git.sesse.net Git - pkanalytics/blob - video_widget.cpp

   1 #define GL_GLEXT_PROTOTYPES
   2
   3 #include "video_widget.h"
   4
   5 #include <assert.h>
   6 #include <pthread.h>
   7 #include <stdint.h>
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <sys/stat.h>
  12 #include <unistd.h>
  13
  14 extern "C" {
  15 #include <libavcodec/avcodec.h>
  16 #include <libavformat/avformat.h>
  17 #include <libavutil/avutil.h>
  18 #include <libavutil/error.h>
  19 #include <libavutil/frame.h>
  20 #include <libavutil/imgutils.h>
  21 #include <libavutil/mem.h>
  22 #include <libavutil/pixfmt.h>
  23 #include <libavutil/opt.h>
  24 #include <libswscale/swscale.h>
  25 }
  26
  27 #include <chrono>
  28 #include <cstdint>
  29 #include <utility>
  30 #include <vector>
  31 #include <unordered_set>
  32
  33 #include "post_to_main_thread.h"
  34
  35 #include <QOpenGLFunctions>
  36 #include <QWheelEvent>
  37 #include <QMouseEvent>
  38 #include <QMouseEvent>
  39 #include <QHBoxLayout>
  40
  41 #define BUFFER_OFFSET(i) ((char *)nullptr + (i))
  42
  43 using namespace std;
  44 using namespace std::chrono;
  45
  46 namespace {
  47
  48 bool is_full_range(const AVPixFmtDescriptor *desc)
  49 {
  50         // This is horrible, but there's no better way that I know of.
  51         return (strchr(desc->name, 'j') != nullptr);
  52 }
  53
  54 AVPixelFormat decide_dst_format(AVPixelFormat src_format)
  55 {
  56         // If this is a non-Y'CbCr format, just convert to 4:4:4 Y'CbCr
  57         // and be done with it. It's too strange to spend a lot of time on.
  58         // (Let's hope there's no alpha.)
  59         const AVPixFmtDescriptor *src_desc = av_pix_fmt_desc_get(src_format);
  60         if (src_desc == nullptr ||
  61             src_desc->nb_components != 3 ||
  62             (src_desc->flags & AV_PIX_FMT_FLAG_RGB)) {
  63                 return AV_PIX_FMT_YUV444P;
  64         }
  65
  66         // The best for us would be Cb and Cr together if possible,
  67         // but FFmpeg doesn't support that except in the special case of
  68         // NV12, so we need to go to planar even for the case of NV12.
  69         // Thus, look for the closest (but no worse) 8-bit planar Y'CbCr format
  70         // that matches in color range. (This will also include the case of
  71         // the source format already being acceptable.)
  72         bool src_full_range = is_full_range(src_desc);
  73         const char *best_format = "yuv444p";
  74         unsigned best_score = numeric_limits<unsigned>::max();
  75         for (const AVPixFmtDescriptor *desc = av_pix_fmt_desc_next(nullptr);
  76              desc;
  77              desc = av_pix_fmt_desc_next(desc)) {
  78                 // Find planar Y'CbCr formats only.
  79                 if (desc->nb_components != 3) continue;
  80                 if (desc->flags & AV_PIX_FMT_FLAG_RGB) continue;
  81                 if (!(desc->flags & AV_PIX_FMT_FLAG_PLANAR)) continue;
  82                 if (desc->comp[0].plane != 0 ||
  83                     desc->comp[1].plane != 1 ||
  84                     desc->comp[2].plane != 2) continue;
  85
  86                 // 8-bit formats only.
  87                 if (desc->flags & AV_PIX_FMT_FLAG_BE) continue;
  88                 if (desc->comp[0].depth != 8) continue;
  89
  90                 // Same or better chroma resolution only.
  91                 int chroma_w_diff = src_desc->log2_chroma_w - desc->log2_chroma_w;
  92                 int chroma_h_diff = src_desc->log2_chroma_h - desc->log2_chroma_h;
  93                 if (chroma_w_diff < 0 || chroma_h_diff < 0)
  94                         continue;
  95
  96                 // Matching full/limited range only.
  97                 if (is_full_range(desc) != src_full_range)
  98                         continue;
  99
 100                 // Pick something with as little excess chroma resolution as possible.
