7 #include <movit/effect.h>
8 #include <movit/effect_chain.h>
9 #include <movit/image_format.h>
10 #include <movit/mix_effect.h>
11 #include <movit/overlay_effect.h>
12 #include <movit/padding_effect.h>
13 #include <movit/resample_effect.h>
14 #include <movit/resize_effect.h>
15 #include <movit/white_balance_effect.h>
16 #include <movit/ycbcr.h>
17 #include <movit/ycbcr_input.h>
26 #include "image_input.h"
34 using namespace movit;
36 extern Mixer *global_mixer;
40 class LuaRefWithDeleter {
42 LuaRefWithDeleter(mutex *m, lua_State *L, int ref) : m(m), L(L), ref(ref) {}
43 ~LuaRefWithDeleter() {
44 unique_lock<mutex> lock(*m);
45 luaL_unref(L, LUA_REGISTRYINDEX, ref);
47 int get() const { return ref; }
50 LuaRefWithDeleter(const LuaRefWithDeleter &) = delete;
57 template<class T, class... Args>
58 int wrap_lua_object(lua_State* L, const char *class_name, Args&&... args)
60 // Construct the C++ object and put it on the stack.
61 void *mem = lua_newuserdata(L, sizeof(T));
62 new(mem) T(std::forward<Args>(args)...);
64 // Look up the metatable named <class_name>, and set it on the new object.
65 luaL_getmetatable(L, class_name);
66 lua_setmetatable(L, -2);
71 Theme *get_theme_updata(lua_State* L)
73 luaL_checktype(L, lua_upvalueindex(1), LUA_TLIGHTUSERDATA);
74 return (Theme *)lua_touserdata(L, lua_upvalueindex(1));
77 Effect *get_effect(lua_State *L, int idx)
79 if (luaL_testudata(L, idx, "WhiteBalanceEffect") ||
80 luaL_testudata(L, idx, "ResampleEffect") ||
81 luaL_testudata(L, idx, "PaddingEffect") ||
82 luaL_testudata(L, idx, "IntegralPaddingEffect") ||
83 luaL_testudata(L, idx, "OverlayEffect") ||
84 luaL_testudata(L, idx, "ResizeEffect") ||
85 luaL_testudata(L, idx, "MixEffect") ||
86 luaL_testudata(L, idx, "ImageInput")) {
87 return (Effect *)lua_touserdata(L, idx);
89 luaL_error(L, "Error: Index #%d was not an Effect type\n", idx);
93 InputState *get_input_state(lua_State *L, int idx)
95 if (luaL_testudata(L, idx, "InputState")) {
96 return (InputState *)lua_touserdata(L, idx);
98 luaL_error(L, "Error: Index #%d was not InputState\n", idx);
102 bool checkbool(lua_State* L, int idx)
104 luaL_checktype(L, idx, LUA_TBOOLEAN);
105 return lua_toboolean(L, idx);
108 std::string checkstdstring(lua_State *L, int index)
111 const char* cstr = lua_tolstring(L, index, &len);
112 return std::string(cstr, len);
115 int EffectChain_new(lua_State* L)
117 assert(lua_gettop(L) == 2);
118 int aspect_w = luaL_checknumber(L, 1);
119 int aspect_h = luaL_checknumber(L, 2);
121 return wrap_lua_object<EffectChain>(L, "EffectChain", aspect_w, aspect_h);
124 int EffectChain_add_live_input(lua_State* L)
126 assert(lua_gettop(L) == 2);
127 Theme *theme = get_theme_updata(L);
128 EffectChain *chain = (EffectChain *)luaL_checkudata(L, 1, "EffectChain");
129 bool override_bounce = checkbool(L, 2);
130 return wrap_lua_object<LiveInputWrapper>(L, "LiveInputWrapper", theme, chain, override_bounce);
133 int EffectChain_add_effect(lua_State* L)
135 assert(lua_gettop(L) >= 2);
136 EffectChain *chain = (EffectChain *)luaL_checkudata(L, 1, "EffectChain");
138 // TODO: Better error reporting.
