[Gdal-dev] gdalwarp segfaults when -ot "COMPRESSION=..." used

[Maciek Sieczka]

Frank

From: "Frank Warmerdam" <fwarmerdam at gmail.com>
> On Sat, 29 Jan 2005 00:28:22 +0100, Maciek Sieczka <werchowyna at pf.pl> 
> wrote:
>> Hi All!
>>
>> Long time no troubles with Gdal, happily - till today. I wanted to 
>> resample
>> a 15 m, Float32, ArcInfoGrid DEM to 1 m. When no compression used it goes
>> fine. But when -ot "COMPRESSION=..." is used a segfault occures (for 
>> either
>> LZW, DEFLATE and PACKBITS). And I need the compression badly because the
>> output is much too big.
>
> Maciek,
>
> I have successfully reproduce the bug with a somewhat similar
> configuration here.  I submitted a bug at:
>
>  http://bugzilla.remotesensing.org/show_bug.cgi?id=757
>
> I am guessing the problem is related to reading and rewriting
> a compressed block in TIFF format.  When you have small output
> files any given block will only be written once so things work.
> When you have a large output file (especially one that is not
> tiled), gdalwarp will handle the image in tiles and this can result
> in scanlines getting written, re-read and then re-written with new
> contents.
>
> In the past this was just unsupported for compressed files.
> However, Andrey has done some work in the last year or two
> to allow rewriting compressed TIFF files.  But I would not be
> surprised to find that in some circumstances this has some sort
> of problem.

Thanks for your answer Frank. I think that the on the fly compression during 
gdalwarp-ing is a very important feature, especially in case of big files - 
where it fails actually. Too bad it doesn't work and strange that nobody has 
reported this bug yet. Happily there is a workaround - using gdal_translate 
to compress the gdalwarp's output, as long as there is enough disc space for 
both files for a while :).

Cheers
Maciek