 101                 unsigned score = (1 << (chroma_w_diff)) << chroma_h_diff;
 102                 if (score < best_score) {
 103                         best_score = score;
 104                         best_format = desc->name;
 105                 }
 106         }
 107         return av_get_pix_fmt(best_format);
 108 }
 109
 110 }  // namespace
 111
 112 bool VideoWidget::process_queued_commands(AVFormatContext *format_ctx, AVCodecContext *video_codec_ctx, int video_stream_index, bool *seeked)
 113 {
 114         // Process any queued commands from other threads.
 115         vector<QueuedCommand> commands;
 116         {
 117                 lock_guard<mutex> lock(queue_mu);
 118                 swap(commands, command_queue);
 119         }
 120
 121         for (const QueuedCommand &cmd : commands) {
 122                 switch (cmd.command) {
 123                 case QueuedCommand::PAUSE:
 124                         paused = true;
 125                         break;
 126                 case QueuedCommand::RESUME:
 127                         paused = false;
 128                         pts_origin = last_pts;
 129                         start = next_frame_start = steady_clock::now();
 130                         break;
 131                 case QueuedCommand::SEEK:
 132                 case QueuedCommand::SEEK_ABSOLUTE:
 133                         // Dealt with below.
 134                         break;
 135                 }
 136         }
 137
 138         // Combine all seeks into one big one. (There are edge cases where this is probably
 139         // subtly wrong, but we'll live with it.)
 140         int64_t base_pts = last_pts;
 141         int64_t relative_seek_ms = 0;
 142         int64_t relative_seek_frames = 0;
 143         for (const QueuedCommand &cmd : commands) {
 144                 if (cmd.command == QueuedCommand::SEEK) {
 145                         relative_seek_ms += cmd.relative_seek_ms;
 146                         relative_seek_frames += cmd.relative_seek_frames;
 147                 } else if (cmd.command == QueuedCommand::SEEK_ABSOLUTE) {
 148                         base_pts = av_rescale_q(cmd.seek_ms, AVRational{ 1, 1000 }, video_timebase);
 149                         relative_seek_ms = 0;
 150                         relative_seek_frames = 0;
 151                 }
 152         }
 153         int64_t relative_seek_pts = av_rescale_q(relative_seek_ms, AVRational{ 1, 1000 }, video_timebase);
 154         if (relative_seek_ms != 0 && relative_seek_pts == 0) {
 155                 // Just to be sure rounding errors don't move us into nothingness.
 156                 relative_seek_pts = (relative_seek_ms > 0) ? 1 : -1;
 157         }
 158         int64_t goal_pts = base_pts + relative_seek_pts;
 159         if (goal_pts != last_pts || relative_seek_frames < 0) {
 160                 avcodec_flush_buffers(video_codec_ctx);
 161                 queued_frames.clear();
 162
 163                 // Seek to the last keyframe before this point.
 164                 int64_t seek_pts = goal_pts;
 165                 if (relative_seek_frames < 0) {
 166                         // If we're frame-skipping backwards, add 100 ms of slop for each frame
 167                         // so we're fairly certain we are able to see the ones we want.
 168                         seek_pts -= av_rescale_q(-relative_seek_frames, AVRational{ 1, 10 }, video_timebase);
 169                 }
 170                 av_seek_frame(format_ctx, video_stream_index, seek_pts, AVSEEK_FLAG_BACKWARD);
 171
 172                 // Decode frames until EOF, or until we see something past our seek point.
 173                 std::deque<AVFrameWithDeleter> queue;
 174                 for ( ;; ) {
 175                         bool error = false;
 176                         AVFrameWithDeleter frame = decode_frame(format_ctx, video_codec_ctx,
 177                                 pathname, video_stream_index, &error);
 178                         if (frame == nullptr || error) {
 179                                 break;
 180                         }
 181
 182                         int64_t frame_pts = frame->pts;
 183                         if (relative_seek_frames < 0) {
 184                                 // Buffer this frame; don't display it unless we know it's the Nth-latest.
 185                                 queue.push_back(std::move(frame));
 186                                 if (queue.size() > uint64_t(-relative_seek_frames) + 1) {
 187                                         queue.pop_front();
 188                                 }
 189                         }
 190                         if (frame_pts >= goal_pts) {
 191                                 if (relative_seek_frames > 0) {
 192                                         --relative_seek_frames;
 193                                 } else {
 194                                         if (relative_seek_frames < 0) {
 195                                                 // Hope we have the right amount.
 196                                                 // The rest will remain in the queue for when we play forward again.