139 Effect *effect = get_effect(L, 2);
140 if (lua_gettop(L) == 2) {
141 if (effect->num_inputs() == 0) {
142 chain->add_input((Input *)effect);
144 chain->add_effect(effect);
147 vector<Effect *> inputs;
148 for (int idx = 3; idx <= lua_gettop(L); ++idx) {
149 if (luaL_testudata(L, idx, "LiveInputWrapper")) {
150 LiveInputWrapper *input = (LiveInputWrapper *)lua_touserdata(L, idx);
151 inputs.push_back(input->get_input());
153 inputs.push_back(get_effect(L, idx));
156 chain->add_effect(effect, inputs);
159 lua_settop(L, 2); // Return the effect itself.
161 // Make sure Lua doesn't garbage-collect it away.
162 lua_pushvalue(L, -1);
163 luaL_ref(L, LUA_REGISTRYINDEX); // TODO: leak?
168 int EffectChain_finalize(lua_State* L)
170 assert(lua_gettop(L) == 2);
171 EffectChain *chain = (EffectChain *)luaL_checkudata(L, 1, "EffectChain");
172 bool is_main_chain = checkbool(L, 2);
174 // Add outputs as needed.
175 // NOTE: If you change any details about the output format, you will need to
176 // also update what's given to the muxer (HTTPD::Mux constructor) and
177 // what's put in the H.264 stream (sps_rbsp()).
178 ImageFormat inout_format;
179 inout_format.color_space = COLORSPACE_REC_709;
181 // Output gamma is tricky. We should output Rec. 709 for TV, except that
182 // we expect to run with web players and others that don't really care and
183 // just output with no conversion. So that means we'll need to output sRGB,
184 // even though H.264 has no setting for that (we use “unspecified”).
185 inout_format.gamma_curve = GAMMA_sRGB;
188 YCbCrFormat output_ycbcr_format;
189 // We actually output 4:2:0 in the end, but chroma subsampling
190 // happens in a pass not run by Movit (see Mixer::subsample_chroma()).
191 output_ycbcr_format.chroma_subsampling_x = 1;
192 output_ycbcr_format.chroma_subsampling_y = 1;
194 // Rec. 709 would be the sane thing to do, but it seems many players
195 // (e.g. MPlayer and VLC) just default to BT.601 coefficients no matter
196 // what (see discussions in e.g. https://trac.ffmpeg.org/ticket/4978).
197 // We _do_ set the right flags, though, so that a player that works
198 // properly doesn't have to guess.
199 output_ycbcr_format.luma_coefficients = YCBCR_REC_601;
200 output_ycbcr_format.full_range = false;
201 output_ycbcr_format.num_levels = 256;
203 chain->add_ycbcr_output(inout_format, OUTPUT_ALPHA_FORMAT_POSTMULTIPLIED, output_ycbcr_format, YCBCR_OUTPUT_SPLIT_Y_AND_CBCR);
204 chain->set_dither_bits(8);
205 chain->set_output_origin(OUTPUT_ORIGIN_TOP_LEFT);
207 chain->add_output(inout_format, OUTPUT_ALPHA_FORMAT_POSTMULTIPLIED);
213 int LiveInputWrapper_connect_signal(lua_State* L)
215 assert(lua_gettop(L) == 2);
216 LiveInputWrapper *input = (LiveInputWrapper *)luaL_checkudata(L, 1, "LiveInputWrapper");
217 int signal_num = luaL_checknumber(L, 2);
218 input->connect_signal(signal_num);
222 int ImageInput_new(lua_State* L)
224 assert(lua_gettop(L) == 1);
225 std::string filename = checkstdstring(L, 1);
226 return wrap_lua_object<ImageInput>(L, "ImageInput", filename);
229 int WhiteBalanceEffect_new(lua_State* L)
231 assert(lua_gettop(L) == 0);
232 return wrap_lua_object<WhiteBalanceEffect>(L, "WhiteBalanceEffect");
235 int ResampleEffect_new(lua_State* L)
237 assert(lua_gettop(L) == 0);
238 return wrap_lua_object<ResampleEffect>(L, "ResampleEffect");
