git.sesse.net Git - nageru/blob - theme.lua

   1 -- The theme is what decides what's actually shown on screen, what kind of
   2 -- transitions are available (if any), and what kind of inputs there are,
   3 -- if any. In general, it drives the entire display logic by creating Movit
   4 -- chains, setting their parameters and then deciding which to show when.
   5 --
   6 -- Themes are written in Lua, which reflects a simplified form of the Movit API
   7 -- where all the low-level details (such as texture formats) are handled by the
   8 -- C++ side and you generally just build chains.
   9
  10 local transition_start = -2.0
  11 local transition_end = -1.0
  12 local zoom_src = 0.0
  13 local zoom_dst = 1.0
  14 local zoom_poi = 0   -- which input to zoom in on
  15 local fade_src_signal = 0
  16 local fade_dst_signal = 0
  17
  18 local input0_neutral_color = {0.5, 0.5, 0.5}
  19 local input1_neutral_color = {0.5, 0.5, 0.5}
  20
  21 local live_signal_num = 0
  22 local preview_signal_num = 1
  23
  24 -- Valid values for live_signal_num and preview_signal_num.
  25 local INPUT0_SIGNAL_NUM = 0
  26 local INPUT1_SIGNAL_NUM = 1
  27 local SBS_SIGNAL_NUM = 2
  28 local STATIC_SIGNAL_NUM = 3
  29
  30 -- “fake” signal number that signifies that we are fading from one input
  31 -- to the next.
  32 local FADE_SIGNAL_NUM = 4
  33
  34 -- Last width/height/resolution for each channel, if we have it.
  35 local last_resolution = {}
  36
  37 -- Utility function to help creating many similar chains that can differ
  38 -- in a free set of chosen parameters.
  39 function make_cartesian_product(parms, callback)
  40         return make_cartesian_product_internal(parms, callback, 1, {})
  41 end
  42
  43 function make_cartesian_product_internal(parms, callback, index, args)
  44         if index > #parms then
  45                 return callback(unpack(args))
  46         end
  47         local ret = {}
  48         for _, value in ipairs(parms[index]) do
  49                 args[index] = value
  50                 ret[value] = make_cartesian_product_internal(parms, callback, index + 1, args)
  51         end
  52         return ret
  53 end
  54
  55 function make_sbs_input(chain, signal, deint, hq)
  56         local input = chain:add_live_input(not deint, deint)  -- Override bounce only if not deinterlacing.
  57         input:connect_signal(signal)
  58         local wb_effect = chain:add_effect(WhiteBalanceEffect.new())
  59
  60         local resample_effect = nil
  61         local resize_effect = nil
  62         if (hq) then
  63                 resample_effect = chain:add_effect(ResampleEffect.new())
  64         else
  65                 resize_effect = chain:add_effect(ResizeEffect.new())
  66         end
  67
  68         local padding_effect = chain:add_effect(IntegralPaddingEffect.new())
  69
  70         return {
  71                 input = input,
  72                 wb_effect = wb_effect,
  73                 resample_effect = resample_effect,
  74                 resize_effect = resize_effect,
  75                 padding_effect = padding_effect
  76         }
  77 end
  78
  79 -- The main live chain.
  80 function make_sbs_chain(input0_deint, input1_deint, hq)
  81         local chain = EffectChain.new(16, 9)
  82
  83         local input0 = make_sbs_input(chain, INPUT0_SIGNAL_NUM, input0_deint, hq)
  84         local input1 = make_sbs_input(chain, INPUT1_SIGNAL_NUM, input1_deint, hq)
  85
  86         input0.padding_effect:set_vec4("border_color", 0.0, 0.0, 0.0, 1.0)
  87         input1.padding_effect:set_vec4("border_color", 0.0, 0.0, 0.0, 0.0)
  88
  89         chain:add_effect(OverlayEffect.new(), input0.padding_effect, input1.padding_effect)
  90         chain:finalize(hq)
  91
  92         return {
  93                 chain = chain,
  94                 input0 = input0,
  95                 input1 = input1
  96         }
  97 end
  98
  99 -- Make all possible combinations of side-by-side chains.
