[Gdal-dev] ECW compression - Extremely slow Linux performance

[Andrew Larcombe]

Frank Warmerdam wrote:
> Andrew Larcombe wrote:
>> Hi,
>>
>> I'm using gdal_translate to convert a 4000px x 4000px uncompressed 
>> 46MB tiff to an ECW file.
>>
>> On a Windows XP laptop (Pentium M 1.6 GHz, 512MB RAM) using the latest 
>> fwtools download the process takes about 6 seconds.
>>
>> On a RedHat Enterprise 3 powered Quad-3.8Ghz processor with 2GB ram 
>> using gdal-1.3.1 built from source the process takes ~120 seconds.
>>
>> In each case the command used is as follows:
>>
>> gdal_translate -of ECW -co "TARGET=90" OSIM_TQ3517_2004-07-07.tif 
>> test.ecw
>>
>> Does anyone have any thoughts on why their is such a considerable 
>> difference in speed, and what I can do to remedy the situation?
> 
> Andrew,
> 
> Have you watched the CPU usage to see if it is 100% on the linux system
> when doing the compression?  If not, then I *suspect* some sort of thread
> switching latency or something similar.
> 
> Best regards,

Frank, Aaron,

Thanks for the prompt replies:

Aaron - yes, in both instances the disk is local. WinXP is a local 
NTFS-formatted filesystem, Linux is ext3 formatted in a (I think) raid 1 
configuration. Incidentally tiff -> jpg compression of the same file 
takes ~1.5 seconds on the Linux box.

Frank - according to top the CPU usage varies but never gets above 20%. 
Does this shed any more light on the issue?

Thanks again,

Andrew

-- 
Andrew Larcombe
andrew at andrewlarcombe.co.uk