[gdal-dev] Problem when creating overviews for large input files with gdaladdo

[Armin Burger]

Hi Even

thanks a lot for the fast reply and the explanation! I will try your 
workaround. The patience needed to wait for the completion of the 
"normal" method seems to be a bit too high, I stopped the last test 
after 4 days...

Best
Armin



On 19/12/16 22:26, Even Rouault wrote:
> Armin,
>
>
>
> This is a "well known" performance issue with the geotiff driver /
> libtiff when switching back and forth between IFD (image file
> directories). At ~ 75%, you start generating overview factor 4 and that
> implies switching regularly between the one previously computed (read
> operations) and the new one (write operations). Each time you switch,
> you need to read and write the TileOffsets and TileByteCounts tags
> (those can be 10's of megabytes large on huge file, and are the root
> cause for the performance problem). With infinite patience, this would
> eventually complete.
>
>
>
> A trick you can use is :
>
>
>
> gdaladdo -ro --config COMPRESS_OVERVIEW LZW INPUT_FILE 2
>
> gdaladdo -ro --config COMPRESS_OVERVIEW LZW INPUT_FILE.ovr 2
>
> gdaladdo -ro --config COMPRESS_OVERVIEW LZW INPUT_FILE.ovr.ovr 2
>
> gdaladdo -ro --config COMPRESS_OVERVIEW LZW INPUT_FILE.ovr.ovr.ovr 2
>
>
>
> Even
>
>
>
>
>
>
>
> --
>
> Spatialys - Geospatial professional services
>
> http://www.spatialys.com
>