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 numbers that signifies that we are fading from one input
  31 -- to the next.
  32 local FADE_VTV_SIGNAL_NUM = 4  -- Video to/from video.
  33 local FADE_VTP_SIGNAL_NUM = 5  -- Video to/from static picture.
  34
  35 -- The main live chain.
  36 function make_sbs_chain(hq)
  37         local chain = EffectChain.new(16, 9)
  38         local input0 = chain:add_live_input(true)
  39         input0:connect_signal(0)
  40         local input0_wb_effect = chain:add_effect(WhiteBalanceEffect.new())
  41         local input1 = chain:add_live_input(true)
  42         input1:connect_signal(1)
  43         local input1_wb_effect = chain:add_effect(WhiteBalanceEffect.new())
  44
  45         local resample_effect = nil
  46         local resize_effect = nil
  47         if (hq) then
  48                 resample_effect = chain:add_effect(ResampleEffect.new(), input0_wb_effect)
  49         else
  50                 resize_effect = chain:add_effect(ResizeEffect.new(), input0_wb_effect)
  51         end
  52
  53         local padding_effect = chain:add_effect(IntegralPaddingEffect.new())
  54         padding_effect:set_vec4("border_color", 0.0, 0.0, 0.0, 1.0)
  55
  56         local resample2_effect = nil
  57         local resize2_effect = nil
  58         if (hq) then
  59                 resample2_effect = chain:add_effect(ResampleEffect.new(), input1_wb_effect)
  60         else
  61                 resize2_effect = chain:add_effect(ResizeEffect.new(), input1_wb_effect)
  62         end
  63         local padding2_effect = chain:add_effect(IntegralPaddingEffect.new())
  64
  65         chain:add_effect(OverlayEffect.new(), padding_effect, padding2_effect)
  66         chain:finalize(hq)
  67
  68         return {
  69                 chain = chain,
  70                 input0 = {
  71                         input = input0,
  72                         white_balance_effect = input0_wb_effect,
  73                         resample_effect = resample_effect,
  74                         resize_effect = resize_effect,
  75                         padding_effect = padding_effect
  76                 },
  77                 input1 = {
  78                         input = input1,
  79                         white_balance_effect = input1_wb_effect,
  80                         resample_effect = resample2_effect,
  81                         resize_effect = resize2_effect,
  82                         padding_effect = padding2_effect
  83                 }
  84         }
  85 end
  86
  87 local main_chain_hq = make_sbs_chain(true)
  88 local main_chain_lq = make_sbs_chain(false)
  89
  90 -- A chain to fade between two inputs (live chain only)
  91 local fade_vtv_chain_hq = EffectChain.new(16, 9)
  92 local fade_vtv_chain_hq_input0 = fade_vtv_chain_hq:add_live_input(true)
  93 local fade_vtv_chain_hq_wb0_effect = fade_vtv_chain_hq:add_effect(WhiteBalanceEffect.new())
  94 local fade_vtv_chain_hq_input1 = fade_vtv_chain_hq:add_live_input(true)
  95 local fade_vtv_chain_hq_wb1_effect = fade_vtv_chain_hq:add_effect(WhiteBalanceEffect.new())
  96 fade_vtv_chain_hq_input0:connect_signal(0)
  97 fade_vtv_chain_hq_input1:connect_signal(1)
  98 local fade_vtv_chain_mix_effect = fade_vtv_chain_hq:add_effect(MixEffect.new(), fade_vtv_chain_hq_wb0_effect, fade_vtv_chain_hq_wb1_effect)
  99 fade_vtv_chain_hq:finalize(true)
 100
 101 -- A chain to fade between an inputs and a picture (live chain only)
 102 local fade_vtp_chain_hq = EffectChain.new(16, 9)
 103 local fade_vtp_chain_hq_input0 = fade_vtp_chain_hq:add_live_input(true)
 104 local fade_vtp_chain_hq_wb0_effect = fade_vtp_chain_hq:add_effect(WhiteBalanceEffect.new())
 105 local fade_vtp_chain_hq_input1 = fade_vtp_chain_hq:add_effect(ImageInput.new("bg.jpeg"))
 106 fade_vtp_chain_hq_input0:connect_signal(0)
 107 local fade_vtp_chain_mix_effect = fade_vtp_chain_hq:add_effect(MixEffect.new(), fade_vtp_chain_hq_wb0_effect, fade_vtp_chain_hq_input1)
 108 fade_vtp_chain_hq:finalize(true)
 109
 110 -- A chain to show a single input on screen (HQ version).
