= RFC 24: GDAL Progressive Data Support = 

Author: Norman Barker[[BR]]
Contact: nbarker@ittvis.com[[BR]]
Status: Development

== Summary ==

To provide an interface for data streaming support to GDAL by overloading the RasterIO function to include a callback function when there are buffer updates.  The RFC focuses on JPIP but should be generic to apply to other streaming / progressive formats.

== Definitions ==

'''JPIP''': JPEG 2000 Interactive Protocol

== Objective ==

To provide a callback function to allow users of a progressive format driver to receive notifications of updates to the underlying dataset for a particular requested region of the data.  The notification mechanism should be accessible to all the swig wrappers.

== Implementation ==

The implementation is a definition of an interface, in particular an overloaded function definition for RasterIO.  Concrete implementations of this interface will follow.  Currently the most convenient JPIP streaming developer library is [http://www.kakadusoftware.com Kakadu] however since GDAL is also developer library, only stubs can be distributed to conform to Kakadu licensing ([http://trac.osgeo.org/gdal/wiki/JP2KAK JP2KAK]).  Commercial vendors are also interested in using GDAL for streaming support and a standard interface will allow these commercial plugins to be incorporated. e.g. [http://www.gdal.org/frmt_jp2ecw.html ECW], [http://www.gdal.org/frmt_mrsid.html MrSID].

=== Proposed Progressive Streaming Sequence of Events ===

''Sequence shows GDALDataset, same sequence for GDALRasterBand''

[[Image(progressive.jpg)]]