 100 local sbs_chains = make_cartesian_product({
 101         {"live", "livedeint"},  -- input0_type
 102         {"live", "livedeint"},  -- input1_type
 103         {true, false}           -- hq
 104 }, function(input0_type, input1_type, hq)
 105         local input0_deint = (input0_type == "livedeint")
 106         local input1_deint = (input1_type == "livedeint")
 107         return make_sbs_chain(input0_deint, input1_deint, hq)
 108 end)
 109
 110 function make_fade_input(chain, signal, live, deint, scale)
 111         local input, wb_effect, resample_effect, last
 112         if live then
 113                 input = chain:add_live_input(false, deint)
 114                 wb_effect = chain:add_effect(WhiteBalanceEffect.new())
 115                 input:connect_signal(signal)
 116                 last = wb_effect
 117         else
 118                 input = chain:add_effect(ImageInput.new("bg.jpeg"))
 119                 last = input
 120         end
 121
 122         -- If we cared about this for the non-main inputs, we would have
 123         -- checked hq here and invoked ResizeEffect instead.
 124         if scale then
 125                 resample_effect = chain:add_effect(ResampleEffect.new())
 126                 last = resample_effect
 127         end
 128
 129         return {
 130                 input = input,
 131                 wb_effect = wb_effect,
 132                 resample_effect = resample_effect,
 133                 last = last
 134         }
 135 end
 136
 137 -- A chain to fade between two inputs, of which either can be a picture
 138 -- or a live input. In practice only used live, but we still support the
 139 -- hq parameter.
 140 function make_fade_chain(input0_live, input0_deint, input0_scale, input1_live, input1_deint, input1_scale, hq)
 141         local chain = EffectChain.new(16, 9)
 142
 143         local input0 = make_fade_input(chain, INPUT0_SIGNAL_NUM, input0_live, input0_deint, input0_scale)
 144         local input1 = make_fade_input(chain, INPUT1_SIGNAL_NUM, input1_live, input1_deint, input1_scale)
 145
 146         local mix_effect = chain:add_effect(MixEffect.new(), input0.last, input1.last)
 147         chain:finalize(hq)
 148
 149         return {
 150                 chain = chain,
 151                 input0 = input0,
 152                 input1 = input1,
 153                 mix_effect = mix_effect
 154         }
 155 end
 156
 157 -- Chains to fade between two inputs, in various configurations.
 158 local fade_chains = make_cartesian_product({
 159         {"static", "live", "livedeint"},  -- input0_type
 160         {true, false},                    -- input0_scale
 161         {"static", "live", "livedeint"},  -- input1_type
 162         {true, false},                    -- input1_scale
 163         {true}                            -- hq
 164 }, function(input0_type, input0_scale, input1_type, input1_scale, hq)
 165         local input0_live = (input0_type ~= "static")
 166         local input1_live = (input1_type ~= "static")
 167         local input0_deint = (input0_type == "livedeint")
 168         local input1_deint = (input1_type == "livedeint")
 169         return make_fade_chain(input0_live, input0_deint, input0_scale, input1_live, input1_deint, input1_scale, hq)
 170 end)
 171
 172 -- A chain to show a single input on screen.
 173 function make_simple_chain(input_deint, input_scale, hq)
 174         local chain = EffectChain.new(16, 9)
 175
 176         local input = chain:add_live_input(false, input_deint)
 177         input:connect_signal(0)  -- First input card. Can be changed whenever you want.
 178         local wb_effect = chain:add_effect(WhiteBalanceEffect.new())
 179         chain:finalize(hq)
 180
 181         local resample_effect, resize_effect
 182         if scale then
 183                 if hq then
 184                         resample_effect = chain:add_effect(ResampleEffect.new())
 185                 else
 186                         resize_effect = chain:add_effect(ResizeEffect.new())
 187                 end
 188         end
 189
 190         return {
 191                 chain = chain,
 192                 input = input,
 193                 wb_effect = wb_effect,
 194                 resample_effect = resample_effect,
 195                 resize_effect = resize_effect
 196         }
 197 end
 198
 199 -- Make all possible combinations of single-input chains.
 200 local simple_chains = make_cartesian_product({
 201         {"live", "livedeint"},  -- input_type
 202         {true, false},          -- input_scale
 203         {true, false}           -- hq
 204 }, function(input_type, input_scale, hq)
 205         local input_deint = (input_type == "livedeint")
 206         return make_simple_chain(input_deint, input_scale, hq)
 207 end)
 208
 209 -- A chain to show a single static picture on screen (HQ version).
