Like I say I don't use codec packs, if you understand how video gets rendered via DirectShow you can get cleaner results with fewer codecs by hand. I think
CCCP is still supposed to be one of the best, the issue in the past has sometimes been that some idiots build codec packs that just install every codec they can find, rather than one good one for each format; or the pack comes loaded with malware, spyware, or adware of some kind that you have to remember to uncheck the box for — if that even works. CCCP had a reputation for doing neither of those.
I've just installed ffdshow tryouts (A codec that supports every video/audio format the ffmpeg library does, i.e. a LOT. It can also load soft-subtitles too) which covers me on the decoding side.
On the splitting side I have Haali which does the best job for Matroska/WebM/MP4 Containers. Realistically the only other container formats you're likely to encounter are AVI (which Windows will have a splitter for anyway) OGM (which Haali can also handle) and FLV (There's a standalone filter in the Media Player Classic - Home Cinema
project, or you could just use that version of Media Player Classic which will have it as an internal filter.)
The only format I've ever really have trouble with via DirectShow (and since I generally play audio in Winamp its an almost insignificant problem for me) is FLAC audio and containers. The filters I've seen are either ones that split and decode (where I would prefer them to split and pass the audio onto ffdshow for decoding) or they split, but for some reason will not connect to ffdshow.
Note that you will need to keep everything either 32-bit or 64-bit or install versions for both. A 32-bit Media Player Classic, for example will only be able to load 32-bit filters.
Edit: I will note that it can be worth knowing how DirectShow builds what it calls filter graphs
, so if you have a problem with a certain file you can try and work it out yourself. For example Nokia's Ovi suite installs a bunch of filters for playing back video recorded from your phone, and they work for that purpose. Unfortunately they seem to break on every other type of MP4 file out there, and yet have the uncanny knack of getting loaded ahead of any other existing MP4 splitters. When they first started breaking I was able to load the broken MP4 file in GraphStudio, see that unfamiliar filters were being used, and their location on the filesystem (i.e. Somewhere below a folder called /Nokia/ in the heirarchy) and unregister them. Then make sure whenever Ovi suite has to update that I promptly unregister them again.