Bash version of https://gist.github.com/segfault-bilibili/767d57c64fc06779787bda19612da3e0

audiofix.sh

#!/bin/bash
# workaround audio bug since Magia Record 3.0.1
# author: segfault-bilibili

# English README
#
# 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.

# 中文说明
#
# 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。

# usage:
# apktool d --no-src --no-res magireco-3.0.2-EX.apk
# audiofix.sh --wdir magireco-3.0.2-EX
# apktool b magireco-3.0.2-EX
# zipalign -p -f -v 4 magireco-3.0.2-EX/dist/magireco-3.0.2-EX.apk magireco-3.0.2-EX-audiofix.apk
# apksigner sign --ks keystore.jks --ks-pass pass:12345678 magireco-3.0.2-EX-audiofix.apk

set -e

check_function() {
    local filename=$1
    local funcname=$2
    local in_func_offset=$3
    local data=$4

    local read_len=$(( ${#data} / 2 ))

    local foundline="$(readelf --wide --dyn-sym "${filename}" | grep -E -m1 "\s+${funcname}$")"
    local offset=$(( "0x$(echo "${foundline}" | awk '{print $2}')" + in_func_offset ))
    local size=$(( "$(echo "${foundline}" | awk '{print $3}')" ))

    if (( in_func_offset < 0 )) || (( read_len <= 0 )) || (( in_func_offset + read_len > size )); then
        echo "invalid in_func_offset or read_len" >&2
        exit 1
    fi

    local func_hex="$(xxd -p -s "${offset}" -l "${read_len}" "${filename}")"
    [[ "${data}" == "${func_hex}" ]]
    local ret=$?
    echo "check funcname=${funcname} offset=${offset} read_len=${read_len} data=${data} func_hex=${func_hex} ret=${ret}" >&2
    return $ret
}

patch_function() {
    local filename=$1
    local funcname=$2
    local in_func_offset=$3
    local data=$4

    local write_len=$(( ${#data} / 2 ))

    local foundline="$(readelf --wide --dyn-sym "${filename}" | grep -E -m1 "\s+${funcname}$")"
    local offset=$(( "0x$(echo "${foundline}" | awk '{print $2}')" + in_func_offset ))
    local size=$(( "$(echo "${foundline}" | awk '{print $3}')" ))

    if (( in_func_offset < 0 )) || (( write_len <= 0 )) || (( in_func_offset + write_len > size )); then
        echo "invalid in_func_offset or write_len" >&2
        exit 1
    fi

    echo "patch funcname=${funcname} offset=${offset} write_len=${write_len} data=${data}" >&2
    echo "${data}" | xxd -p -s "${offset}" -l "${write_len}" -r - "${filename}"
    local ret=$?
    if (( ret != 0 )); then
        exit $ret;
    fi
}

patch_for_arch() {
    local arch=$1
    local check_offset=$2
    local check_data=$3
    local patch_offset=$4
    local patch_data=$5

    local func_to_patch="criNcv_GetHardwareSamplingRate_ANDROID"
    local file_to_patch="./lib/${arch}/libmadomagi_native.so"

    if [ -d "./lib/$arch" ]; then
        if check_function "${file_to_patch}" "${func_to_patch}" "${check_offset}" "${check_data}"; then
            patch_function "${file_to_patch}" "${func_to_patch}" "${patch_offset}" "${patch_data}"
            check_function "${file_to_patch}" "${func_to_patch}" "${patch_offset}" "${patch_data}" || exit 1
        else
            echo "check failed"
            exit 1;
        fi
    else
        echo "skip arch ${arch}"
    fi
}

wdir=""
while (($# > 0)); do
    case "$1" in
        --wdir)
            if [ $# -gt 1 ] && [ -n "$2" ]; then
                wdir=$2
            fi
            ;;
    esac
    shift 1
done

if [ ! -n "$wdir" ]; then
    echo "please specify --wdir work_dir"
    exit 2
fi

cd "$wdir"

patch_for_arch arm64-v8a 8 "c0035fd6" 4 "00709752"
patch_for_arch armeabi-v7a 8 "1eff2fe1" 4 "800b0be3"