Switch default gamma input curve to Rec. 709.

[nageru] / theme.cpp

diff --git a/theme.cpp b/theme.cpp
index 4843b0cd3fff65519d2eaea3243c9eb69dd64271..1536503adcece94f4ba20b7e2d626eb1604b86c0 100644 (file)
--- a/theme.cpp
+++ b/theme.cpp
@@ -123,15 +123,29 @@ int EffectChain_finalize(lua_State* L)
        bool is_main_chain = checkbool(L, 2);
 
        // Add outputs as needed.
+       // NOTE: If you change any details about the output format, you will need to
+       // also update what's given to the muxer (HTTPD::Mux constructor) and
+       // what's put in the H.264 stream (sps_rbsp()).
        ImageFormat inout_format;
-       inout_format.color_space = COLORSPACE_sRGB;
+       inout_format.color_space = COLORSPACE_REC_709;
+
+       // Gamma curve depends on the input signal, and we don't really get any
+       // indications. A camera would be expected to do Rec. 709, but
+       // I haven't checked if any do in practice. However, computers _do_ output
+       // in sRGB gamma (ie., they don't convert from sRGB to Rec. 709), and
+       // I wouldn't really be surprised if most non-professional cameras do, too.
+       // So we pick sRGB as the least evil here.
        inout_format.gamma_curve = GAMMA_sRGB;
+
        if (is_main_chain) {
                YCbCrFormat output_ycbcr_format;
+               // We actually output 4:2:0 in the end, but chroma subsampling
+               // happens in a pass not run by Movit (see Mixer::subsample_chroma()).
                output_ycbcr_format.chroma_subsampling_x = 1;
                output_ycbcr_format.chroma_subsampling_y = 1;
                output_ycbcr_format.luma_coefficients = YCBCR_REC_709;
-               output_ycbcr_format.full_range = false;
+               output_ycbcr_format.full_range = true;
+               output_ycbcr_format.num_levels = 256;
 
                chain->add_ycbcr_output(inout_format, OUTPUT_ALPHA_FORMAT_POSTMULTIPLIED, output_ycbcr_format, YCBCR_OUTPUT_SPLIT_Y_AND_CBCR);
                chain->set_dither_bits(8);
@@ -319,6 +333,11 @@ LiveInputWrapper::LiveInputWrapper(Theme *theme, EffectChain *chain, bool overri
        inout_format.color_space = COLORSPACE_sRGB;
        inout_format.gamma_curve = GAMMA_sRGB;
 
+       // The Blackmagic driver docs claim that the device outputs Y'CbCr
+       // according to Rec. 601, but practical testing indicates it definitely
+       // is Rec. 709 (at least up to errors attributable to rounding errors).
+       // Perhaps 601 was only to indicate the subsampling positions, not the
+       // colorspace itself? Tested with a Lenovo X1 gen 3 as input.
        YCbCrFormat input_ycbcr_format;
        input_ycbcr_format.chroma_subsampling_x = 2;
        input_ycbcr_format.chroma_subsampling_y = 1;
@@ -326,7 +345,7 @@ LiveInputWrapper::LiveInputWrapper(Theme *theme, EffectChain *chain, bool overri
        input_ycbcr_format.cr_x_position = 0.0;
        input_ycbcr_format.cb_y_position = 0.5;
        input_ycbcr_format.cr_y_position = 0.5;
-       input_ycbcr_format.luma_coefficients = YCBCR_REC_601;
+       input_ycbcr_format.luma_coefficients = YCBCR_REC_709;
        input_ycbcr_format.full_range = false;
 
        if (override_bounce) {
@@ -376,22 +395,27 @@ Theme::Theme(const char *filename, ResourcePool *resource_pool)
        }
 
        num_channels = luaL_checknumber(L, 1);
+       lua_pop(L, 1);
+       assert(lua_gettop(L) == 0);
 }
 
 void Theme::register_class(const char *class_name, const luaL_Reg *funcs)
 {
+       assert(lua_gettop(L) == 0);
        luaL_newmetatable(L, class_name);
        lua_pushlightuserdata(L, this);
        luaL_setfuncs(L, funcs, 1);
        lua_pushvalue(L, -1);
        lua_setfield(L, -2, "__index");
        lua_setglobal(L, class_name);
+       assert(lua_gettop(L) == 0);
 }
 
 pair<EffectChain *, function<void()>>
 Theme::get_chain(unsigned num, float t, unsigned width, unsigned height)
 {
        unique_lock<mutex> lock(m);
+       assert(lua_gettop(L) == 0);
        lua_getglobal(L, "get_chain");  /* function to be called */
        lua_pushnumber(L, num);
        lua_pushnumber(L, t);
@@ -411,6 +435,7 @@ Theme::get_chain(unsigned num, float t, unsigned width, unsigned height)
        lua_pushvalue(L, -1);
        int funcref = luaL_ref(L, LUA_REGISTRYINDEX);  // TODO: leak!
        lua_pop(L, 2);
+       assert(lua_gettop(L) == 0);
        return make_pair(chain, [this, funcref]{
                unique_lock<mutex> lock(m);
 
@@ -420,6 +445,7 @@ Theme::get_chain(unsigned num, float t, unsigned width, unsigned height)
                        fprintf(stderr, "error running chain setup callback: %s\n", lua_tostring(L, -1));
                        exit(1);
                }
+               assert(lua_gettop(L) == 0);
        });
 }
 
@@ -439,6 +465,8 @@ std::vector<std::string> Theme::get_transition_names(float t)
                ret.push_back(lua_tostring(L, -1));
                lua_pop(L, 1);
        }
+       lua_pop(L, 1);
+       assert(lua_gettop(L) == 0);
        return ret;
 }      
 
@@ -459,6 +487,7 @@ void Theme::transition_clicked(int transition_num, float t)
                fprintf(stderr, "error running function `transition_clicked': %s\n", lua_tostring(L, -1));
                exit(1);
        }
+       assert(lua_gettop(L) == 0);
 }
 
 void Theme::channel_clicked(int preview_num)
@@ -471,4 +500,5 @@ void Theme::channel_clicked(int preview_num)
                fprintf(stderr, "error running function `channel_clicked': %s\n", lua_tostring(L, -1));
                exit(1);
        }
+       assert(lua_gettop(L) == 0);
 }