241 int PaddingEffect_new(lua_State* L)
243 assert(lua_gettop(L) == 0);
244 return wrap_lua_object<PaddingEffect>(L, "PaddingEffect");
247 int IntegralPaddingEffect_new(lua_State* L)
249 assert(lua_gettop(L) == 0);
250 return wrap_lua_object<IntegralPaddingEffect>(L, "IntegralPaddingEffect");
253 int OverlayEffect_new(lua_State* L)
255 assert(lua_gettop(L) == 0);
256 return wrap_lua_object<OverlayEffect>(L, "OverlayEffect");
259 int ResizeEffect_new(lua_State* L)
261 assert(lua_gettop(L) == 0);
262 return wrap_lua_object<ResizeEffect>(L, "ResizeEffect");
265 int MixEffect_new(lua_State* L)
267 assert(lua_gettop(L) == 0);
268 return wrap_lua_object<MixEffect>(L, "MixEffect");
271 int InputState_gc(lua_State* L)
273 assert(lua_gettop(L) == 1);
274 InputState *input_state = get_input_state(L, 1);
275 input_state->~InputState();
279 int InputState_get_width(lua_State* L)
281 assert(lua_gettop(L) == 2);
282 InputState *input_state = (InputState *)lua_touserdata(L, 1);
283 Theme *theme = get_theme_updata(L);
284 int signal_num = theme->map_signal(luaL_checknumber(L, 2));
285 BufferedFrame frame = input_state->buffered_frames[signal_num][0];
286 const PBOFrameAllocator::Userdata *userdata = (const PBOFrameAllocator::Userdata *)frame.frame->userdata;
287 lua_pushnumber(L, userdata->last_width[frame.field_number]);
291 int InputState_get_height(lua_State* L)
293 assert(lua_gettop(L) == 2);
294 InputState *input_state = (InputState *)lua_touserdata(L, 1);
295 Theme *theme = get_theme_updata(L);
296 int signal_num = theme->map_signal(luaL_checknumber(L, 2));
297 BufferedFrame frame = input_state->buffered_frames[signal_num][0];
298 const PBOFrameAllocator::Userdata *userdata = (const PBOFrameAllocator::Userdata *)frame.frame->userdata;
299 lua_pushnumber(L, userdata->last_height[frame.field_number]);
303 int Effect_set_float(lua_State *L)
305 assert(lua_gettop(L) == 3);
306 Effect *effect = (Effect *)get_effect(L, 1);
307 std::string key = checkstdstring(L, 2);
308 float value = luaL_checknumber(L, 3);
309 if (!effect->set_float(key, value)) {
310 luaL_error(L, "Effect refused set_float(\"%s\", %d) (invalid key?)", key.c_str(), int(value));
315 int Effect_set_int(lua_State *L)
317 assert(lua_gettop(L) == 3);
318 Effect *effect = (Effect *)get_effect(L, 1);
319 std::string key = checkstdstring(L, 2);
320 float value = luaL_checknumber(L, 3);
321 if (!effect->set_int(key, value)) {
322 luaL_error(L, "Effect refused set_int(\"%s\", %d) (invalid key?)", key.c_str(), int(value));
327 int Effect_set_vec3(lua_State *L)
329 assert(lua_gettop(L) == 5);
330 Effect *effect = (Effect *)get_effect(L, 1);
331 std::string key = checkstdstring(L, 2);
333 v[0] = luaL_checknumber(L, 3);
334 v[1] = luaL_checknumber(L, 4);
335 v[2] = luaL_checknumber(L, 5);
336 if (!effect->set_vec3(key, v)) {
337 luaL_error(L, "Effect refused set_vec3(\"%s\", %f, %f, %f) (invalid key?)", key.c_str(),
343 int Effect_set_vec4(lua_State *L)
345 assert(lua_gettop(L) == 6);
346 Effect *effect = (Effect *)get_effect(L, 1);
347 std::string key = checkstdstring(L, 2);
349 v[0] = luaL_checknumber(L, 3);
350 v[1] = luaL_checknumber(L, 4);
351 v[2] = luaL_checknumber(L, 5);
352 v[3] = luaL_checknumber(L, 6);
353 if (!effect->set_vec4(key, v)) {
354 luaL_error(L, "Effect refused set_vec4(\"%s\", %f, %f, %f, %f) (invalid key?)", key.c_str(),
