[mapserver-users] Mr Sid vs ECW

[Andy Colson]

On 7/6/2010 11:10 AM, Mark Volz wrote:
> Hello,
>
> Which format is faster ECW or Mr Sid for a large image? P.S. I don’t
> think I will be able to use a tile cache for the application I am
> developing.
>
> Thanks
>
> Mark Volz
>
> GIS Specialist
>

Go with ECW.  If you have huge CPU power you may not notice, but I run 
my maps on AMD64 X2 3800+.  Most of the time the cpu sits around 5-10%, 
but MrSID uses huge amounts of cpu to uncompress.  Its noticeably slower.

ECW will be a little bit bigger on disk, but does not use much at all 
for CPU to uncompress.

MrSID is even worse when you have a frontend (like OpenLayers) request 
tiles... it'll request two or three smaller tiles at a time.  My dual 
core was just pegged with requests.  Switching to ECW is smooth, 
regardless whether your frontend requests one big image or many small.

I can recommend Global Mapper as an image converter.  I had several 
gigabytes of MrSid split into thousands of files, and GM converted it 
into one single ECW, several gigabyes in size.

-Andy