# PSNR

From Avisynth wiki

**PSNR** stands for **P**eak **S**ignal-to-**N**oise **R**atio. It is used as a measure of video quality. It is expressed in decibels. It's defined as

where *I *is the reference image, *K *is the image under test, and *MSE *is the Mean Squared Error between the two:

Where *M *is the number of pixels in a frame (*width* **·** *height*)

The double-Σ term states that (*j*,*k*) runs over all the pixels, summing the square of the difference between reference image *I* and test image *K*.

**External Links**

- For more details see wikipedia:PSNR.
- See also, wikipedia:SSIM (Structural SIMilarity), another widely-used quality measure.
- See also, wikipedia:Video Quality for a discussion of the difficulties involved in trying to make an "objective" quality measurement.