What are the differences among MG2, MG3, MG4 and JPEG 2000 formats?
MrSID® Generation 2 (MG2)
MrSID Generation 2 is the original MrSID format and is still supported in geospatial applications. MG2 is limited to 2GB in file size and is essentially for compression only. It does not support the more advanced capabilities available in MrSID Generation 3, MrSID Generation 4 and JPEG 2000.
MrSID Generation 3 (MG3)
MrSID Generation 3 followed and improved upon MG2. MG3 supports unlimited file sizes, lossless encoding with optimization, manipulation functions such as area of interest encoding. MG3′s optimization capabilities mean that you do not have to run another encoding process to increase the compression ratio, crop your image, or encode an area of interest.
MrSID Generation 4 (MG4™)
MrSID Generation 4 (MG4) is the most current version of the MrSID technology and file format. The key new features of MG4 are:
- multispectral (and hyperspectral) support
- alpha band support
- support for LiDAR point cloud data
- an improved mechanism for composite mosaicking
Support for multispectral imagery in MG4 enables users to compress 4-band NAIP data, LiDAR data, 8-band Landsat data or even 224-band AVIRIS data, losslessly or with LizardTech’s usual high-quality lossless compression. The MG4 format also adds support for alpha bands, enabling users to add true transparency to their compressed imagery. Imagery compressed to MG4 can be viewed with one of LizardTech’s free viewers and most third-party applications.
JPEG 2000 (JP2)
JPEG 2000 is an ISO standard that allows for more user-specified encode parameters than MrSID, a customizability that gives it the potential to perform better than MrSID at decode time, provided that the parameters chosen correctly anticipate the particular workflow that the imagery is used for. JP2 typically compresses faster than MG3, and until the release of MrSID Generation 4 (MG4) it was the only LizardTech format that supported multispectral imagery.
Differences Among the MG2, MG3, and MG4 Formats
As the MrSID technology has evolved over the years, the range of capabilities supported has evolved as well. Specifically:
- MG2 does not support lossless compression
- MG2 does not support optimization
- MG2 does not support composite images
- Only MG4 supports signed integer data
- Only MG4 supports alpha masking
- Only MG4 supports multispectral and hyperspectral imagery
- Only MG4 supports LiDAR
- While MG3 composite mosaics can contain MG2 files, MG4 composite mosaics must be made up of only MG4 files.
Differences between MrSID and JPEG 2000
While MrSID was designed especially for geospatial images, JPEG 2000 does not specify a standard method for handling geospatial or any other metadata, which has hampered its adoption in the geospatial industry. However, JPEG 2000 supports XML, and recent developments that facilitate encoding XML-based Geography Markup Language (GML) metadata in JP2 files are paving the way for greater interoperability between JP2 and geospatial applications.
This article was last updated or verified on 9 September 2016.