git.sesse.net Git - nageru/blob - mixer.cpp

   1 #define GL_GLEXT_PROTOTYPES 1
   2 #define NO_SDL_GLEXT 1
   3 #define NUM_CARDS 2
   4
   5 #define WIDTH 1280
   6 #define HEIGHT 720
   7
   8 #include <epoxy/gl.h>
   9 #include <epoxy/egl.h>
  10
  11 #undef Success
  12
  13 #include <assert.h>
  14 #include <features.h>
  15 #include <math.h>
  16 #include <png.h>
  17 #include <pngconf.h>
  18 #include <setjmp.h>
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <sys/time.h>
  22 #include <time.h>
  23 #include <mutex>
  24 #include <queue>
  25 #include <condition_variable>
  26
  27 #include <diffusion_effect.h>
  28 #include <effect.h>
  29 #include <effect_chain.h>
  30 #include <flat_input.h>
  31 #include <image_format.h>
  32 #include <init.h>
  33 #include <lift_gamma_gain_effect.h>
  34 #include <saturation_effect.h>
  35 #include <util.h>
  36 #include <ycbcr_input.h>
  37 #include <vignette_effect.h>
  38 #include <resample_effect.h>
  39 #include <resize_effect.h>
  40 #include <overlay_effect.h>
  41 #include <padding_effect.h>
  42 #include <white_balance_effect.h>
  43 #include <ycbcr.h>
  44 #include <resource_pool.h>
  45 #include <effect_util.h>
  46
  47 #include <EGL/egl.h>
  48
  49 #include "h264encode.h"
  50 #include "context.h"
  51 #include "bmusb.h"
  52 #include "pbo_frame_allocator.h"
  53
  54 using namespace movit;
  55 using namespace std;
  56 using namespace std::placeholders;
  57
  58
  59 std::mutex bmusb_mutex;  // protects <cards>
  60
  61 struct CaptureCard {
  62         BMUSBCapture *usb;
  63
  64         // Threading stuff
  65         bool thread_initialized;
  66         QSurface *surface;
  67         QOpenGLContext *context;
  68
  69         bool new_data_ready;  // Whether new_frame contains anything.
  70         PBOFrameAllocator::Frame new_frame;
  71         GLsync new_data_ready_fence;  // Whether new_frame is ready for rendering.
  72         std::condition_variable new_data_ready_changed;  // Set whenever new_data_ready is changed.
  73 };
  74 CaptureCard cards[NUM_CARDS];
  75
  76 void bm_frame(int card_index, uint16_t timecode,
  77               FrameAllocator::Frame video_frame, size_t video_offset, uint16_t video_format,
  78               FrameAllocator::Frame audio_frame, size_t audio_offset, uint16_t audio_format)
  79 {
  80         CaptureCard *card = &cards[card_index];
  81         if (!card->thread_initialized) {
  82                 printf("initializing context for bmusb thread %d\n", card_index);
  83                 eglBindAPI(EGL_OPENGL_API);
  84                 card->context = create_context();
  85                 if (!make_current(card->context, card->surface)) {
  86                         printf("failed to create bmusb context\n");
  87                         exit(1);
  88                 }
  89                 card->thread_initialized = true;
  90         }
  91
  92         if (video_frame.len - video_offset != 1280 * 750 * 2) {
  93                 printf("dropping frame with wrong length (%ld)\n", video_frame.len - video_offset);
  94                 FILE *fp = fopen("frame.raw", "wb");
  95                 fwrite(video_frame.data, video_frame.len, 1, fp);
  96                 fclose(fp);
  97                 //exit(1);
  98                 card->usb->get_video_frame_allocator()->release_frame(video_frame);
  99                 card->usb->get_audio_frame_allocator()->release_frame(audio_frame);
 100                 return;
 101         }
 102         {
 103                 // Wait until the previous frame was consumed.
