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Why does processing Multiresolution Seamless Image Database (MrSID) files take a long time?
Multiresolution Seamless Image Database (MrSID) is a proprietary lossy compression technique developed by LizardTech for maintaining the quality of large compressed raster data. Compressing the raster data reduces the file size for storage and improves the reading performance of the data since a reduced amount of data is being read or transferred. A raster data file of 40 GB can be compressed down to 2 GB as a .sid file.
However, when drawing or using a .sid file as an input for a geoprocessing tool such as the Mosaic To New Raster tool, the raster data must be decompressed, resulting in slower performance or taking a long time to process, depending on the uncompressed size of the file and the resources of the processing hardware. The more highly compressed the raster, the longer it takes to decompress.
Users can view the raster dataset properties of the file to identify the uncompressed size of the .sid file. For more information on raster dataset properties, see the following ArcGIS Help: Raster dataset properties.
Therefore, users are encouraged to use .sid files only for read-only functions. To process .sid files for display purposes, consider using alternative methods that do not require any geoprocessing tools. For example, instead of mosaicking a large amount of .sid files with the Mosaic To New Raster tool, bring the .sid files and group them into their own group layer instead. Users can also convert MrSID files to other formats using LizardTech's proprietary GeoExpress.