Hi,
I have filed a new ticket for this:
http://trac.osgeo.org/gdal/ticket/3165
A summary of my tests with gdalinfo -mm
Processing 9 .sid files via a .vrt takes 2h:47m
Processing 9 .sid files directly takes 0h:57m
Processing 24 .tif files via a .vrt takes 0h:27m
Processing 24 .tif files directly t
Hi list
Craig Leat:
> I need to investigate further, but I am suspecting that this issue may
> be specific to the MrSid format.
I have tested further and can report as follows:
1. I have 24 MrSid files with overview levels 2 4 8 16 32 64 128
2. I can point QGIS to the directory and load all these
Because JPEG2000 images inherently contain a pyramid of reduced
resolution images, the Kakadu Software demo application kdu_expand,
that is available for free for Win32, Mac OS X, Linux, Solaris,
provides a very fast way to create reduced resolution overview images.
For me, the kdu_expand -
Hi Frank and Even
I need to investigate further, but I am suspecting that this issue may
be specific to the MrSid format. My tests have been with a collection
of 24 sid images. I just went back to an older project where I have
188 tiles in GeoTiff format (and similar base resolution) and QGIS
work
Selon Frank Warmerdam :
Craig,
Sorry for giving you wrong directions. Frank is obviously right. I somehow got
confused by the fact that the VRT driver doesn't expose overviews, but its
implementation of RasterIO() can indeed use overviews of the underlying rasters.
I could check it with OpenEV by
Even Rouault wrote:
Selon Craig Leat :
Craig,
I suppose you are speaking about bad performance when not viewing the VRT at its
full resolution ? (at full resolution, the overhead of VRT should be small
hopefully)
I'm afraid there's little you can do to improve the situation in a simple way.
As
Hi Even
Thanks for your valuable comments. If I understand you correctly I can
either access the overviews in the tiles by hand crafting vrt files
for each overview level or sacrifice disk space and generate external
overviews using your gdalwarp trick [1].
A comment from Frank [2] back in 2005 c
Selon Craig Leat :
Craig,
I suppose you are speaking about bad performance when not viewing the VRT at its
full resolution ? (at full resolution, the overhead of VRT should be small
hopefully)
I'm afraid there's little you can do to improve the situation in a simple way.
As you noticed, the VRT
Hi
I am having performance issues with gdal raster vrt files and since I
am not experienced with this format I am hoping someone can offer some
advice. I built the vrt files from a collection of MrSid images using
gdalbuildvrt. I then used sed to add the tag and changed from
to . I am using QGIS