 104                 std::unique_lock<std::mutex> lock(bmusb_mutex);
 105                 card->new_data_ready_changed.wait(lock, [card]{ return !card->new_data_ready; });
 106         }
 107         GLuint pbo = (GLint)(intptr_t)video_frame.userdata;
 108         check_error();
 109         glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbo);
 110         check_error();
 111         glFlushMappedBufferRange(GL_PIXEL_UNPACK_BUFFER, 0, video_frame.size);
 112         check_error();
 113         //glMemoryBarrier(GL_CLIENT_MAPPED_BUFFER_BARRIER_BIT);
 114         //check_error();
 115         GLsync fence = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, /*flags=*/0);
 116         check_error();
 117         assert(fence != nullptr);
 118         {
 119                 std::unique_lock<std::mutex> lock(bmusb_mutex);
 120                 card->new_data_ready = true;
 121                 card->new_frame = video_frame;
 122                 card->new_data_ready_fence = fence;
 123                 card->new_data_ready_changed.notify_all();
 124         }
 125
 126         // Video frame will be released later.
 127         card->usb->get_audio_frame_allocator()->release_frame(audio_frame);
 128 }
 129
 130 void place_rectangle(Effect *resample_effect, Effect *padding_effect, float x0, float y0, float x1, float y1)
 131 {
 132         float srcx0 = 0.0f;
 133         float srcx1 = 1.0f;
 134         float srcy0 = 0.0f;
 135         float srcy1 = 1.0f;
 136
 137         // Cull.
 138         if (x0 > 1280.0 || x1 < 0.0 || y0 > 720.0 || y1 < 0.0) {
 139                 CHECK(resample_effect->set_int("width", 1));
 140                 CHECK(resample_effect->set_int("height", 1));
 141                 CHECK(resample_effect->set_float("zoom_x", 1280.0));
 142                 CHECK(resample_effect->set_float("zoom_y", 720.0));
 143                 CHECK(padding_effect->set_int("left", 2000));
 144                 CHECK(padding_effect->set_int("top", 2000));
 145                 return;
 146         }
 147
 148         // Clip. (TODO: Clip on upper/left sides, too.)
 149         if (x1 > 1280.0) {
 150                 srcx1 = (1280.0 - x0) / (x1 - x0);
 151                 x1 = 1280.0;
 152         }
 153         if (y1 > 720.0) {
 154                 srcy1 = (720.0 - y0) / (y1 - y0);
 155                 y1 = 720.0;
 156         }
 157
 158         float x_subpixel_offset = x0 - floor(x0);
 159         float y_subpixel_offset = y0 - floor(y0);
 160
 161         // Resampling must be to an integral number of pixels. Round up,
 162         // and then add an extra pixel so we have some leeway for the border.
 163         int width = int(ceil(x1 - x0)) + 1;
 164         int height = int(ceil(y1 - y0)) + 1;
 165         CHECK(resample_effect->set_int("width", width));
 166         CHECK(resample_effect->set_int("height", height));
 167
 168         // Correct the discrepancy with zoom. (This will leave a small
 169         // excess edge of pixels and subpixels, which we'll correct for soon.)
 170         float zoom_x = (x1 - x0) / (width * (srcx1 - srcx0));
 171         float zoom_y = (y1 - y0) / (height * (srcy1 - srcy0));
 172         CHECK(resample_effect->set_float("zoom_x", zoom_x));
 173         CHECK(resample_effect->set_float("zoom_y", zoom_y));
 174         CHECK(resample_effect->set_float("zoom_center_x", 0.0f));
 175         CHECK(resample_effect->set_float("zoom_center_y", 0.0f));
 176
 177         // Padding must also be to a whole-pixel offset.
 178         CHECK(padding_effect->set_int("left", floor(x0)));
 179         CHECK(padding_effect->set_int("top", floor(y0)));
 180
 181         // Correct _that_ discrepancy by subpixel offset in the resampling.
 182         CHECK(resample_effect->set_float("left", -x_subpixel_offset / zoom_x));
 183         CHECK(resample_effect->set_float("top", -y_subpixel_offset / zoom_y));
 184
 185         // Finally, adjust the border so it is exactly where we want it.