 210 local static_chain_hq = EffectChain.new(16, 9)
 211 local static_chain_hq_input = static_chain_hq:add_effect(ImageInput.new("bg.jpeg"))
 212 static_chain_hq:finalize(true)
 213
 214 -- A chain to show a single static picture on screen (LQ version).
 215 local static_chain_lq = EffectChain.new(16, 9)
 216 local static_chain_lq_input = static_chain_lq:add_effect(ImageInput.new("bg.jpeg"))
 217 static_chain_lq:finalize(false)
 218
 219 -- Used for indexing into the tables of chains.
 220 function get_input_type(signals, signal_num)
 221         if signal_num == STATIC_SIGNAL_NUM then
 222                 return "static"
 223         elseif signals:get_interlaced(signal_num) then
 224                 return "livedeint"
 225         else
 226                 return "live"
 227         end
 228 end
 229
 230 function needs_scale(signals, signal_num, width, height)
 231         return (signals:get_width(signal_num) ~= width or signals:get_height(signal_num) ~= height)
 232 end
 233
 234 function set_scale_parameters_if_needed(chain_or_input, width, height)
 235         if chain_or_input.resample_effect then
 236                 chain_or_input.resample_effect:set_int("width", width)
 237                 chain_or_input.resample_effect:set_int("height", height)
 238         elseif chain_or_input.resize_effect then
 239                 chain_or_input.resize_effect:set_int("width", width)
 240                 chain_or_input.resize_effect:set_int("height", height)
 241         end
 242 end
 243
 244 -- Returns the number of outputs in addition to the live (0) and preview (1).
 245 -- Called only once, at the start of the program.
 246 function num_channels()
 247         return 4
 248 end
 249
 250 -- Helper function to write e.g. “60” or “59.94”.
 251 function get_frame_rate(signal_num)
 252         local nom = last_resolution[signal_num].frame_rate_nom
 253         local den = last_resolution[signal_num].frame_rate_den
 254         if last_resolution[signal_num].interlaced then
 255                 nom = nom * 2
 256         end
 257         if nom % den == 0 then
 258                 return nom / den
 259         else
 260                 return string.format("%.2f", num / den)
 261         end
 262 end
 263
 264 -- Helper function to write e.g. “720p60”.
 265 function get_channel_resolution(signal_num)
 266         if last_resolution[signal_num] then
 267                 if last_resolution[signal_num].height == 0 or
 268                    last_resolution[signal_num].height == 525 then
 269                         return "no signal"
 270                 elseif last_resolution[signal_num].interlaced then
 271                         return (last_resolution[signal_num].height * 2) .. "i" .. get_frame_rate(signal_num)
 272                 else
 273                         return last_resolution[signal_num].height .. "p" .. get_frame_rate(signal_num)
 274                 end
 275         else
 276                 return "no signal"
 277         end
 278 end
 279
 280 -- Returns the name for each additional channel (starting from 2).
 281 -- Called at the start of the program, and then each frame for live
 282 -- channels in case they change resolution.
 283 function channel_name(channel)
 284         if channel == 2 then
 285                 return "Input 1 (" .. get_channel_resolution(0) .. ")"
 286         elseif channel == 3 then
 287                 return "Input 2 (" .. get_channel_resolution(1) .. ")"
 288         elseif channel == 4 then
 289                 return "Side-by-side"
 290         elseif channel == 5 then
 291                 return "Static picture"
 292         end
 293 end
 294
 295 -- Returns if a given channel supports setting white balance (starting from 2).
 296 -- Called only once for each channel, at the start of the program.
 297 function supports_set_wb(channel)
 298         return channel == 2 or channel == 3
 299 end
 300
 301 -- Gets called with a new gray point when the white balance is changing.
 302 -- The color is in linear light (not sRGB gamma).
 303 function set_wb(channel, red, green, blue)
 304         if channel == 2 then
 305                 input0_neutral_color = { red, green, blue }
 306         elseif channel == 3 then
 307                 input1_neutral_color = { red, green, blue }
 308         end
 309 end
 310
 311 function finish_transitions(t)
 312         -- If live is SBS but de-facto single, make it so.
 313         if live_signal_num == SBS_SIGNAL_NUM and t >= transition_end and zoom_dst == 1.0 then
 314                 live_signal_num = zoom_poi
 315         end
 316
 317         -- If live is fade but de-facto single, make it so.
