Specifically for Layer:
See on github "distrib" folder: readme.txt and readme_history.txt (latter is a bit more verbose)
Code:
- Layer: big update
Previously Layer was working only for RGB32 and YUY2. Overlay was used primarily for YUV. Now Layer accepts practically all formats (no RGB24).
Note that some modes can be similar to Overlay, but the two filters are still different.
Overlay accepts mask clip, Layer would use existing A plane.
Overlay "blend" is Layer "add", Overlay "add" is different.
Lighten and darken is a bit different in Overlay.
Layer has "placement" parameter for proper mask positioning over chroma.
- Support for all 8-32 bit Y and planar YUV/YUVA and planar RGB/RGBA formats
When overlay clip is YUVA and RGBA, then alpha channels of overlay clip are used (similarly to RGB32 and RGB64 formats)
Non-alpha plane YUV/planar RGB color spaces act as having a fully transparent alpha channel (like the former YUY2 only working mode)
Note: now if destination is YUVA/RGBA, the overlay clip also has to be Alpha-aware type.
Now A channel is not updated for YUVA targets, but RGBA targets do get the Alpha updated (like the old RGB32 mode did)
Todo: allow non-Alpha destination and Alpha-Overlay
- New parameter: float "opacity" (0.0 .. 1.0) optionally replaces the previous "level". Similar to "opacity" in "Overlay"
For usage of "level" see http://avisynth.nl/index.php/Layer
"opacity" parameter is bit depth independent, one does not have to fiddle with it like had to with level (which was maxed with level=257 when RGB32 but level=256 for YUY2/YUV)
- threshold parameter (used for lighten/darken) is autoscaled.
Keep it between 0 and 255, same as it was used for 8 bit videos.
- new parameter: string "placement" default "mpeg2".
Possible values: "mpeg2" (default), "mpeg1".
Used in "mul", "darken" and "lighten", "add" and "subtract" modes with planar YUV 4:2:0 or 4:2:2 color spaces (not available for YUY2)
in order to properly apply luma/overlay mask on U and V chroma channels.
- Fix some out-of-frame memory access in YUY2 C code
- Fix: Add proper rounding for add/subtract/lighten/darken calculations. (YUY2, RGB32, 8 bit YUV and 8 bit Planar RGB)
- Fix: "lighten" and "darken" gave different results between yuy2 and rgb32 when Threshold<>0
Fixed "darken" for RGB32 when Threshold<>0
Fixed "lighten" and "darken" for YUY2 when Threshold<>0
All the above was done by specification:
Add: "Where overlay is brigher by threshold" => e.g. Where overlay is brigther by 10 => Where overlay > src + 10
Calculation: alpha_mask = ovr > (src + thresh) ? level : 0;
Add: "Where overlay is darker by threshold" => e.g. Where overlay is darker by 10 => Where overlay < src - 10
Calculation: alpha_mask = ovr < (src - thresh) ? level : 0;
The only correct case of the above was "lighten" for RGB32, even in Classic Avisynth. Note: Threshold=0 was O.K.
- (Just an info: existing lighten/darken code for YUY2 is still not correct, messing up chroma a bit,
since it uses weights from even luma positions (0,2,4,...) for U, and odd luma positions (1,3,5,...) for V)