This adds the ability to use a secondary black-and-white video as a mask
between source A and B of the transition. The greyscale value of each
pixel is used as the "slider" value in a linear interpolation between the
corresponding pixels in source A and source B.
The track matte can either be in the same file as the stinger itself
(next to the stinger or under the stinger, doubling the width or height
of the stinger depending of the selected layout) or a in a separate
dedicated file.
The same file/separate file behavior is controlled by the
"Matte Layout" option in the stinger settings.
This also enables hardware decoding by default for stingers.
Note: per c2a2bc5e4027f9e4cba75989f0591200eef8c768 this will not affect
webm files with alpha.
The file duration is a bit of an estimate. This adds 500ms to the
estimated stinger media file duration to help ensure stinger videos
play back in full without getting cut off prematurely.
Code submissions have continually suffered from formatting
inconsistencies that constantly have to be addressed. Using
clang-format simplifies this by making code formatting more consistent,
and allows automation of the code formatting so that maintainers can
focus more on the code itself instead of code formatting.
There are cases where alpha is multiplied unnecessarily. This change
attempts to use premultiplied alpha blending for composition.
To keep this change simple, The filter chain will continue to use
straight alpha. Otherwise, every source would need to modified to output
premultiplied, and every filter modified for premultiplied input.
"DrawAlphaDivide" shader techniques have been added to convert from
premultiplied alpha to straight alpha for final output. "DrawMatrix"
techniques ignore alpha, so they do not appear to need changing.
One remaining issue is that scale effects are set up here to use the
same shader logic for both scale filters (straight alpha - incorrectly),
and output composition (premultiplied alpha - correctly). A fix could be
made to add additional shaders for straight alpha, but the "real" fix
may be to eliminate the straight alpha path at some point.
For graphics, SrcBlendAlpha and DestBlendAlpha were both ONE, and could
combine together to form alpha values greater than one. This is not as
noticeable of a problem for UNORM targets because the channels are
clamped, but it will likely become a problem in more situations if FLOAT
targets are used.
This change switches DestBlendAlpha to INVSRCALPHA. The blending
behavior of stacked transparents is preserved without overflowing the
alpha channel.
obs-transitions: Use premultiplied alpha blend, and simplify shaders
because both inputs and outputs use premultiplied alpha now.
Fixes https://obsproject.com/mantis/view.php?id=1108
If the transition point was above or equal to 1.0, it would cause a
divide by 0 error a few lines down. This could cause audio data to
become corrupted with NAN audio data when mixing, which can cause
certain audio encoders (namely the FFmpeg AAC encoder) to fail.
It was possible for the transition point to be above or equal to 1.0 if
the stinger media file was no longer loadable for whatever reason.
Add option in properties that let you choose how audio is mixed during
transition:
- Fade Out/Fade In (existing behavior, default)
- Crossfade
Closesjp9000/obs-studio#1028
Allows using a video file as a means of transitioning, transitioning two
targets at a specific time during the video playback. Audio for target
A fades out to the transition point, and then audio for target B fades
in after the transition point.
In transitions, because the 'to' and 'from' are always rendered to
textures, the end result will always have premultiplied alpha. This
would cause alpha to have blackish edges during transition, and cause
semi-transparent images to appear darker than they were supposed to.
To replicate, simply set the transparency of a source to 50%, then
transition between that scene and another scene. The source will appear
to "pop" in and out unnaturally due to the premultiplied alpha effect of
the render targets.
To fix this, the solution is to simply convert premultiplied alpha to
straight alpha in the transition pixel shaders.
