Emulate glReadPixels of GL_ALPHA.
[movit] / ycbcr_input.cpp
1 #include <Eigen/Core>
2 #include <Eigen/LU>
3 #include <epoxy/gl.h>
4 #include <assert.h>
5 #include <stdio.h>
6 #include <string.h>
7
8 #include "effect_util.h"
9 #include "resource_pool.h"
10 #include "util.h"
11 #include "ycbcr_input.h"
12
13 using namespace Eigen;
14 using namespace std;
15
16 namespace movit {
17
18 namespace {
19
20 // OpenGL has texel center in (0.5, 0.5), but different formats have
21 // chroma in various other places. If luma samples are X, the chroma
22 // sample is *, and subsampling is 3x3, the situation with chroma
23 // center in (0.5, 0.5) looks approximately like this:
24 //
25 //   X   X
26 //     *   
27 //   X   X
28 //
29 // If, on the other hand, chroma center is in (0.0, 0.5) (common
30 // for e.g. MPEG-4), the figure changes to:
31 //
32 //   X   X
33 //   *      
34 //   X   X
35 //
36 // In other words, (0.0, 0.0) means that the chroma sample is exactly
37 // co-sited on top of the top-left luma sample. Note, however, that
38 // this is _not_ 0.5 texels to the left, since the OpenGL's texel center
39 // is in (0.5, 0.5); it is in (0.25, 0.25). In a sense, the four luma samples
40 // define a square where chroma position (0.0, 0.0) is in texel position
41 // (0.25, 0.25) and chroma position (1.0, 1.0) is in texel position (0.75, 0.75)
42 // (the outer border shows the borders of the texel itself, ie. from
43 // (0, 0) to (1, 1)):
44 //
45 //  ---------
46 // |         |
47 // |  X---X  |
48 // |  | * |  |
49 // |  X---X  |
50 // |         |
51 //  ---------
52 //
53 // Also note that if we have no subsampling, the square will have zero
54 // area and the chroma position does not matter at all.
55 float compute_chroma_offset(float pos, unsigned subsampling_factor, unsigned resolution)
56 {
57         float local_chroma_pos = (0.5 + pos * (subsampling_factor - 1)) / subsampling_factor;
58         return (0.5 - local_chroma_pos) / resolution;
59 }
60
61 }  // namespace
62
63 YCbCrInput::YCbCrInput(const ImageFormat &image_format,
64                        const YCbCrFormat &ycbcr_format,
65                        unsigned width, unsigned height)
66         : image_format(image_format),
67           ycbcr_format(ycbcr_format),
68           needs_mipmaps(false),
69           width(width),
70           height(height),
71           resource_pool(NULL)
72 {
73         pbos[0] = pbos[1] = pbos[2] = 0;
74         texture_num[0] = texture_num[1] = texture_num[2] = 0;
75
76         assert(width % ycbcr_format.chroma_subsampling_x == 0);
77         pitch[0] = widths[0] = width;
78         pitch[1] = widths[1] = width / ycbcr_format.chroma_subsampling_x;
79         pitch[2] = widths[2] = width / ycbcr_format.chroma_subsampling_x;
80
81         assert(height % ycbcr_format.chroma_subsampling_y == 0);
82         heights[0] = height;
83         heights[1] = height / ycbcr_format.chroma_subsampling_y;
84         heights[2] = height / ycbcr_format.chroma_subsampling_y;
85
86         pixel_data[0] = pixel_data[1] = pixel_data[2] = NULL;
87
88         register_int("needs_mipmaps", &needs_mipmaps);
89 }
90
91 YCbCrInput::~YCbCrInput()
92 {
93         for (unsigned channel = 0; channel < 3; ++channel) {
94                 if (texture_num[channel] != 0) {
95                         resource_pool->release_2d_texture(texture_num[channel]);
96                 }
97         }
98 }
99
100 void YCbCrInput::set_gl_state(GLuint glsl_program_num, const string& prefix, unsigned *sampler_num)
101 {
102         for (unsigned channel = 0; channel < 3; ++channel) {
103                 glActiveTexture(GL_TEXTURE0 + *sampler_num + channel);
104                 check_error();
105
106                 if (texture_num[channel] == 0) {
107                         // (Re-)upload the texture.
108                         texture_num[channel] = resource_pool->create_2d_texture(GL_R8, widths[channel], heights[channel]);
109                         glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
110                         check_error();
111                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
112                         check_error();
113                         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[channel]);
114                         check_error();
115                         glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
116                         check_error();
117                         glPixelStorei(GL_UNPACK_ROW_LENGTH, pitch[channel]);
118                         check_error();
119                         glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, widths[channel], heights[channel], GL_RED, GL_UNSIGNED_BYTE, pixel_data[channel]);
120                         check_error();
121                         glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
122                         check_error();
123                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
124                         check_error();
125                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
126                         check_error();
127                 } else {
128                         glBindTexture(GL_TEXTURE_2D, texture_num[channel]);
129                         check_error();
130                 }
131         }
132
133         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
134         check_error();
135
136         // Bind samplers.
