Need help with Avisynth filters.

[shukers]

Hi
I`m working on codec optimizations and I need to compare two videos for different parameters like SSIM, MSE etc.I`m trying to get SSIM from avisynth
I`m totally new to avisynth. I went through the basic scripting and these are the procedures i followed :
1. installed avisynth 2.58.
2. wrote couple of basic scripts.
3. tried the follwoing script for ssim but for some reason it doesnt work :
ssim(test1.yuv,ref.yuv,"results.csv","averageSSIM.txt",lumimask=true) http://forum.doom9.org/showthread.php?p=370323

Could someone point out the mistakes I`m doing?
Help is greatly appreciated.