Compare

Compares two clips (the "filtered" clip and the "original" clip) and returns the following data for each frame:

Mean Absolute Deviation ¹

(minimum, average, maximum)

Mean Deviation

(minimum, average, maximum)

Max. Positive Deviation

Max. Negative Deviation

Peak Signal-to-Noise Ratio (PSNR) ²

(minimum, average, maximum)

PSNR

(cumulative)

These data are displayed on screen by default (see example image), or can optionally be written to a logfile.

By default a PSNR graph is displayed; this graph shows overall PSNR visually as a timeline that grows left-to-right along the bottom of the screen as the clip plays.

Syntax and Parameters

Compare(clip clip_filtered, clip clip_original
      [, string channels, string logfile, bool show_graph ] )

clip  clip_filtered, clip_original =

The "filtered" clip and the "original" clip. Size and color formats must match.

Color format may be RGB24, RGB32, YUY2 or YV12.

The "filtered" clip is returned.

string  channels = ""

Set the color channels to be compared with a combination of R,G,B [,A] or Y,U,V, depending on the source color format.

By default, all channels are compared.

bool  show_graph = true

If true, (the default) the PSNR graph is drawn on the screen.

string  logfile = ""

If specified, the results will be written to a file, and not drawn on the clip.

Using a logfile is much faster if you need to compare a lot of frames.

Examples

• Basic usage – display differences on screen:

FFmpegSource2("sintel.mp4")
A=BicubicResize(640, 272)
B=A.Sharpen(1.0) ## Sharpen is our filter under test
return Compare(B, A)

• Create a log file:

Compare(clip1, clip2, "", "compare.log")

• Compare chroma channels only:

Compare(clip1, clip2, "UV")