 318         if live_signal_num == FADE_SIGNAL_NUM and t >= transition_end then
 319                 live_signal_num = fade_dst_signal
 320         end
 321 end
 322
 323 -- Called every frame.
 324 function get_transitions(t)
 325         finish_transitions(t)
 326
 327         if live_signal_num == preview_signal_num then
 328                 return {}
 329         end
 330
 331         if live_signal_num == SBS_SIGNAL_NUM and t >= transition_start and t <= transition_end then
 332                 -- Zoom in progress.
 333                 return {"Cut"}
 334         end
 335
 336         if (live_signal_num == INPUT0_SIGNAL_NUM or
 337             live_signal_num == INPUT1_SIGNAL_NUM or
 338             live_signal_num == STATIC_SIGNAL_NUM) and
 339            (preview_signal_num == INPUT0_SIGNAL_NUM or
 340             preview_signal_num == INPUT1_SIGNAL_NUM or
 341             preview_signal_num == STATIC_SIGNAL_NUM) then
 342                 return {"Cut", "", "Fade"}
 343         end
 344
 345         -- Various zooms.
 346         if live_signal_num == SBS_SIGNAL_NUM and
 347            (preview_signal_num == INPUT0_SIGNAL_NUM or preview_signal_num == INPUT1_SIGNAL_NUM) then
 348                 return {"Cut", "Zoom in"}
 349         elseif (live_signal_num == INPUT0_SIGNAL_NUM or live_signal_num == INPUT1_SIGNAL_NUM) and
 350                preview_signal_num == SBS_SIGNAL_NUM then
 351                 return {"Cut", "Zoom out"}
 352         end
 353
 354         return {"Cut"}
 355 end
 356
 357 function transition_clicked(num, t)
 358         if num == 0 then
 359                 -- Cut.
 360                 if live_signal_num == FADE_SIGNAL_NUM then
 361                         -- Ongoing fade; finish it immediately.
 362                         finish_transitions(transition_end)
 363                 end
 364
 365                 local temp = live_signal_num
 366                 live_signal_num = preview_signal_num
 367                 preview_signal_num = temp
 368
 369                 if live_signal_num == SBS_SIGNAL_NUM then
 370                         -- Just cut to SBS, we need to reset any zooms.
 371                         zoom_src = 1.0
 372                         zoom_dst = 0.0
 373                         transition_start = -2.0
 374                         transition_end = -1.0
 375                 end
 376         elseif num == 1 then
 377                 -- Zoom.
 378
 379                 finish_transitions(t)
 380
 381                 if live_signal_num == preview_signal_num then
 382                         -- Nothing to do.
 383                         return
 384                 end
 385
 386                 if (live_signal_num == INPUT0_SIGNAL_NUM and preview_signal_num == INPUT1_SIGNAL_NUM) or
 387                    (live_signal_num == INPUT1_SIGNAL_NUM and preview_signal_num == INPUT0_SIGNAL_NUM) then
 388                         -- We can't zoom between these. Just make a cut.
 389                         io.write("Cutting from " .. live_signal_num .. " to " .. live_signal_num .. "\n")
 390                         local temp = live_signal_num
 391                         live_signal_num = preview_signal_num
 392                         preview_signal_num = temp
 393                         return
 394                 end
 395
 396                 if live_signal_num == SBS_SIGNAL_NUM and
 397                    (preview_signal_num == INPUT0_SIGNAL_NUM or preview_signal_num == INPUT1_SIGNAL_NUM) then
 398                         -- Zoom in from SBS to single.
 399                         transition_start = t
 400                         transition_end = t + 1.0
 401                         zoom_src = 0.0
 402                         zoom_dst = 1.0
 403                         zoom_poi = preview_signal_num
 404                         preview_signal_num = SBS_SIGNAL_NUM
 405                 elseif (live_signal_num == INPUT0_SIGNAL_NUM or live_signal_num == INPUT1_SIGNAL_NUM) and
 406                        preview_signal_num == SBS_SIGNAL_NUM then
 407                         -- Zoom out from single to SBS.
 408                         transition_start = t
 409                         transition_end = t + 1.0
 410                         zoom_src = 1.0
 411                         zoom_dst = 0.0
 412                         preview_signal_num = live_signal_num
 413                         zoom_poi = live_signal_num
 414                         live_signal_num = SBS_SIGNAL_NUM
 415                 end
 416         elseif num == 2 then
 417                 finish_transitions(t)
 418
 419                 -- Fade.