 186         CHECK(padding_effect->set_float("border_offset_left", x_subpixel_offset));
 187         CHECK(padding_effect->set_float("border_offset_right", x1 - (floor(x0) + width)));
 188         CHECK(padding_effect->set_float("border_offset_top", y_subpixel_offset));
 189         CHECK(padding_effect->set_float("border_offset_bottom", y1 - (floor(y0) + height)));
 190 }
 191
 192 static bool quit = false;
 193
 194 void mixer_thread_func(QSurface *surface, QSurface *surface2, QSurface *surface3, QSurface *surface4)
 195 {
 196         cards[0].surface = surface3;
 197 #if NUM_CARDS == 2
 198         cards[1].surface = surface4;
 199 #endif
 200
 201         eglBindAPI(EGL_OPENGL_API);
 202         QOpenGLContext *context = create_context();
 203         if (!make_current(context, surface)) {
 204                 printf("oops\n");
 205                 exit(1);
 206         }
 207
 208         CHECK(init_movit(MOVIT_SHADER_DIR, MOVIT_DEBUG_OFF));
 209         check_error();
 210
 211         EffectChain chain(WIDTH, HEIGHT);
 212         check_error();
 213
 214         ImageFormat inout_format;
 215         inout_format.color_space = COLORSPACE_sRGB;
 216         inout_format.gamma_curve = GAMMA_sRGB;
 217
 218         YCbCrFormat ycbcr_format;
 219         ycbcr_format.chroma_subsampling_x = 2;
 220         ycbcr_format.chroma_subsampling_y = 1;
 221         ycbcr_format.cb_x_position = 0.0;
 222         ycbcr_format.cr_x_position = 0.0;
 223         ycbcr_format.cb_y_position = 0.5;
 224         ycbcr_format.cr_y_position = 0.5;
 225         ycbcr_format.luma_coefficients = YCBCR_REC_601;
 226         ycbcr_format.full_range = false;
 227
 228         YCbCrInput *input[NUM_CARDS];
 229
 230         input[0] = new YCbCrInput(inout_format, ycbcr_format, WIDTH, HEIGHT, YCBCR_INPUT_SPLIT_Y_AND_CBCR);
 231         chain.add_input(input[0]);
 232         input[1] = new YCbCrInput(inout_format, ycbcr_format, WIDTH, HEIGHT, YCBCR_INPUT_SPLIT_Y_AND_CBCR);
 233         chain.add_input(input[1]);
 234         Effect *resample_effect = chain.add_effect(new ResampleEffect(), input[0]);
 235         Effect *padding_effect = chain.add_effect(new IntegralPaddingEffect());
 236         float border_color[] = { 0.0f, 0.0f, 0.0f, 1.0f };
 237         CHECK(padding_effect->set_vec4("border_color", border_color));
 238
 239         Effect *resample2_effect = chain.add_effect(new ResampleEffect(), input[1]);
 240         Effect *saturation_effect = chain.add_effect(new SaturationEffect());
 241         CHECK(saturation_effect->set_float("saturation", 0.3f));
 242         Effect *wb_effect = chain.add_effect(new WhiteBalanceEffect());
 243         CHECK(wb_effect->set_float("output_color_temperature", 3500.0));
 244         Effect *padding2_effect = chain.add_effect(new IntegralPaddingEffect());
 245
 246         chain.add_effect(new OverlayEffect(), padding_effect, padding2_effect);
 247
 248         ycbcr_format.chroma_subsampling_x = 1;
 249
 250         chain.add_ycbcr_output(inout_format, OUTPUT_ALPHA_FORMAT_POSTMULTIPLIED, ycbcr_format, YCBCR_OUTPUT_SPLIT_Y_AND_CBCR);
 251         chain.set_dither_bits(8);
 252         chain.set_output_origin(OUTPUT_ORIGIN_TOP_LEFT);
 253         chain.finalize();
 254
 255         H264Encoder h264_encoder(surface2, WIDTH, HEIGHT, "test.mp4");
 256
 257         printf("Configuring first card...\n");
 258         cards[0].usb = new BMUSBCapture(0x1edb, 0xbd3b);  // 0xbd4f
 259         //cards[0].usb = new BMUSBCapture(0x1edb, 0xbd4f);
 260         cards[0].usb->set_frame_callback(std::bind(bm_frame, 0, _1, _2, _3, _4, _5, _6, _7));
 261         std::unique_ptr<PBOFrameAllocator> pbo_allocator1(new PBOFrameAllocator(1280 * 750 * 2 + 44));
 262         cards[0].usb->set_video_frame_allocator(pbo_allocator1.get());
 263         cards[0].usb->configure_card();
 264
 265         std::unique_ptr<PBOFrameAllocator> pbo_allocator2(new PBOFrameAllocator(1280 * 750 * 2 + 44));
 266         if (NUM_CARDS == 2) {
 267                 printf("Configuring second card...\n");
 268                 cards[1].usb = new BMUSBCapture(0x1edb, 0xbd4f);
 269                 cards[1].usb->set_frame_callback(std::bind(bm_frame, 1, _1, _2, _3, _4, _5, _6, _7));
