[sldev] VWR-13511 : Occasional crashes in OpenJPEG

[Dzonatas Sol]

Philippe Bossut (Merov Linden) wrote:
> KDU is flat out 3 times faster to decode than OpenJPEG. The ratio is  
> consistent throughout the whole session.
>   

Until OpenJPEG v2, this 3x factor is simply due to the fact that KDU is 
able to pull metadata without any decode on any resolution level. The 
API for v1.x didn't have a call to extract just the header like the v2 
of the API does. Therefore, at least up to 2x of that that 3x factor can 
be accounted for in time wasted to decode resolution levels when it 
didn't need to in order to just get metadata out of the header.

Also, the default compile options on the OpenJPEG library does not have 
tree-vectorization optimization turned on. Without tree-vectorization, 
only a few picked areas of the code get SSE optimization. With 
tree-vectorization, the compiler will vectorize as much as it can as the 
code is written in a way to enable such tree-vectorization. Do note that 
tree-vectorization is not on by default because not everybody compiles 
with GCC, and MSVS did not support tree-vectorization.

As for the metadata only mentioned above, that is fixed in OpenJPEG v2.