General Compression Discussion Thread

[romulus_ut3]

I used the search function and I was unable to find a thread for the sole purpose of troubleshooting/discussing just compression issues, hence I decided to start this thread.

The purpose of this thread is simple, troubleshooting issues related to compression and each and everyone is more than welcome to post their issues here.

I will go first.

So I have Left 4 Dead 2, which takes up 12 GB of space when installed, so I decided to compress it to a more convenient size for backup purposes.

I used the following method to compress the whole directory:

msc+pzlib64+srep64+xz

My arc.ini is as follows:

[External compressor:msc]
header = 0
packcmd = MSC c -v -wav=1 -raw=1 -bmp=1 -ddsraw=1 -ddsdxt=1 -mp3=1 -bmf=9s -tak=9 -dxt=1 -lzma=hc4,lc8,lp2,pb2,fb273,mc1000 $$arcdatafile$$.tmp $$arcpackedfile$$.tmp

[External compressor:pzlib64]
header = 0
packcmd   = pzlib64 e -m2 -x -r9 -t100p $$arcdatafile$$.tmp -o $$arcpackedfile$$.tmp
unpackcmd = pzlib64 d -t100p - -o - <stdin> <stdout>

[External compressor:srep64]
header = 0
packcmd   = srep64 -m5f -d1g -a2 $$arcdatafile$$.tmp $$arcpackedfile$$.tmp
unpackcmd = srep64 -d -s -- <stdin> <stdout>

[External compressor:xz]
header = 0
packcmd   = xz a -txz -an -mcrc=0 -m1=lzma2:d1280m:fb=273:mf=bt4:mc=1000000:lc=4:lp=0 -mmt=3 -mx9 -si -so <stdin> <stdout>
unpackcmd = dec x -txz -an -y -si -so <stdin> <stdout>

When I compress the whole directory to a single archive, the output archive weighs 4.73 GB. 4.73 is just above the capacity of DVD5, a medium which I am planning to backup my game to. So if I move some files elsewhere and compress them separately using the exact same method, the total output becomes 5.27(!) GB.

What am I doing wrong that's causing the increase in output size by 600 MB opposed to a single archive?