355 v[0], v[1], v[2], v[3]);
360 const luaL_Reg EffectChain_funcs[] = {
361 { "new", EffectChain_new },
362 { "add_live_input", EffectChain_add_live_input },
363 { "add_effect", EffectChain_add_effect },
364 { "finalize", EffectChain_finalize },
368 const luaL_Reg LiveInputWrapper_funcs[] = {
369 { "connect_signal", LiveInputWrapper_connect_signal },
373 const luaL_Reg ImageInput_funcs[] = {
374 { "new", ImageInput_new },
375 { "set_float", Effect_set_float },
376 { "set_int", Effect_set_int },
377 { "set_vec3", Effect_set_vec3 },
378 { "set_vec4", Effect_set_vec4 },
382 const luaL_Reg WhiteBalanceEffect_funcs[] = {
383 { "new", WhiteBalanceEffect_new },
384 { "set_float", Effect_set_float },
385 { "set_int", Effect_set_int },
386 { "set_vec3", Effect_set_vec3 },
387 { "set_vec4", Effect_set_vec4 },
391 const luaL_Reg ResampleEffect_funcs[] = {
392 { "new", ResampleEffect_new },
393 { "set_float", Effect_set_float },
394 { "set_int", Effect_set_int },
395 { "set_vec3", Effect_set_vec3 },
396 { "set_vec4", Effect_set_vec4 },
400 const luaL_Reg PaddingEffect_funcs[] = {
401 { "new", PaddingEffect_new },
402 { "set_float", Effect_set_float },
403 { "set_int", Effect_set_int },
404 { "set_vec3", Effect_set_vec3 },
405 { "set_vec4", Effect_set_vec4 },
409 const luaL_Reg IntegralPaddingEffect_funcs[] = {
410 { "new", IntegralPaddingEffect_new },
411 { "set_float", Effect_set_float },
412 { "set_int", Effect_set_int },
413 { "set_vec3", Effect_set_vec3 },
414 { "set_vec4", Effect_set_vec4 },
418 const luaL_Reg OverlayEffect_funcs[] = {
419 { "new", OverlayEffect_new },
420 { "set_float", Effect_set_float },
421 { "set_int", Effect_set_int },
422 { "set_vec3", Effect_set_vec3 },
423 { "set_vec4", Effect_set_vec4 },
427 const luaL_Reg ResizeEffect_funcs[] = {
428 { "new", ResizeEffect_new },
429 { "set_float", Effect_set_float },
430 { "set_int", Effect_set_int },
431 { "set_vec3", Effect_set_vec3 },
432 { "set_vec4", Effect_set_vec4 },
436 const luaL_Reg MixEffect_funcs[] = {
437 { "new", MixEffect_new },
438 { "set_float", Effect_set_float },
439 { "set_int", Effect_set_int },
440 { "set_vec3", Effect_set_vec3 },
441 { "set_vec4", Effect_set_vec4 },
445 const luaL_Reg InputState_funcs[] = {
446 { "__gc", InputState_gc },
447 { "get_width", InputState_get_width },
448 { "get_height", InputState_get_height },
454 LiveInputWrapper::LiveInputWrapper(Theme *theme, EffectChain *chain, bool override_bounce)
457 ImageFormat inout_format;
458 inout_format.color_space = COLORSPACE_sRGB;
460 // Gamma curve depends on the input signal, and we don't really get any
461 // indications. A camera would be expected to do Rec. 709, but
462 // I haven't checked if any do in practice. However, computers _do_ output
463 // in sRGB gamma (ie., they don't convert from sRGB to Rec. 709), and
464 // I wouldn't really be surprised if most non-professional cameras do, too.
465 // So we pick sRGB as the least evil here.
466 inout_format.gamma_curve = GAMMA_sRGB;
468 // The Blackmagic driver docs claim that the device outputs Y'CbCr
469 // according to Rec. 601, but practical testing indicates it definitely
470 // is Rec. 709 (at least up to errors attributable to rounding errors).
471 // Perhaps 601 was only to indicate the subsampling positions, not the
472 // colorspace itself? Tested with a Lenovo X1 gen 3 as input.