 197                                                 frame = std::move(queue.front());
 198                                                 queue.pop_front();
 199                                                 queued_frames = std::move(queue);
 200                                         }
 201                                         video_window->set_current_frame(make_video_frame(frame.get()));
 202                                         update();
 203                                         store_pts(frame->pts);
 204                                         break;
 205                                 }
 206                         }
 207                 }
 208
 209                 // NOTE: We keep pause status as-is.
 210
 211                 pts_origin = last_pts;
 212                 start = next_frame_start = last_frame = steady_clock::now();
 213                 if (seeked) {
 214                         *seeked = true;
 215                 }
 216         } else if (relative_seek_frames > 0) {
 217                 // The base PTS is fine, we only need to skip a few frames forwards.
 218                 while (relative_seek_frames > 1) {
 219                         // Eat a frame (ignore errors).
 220                         bool error;
 221                         decode_frame(format_ctx, video_codec_ctx, pathname, video_stream_index, &error);
 222                         --relative_seek_frames;
 223                 }
 224
 225                 // Display the last one.
 226                 bool error;
 227                 AVFrameWithDeleter frame = decode_frame(format_ctx, video_codec_ctx,
 228                         pathname, video_stream_index, &error);
 229                 if (frame == nullptr || error) {
 230                         return true;
 231                 }
 232                 video_window->set_current_frame(make_video_frame(frame.get()));
 233                 update();
 234                 store_pts(frame->pts);
 235         }
 236         return false;
 237 }
 238
 239 VideoWidget::VideoWidget(QWidget *parent)
 240         : QWidget(parent),
 241           video_window(new VideoWindow(this)) {
 242         setLayout(new QHBoxLayout);
 243         layout()->addWidget(QWidget::createWindowContainer(video_window));
 244
 245         // ...
 246         connect(video_window, &VideoWindow::mouse_wheel, this, &VideoWidget::wheelEvent);
 247         connect(video_window, &VideoWindow::mouse_pressed, this, &VideoWidget::mousePressEvent);
 248         connect(video_window, &VideoWindow::mouse_released, this, &VideoWidget::mouseReleaseEvent);
 249         connect(video_window, &VideoWindow::mouse_moved, this, &VideoWidget::mouseMoveEvent);
 250 }
 251
 252 GLuint compile_shader(const string &shader_src, GLenum type)
 253 {
 254         GLuint obj = glCreateShader(type);
 255         const GLchar* source[] = { shader_src.data() };
 256         const GLint length[] = { (GLint)shader_src.size() };
 257         glShaderSource(obj, 1, source, length);
 258         glCompileShader(obj);
 259
 260         GLchar info_log[4096];
 261         GLsizei log_length = sizeof(info_log) - 1;
 262         glGetShaderInfoLog(obj, log_length, &log_length, info_log);
 263         info_log[log_length] = 0;
 264         if (strlen(info_log) > 0) {
 265                 fprintf(stderr, "Shader compile log: %s\n", info_log);
 266         }
 267
 268         GLint status;
 269         glGetShaderiv(obj, GL_COMPILE_STATUS, &status);
 270         if (status == GL_FALSE) {
 271                 // Add some line numbers to easier identify compile errors.
 272                 string src_with_lines = "/*   1 */ ";
 273                 size_t lineno = 1;
 274                 for (char ch : shader_src) {
 275                         src_with_lines.push_back(ch);
 276                         if (ch == '\n') {
 277                                 char buf[32];
 278                                 snprintf(buf, sizeof(buf), "/* %3zu */ ", ++lineno);
 279                                 src_with_lines += buf;
 280                         }
 281                 }
 282
 283                 fprintf(stderr, "Failed to compile shader:\n%s\n", src_with_lines.c_str());
 284                 exit(1);
 285         }
 286
 287         return obj;
 288 }
 289
 290 void VideoWindow::initializeGL()
 291 {
 292         glDisable(GL_BLEND);
 293         glDisable(GL_DEPTH_TEST);
 294         glDepthMask(GL_FALSE);
 295         glCreateTextures(GL_TEXTURE_2D, 3, tex);
 296
 297         ycbcr_vertex_shader = compile_shader(R"(
 298 #version 460 core
 299
 300 layout(location = 0) in vec2 position;
 301 layout(location = 1) in vec2 texcoord;
 302 out vec2 tc;
 303
 304 void main()
 305 {
 306         // The result of glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0) is:
 307         //
 308         //   2.000  0.000  0.000 -1.000
 309         //   0.000  2.000  0.000 -1.000
 310         //   0.000  0.000 -2.000 -1.000
 311         //   0.000  0.000  0.000  1.000
 312         gl_Position = vec4(2.0 * position.x - 1.0, 2.0 * position.y - 1.0, -1.0, 1.0);
 313         tc = texcoord;
 314         tc.y = 1.0f - tc.y;
 315 }
 316 )", GL_VERTEX_SHADER);
 317         ycbcr_fragment_shader = compile_shader(R"(
 318 #version 460 core
 319
 320 layout(location = 0) uniform sampler2D tex_y;
 321 layout(location = 1) uniform sampler2D tex_cb;
 322 layout(location = 2) uniform sampler2D tex_cr;
 323 layout(location = 3) uniform vec2 cbcr_offset;
 324
 325 in vec2 tc;
 326 out vec4 FragColor;
 327
 328 // Computed statically by Movit, for limited-range BT.709.