 270                 cards[1].usb->set_video_frame_allocator(pbo_allocator2.get());
 271                 cards[1].usb->configure_card();
 272         }
 273
 274         BMUSBCapture::start_bm_thread();
 275
 276         for (int card_index = 0; card_index < NUM_CARDS; ++card_index) {
 277                 cards[card_index].usb->start_bm_capture();
 278         }
 279
 280         int frame = 0;
 281 #if _POSIX_C_SOURCE >= 199309L
 282         struct timespec start, now;
 283         clock_gettime(CLOCK_MONOTONIC, &start);
 284 #else
 285         struct timeval start, now;
 286         gettimeofday(&start, NULL);
 287 #endif
 288
 289         PBOFrameAllocator::Frame bmusb_current_rendering_frame[NUM_CARDS];
 290         for (int card_index = 0; card_index < NUM_CARDS; ++card_index) {
 291                 bmusb_current_rendering_frame[card_index] =
 292                         cards[card_index].usb->get_video_frame_allocator()->alloc_frame();
 293                 GLint input_tex_pbo = (GLint)(intptr_t)bmusb_current_rendering_frame[card_index].userdata;
 294                 input[card_index]->set_pixel_data(0, nullptr, input_tex_pbo);
 295                 input[card_index]->set_pixel_data(1, nullptr, input_tex_pbo);
 296                 check_error();
 297         }
 298
 299         //chain.enable_phase_timing(true);
 300
 301         // Set up stuff for NV12 conversion.
 302         ResourcePool *resource_pool = chain.get_resource_pool();
 303         GLuint chroma_tex = resource_pool->create_2d_texture(GL_RG8, WIDTH, HEIGHT);
 304
 305         // Cb/Cr shader.
 306         string cbcr_vert_shader = read_file("vs-cbcr.130.vert");
 307         string cbcr_frag_shader =
 308                 "#version 130 \n"
 309                 "in vec2 tc0; \n"
 310                 "uniform sampler2D cbcr_tex; \n"
 311                 "void main() { \n"
 312                 "    gl_FragColor = texture2D(cbcr_tex, tc0); \n"
 313                 "} \n";
 314         GLuint cbcr_program_num = resource_pool->compile_glsl_program(cbcr_vert_shader, cbcr_frag_shader);
 315
 316         GLuint vao;
 317         glGenVertexArrays(1, &vao);
 318         check_error();
 319
 320         while (!quit) {
 321                 ++frame;
 322
 323                 //int width0 = lrintf(848 * (1.0 + 0.2 * sin(frame * 0.02)));
 324                 int width0 = 848;
 325                 int height0 = lrintf(width0 * 9.0 / 16.0);
 326
 327                 //float top0 = 96 + 48 * sin(frame * 0.005);
 328                 //float left0 = 96 + 48 * cos(frame * 0.006);
 329                 float top0 = 48;
 330                 float left0 = 16;
 331                 float bottom0 = top0 + height0;
 332                 float right0 = left0 + width0;
 333
 334                 int width1 = 384;
 335                 int height1 = 216;
 336
 337                 float bottom1 = 720 - 48;
 338                 float right1 = 1280 - 16;
 339                 float top1 = bottom1 - height1;
 340                 float left1 = right1 - width1;
 341
 342                 float t = 0.5 + 0.5 * cos(frame * 0.006);
 343                 //float t = 0.0;
 344                 float scale0 = 1.0 + t * (1280.0 / 848.0 - 1.0);
 345                 float tx0 = 0.0 + t * (-16.0 * scale0);
 346                 float ty0 = 0.0 + t * (-48.0 * scale0);
 347
 348                 top0 = top0 * scale0 + ty0;
 349                 bottom0 = bottom0 * scale0 + ty0;
 350                 left0 = left0 * scale0 + tx0;
 351                 right0 = right0 * scale0 + tx0;
 352
 353                 top1 = top1 * scale0 + ty0;
 354                 bottom1 = bottom1 * scale0 + ty0;
 355                 left1 = left1 * scale0 + tx0;
 356                 right1 = right1 * scale0 + tx0;
 357
 358                 place_rectangle(resample_effect, padding_effect, left0, top0, right0, bottom0);
 359                 place_rectangle(resample2_effect, padding2_effect, left1, top1, right1, bottom1);
 360
 361                 CaptureCard card_copy[NUM_CARDS];
 362
 363                 {
 364                         std::unique_lock<std::mutex> lock(bmusb_mutex);
 365
 366                         // The first card is the master timer, so wait for it to have a new frame.
