We use ECW compressor shipped with ERDAS Imagine to export Orthoimagery for our different departments. Because we are facing problems with the Imagine license server, we had to choose GDAL (built with ECW SDK) as a fallback solution. Because the Orthotiles are all approximately 100MB large, thats possible.
As a compression ratio we use 1:20. With ERDAS ECW compressor (it does not matter if we use the licensed one or the free edition from some years ago) the images are all compressed to approximately 4 to 6 MB each.
With GDAL and the same compression ratio, the images got 10 to 20 (!) MB each. ALso some of the files cannot be opened afterwards. Also when I increase the compression ratio (to 1:30 for example) the imagefiles get smaller but face a lack of imagequality very quickly.
Why is GDALs compression significantly more worse than ECW Compressor, when they are both based on the same libraries from the ECW SDK?
Is it because GDALs implementation is so buggy or because ERDAS is keeping its Aces on their sleeve?
EDIT: Yeah, I know that this is truly a naive question ;)