MaskTools2/Mt merge

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It's the backbone of the framework. It merges two clips according to the mask. The bigger the mask value, the more the second clip will be taken into account.

For 8 bits the actual formula is:
y = ((256 - m) * x1 + m * x2 + 128) / 256

Since v2.2.7: keep original pixels from clip1/2 when mask is exactly 0 or 255:
y = (m == 0) ? x1 : (m == 255) ? x2 : ((256 - m) * x1 + m * x2 + 128) / 256

For 10-12-14-16 bits the minimum value is 0, maximum value is 1023, 4095, 16383, 65535 accordingly.
y = (m == minvalue) ? x1 : (m == maxvalue) ? x2 : ((2^bitdepth - m) * x1 + m * x2 + 2^(bitdepth-1)) / (2^bitdepth)

For 32 bit float the actual formula is:
y = (1.0 - m) * x1 + m * x2

Syntax and Parameters

mt_merge (clip, clip, clip, bool "luma", int "Y", int "U", int "V", string "chroma", int "offX", int "offY", int "w", int "h")

or since v2.2.15

mt_merge (clip, clip, clip, bool "luma", float "Y", float "U", float "V", string "chroma", int "offX", int "offY", int "w", int "h", float "A", string "cplace")

clip   =
Input clip one.

clip   =
Input clip two.

clip   =
Mask input clip.

bool  luma = false
luma is a special mode, where only the the first plane (luma or red plane) of the mask is used to process all three channels.
Note: when luma=true, it forces chroma processing (chroma="process" or u=3, v=3).

int  Y = 3
int  U = 2
int  V = 2
int  A = 2
These values describe the actual processing mode that is to be used on each plane / channel. Here is how the modes are coded :
  • x = -255...0 : all the pixels of the plane will be set to -x. (-255..0 range can of course differ when non-8 bit video formats are used)
  • x = 1 : the plane will not be processed. That means the content of the plane after the filter is pure garbage.
  • x = 2 : the plane of the first input clip will be copied.
  • x = 3 : the plane will be processed with the processing the filter is designed to do.
  • x = 4 : the plane of the second input clip will be copied.
U, V and A are defaulted to 2 (that way, the resulting clip contains the chroma (alpha) of clip1, and looks right).
Note: when luma=true, the u and v parameters are overridden and set to u=3, v=3 internally.

string  chroma = ""
When defined, the value contained in this string will overwrite the u & v processing modes.
This is a nice addition proposed by mg262 that makes the filter more user friendly. Allowed values for chroma are:
  • "process" : set u = v = 3.
  • "copy" or "copy first" : set u = v = 2.
  • "copy second" : set u = v = 4.
  • "xxx", where xxx is a number : set u = v = -xxx.
Note: when luma=true, the chroma parameter is overridden and set to chroma="process" internally.

int  offX = 0
int  offY = 0
offX and offY are the top left coordinates of the box where the actual processing shall occur. Everything outside that box will be garbage.

int  w = -1
int  h = -1
w and h are the width and height of the processed box. -1 means that the box extends to the lower right corner of the video. That also means that default settings are meant to process the whole picture.

string  cplace = "mpeg2"
Parameter defines chroma placement hint for 4:2:0 and 4:2:2 formats. Introduced in v2.2.15.
  • "mpeg1" : Simple block averaging (e.g. average 2x2 pixels to a single YV12 chroma mask)
  • "mpeg2" : default
  • "topleft" : only for 4:2:0 videos. (added in v2.2.27)


mt_merge with default settings: (TO DO)

clip1 = original
clip2 = processed
mask  = mask
mt_merge(clip1, clip2, mask, Y=3, U=2, V=2, chroma="", w=-1, h=-1)

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