473 YCbCrFormat input_ycbcr_format;
474 input_ycbcr_format.chroma_subsampling_x = 2;
475 input_ycbcr_format.chroma_subsampling_y = 1;
476 input_ycbcr_format.cb_x_position = 0.0;
477 input_ycbcr_format.cr_x_position = 0.0;
478 input_ycbcr_format.cb_y_position = 0.5;
479 input_ycbcr_format.cr_y_position = 0.5;
480 input_ycbcr_format.luma_coefficients = YCBCR_REC_709;
481 input_ycbcr_format.full_range = false;
483 if (override_bounce) {
484 input = new NonBouncingYCbCrInput(inout_format, input_ycbcr_format, WIDTH, HEIGHT, YCBCR_INPUT_SPLIT_Y_AND_CBCR);
486 input = new YCbCrInput(inout_format, input_ycbcr_format, WIDTH, HEIGHT, YCBCR_INPUT_SPLIT_Y_AND_CBCR);
488 chain->add_input(input);
491 void LiveInputWrapper::connect_signal(int signal_num)
493 if (global_mixer == nullptr) {
498 signal_num = theme->map_signal(signal_num);
500 BufferedFrame frame = theme->input_state->buffered_frames[signal_num][0];
501 const PBOFrameAllocator::Userdata *userdata = (const PBOFrameAllocator::Userdata *)frame.frame->userdata;
503 input->set_texture_num(0, userdata->tex_y[frame.field_number]);
504 input->set_texture_num(1, userdata->tex_cbcr[frame.field_number]);
505 input->set_width(userdata->last_width[frame.field_number]);
506 input->set_height(userdata->last_height[frame.field_number]);
509 Theme::Theme(const char *filename, ResourcePool *resource_pool, unsigned num_cards)
510 : resource_pool(resource_pool), num_cards(num_cards)
515 register_class("EffectChain", EffectChain_funcs);
516 register_class("LiveInputWrapper", LiveInputWrapper_funcs);
517 register_class("ImageInput", ImageInput_funcs);
518 register_class("WhiteBalanceEffect", WhiteBalanceEffect_funcs);
519 register_class("ResampleEffect", ResampleEffect_funcs);
520 register_class("PaddingEffect", PaddingEffect_funcs);
521 register_class("IntegralPaddingEffect", IntegralPaddingEffect_funcs);
522 register_class("OverlayEffect", OverlayEffect_funcs);
523 register_class("ResizeEffect", ResizeEffect_funcs);
524 register_class("MixEffect", MixEffect_funcs);
525 register_class("InputState", InputState_funcs);
529 if (luaL_dofile(L, filename)) {
530 fprintf(stderr, "error: %s\n", lua_tostring(L, -1));
534 assert(lua_gettop(L) == 0);
536 // Ask it for the number of channels.
537 lua_getglobal(L, "num_channels");
539 if (lua_pcall(L, 0, 1, 0) != 0) {
540 fprintf(stderr, "error running function `num_channels': %s\n", lua_tostring(L, -1));
544 num_channels = luaL_checknumber(L, 1);
546 assert(lua_gettop(L) == 0);
549 void Theme::register_class(const char *class_name, const luaL_Reg *funcs)
551 assert(lua_gettop(L) == 0);
552 luaL_newmetatable(L, class_name); // mt = {}
553 lua_pushlightuserdata(L, this);
554 luaL_setfuncs(L, funcs, 1); // for (name,f in funcs) { mt[name] = f, with upvalue {theme} }
555 lua_pushvalue(L, -1);
556 lua_setfield(L, -2, "__index"); // mt.__index = mt
557 lua_setglobal(L, class_name); // ClassName = mt
558 assert(lua_gettop(L) == 0);
561 Theme::Chain Theme::get_chain(unsigned num, float t, unsigned width, unsigned height, InputState input_state)
565 unique_lock<mutex> lock(m);
566 assert(lua_gettop(L) == 0);
567 lua_getglobal(L, "get_chain"); /* function to be called */
568 lua_pushnumber(L, num);
569 lua_pushnumber(L, t);
570 lua_pushnumber(L, width);
571 lua_pushnumber(L, height);
572 wrap_lua_object<InputState>(L, "InputState", input_state);
574 if (lua_pcall(L, 5, 2, 0) != 0) {
575 fprintf(stderr, "error running function `get_chain': %s\n", lua_tostring(L, -1));
579 chain.chain = (EffectChain *)luaL_checkudata(L, -2, "EffectChain");
580 if (!lua_isfunction(L, -1)) {
581 fprintf(stderr, "Argument #-1 should be a function\n");
584 lua_pushvalue(L, -1);
585 shared_ptr<LuaRefWithDeleter> funcref(new LuaRefWithDeleter(&m, L, luaL_ref(L, LUA_REGISTRYINDEX)));
587 assert(lua_gettop(L) == 0);
589 chain.setup_chain = [this, funcref, input_state]{
590 unique_lock<mutex> lock(m);
592 this->input_state = &input_state;
594 // Set up state, including connecting signals.