 367                         // TODO: Make configurable, and with a timeout.
 368                         cards[0].new_data_ready_changed.wait(lock, []{ return cards[0].new_data_ready; });
 369
 370                         for (int card_index = 0; card_index < NUM_CARDS; ++card_index) {
 371                                 CaptureCard *card = &cards[card_index];
 372                                 card_copy[card_index].usb = card->usb;
 373                                 card_copy[card_index].new_data_ready = card->new_data_ready;
 374                                 card_copy[card_index].new_frame = card->new_frame;
 375                                 card_copy[card_index].new_data_ready_fence = card->new_data_ready_fence;
 376                                 card->new_data_ready = false;
 377                                 card->new_data_ready_changed.notify_all();
 378                         }
 379                 }
 380
 381                 vector<FrameAllocator::Frame> input_frames_to_release;
 382
 383                 for (int card_index = 0; card_index < NUM_CARDS; ++card_index) {
 384                         CaptureCard *card = &card_copy[card_index];
 385                         if (!card->new_data_ready)
 386                                 continue;
 387
 388                         // Now we're done with the previous frame, so we can definitely
 389                         // release it when this is done rendering. (Actually, we could do
 390                         // it one frame earlier, but before we have a new one, there's no
 391                         // knowing when the current one is released.)
 392                         input_frames_to_release.push_back(bmusb_current_rendering_frame[card_index]);
 393                         bmusb_current_rendering_frame[card_index] = card->new_frame;
 394
 395                         // The new texture might still be uploaded,
 396                         // tell the GPU to wait until it's there.
 397                         if (card->new_data_ready_fence)
 398                                 glWaitSync(card->new_data_ready_fence, /*flags=*/0, GL_TIMEOUT_IGNORED);
 399                         check_error();
 400                         glDeleteSync(card->new_data_ready_fence);
 401                         check_error();
 402                         GLint input_tex_pbo = (GLint)(intptr_t)card->new_frame.userdata;
 403                         input[card_index]->set_pixel_data(0, (unsigned char *)BUFFER_OFFSET((1280 * 750 * 2 + 44) / 2 + 1280 * 25 + 22), input_tex_pbo);
 404                         input[card_index]->set_pixel_data(1, (unsigned char *)BUFFER_OFFSET(1280 * 25 + 22), input_tex_pbo);
 405
 406                         if (NUM_CARDS == 1) {
 407                                 // Set to the other one, too.
 408                                 input[1]->set_pixel_data(0, (unsigned char *)BUFFER_OFFSET((1280 * 750 * 2 + 44) / 2 + 1280 * 25 + 22), input_tex_pbo);
 409                                 input[1]->set_pixel_data(1, (unsigned char *)BUFFER_OFFSET(1280 * 25 + 22), input_tex_pbo);
 410                         }
 411                 }
 412
 413                 GLuint y_tex, cbcr_tex;
 414                 bool got_frame = h264_encoder.begin_frame(&y_tex, &cbcr_tex);
 415                 assert(got_frame);
 416
 417                 // Render chain.
 418                 {
 419                         GLuint ycbcr_fbo = resource_pool->create_fbo(y_tex, chroma_tex);
 420                         chain.render_to_fbo(ycbcr_fbo, WIDTH, HEIGHT);
 421                         resource_pool->release_fbo(ycbcr_fbo);
 422                 }
 423
 424                 // Set up for extraction.