 420                 if (live_signal_num ~= preview_signal_num) and
 421                    (live_signal_num == INPUT0_SIGNAL_NUM or
 422                     live_signal_num == INPUT1_SIGNAL_NUM or
 423                     live_signal_num == STATIC_SIGNAL_NUM) and
 424                    (preview_signal_num == INPUT0_SIGNAL_NUM or
 425                     preview_signal_num == INPUT1_SIGNAL_NUM or
 426                     preview_signal_num == STATIC_SIGNAL_NUM) then
 427                         transition_start = t
 428                         transition_end = t + 1.0
 429                         fade_src_signal = live_signal_num
 430                         fade_dst_signal = preview_signal_num
 431                         preview_signal_num = live_signal_num
 432                         live_signal_num = FADE_SIGNAL_NUM
 433                 else
 434                         -- Fades involving SBS are ignored (we have no chain for it).
 435                 end
 436         end
 437 end
 438
 439 function channel_clicked(num)
 440         preview_signal_num = num
 441 end
 442
 443 -- Called every frame. Get the chain for displaying at input <num>,
 444 -- where 0 is live, 1 is preview, 2 is the first channel to display
 445 -- in the bottom bar, and so on up to num_channels()+1. t is the
 446 -- current time in seconds. width and height are the dimensions of
 447 -- the output, although you can ignore them if you don't need them
 448 -- (they're useful if you want to e.g. know what to resample by).
 449 --
 450 -- <signals> is basically an exposed InputState, which you can use to
 451 -- query for information about the signals at the point of the current
 452 -- frame. In particular, you can call get_width() and get_height()
 453 -- for any signal number, and use that to e.g. assist in chain selection.
 454 --
 455 -- You should return two objects; the chain itself, and then a
 456 -- function (taking no parameters) that is run just before rendering.
 457 -- The function needs to call connect_signal on any inputs, so that
 458 -- it gets updated video data for the given frame. (You are allowed
 459 -- to switch which input your input is getting from between frames,
 460 -- but not calling connect_signal results in undefined behavior.)
 461 -- If you want to change any parameters in the chain, this is also
 462 -- the right place.
 463 --
 464 -- NOTE: The chain returned must be finalized with the Y'CbCr flag
 465 -- if and only if num==0.
 466 function get_chain(num, t, width, height, signals)
 467         for signal_num=0,1 do
 468                 last_resolution[signal_num] = {
 469                         width = signals:get_width(signal_num),
 470                         height = signals:get_height(signal_num),
 471                         interlaced = signals:get_interlaced(signal_num),
 472                         frame_rate_nom = signals:get_frame_rate_nom(signal_num),
 473                         frame_rate_den = signals:get_frame_rate_den(signal_num)
 474                 }
 475         end
 476
 477         if num == 0 then  -- Live.
 478                 if live_signal_num == INPUT0_SIGNAL_NUM or live_signal_num == INPUT1_SIGNAL_NUM then  -- Plain input.
 479                         local input_type = get_input_type(signals, live_signal_num)
 480                         local input_scale = needs_scale(signals, live_signal_num, width, height)
 481                         local chain = simple_chains[input_type][input_scale][true]
 482                         prepare = function()
 483                                 chain.input:connect_signal(live_signal_num)
 484                                 set_scale_parameters_if_needed(chain, width, height)
 485                                 set_neutral_color_from_signal(chain.wb_effect, live_signal_num)
 486                         end
 487                         return chain.chain, prepare
 488                 elseif live_signal_num == STATIC_SIGNAL_NUM then  -- Static picture.
 489                         prepare = function()
 490                         end
 491                         return static_chain_hq, prepare
 492                 elseif live_signal_num == FADE_SIGNAL_NUM then  -- Fade.
