Refactoring analysis downmix to use sig scaling #637

Job	Run time
CMake MINGW	1m 10s
Test build with CMake 3.16.0	1m 49s
CMake/Android/So/ARMv8/Release	20s
CMake/Android/So/X86/Release	21s
CMake/Android/So/X64/Release	14s
CMake/Windows/Dll/X86/Release	1m 24s
CMake/Windows/Dll/X64/Release	1m 18s
CMake/Windows/Dll/ARMv8/Release	1m 40s
CMake/Linux/So/X64/Release	30s
CMake/MacOSX/So/X64/Release	31s
CMake/MacOSX/Framework/X64/Release	1m 16s
CMake/iOS/Dll/arm64/Release	42s
CMake/iOS/Framework/arm64/Release	31s
CMake/Windows/Lib/X86/Release	1m 53s
CMake/Windows/Lib/X64/Release	2m 42s
CMake/Windows/Lib/armv8/Release	1m 36s
CMake/Linux/Lib/X64/Release	1m 0s
CMake/MacOSX/Lib/X64/Release	1m 16s
CMake/iOS/Lib/arm64/Release	39s
CMake/Android/Lib/ARMv8/Release	21s
CMake/Android/Lib/X86/Release	20s
CMake/Android/Lib/X64/Release	23s
CMake/CustomModes/Linux/Lib/X64/Release	1m 19s
CMake/AssertionsFuzz/Windows/Lib/X64/Release	2m 46s
CMake/AssertionsFuzz/Linux/Lib/X64/Release	1m 0s
CMake/AssertionsFuzz/MacOSX/Lib/X64/Release	1m 22s
	28m 23s

Provide feedback