 425                 float vertices[] = {
 426                         0.0f, 2.0f,
 427                         0.0f, 0.0f,
 428                         2.0f, 0.0f
 429                 };
 430
 431                 glBindVertexArray(vao);
 432                 check_error();
 433
 434                 // Extract Cb/Cr.
 435                 GLuint cbcr_fbo = resource_pool->create_fbo(cbcr_tex);
 436                 glBindFramebuffer(GL_FRAMEBUFFER, cbcr_fbo);
 437                 glViewport(0, 0, WIDTH/2, HEIGHT/2);
 438                 check_error();
 439                 GLsync fence;
 440                 {
 441                         glUseProgram(cbcr_program_num);
 442                         check_error();
 443
 444                         glActiveTexture(GL_TEXTURE0);
 445                         check_error();
 446                         glBindTexture(GL_TEXTURE_2D, chroma_tex);
 447                         check_error();
 448                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 449                         check_error();
 450                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 451                         check_error();
 452                         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 453                         check_error();
 454
 455                         float chroma_offset_0[] = { -0.5f / WIDTH, 0.0f };
 456                         set_uniform_vec2(cbcr_program_num, "foo", "chroma_offset_0", chroma_offset_0);
 457
 458                         GLuint position_vbo = fill_vertex_attribute(cbcr_program_num, "position", 2, GL_FLOAT, sizeof(vertices), vertices);
 459                         GLuint texcoord_vbo = fill_vertex_attribute(cbcr_program_num, "texcoord", 2, GL_FLOAT, sizeof(vertices), vertices);  // Same as vertices.
 460
 461                         glDrawArrays(GL_TRIANGLES, 0, 3);
 462                         check_error();
 463
 464                         cleanup_vertex_attribute(cbcr_program_num, "position", position_vbo);
 465                         cleanup_vertex_attribute(cbcr_program_num, "texcoord", texcoord_vbo);
 466
 467                         glUseProgram(0);
 468                         check_error();
 469
 470                         fence = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, /*flags=*/0);
 471                         check_error();
 472
 473                         resource_pool->release_fbo(cbcr_fbo);
 474                 }
 475
 476                 h264_encoder.end_frame(fence, input_frames_to_release);
 477
 478
 479 #if 1
 480 #if _POSIX_C_SOURCE >= 199309L
 481                 clock_gettime(CLOCK_MONOTONIC, &now);
 482                 double elapsed = now.tv_sec - start.tv_sec +
 483                         1e-9 * (now.tv_nsec - start.tv_nsec);
 484 #else
 485                 gettimeofday(&now, NULL);
 486                 double elapsed = now.tv_sec - start.tv_sec +
 487                         1e-6 * (now.tv_usec - start.tv_usec);
 488 #endif
 489                 if (frame % 100 == 0) {
 490                         printf("%d frames in %.3f seconds = %.1f fps (%.1f ms/frame)\n",
 491                                 frame, elapsed, frame / elapsed,
 492                                 1e3 * elapsed / frame);
 493                 //      chain.print_phase_timing();
 494                 }
 495
 496                 // Reset every 100 frames, so that local variations in frame times
 497                 // (especially for the first few frames, when the shaders are
 498                 // compiled etc.) don't make it hard to measure for the entire
 499                 // remaining duration of the program.
 500                 if (frame == 10000) {
 501                         frame = 0;
 502                         start = now;
 503                 }
 504 #endif
 505         }
 506         glDeleteVertexArrays(1, &vao);
 507         resource_pool->release_glsl_program(cbcr_program_num);
 508         resource_pool->release_2d_texture(chroma_tex);
 509         BMUSBCapture::stop_bm_thread();
 510 }
 511
 512 std::thread mixer_thread;
 513
 514 void start_mixer(QSurface *surface, QSurface *surface2, QSurface *surface3, QSurface *surface4)
 515 {
 516         mixer_thread = std::thread([surface, surface2, surface3, surface4]{
 517                 mixer_thread_func(surface, surface2, surface3, surface4);
 518         });
 519 }
 520
 521 void mixer_quit()
 522 {
 523         quit = true;
 524         mixer_thread.join();
 525 }