[Gdal-dev] Re: gdal_translate unable to allocate buffer

[WolfgangZ]

Even Rouault schrieb:
> Wolfgang,
> 
> I think this is a known issue :  VRT made of several thousands of single 
> images don't work (on Linux at least). Currently the VRT driver first opens 
> all images before doing any translation to GTIF. And at a moment, you reach 
> the limit of maximum simultaneous open files, which is 1024 on a typical 
> Linux system.

I know that limit on linux. Windows was able to handle higher counts 
without knowing the actual limit.

> See http://trac.osgeo.org/gdal/ticket/1781.
> In this ticket, I've attached a patch called 
> gdal_svn_gdalbuildvrt_with_proxy.patch which is not included in GDAL. It 
> works for me (I can handle big VRT with it), but contains 
> not-really-good-looking pieces of code that should be improved for inclusion 
> in GDAL tree...  You would need to 
> add -DUSE_GDAL_PROXY_FOR_VRT  -DI_CAN_LIVE_WITH_THIS_GDAL_PROXY_NASTY_THING 
> on compilation line to get the best of it...

I don't really know how to compile gdal on my own. I only have limited 
experience in Fortran but absolutely no knowledge in C. Need to look for 
a (free) compiler.

> 
> We should maybe document that problem in the VRT driver documentation for the 
> moment and hope that someone comes with a better fix.
> I think a better fix would be easier if we can extend the VRT XML format to 
> add information about source files, such as width and height.
> 

The documentation should really be extended to show the limits of the 
VRT driver. VRT provides really nice features but perhaps there should 
be a SVRT (Simple VRT) which is limited to same tile size, same file 
type, same compression) and why is there a need to open all tiles at 
all? You need to open only that files where you need to read from?!

I really would like the VRT driver to be improved.

Regards
Wolfgang