 493                         local input0_type = get_input_type(signals, fade_src_signal)
 494                         local input0_scale = needs_scale(signals, fade_src_signal, width, height)
 495                         local input1_type = get_input_type(signals, fade_dst_signal)
 496                         local input1_scale = needs_scale(signals, fade_dst_signal, width, height)
 497                         local chain = fade_chains[input0_type][input0_scale][input1_type][input1_scale][true]
 498                         prepare = function()
 499                                 if input0_type == "live" then
 500                                         chain.input0.input:connect_signal(fade_src_signal)
 501                                         set_neutral_color_from_signal(chain.input0.wb_effect, fade_src_signal)
 502                                 end
 503                                 set_scale_parameters_if_needed(chain.input0, width, height)
 504                                 if input1_type == "live" then
 505                                         chain.input1.input:connect_signal(fade_dst_signal)
 506                                         set_neutral_color_from_signal(chain.input1.wb_effect, fade_dst_signal)
 507                                 end
 508                                 set_scale_parameters_if_needed(chain.input1, width, height)
 509                                 local tt = calc_fade_progress(t, transition_start, transition_end)
 510
 511                                 chain.mix_effect:set_float("strength_first", 1.0 - tt)
 512                                 chain.mix_effect:set_float("strength_second", tt)
 513                         end
 514                         return chain.chain, prepare
 515                 end
 516
 517                 -- SBS code (live_signal_num == SBS_SIGNAL_NUM).
 518                 local input0_type = get_input_type(signals, INPUT0_SIGNAL_NUM)
 519                 local input1_type = get_input_type(signals, INPUT1_SIGNAL_NUM)
 520                 if t > transition_end and zoom_dst == 1.0 then
 521                         -- Special case: Show only the single image on screen.
 522                         local input0_scale = needs_scale(signals, fade_src_signal, width, height)
 523                         local chain = simple_chains[input0_type][input0_scale][true]
 524                         prepare = function()
 525                                 chain.input:connect_signal(INPUT0_SIGNAL_NUM)
 526                                 set_scale_parameters_if_needed(chain, width, height)
 527                                 set_neutral_color(chain.wb_effect, input0_neutral_color)
 528                         end
 529                         return chain.chain, prepare
 530                 end
 531                 local chain = sbs_chains[input0_type][input1_type][true]
 532                 prepare = function()
 533                         if t < transition_start then
 534                                 prepare_sbs_chain(chain, zoom_src, width, height)
 535                         elseif t > transition_end then
 536                                 prepare_sbs_chain(chain, zoom_dst, width, height)
 537                         else
 538                                 local tt = (t - transition_start) / (transition_end - transition_start)
 539                                 -- Smooth it a bit.
 540                                 tt = math.sin(tt * 3.14159265358 * 0.5)
 541                                 prepare_sbs_chain(chain, zoom_src + (zoom_dst - zoom_src) * tt, width, height)
 542                         end
 543                 end
 544                 return chain.chain, prepare
 545         end
 546         if num == 1 then  -- Preview.
 547                 num = preview_signal_num + 2
 548         end
 549
 550         -- Individual preview inputs.
 551         if num == INPUT0_SIGNAL_NUM + 2 then
 552                 local input_type = get_input_type(signals, INPUT0_SIGNAL_NUM)
 553                 local input_scale = needs_scale(signals, INPUT0_SIGNAL_NUM, width, height)
 554                 local chain = simple_chains[input_type][input_scale][false]
 555                 prepare = function()
 556                         chain.input:connect_signal(INPUT0_SIGNAL_NUM)
 557                         set_scale_parameters_if_needed(chain, width, height)
 558                         set_neutral_color(chain.wb_effect, input0_neutral_color)
 559                 end
 560                 return chain.chain, prepare
 561         end
 562         if num == INPUT1_SIGNAL_NUM + 2 then
 563                 local input_type = get_input_type(signals, INPUT1_SIGNAL_NUM)
 564                 local input_scale = needs_scale(signals, INPUT1_SIGNAL_NUM, width, height)
 565                 local chain = simple_chains[input_type][input_scale][false]
 566                 prepare = function()
 567                         chain.input:connect_signal(INPUT1_SIGNAL_NUM)
 568                         set_scale_parameters_if_needed(chain, width, height)
 569                         set_neutral_color(chain.wb_effect, input1_neutral_color)
 570                 end
 571                 return chain.chain, prepare
 572         end
 573         if num == SBS_SIGNAL_NUM + 2 then
 574                 local input0_type = get_input_type(signals, INPUT0_SIGNAL_NUM)
 575                 local input1_type = get_input_type(signals, INPUT1_SIGNAL_NUM)
 576                 local chain = sbs_chains[input0_type][input1_type][false]
 577                 prepare = function()
 578                         prepare_sbs_chain(chain, 0.0, width, height)
 579                 end
 580                 return chain.chain, prepare
 581         end
 582         if num == STATIC_SIGNAL_NUM + 2 then
 583                 prepare = function()
 584                 end
 585                 return static_chain_lq, prepare
 586         end
 587 end
 588
 589 function place_rectangle(resample_effect, resize_effect, padding_effect, x0, y0, x1, y1, screen_width, screen_height, input_width, input_height)
 590         local srcx0 = 0.0
 591         local srcx1 = 1.0
 592         local srcy0 = 0.0
 593         local srcy1 = 1.0
 594
 595         -- Cull.