 111 local simple_chain_hq = EffectChain.new(16, 9)
 112 local simple_chain_hq_input = simple_chain_hq:add_live_input(true)
 113 simple_chain_hq_input:connect_signal(0)  -- First input card. Can be changed whenever you want.
 114 local simple_chain_hq_wb_effect = simple_chain_hq:add_effect(WhiteBalanceEffect.new())
 115 simple_chain_hq:finalize(true)
 116
 117 -- A chain to show a single input on screen (LQ version).
 118 local simple_chain_lq = EffectChain.new(16, 9)
 119 local simple_chain_lq_input = simple_chain_lq:add_live_input(true)
 120 simple_chain_lq_input:connect_signal(0)  -- First input card. Can be changed whenever you want.
 121 local simple_chain_lq_wb_effect = simple_chain_lq:add_effect(WhiteBalanceEffect.new())
 122 simple_chain_lq:finalize(false)
 123
 124 -- A chain to show a single static picture on screen (HQ version).
 125 local static_chain_hq = EffectChain.new(16, 9)
 126 local static_chain_hq_input = static_chain_hq:add_effect(ImageInput.new("bg.jpeg"))
 127 static_chain_hq:finalize(true)
 128
 129 -- A chain to show a single static picture on screen (LQ version).
 130 local static_chain_lq = EffectChain.new(16, 9)
 131 local static_chain_lq_input = static_chain_lq:add_effect(ImageInput.new("bg.jpeg"))
 132 static_chain_lq:finalize(false)
 133
 134 -- Returns the number of outputs in addition to the live (0) and preview (1).
 135 -- Called only once, at the start of the program.
 136 function num_channels()
 137         return 4
 138 end
 139
 140 -- Returns the name for each additional channel (starting from 2).
 141 -- Called only once for each channel, at the start of the program.
 142 function channel_name(channel)
 143         if channel == 2 then
 144                 return "Input 1"
 145         elseif channel == 3 then
 146                 return "Input 2"
 147         elseif channel == 4 then
 148                 return "Side-by-side"
 149         elseif channel == 5 then
 150                 return "Static picture"
 151         end
 152 end
 153
 154 -- Returns if a given channel supports setting white balance (starting from 2).
 155 -- Called only once for each channel, at the start of the program.
 156 function supports_set_wb(channel)
 157         return channel == 2 or channel == 3
 158 end
 159
 160 -- Gets called with a new gray point when the white balance is changing.
 161 -- The color is in linear light (not sRGB gamma).
 162 function set_wb(channel, red, green, blue)
 163         if channel == 2 then
 164                 input0_neutral_color = { red, green, blue }
 165         elseif channel == 3 then
 166                 input1_neutral_color = { red, green, blue }
 167         end
 168 end
 169
 170 function finish_transitions(t)
 171         -- If live is SBS but de-facto single, make it so.
 172         if live_signal_num == SBS_SIGNAL_NUM and t >= transition_end and zoom_dst == 1.0 then
 173                 live_signal_num = zoom_poi
 174         end
 175
 176         -- If live is fade but de-facto single, make it so.
 177         if (live_signal_num == FADE_VTV_SIGNAL_NUM or live_signal_num == FADE_VTP_SIGNAL_NUM) and t >= transition_end then
 178                 live_signal_num = fade_dst_signal
 179         end
 180 end
 181
 182 -- Called every frame.
 183 function get_transitions(t)
 184         finish_transitions(t)
 185
 186         if live_signal_num == preview_signal_num then
 187                 return {}
 188         end
 189
 190         if live_signal_num == SBS_SIGNAL_NUM and t >= transition_start and t <= transition_end then
 191                 -- Zoom in progress.