137         set_uniform_int(glsl_program_num, prefix, "tex_y", *sampler_num + 0);
138         set_uniform_int(glsl_program_num, prefix, "tex_cb", *sampler_num + 1);
139         set_uniform_int(glsl_program_num, prefix, "tex_cr", *sampler_num + 2);
140
141         *sampler_num += 3;
142 }
143
144 string YCbCrInput::output_fragment_shader()
145 {
146         float coeff[3], offset[3], scale[3];
147
148         switch (ycbcr_format.luma_coefficients) {
149         case YCBCR_REC_601:
150                 // Rec. 601, page 2.
151                 coeff[0] = 0.299;
152                 coeff[1] = 0.587;
153                 coeff[2] = 0.114;
154                 break;
155
156         case YCBCR_REC_709:
157                 // Rec. 709, page 19.
158                 coeff[0] = 0.2126;
159                 coeff[1] = 0.7152;
160                 coeff[2] = 0.0722;
161                 break;
162
163         case YCBCR_REC_2020:
164                 // Rec. 2020, page 4.
165                 coeff[0] = 0.2627;
166                 coeff[1] = 0.6780;
167                 coeff[2] = 0.0593;
168                 break;
169
170         default:
171                 assert(false);
172         }
173
174         if (ycbcr_format.full_range) {
175                 offset[0] = 0.0 / 255.0;
176                 offset[1] = 128.0 / 255.0;
177                 offset[2] = 128.0 / 255.0;
178
179                 scale[0] = 1.0;
180                 scale[1] = 1.0;
181                 scale[2] = 1.0;
182         } else {
183                 // Rec. 601, page 4; Rec. 709, page 19; Rec. 2020, page 4.
184                 offset[0] = 16.0 / 255.0;
185                 offset[1] = 128.0 / 255.0;
186                 offset[2] = 128.0 / 255.0;
187
188                 scale[0] = 255.0 / 219.0;
189                 scale[1] = 255.0 / 224.0;
190                 scale[2] = 255.0 / 224.0;
191         }
192
193         // Matrix to convert RGB to YCbCr. See e.g. Rec. 601.
194         Matrix3d rgb_to_ycbcr;
195         rgb_to_ycbcr(0,0) = coeff[0];
196         rgb_to_ycbcr(0,1) = coeff[1];
197         rgb_to_ycbcr(0,2) = coeff[2];
198
199         float cb_fac = (224.0 / 219.0) / (coeff[0] + coeff[1] + 1.0f - coeff[2]);
200         rgb_to_ycbcr(1,0) = -coeff[0] * cb_fac;
201         rgb_to_ycbcr(1,1) = -coeff[1] * cb_fac;
202         rgb_to_ycbcr(1,2) = (1.0f - coeff[2]) * cb_fac;
203
204         float cr_fac = (224.0 / 219.0) / (1.0f - coeff[0] + coeff[1] + coeff[2]);
205         rgb_to_ycbcr(2,0) = (1.0f - coeff[0]) * cr_fac;
206         rgb_to_ycbcr(2,1) = -coeff[1] * cr_fac;
207         rgb_to_ycbcr(2,2) = -coeff[2] * cr_fac;
208
209         // Inverting the matrix gives us what we need to go from YCbCr back to RGB.
210         Matrix3d ycbcr_to_rgb = rgb_to_ycbcr.inverse();
211
212         string frag_shader;
213
214         frag_shader = output_glsl_mat3("PREFIX(inv_ycbcr_matrix)", ycbcr_to_rgb);
215
216         char buf[256];
217         sprintf(buf, "const vec3 PREFIX(offset) = vec3(%.8f, %.8f, %.8f);\n",
218                 offset[0], offset[1], offset[2]);
219         frag_shader += buf;
220
221         sprintf(buf, "const vec3 PREFIX(scale) = vec3(%.8f, %.8f, %.8f);\n",
222                 scale[0], scale[1], scale[2]);
223         frag_shader += buf;
224
225         float cb_offset_x = compute_chroma_offset(
226                 ycbcr_format.cb_x_position, ycbcr_format.chroma_subsampling_x, widths[1]);
227         float cb_offset_y = compute_chroma_offset(
228                 ycbcr_format.cb_y_position, ycbcr_format.chroma_subsampling_y, heights[1]);
229         sprintf(buf, "const vec2 PREFIX(cb_offset) = vec2(%.8f, %.8f);\n",
230                 cb_offset_x, cb_offset_y);
231         frag_shader += buf;
232
233         float cr_offset_x = compute_chroma_offset(
234                 ycbcr_format.cr_x_position, ycbcr_format.chroma_subsampling_x, widths[2]);
235         float cr_offset_y = compute_chroma_offset(
236                 ycbcr_format.cr_y_position, ycbcr_format.chroma_subsampling_y, heights[2]);
237         sprintf(buf, "const vec2 PREFIX(cr_offset) = vec2(%.8f, %.8f);\n",
238                 cr_offset_x, cr_offset_y);
239         frag_shader += buf;
240
241         frag_shader += read_file("ycbcr_input.frag");
242         return frag_shader;
243 }
244
245 void YCbCrInput::invalidate_pixel_data()
246 {
247         for (unsigned channel = 0; channel < 3; ++channel) {
248                 if (texture_num[channel] != 0) {
249                         resource_pool->release_2d_texture(texture_num[channel]);
250                         texture_num[channel] = 0;
251                 }
252         }
253 }
254
255 }  // namespace movit