--- /dev/null
+-- The theme is what decides what's actually shown on screen, what kind of
+-- transitions are available (if any), and what kind of inputs there are,
+-- if any. In general, it drives the entire display logic by creating Movit
+-- chains, setting their parameters and then deciding which to show when.
+--
+-- Themes are written in Lua, which reflects a simplified form of the Movit API
+-- where all the low-level details (such as texture formats) are handled by the
+-- C++ side and you generally just build chains.
+--
+-- This is a much simpler theme than the default theme; it only allows you to
+-- switch between inputs and set white balance, no transitions or the likes.
+-- Thus, it should be simpler to understand.
+
+local input_neutral_color = {{0.5, 0.5, 0.5}, {0.5, 0.5, 0.5}}
+
+local live_signal_num = 0
+local preview_signal_num = 1
+
+-- A chain to show a single input, with white balance. In a real example,
+-- we'd probably want to support deinterlacing and high-quality scaling
+-- (if the input isn't exactly what we want). However, we don't want these
+-- things always on, so we'd need to generate more chains for the various
+-- cases. In such a simple example, just having two is fine.
+function make_simple_chain(hq)
+ local chain = EffectChain.new(16, 9)
+
+ local input = chain:add_live_input(false, false) -- No deinterlacing, no bounce override.
+ input:connect_signal(0) -- First input card. Can be changed whenever you want.
+ local wb_effect = chain:add_effect(WhiteBalanceEffect.new())
+ chain:finalize(hq)
+
+ return {
+ chain = chain,
+ input = input,
+ wb_effect = wb_effect,
+ }
+end
+
+-- We only make two chains; one for the live view and one for the previews.
+-- (Since they have different outputs, you cannot mix and match them.)
+local simple_hq_chain = make_simple_chain(true)
+local simple_lq_chain = make_simple_chain(false)
+
+-- API ENTRY POINT
+-- Returns the number of outputs in addition to the live (0) and preview (1).
+-- Called only once, at the start of the program.
+function num_channels()
+ return 2
+end
+
+-- API ENTRY POINT
+-- Returns the name for each additional channel (starting from 2).
+-- Called at the start of the program, and then each frame for live
+-- channels in case they change resolution.
+function channel_name(channel)
+ if channel == 2 then
+ return "First input"
+ elseif channel == 3 then
+ return "Second input"
+ end
+end
+
+-- API ENTRY POINT
+-- Returns, given a channel number, which signal it corresponds to (starting from 0).
+-- Should return -1 if the channel does not correspond to a simple signal.
+-- (The information is used for whether right-click on the channel should bring up
+-- an input selector or not.)
+-- Called once for each channel, at the start of the program.
+-- Will never be called for live (0) or preview (1).
+function channel_signal(channel)
+ if channel == 2 then
+ return 0
+ elseif channel == 3 then
+ return 1
+ else
+ return -1
+ end
+end
+
+-- API ENTRY POINT
+-- Returns if a given channel supports setting white balance (starting from 2).
+-- Called only once for each channel, at the start of the program.
+function supports_set_wb(channel)
+ return channel == 2 or channel == 3
+end
+
+-- API ENTRY POINT
+-- Gets called with a new gray point when the white balance is changing.
+-- The color is in linear light (not sRGB gamma).
+function set_wb(channel, red, green, blue)
+ if channel == 2 then
+ input_neutral_color[0] = { red, green, blue }
+ elseif channel == 3 then
+ input_neutral_color[1] = { red, green, blue }
+ end
+end
+
+-- API ENTRY POINT
+-- Called every frame.
+function get_transitions(t)
+ if live_signal_num == preview_signal_num then
+ -- No transitions possible.
+ return {}
+ else
+ return {"Cut"}
+ end
+end
+
+-- API ENTRY POINT
+-- Called when the user clicks a transition button. For our case,
+-- we only do cuts, so we ignore the parameters; just switch live and preview.
+function transition_clicked(num, t)
+ local temp = live_signal_num
+ live_signal_num = preview_signal_num
+ preview_signal_num = temp
+end
+
+-- API ENTRY POINT
+function channel_clicked(num)
+ preview_signal_num = num
+end
+
+-- API ENTRY POINT
+-- Called every frame. Get the chain for displaying at input <num>,
+-- where 0 is live, 1 is preview, 2 is the first channel to display
+-- in the bottom bar, and so on up to num_channels()+1. t is the
+-- current time in seconds. width and height are the dimensions of
+-- the output, although you can ignore them if you don't need them
+-- (they're useful if you want to e.g. know what to resample by).
+--
+-- <signals> is basically an exposed InputState, which you can use to
+-- query for information about the signals at the point of the current
+-- frame. In particular, you can call get_width() and get_height()
+-- for any signal number, and use that to e.g. assist in chain selection.
+--
+-- You should return two objects; the chain itself, and then a
+-- function (taking no parameters) that is run just before rendering.
+-- The function needs to call connect_signal on any inputs, so that
+-- it gets updated video data for the given frame. (You are allowed
+-- to switch which input your input is getting from between frames,
+-- but not calling connect_signal results in undefined behavior.)
+-- If you want to change any parameters in the chain, this is also
+-- the right place.
+--
+-- NOTE: The chain returned must be finalized with the Y'CbCr flag
+-- if and only if num==0.
+function get_chain(num, t, width, height, signals)
+ local chain, signal_num
+ if num == 0 then -- Live (right pane).
+ chain = simple_hq_chain
+ signal_num = live_signal_num
+ elseif num == 1 then -- Preview (left pane).
+ chain = simple_lq_chain
+ signal_num = preview_signal_num
+ else -- One of the two previews (bottom panes).
+ chain = simple_lq_chain
+ signal_num = num - 2
+ end
+
+ prepare = function()
+ chain.input:connect_signal(signal_num)
+ local color = input_neutral_color[signal_num + 1]
+ chain.wb_effect:set_vec3("neutral_color", color[1], color[2], color[3])
+ end
+ return chain.chain, prepare
+end
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