 192                 return {"Cut"}
 193         end
 194
 195         if (live_signal_num == INPUT0_SIGNAL_NUM or
 196             live_signal_num == INPUT1_SIGNAL_NUM or
 197             live_signal_num == STATIC_SIGNAL_NUM) and
 198            (preview_signal_num == INPUT0_SIGNAL_NUM or
 199             preview_signal_num == INPUT1_SIGNAL_NUM or
 200             preview_signal_num == STATIC_SIGNAL_NUM) then
 201                 return {"Cut", "", "Fade"}
 202         end
 203
 204         -- Various zooms.
 205         if live_signal_num == SBS_SIGNAL_NUM and
 206            (preview_signal_num == INPUT0_SIGNAL_NUM or preview_signal_num == INPUT1_SIGNAL_NUM) then
 207                 return {"Cut", "Zoom in"}
 208         elseif (live_signal_num == INPUT0_SIGNAL_NUM or live_signal_num == INPUT1_SIGNAL_NUM) and
 209                preview_signal_num == SBS_SIGNAL_NUM then
 210                 return {"Cut", "Zoom out"}
 211         end
 212
 213         return {"Cut"}
 214 end
 215
 216 function transition_clicked(num, t)
 217         if num == 0 then
 218                 -- Cut.
 219                 if live_signal_num == FADE_VTV_SIGNAL_NUM or live_signal_num == FADE_VTP_SIGNAL_NUM then
 220                         -- Ongoing fade; finish it immediately.
 221                         finish_transitions(transition_end)
 222                 end
 223
 224                 local temp = live_signal_num
 225                 live_signal_num = preview_signal_num
 226                 preview_signal_num = temp
 227
 228                 if live_signal_num == SBS_SIGNAL_NUM then
 229                         -- Just cut to SBS, we need to reset any zooms.
 230                         zoom_src = 1.0
 231                         zoom_dst = 0.0
 232                         transition_start = -2.0
 233                         transition_end = -1.0
 234                 end
 235         elseif num == 1 then
 236                 -- Zoom.
 237
 238                 finish_transitions(t)
 239
 240                 if live_signal_num == preview_signal_num then
 241                         -- Nothing to do.
 242                         return
 243                 end
 244
 245                 if (live_signal_num == INPUT0_SIGNAL_NUM and preview_signal_num == INPUT1_SIGNAL_NUM) or
 246                    (live_signal_num == INPUT1_SIGNAL_NUM and preview_signal_num == INPUT0_SIGNAL_NUM) then
 247                         -- We can't zoom between these. Just make a cut.
 248                         io.write("Cutting from " .. live_signal_num .. " to " .. live_signal_num .. "\n")
 249                         local temp = live_signal_num
 250                         live_signal_num = preview_signal_num
 251                         preview_signal_num = temp
 252                         return
 253                 end
 254
 255                 if live_signal_num == SBS_SIGNAL_NUM and
 256                    (preview_signal_num == INPUT0_SIGNAL_NUM or preview_signal_num == INPUT1_SIGNAL_NUM) then
 257                         -- Zoom in from SBS to single.
 258                         transition_start = t
 259                         transition_end = t + 1.0
 260                         zoom_src = 0.0
 261                         zoom_dst = 1.0
 262                         zoom_poi = preview_signal_num
 263                         preview_signal_num = SBS_SIGNAL_NUM
 264                 elseif (live_signal_num == INPUT0_SIGNAL_NUM or live_signal_num == INPUT1_SIGNAL_NUM) and
 265                        preview_signal_num == SBS_SIGNAL_NUM then
 266                         -- Zoom out from single to SBS.
 267                         transition_start = t
 268                         transition_end = t + 1.0
 269                         zoom_src = 1.0
 270                         zoom_dst = 0.0
 271                         preview_signal_num = live_signal_num
 272                         zoom_poi = live_signal_num
 273                         live_signal_num = SBS_SIGNAL_NUM
 274                 end
 275         elseif num == 2 then
 276                 finish_transitions(t)
 277
 278                 -- Fade.