 596         if x0 > screen_width or x1 < 0.0 or y0 > screen_height or y1 < 0.0 then
 597                 resample_effect:set_int("width", 1)
 598                 resample_effect:set_int("height", 1)
 599                 resample_effect:set_float("zoom_x", screen_width)
 600                 resample_effect:set_float("zoom_y", screen_height)
 601                 padding_effect:set_int("left", screen_width + 100)
 602                 padding_effect:set_int("top", screen_height + 100)
 603                 return
 604         end
 605
 606         -- Clip.
 607         if x0 < 0 then
 608                 srcx0 = -x0 / (x1 - x0)
 609                 x0 = 0
 610         end
 611         if y0 < 0 then
 612                 srcy0 = -y0 / (y1 - y0)
 613                 y0 = 0
 614         end
 615         if x1 > screen_width then
 616                 srcx1 = (screen_width - x0) / (x1 - x0)
 617                 x1 = screen_width
 618         end
 619         if y1 > screen_height then
 620                 srcy1 = (screen_height - y0) / (y1 - y0)
 621                 y1 = screen_height
 622         end
 623
 624         if resample_effect ~= nil then
 625                 -- High-quality resampling.
 626                 local x_subpixel_offset = x0 - math.floor(x0)
 627                 local y_subpixel_offset = y0 - math.floor(y0)
 628
 629                 -- Resampling must be to an integral number of pixels. Round up,
 630                 -- and then add an extra pixel so we have some leeway for the border.
 631                 local width = math.ceil(x1 - x0) + 1
 632                 local height = math.ceil(y1 - y0) + 1
 633                 resample_effect:set_int("width", width)
 634                 resample_effect:set_int("height", height)
 635
 636                 -- Correct the discrepancy with zoom. (This will leave a small
 637                 -- excess edge of pixels and subpixels, which we'll correct for soon.)
 638                 local zoom_x = (x1 - x0) / (width * (srcx1 - srcx0))
 639                 local zoom_y = (y1 - y0) / (height * (srcy1 - srcy0))
 640                 resample_effect:set_float("zoom_x", zoom_x)
 641                 resample_effect:set_float("zoom_y", zoom_y)
 642                 resample_effect:set_float("zoom_center_x", 0.0)
 643                 resample_effect:set_float("zoom_center_y", 0.0)
 644
 645                 -- Padding must also be to a whole-pixel offset.
 646                 padding_effect:set_int("left", math.floor(x0))
 647                 padding_effect:set_int("top", math.floor(y0))
 648
 649                 -- Correct _that_ discrepancy by subpixel offset in the resampling.
 650                 resample_effect:set_float("left", srcx0 * input_width - x_subpixel_offset / zoom_x)
 651                 resample_effect:set_float("top", srcy0 * input_height - y_subpixel_offset / zoom_y)
 652
 653                 -- Finally, adjust the border so it is exactly where we want it.
 654                 padding_effect:set_float("border_offset_left", x_subpixel_offset)
 655                 padding_effect:set_float("border_offset_right", x1 - (math.floor(x0) + width))
 656                 padding_effect:set_float("border_offset_top", y_subpixel_offset)
 657                 padding_effect:set_float("border_offset_bottom", y1 - (math.floor(y0) + height))
 658         else
 659                 -- Lower-quality simple resizing.
 660                 local width = round(x1 - x0)
 661                 local height = round(y1 - y0)
 662                 resize_effect:set_int("width", width)
 663                 resize_effect:set_int("height", height)
 664
 665                 -- Padding must also be to a whole-pixel offset.
 666                 padding_effect:set_int("left", math.floor(x0))
 667                 padding_effect:set_int("top", math.floor(y0))
 668         end
 669 end
 670
 671 -- This is broken, of course (even for positive numbers), but Lua doesn't give us access to real rounding.
