From my experience a lot of codecs have some wrong things in them and those things are usually introduced during codec creation. As for containers, I’ve expressed my opinion before.
It is very bad when some codec is being developed and then suddenly it’s declared released. You’re left with a pile of code that has somehow evolved into current shape and probably even the author has no idea how it works. Two examples â€” Snow and Speex. The first one is wavelet-based codec that performed quite well back in DiVX 3/4 days, the other one is a speech codec that also gained some popularity and was even included as one of Flash audio codecs. So the codecs by themselves should not be that bad but there’s only one implementation and no specification. There were several attempts to make Snow developer write a specification for it (for money!) but he always refused. FFV1 is faring somewhat better since it has some rudimentary specification and hopefully standardisation efforts will bring us independent implementations and full specification (yes, I’m an
idiot optimist). What would be a proper way to design a codec in my opinion? Create test version, play with it till you achieve good result or release a known beta, write specification, throw away old code and reimplement version 1 from scratch. Repeat for version 2 etc.
I think I’ve complained before that this situation is very common with proprietary codecs too. They have inhouse encoder and decoder implementation with encoder bugs compensated in the decoder. Stupid motion compensation in RealVideo 4 is one of those “features”. Or pre-RTM WMV9 with its block pattern coding though it’s supposed to be beta anyway.
There is even worse case â€” when codec author decides to embed all development history into decoder maintaining backward compatibility. The worst offender is Monkey Audio with its subtle bitstream changes at every version and having two dozen versions. Another “good” example is HEVC with its ever-changing bitstream format. Different major versions of reference software introduce serious bitstream changes, like HM8 -> HM10 transition remapped all NAL IDs. IIRC superseded version of ITU H.265 was for 4:2:0 subsampling only. Honestly, I shan’t cry if this codec dies because of idiotic licensing terms (and maybe it should really be contained only in FLV). Speaking of HEVC idiocies, VP9 got new features in new profiles including 4:4:0 subsampling. In my opinion one should kill this creeping featurism especially if you don’t have proper profiling/versioning system and even them introduce new features sparingly.
At least there’s still hope for Daala to be developed properly.