 279                 if (live_signal_num == INPUT0_SIGNAL_NUM and preview_signal_num == INPUT1_SIGNAL_NUM) or
 280                    (live_signal_num == INPUT1_SIGNAL_NUM and preview_signal_num == INPUT0_SIGNAL_NUM) then
 281                         transition_start = t
 282                         transition_end = t + 1.0
 283                         fade_src_signal = live_signal_num
 284                         fade_dst_signal = preview_signal_num
 285                         preview_signal_num = live_signal_num
 286                         live_signal_num = FADE_VTV_SIGNAL_NUM
 287                 elseif ((live_signal_num == INPUT0_SIGNAL_NUM or live_signal_num == INPUT1_SIGNAL_NUM) and
 288                         preview_signal_num == STATIC_SIGNAL_NUM) or
 289                        ((preview_signal_num == INPUT0_SIGNAL_NUM or preview_signal_num == INPUT1_SIGNAL_NUM) and
 290                         live_signal_num == STATIC_SIGNAL_NUM) then
 291                         transition_start = t
 292                         transition_end = t + 1.0
 293                         fade_src_signal = live_signal_num
 294                         fade_dst_signal = preview_signal_num
 295                         preview_signal_num = live_signal_num
 296                         live_signal_num = FADE_VTP_SIGNAL_NUM
 297                 else
 298                         -- Fades involving SBS are ignored (we have no chain for it).
 299                 end
 300         end
 301 end
 302
 303 function channel_clicked(num)
 304         preview_signal_num = num
 305 end
 306
 307 -- Called every frame. Get the chain for displaying at input <num>,
 308 -- where 0 is live, 1 is preview, 2 is the first channel to display
 309 -- in the bottom bar, and so on up to num_channels()+1. t is the
 310 -- current time in seconds. width and height are the dimensions of
 311 -- the output, although you can ignore them if you don't need them
 312 -- (they're useful if you want to e.g. know what to resample by).
 313 --
 314 -- You should return two objects; the chain itself, and then a
 315 -- function (taking no parameters) that is run just before rendering.
 316 -- The function needs to call connect_signal on any inputs, so that
 317 -- it gets updated video data for the given frame. (You are allowed
 318 -- to switch which input your input is getting from between frames,
 319 -- but not calling connect_signal results in undefined behavior.)
 320 -- If you want to change any parameters in the chain, this is also
 321 -- the right place.
 322 --
 323 -- NOTE: The chain returned must be finalized with the Y'CbCr flag
 324 -- if and only if num==0.
 325 function get_chain(num, t, width, height)
 326         if num == 0 then  -- Live.
 327                 if live_signal_num == INPUT0_SIGNAL_NUM or live_signal_num == INPUT1_SIGNAL_NUM then  -- Plain input.
 328                         prepare = function()
 329                                 simple_chain_hq_input:connect_signal(live_signal_num)
 330                                 set_neutral_color_from_signal(simple_chain_hq_wb_effect, live_signal_num)
 331                         end
 332                         return simple_chain_hq, prepare
 333                 elseif live_signal_num == STATIC_SIGNAL_NUM then  -- Static picture.
 334                         prepare = function()
 335                         end
 336                         return static_chain_hq, prepare
 337                 elseif live_signal_num == FADE_VTV_SIGNAL_NUM then  -- Fade video-to-video.
 338                         prepare = function()
 339                                 fade_vtv_chain_hq_input0:connect_signal(fade_src_signal)
 340                                 set_neutral_color_from_signal(fade_vtv_chain_hq_wb0_effect, fade_src_signal)
 341                                 fade_vtv_chain_hq_input1:connect_signal(fade_dst_signal)
 342                                 set_neutral_color_from_signal(fade_vtv_chain_hq_wb1_effect, fade_dst_signal)
 343                                 local tt = calc_fade_progress(t, transition_start, transition_end)
 344
 345                                 fade_vtv_chain_mix_effect:set_float("strength_first", 1.0 - tt)
 346                                 fade_vtv_chain_mix_effect:set_float("strength_second", tt)
 347                         end
 348                         return fade_vtv_chain_hq, prepare
 349                 elseif live_signal_num == FADE_VTP_SIGNAL_NUM then  -- Fade video-to-picture (or picture-to-video).