 672 function round(x)
 673         return math.floor(x + 0.5)
 674 end
 675
 676 function lerp(a, b, t)
 677         return a + (b - a) * t
 678 end
 679
 680 function prepare_sbs_chain(chain, t, screen_width, screen_height)
 681         chain.input0.input:connect_signal(0)
 682         chain.input1.input:connect_signal(1)
 683         set_neutral_color(chain.input0.wb_effect, input0_neutral_color)
 684         set_neutral_color(chain.input1.wb_effect, input1_neutral_color)
 685
 686         -- First input is positioned (16,48) from top-left.
 687         local width0 = round(848 * screen_width/1280.0)
 688         local height0 = round(width0 * 9.0 / 16.0)
 689
 690         local top0 = 48 * screen_height/720.0
 691         local left0 = 16 * screen_width/1280.0
 692         local bottom0 = top0 + height0
 693         local right0 = left0 + width0
 694
 695         -- Second input is positioned (16,48) from the bottom-right.
 696         local width1 = round(384 * screen_width/1280.0)
 697         local height1 = round(216 * screen_height/720.0)
 698
 699         local bottom1 = screen_height - 48 * screen_height/720.0
 700         local right1 = screen_width - 16 * screen_width/1280.0
 701         local top1 = bottom1 - height1
 702         local left1 = right1 - width1
 703
 704         -- Interpolate between the fullscreen and side-by-side views.
 705         local scale0, tx0, tx0
 706         if zoom_poi == INPUT0_SIGNAL_NUM then
 707                 local new_left0 = lerp(left0, 0, t)
 708                 local new_right0 = lerp(right0, screen_width, t)
 709                 local new_top0 = lerp(top0, 0, t)
 710                 local new_bottom0 = lerp(bottom0, screen_height, t)
 711
 712                 scale0 = (new_right0 - new_left0) / width0  -- Same vertically and horizonally.
 713                 tx0 = new_left0 - left0 * scale0
 714                 ty0 = new_top0 - top0 * scale0
 715         else
 716                 local new_left1 = lerp(left1, 0, t)
 717                 local new_right1 = lerp(right1, screen_width, t)
 718                 local new_top1 = lerp(top1, 0, t)
 719                 local new_bottom1 = lerp(bottom1, screen_height, t)
 720
 721                 scale0 = (new_right1 - new_left1) / width1  -- Same vertically and horizonally.
 722                 tx0 = new_left1 - left1 * scale0
 723                 ty0 = new_top1 - top1 * scale0
 724         end
 725
 726         top0 = top0 * scale0 + ty0
 727         bottom0 = bottom0 * scale0 + ty0
 728         left0 = left0 * scale0 + tx0
 729         right0 = right0 * scale0 + tx0
 730
 731         top1 = top1 * scale0 + ty0
 732         bottom1 = bottom1 * scale0 + ty0
 733         left1 = left1 * scale0 + tx0
 734         right1 = right1 * scale0 + tx0
 735         place_rectangle(chain.input0.resample_effect, chain.input0.resize_effect, chain.input0.padding_effect, left0, top0, right0, bottom0, screen_width, screen_height, 1280, 720)
 736         place_rectangle(chain.input1.resample_effect, chain.input1.resize_effect, chain.input1.padding_effect, left1, top1, right1, bottom1, screen_width, screen_height, 1280, 720)
 737 end
 738
 739 function set_neutral_color(effect, color)
 740         effect:set_vec3("neutral_color", color[1], color[2], color[3])
 741 end
 742
 743 function set_neutral_color_from_signal(effect, signal)
 744         if signal == INPUT0_SIGNAL_NUM then
 745                 set_neutral_color(effect, input0_neutral_color)
 746         else
 747                 set_neutral_color(effect, input1_neutral_color)
 748         end
 749 end
 750
 751 function calc_fade_progress(t, transition_start, transition_end)
 752         local tt = (t - transition_start) / (transition_end - transition_start)
 753         if tt < 0.0 then
 754                 tt = 0.0
 755         elseif tt > 1.0 then
 756                 tt = 1.0
 757         end
 758
 759         -- Make the fade look maybe a tad more natural, by pumping it
 760         -- through a sigmoid function.
 761         tt = 10.0 * tt - 5.0
 762         tt = 1.0 / (1.0 + math.exp(-tt))
 763
 764         return tt
 765 end