种修改的APK文件名含有"-audiofix"后缀，比如：
"magireco-3.0.2-EX-audiofix.apk"。

导致这个bug的根本原因还不太清楚。可能是某种采样率不匹配。

据观察，音频被拉长到正好108.84%，和 48 / 44.1 = 108.84% 吻合。
再加上目前观察到只有系统音频输出采样率是44.1kHz的环境才有这个问题；
就可以猜测，如果欺骗游戏、使其认为系统音频输出采样率是48kHz（而不是实际值44.1kHz）
就能让问题消失——实际上也确实消失了，至少在有限的测试里是这样。

然而，现在还并不清楚为什么这一招看上去能奏效。