 350                         prepare = function()
 351                                 local tt
 352                                 if fade_src_signal == STATIC_SIGNAL_NUM then
 353                                         fade_vtp_chain_hq_input0:connect_signal(fade_dst_signal)
 354                                         set_neutral_color_from_signal(fade_vtp_chain_hq_wb0_effect, fade_dst_signal)
 355                                         tt = 1.0 - calc_fade_progress(t, transition_start, transition_end)
 356                                 else
 357                                         fade_vtp_chain_hq_input0:connect_signal(fade_src_signal)
 358                                         set_neutral_color_from_signal(fade_vtp_chain_hq_wb0_effect, fade_src_signal)
 359                                         tt = calc_fade_progress(t, transition_start, transition_end)
 360                                 end
 361                                 fade_vtp_chain_mix_effect:set_float("strength_first", 1.0 - tt)
 362                                 fade_vtp_chain_mix_effect:set_float("strength_second", tt)
 363                         end
 364                         return fade_vtp_chain_hq, prepare
 365                 end
 366
 367                 -- SBS code (live_signal_num == SBS_SIGNAL_NUM).
 368                 if t > transition_end and zoom_dst == 1.0 then
 369                         -- Special case: Show only the single image on screen.
 370                         prepare = function()
 371                                 simple_chain_hq_input:connect_signal(INPUT0_SIGNAL_NUM)
 372                                 set_neutral_color(simple_chain_hq_wb_effect, input0_neutral_color)
 373                         end
 374                         return simple_chain_hq, prepare
 375                 end
 376                 prepare = function()
 377                         if t < transition_start then
 378                                 prepare_sbs_chain(main_chain_hq, zoom_src, width, height)
 379                         elseif t > transition_end then
 380                                 prepare_sbs_chain(main_chain_hq, zoom_dst, width, height)
 381                         else
 382                                 local tt = (t - transition_start) / (transition_end - transition_start)
 383                                 -- Smooth it a bit.
 384                                 tt = math.sin(tt * 3.14159265358 * 0.5)
 385                                 prepare_sbs_chain(main_chain_hq, zoom_src + (zoom_dst - zoom_src) * tt, width, height)
 386                         end
 387                 end
 388                 return main_chain_hq.chain, prepare
 389         end
 390         if num == 1 then  -- Preview.
 391                 num = preview_signal_num + 2
 392         end
 393         if num == INPUT0_SIGNAL_NUM + 2 then
 394                 prepare = function()
 395                         simple_chain_lq_input:connect_signal(0)
 396                         set_neutral_color(simple_chain_lq_wb_effect, input0_neutral_color)
 397                 end
 398                 return simple_chain_lq, prepare
 399         end
 400         if num == INPUT1_SIGNAL_NUM + 2 then
 401                 prepare = function()
 402                         simple_chain_lq_input:connect_signal(1)
 403                         set_neutral_color(simple_chain_lq_wb_effect, input1_neutral_color)
 404                 end
 405                 return simple_chain_lq, prepare
 406         end
 407         if num == SBS_SIGNAL_NUM + 2 then
 408                 prepare = function()
 409                         prepare_sbs_chain(main_chain_lq, 0.0, width, height)
 410                 end
 411                 return main_chain_lq.chain, prepare
 412         end
 413         if num == STATIC_SIGNAL_NUM + 2 then
 414                 prepare = function()
 415                 end
 416                 return static_chain_lq, prepare
 417         end
 418 end
 419
 420 function place_rectangle(resample_effect, resize_effect, padding_effect, x0, y0, x1, y1, screen_width, screen_height, input_width, input_height)
 421         local srcx0 = 0.0
 422         local srcx1 = 1.0
 423         local srcy0 = 0.0
 424         local srcy1 = 1.0
 425
 426         -- Cull.