595 lua_rawgeti(L, LUA_REGISTRYINDEX, funcref->get());
596 if (lua_pcall(L, 0, 0, 0) != 0) {
597 fprintf(stderr, "error running chain setup callback: %s\n", lua_tostring(L, -1));
600 assert(lua_gettop(L) == 0);
603 // TODO: Can we do better, e.g. by running setup_chain() and seeing what it references?
604 // Actually, setup_chain does maybe hold all the references we need now anyway?
605 for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
606 for (unsigned frame_num = 0; frame_num < FRAME_HISTORY_LENGTH; ++frame_num) {
607 chain.input_frames.push_back(input_state.buffered_frames[card_index][frame_num].frame);
614 std::string Theme::get_channel_name(unsigned channel)
616 unique_lock<mutex> lock(m);
617 lua_getglobal(L, "channel_name");
618 lua_pushnumber(L, channel);
619 if (lua_pcall(L, 1, 1, 0) != 0) {
620 fprintf(stderr, "error running function `channel_nam': %s\n", lua_tostring(L, -1));
624 std::string ret = lua_tostring(L, -1);
626 assert(lua_gettop(L) == 0);
630 bool Theme::get_supports_set_wb(unsigned channel)
632 unique_lock<mutex> lock(m);
633 lua_getglobal(L, "supports_set_wb");
634 lua_pushnumber(L, channel);
635 if (lua_pcall(L, 1, 1, 0) != 0) {
636 fprintf(stderr, "error running function `supports_set_wb': %s\n", lua_tostring(L, -1));
640 bool ret = checkbool(L, -1);
642 assert(lua_gettop(L) == 0);
646 void Theme::set_wb(unsigned channel, double r, double g, double b)
648 unique_lock<mutex> lock(m);
649 lua_getglobal(L, "set_wb");
650 lua_pushnumber(L, channel);
651 lua_pushnumber(L, r);
652 lua_pushnumber(L, g);
653 lua_pushnumber(L, b);
654 if (lua_pcall(L, 4, 0, 0) != 0) {
655 fprintf(stderr, "error running function `set_wb': %s\n", lua_tostring(L, -1));
659 assert(lua_gettop(L) == 0);
662 std::vector<std::string> Theme::get_transition_names(float t)
664 unique_lock<mutex> lock(m);
665 lua_getglobal(L, "get_transitions");
666 lua_pushnumber(L, t);
667 if (lua_pcall(L, 1, 1, 0) != 0) {
668 fprintf(stderr, "error running function `get_transitions': %s\n", lua_tostring(L, -1));
672 std::vector<std::string> ret;
674 while (lua_next(L, -2) != 0) {
675 ret.push_back(lua_tostring(L, -1));
679 assert(lua_gettop(L) == 0);
683 int Theme::map_signal(int signal_num)
685 if (signal_num >= int(num_cards)) {
686 if (signals_warned_about.insert(signal_num).second) {
687 fprintf(stderr, "WARNING: Theme asked for input %d, but we only have %u card(s).\n", signal_num, num_cards);
688 fprintf(stderr, "Mapping to card %d instead.\n", signal_num % num_cards);
690 signal_num %= num_cards;
695 void Theme::transition_clicked(int transition_num, float t)
697 unique_lock<mutex> lock(m);
698 lua_getglobal(L, "transition_clicked");
699 lua_pushnumber(L, transition_num);
700 lua_pushnumber(L, t);
702 if (lua_pcall(L, 2, 0, 0) != 0) {
703 fprintf(stderr, "error running function `transition_clicked': %s\n", lua_tostring(L, -1));
706 assert(lua_gettop(L) == 0);
709 void Theme::channel_clicked(int preview_num)
711 unique_lock<mutex> lock(m);
712 lua_getglobal(L, "channel_clicked");
713 lua_pushnumber(L, preview_num);
715 if (lua_pcall(L, 1, 0, 0) != 0) {
716 fprintf(stderr, "error running function `channel_clicked': %s\n", lua_tostring(L, -1));
719 assert(lua_gettop(L) == 0);