 427         if x0 > screen_width or x1 < 0.0 or y0 > screen_height or y1 < 0.0 then
 428                 resample_effect:set_int("width", 1)
 429                 resample_effect:set_int("height", 1)
 430                 resample_effect:set_float("zoom_x", screen_width)
 431                 resample_effect:set_float("zoom_y", screen_height)
 432                 padding_effect:set_int("left", screen_width + 100)
 433                 padding_effect:set_int("top", screen_height + 100)
 434                 return
 435         end
 436
 437         -- Clip.
 438         if x0 < 0 then
 439                 srcx0 = -x0 / (x1 - x0)
 440                 x0 = 0
 441         end
 442         if y0 < 0 then
 443                 srcy0 = -y0 / (y1 - y0)
 444                 y0 = 0
 445         end
 446         if x1 > screen_width then
 447                 srcx1 = (screen_width - x0) / (x1 - x0)
 448                 x1 = screen_width
 449         end
 450         if y1 > screen_height then
 451                 srcy1 = (screen_height - y0) / (y1 - y0)
 452                 y1 = screen_height
 453         end
 454
 455         if resample_effect ~= nil then
 456                 -- High-quality resampling.
 457                 local x_subpixel_offset = x0 - math.floor(x0)
 458                 local y_subpixel_offset = y0 - math.floor(y0)
 459
 460                 -- Resampling must be to an integral number of pixels. Round up,
 461                 -- and then add an extra pixel so we have some leeway for the border.
 462                 local width = math.ceil(x1 - x0) + 1
 463                 local height = math.ceil(y1 - y0) + 1
 464                 resample_effect:set_int("width", width)
 465                 resample_effect:set_int("height", height)
 466
 467                 -- Correct the discrepancy with zoom. (This will leave a small
 468                 -- excess edge of pixels and subpixels, which we'll correct for soon.)
 469                 local zoom_x = (x1 - x0) / (width * (srcx1 - srcx0))
 470                 local zoom_y = (y1 - y0) / (height * (srcy1 - srcy0))
 471                 resample_effect:set_float("zoom_x", zoom_x)
 472                 resample_effect:set_float("zoom_y", zoom_y)
 473                 resample_effect:set_float("zoom_center_x", 0.0)
 474                 resample_effect:set_float("zoom_center_y", 0.0)
 475
 476                 -- Padding must also be to a whole-pixel offset.
 477                 padding_effect:set_int("left", math.floor(x0))
 478                 padding_effect:set_int("top", math.floor(y0))
 479
 480                 -- Correct _that_ discrepancy by subpixel offset in the resampling.
 481                 resample_effect:set_float("left", srcx0 * input_width - x_subpixel_offset / zoom_x)
 482                 resample_effect:set_float("top", srcy0 * input_height - y_subpixel_offset / zoom_y)
 483
 484                 -- Finally, adjust the border so it is exactly where we want it.
 485                 padding_effect:set_float("border_offset_left", x_subpixel_offset)
 486                 padding_effect:set_float("border_offset_right", x1 - (math.floor(x0) + width))
 487                 padding_effect:set_float("border_offset_top", y_subpixel_offset)
 488                 padding_effect:set_float("border_offset_bottom", y1 - (math.floor(y0) + height))
 489         else
 490                 -- Lower-quality simple resizing.
 491                 local width = round(x1 - x0)
 492                 local height = round(y1 - y0)
 493                 resize_effect:set_int("width", width)
 494                 resize_effect:set_int("height", height)
 495
 496                 -- Padding must also be to a whole-pixel offset.
 497                 padding_effect:set_int("left", math.floor(x0))
 498                 padding_effect:set_int("top", math.floor(y0))
 499         end
 500 end
 501
 502 -- This is broken, of course (even for positive numbers), but Lua doesn't give us access to real rounding.
 503 function round(x)
 504         return math.floor(x + 0.5)
 505 end
 506
 507 function lerp(a, b, t)
 508         return a + (b - a) * t
 509 end
 510
 511 function prepare_sbs_chain(chain, t, screen_width, screen_height)
 512         chain.input0.input:connect_signal(0)
 513         chain.input1.input:connect_signal(1)
 514         set_neutral_color(chain.input0.white_balance_effect, input0_neutral_color)
 515         set_neutral_color(chain.input1.white_balance_effect, input1_neutral_color)
 516
 517         -- First input is positioned (16,48) from top-left.
 518         local width0 = round(848 * screen_width/1280.0)
 519         local height0 = round(width0 * 9.0 / 16.0)
 520
 521         local top0 = 48 * screen_height/720.0
 522         local left0 = 16 * screen_width/1280.0
 523         local bottom0 = top0 + height0
 524         local right0 = left0 + width0
 525
 526         -- Second input is positioned (16,48) from the bottom-right.
 527         local width1 = round(384 * screen_width/1280.0)
 528         local height1 = round(216 * screen_height/720.0)
 529
 530         local bottom1 = screen_height - 48 * screen_height/720.0
 531         local right1 = screen_width - 16 * screen_width/1280.0
 532         local top1 = bottom1 - height1
 533         local left1 = right1 - width1
 534
 535         -- Interpolate between the fullscreen and side-by-side views.
 536         local scale0, tx0, tx0
 537         if zoom_poi == INPUT0_SIGNAL_NUM then
 538                 local new_left0 = lerp(left0, 0, t)
 539                 local new_right0 = lerp(right0, screen_width, t)
 540                 local new_top0 = lerp(top0, 0, t)
 541                 local new_bottom0 = lerp(bottom0, screen_height, t)
 542
 543                 scale0 = (new_right0 - new_left0) / width0  -- Same vertically and horizonally.
 544                 tx0 = new_left0 - left0 * scale0
 545                 ty0 = new_top0 - top0 * scale0
 546         else
 547                 local new_left1 = lerp(left1, 0, t)
 548                 local new_right1 = lerp(right1, screen_width, t)
 549                 local new_top1 = lerp(top1, 0, t)
 550                 local new_bottom1 = lerp(bottom1, screen_height, t)
 551
 552                 scale0 = (new_right1 - new_left1) / width1  -- Same vertically and horizonally.
 553                 tx0 = new_left1 - left1 * scale0
 554                 ty0 = new_top1 - top1 * scale0
 555         end
 556
 557         top0 = top0 * scale0 + ty0
 558         bottom0 = bottom0 * scale0 + ty0
 559         left0 = left0 * scale0 + tx0
 560         right0 = right0 * scale0 + tx0
 561
 562         top1 = top1 * scale0 + ty0
 563         bottom1 = bottom1 * scale0 + ty0
 564         left1 = left1 * scale0 + tx0
 565         right1 = right1 * scale0 + tx0
 566         place_rectangle(chain.input0.resample_effect, chain.input0.resize_effect, chain.input0.padding_effect, left0, top0, right0, bottom0, screen_width, screen_height, 1280, 720)
 567         place_rectangle(chain.input1.resample_effect, chain.input1.resize_effect, chain.input1.padding_effect, left1, top1, right1, bottom1, screen_width, screen_height, 1280, 720)
 568 end
 569
 570 function set_neutral_color(effect, color)
 571         effect:set_vec3("neutral_color", color[1], color[2], color[3])
 572 end
 573
 574 function set_neutral_color_from_signal(effect, signal)
 575         if signal == INPUT0_SIGNAL_NUM then
 576                 set_neutral_color(effect, input0_neutral_color)
 577         else
 578                 set_neutral_color(effect, input1_neutral_color)
 579         end
 580 end
 581
 582 function calc_fade_progress(t, transition_start, transition_end)
 583         local tt = (t - transition_start) / (transition_end - transition_start)
 584         if tt < 0.0 then
 585                 tt = 0.0
 586         elseif tt > 1.0 then
 587                 tt = 1.0
 588         end
 589
 590         -- Make the fade look maybe a tad more natural, by pumping it
 591         -- through a sigmoid function.
 592         tt = 10.0 * tt - 5.0
 593         tt = 1.0 / (1.0 + math.exp(-tt))
 594
 595         return tt
 596 end