 329 // (We don't check whether the input could be BT.601 or BT.2020 currently, or full-range)
 330 const mat3 inv_ycbcr_matrix = mat3(
 331         1.16438f, 1.16438f, 1.16438f,
 332         0.0f, -0.21325f, 2.11240f,
 333         1.79274f, -0.53291f, 0.0f
 334 );
 335
 336 void main()
 337 {
 338         if (tc.x < 0.0 || tc.x > 1.0 || tc.y < 0.0 || tc.y > 1.0) {
 339                 FragColor.rgba = vec4(0.0f, 0.0f, 0.0f, 1.0f);
 340                 return;
 341         }
 342
 343         vec3 ycbcr;
 344         ycbcr.r = texture(tex_y, tc).r;
 345         ycbcr.g = texture(tex_cb, tc + cbcr_offset).r;
 346         ycbcr.b = texture(tex_cr, tc + cbcr_offset).r;
 347         ycbcr -= vec3(16.0f / 255.0f, 128.0f / 255.0f, 128.0f / 255.0f);
 348         FragColor.rgb = inv_ycbcr_matrix * ycbcr;
 349         FragColor.a = 1.0f;
 350 }
 351 )", GL_FRAGMENT_SHADER);
 352         ycbcr_program = glCreateProgram();
 353         glAttachShader(ycbcr_program, ycbcr_vertex_shader);
 354         glAttachShader(ycbcr_program, ycbcr_fragment_shader);
 355         glLinkProgram(ycbcr_program);
 356
 357         GLint success;
 358         glGetProgramiv(ycbcr_program, GL_LINK_STATUS, &success);
 359         if (success == GL_FALSE) {
 360                 GLchar error_log[1024] = {0};
 361                 glGetProgramInfoLog(ycbcr_program, 1024, nullptr, error_log);
 362                 fprintf(stderr, "Error linking program: %s\n", error_log);
 363                 exit(1);
 364         }
 365
 366         glCreateSamplers(1, &bilinear_sampler);
 367         glSamplerParameteri(bilinear_sampler, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
 368         glSamplerParameteri(bilinear_sampler, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
 369         glSamplerParameteri(bilinear_sampler, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 370         glSamplerParameteri(bilinear_sampler, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 371 }
 372
 373 void VideoWindow::resizeGL(int w, int h)
 374 {
 375         glViewport(0, 0, w, h);
 376         display_aspect = double(w) / h;
 377 }
 378
 379 int num_levels(GLuint width, GLuint height)
 380 {
 381         int levels = 1;
 382         while (width > 1 || height > 1) {
 383                 width = max(width / 2, 1u);
 384                 height = max(height / 2, 1u);
 385                 ++levels;
 386         }
 387         return levels;
 388 }
 389
 390 void VideoWindow::paintGL()
 391 {
 392         std::shared_ptr<VideoWidget::Frame> frame;
 393         {
 394                 lock_guard lock(current_frame_mu);
 395                 frame = current_frame;
 396         }
 397         if (frame == nullptr) {
 398                 glClear(GL_COLOR_BUFFER_BIT);
 399                 return;
 400         }
 401
 402         glUseProgram(ycbcr_program);
 403         if (frame->width != last_width || frame->height != last_height) {
 404                 glTextureStorage2D(tex[0], num_levels(frame->width, frame->height), GL_R8, frame->width, frame->height);
 405         }
 406         if (frame->chroma_width != last_chroma_width || frame->chroma_height != last_chroma_height) {
 407                 for (GLuint num : { tex[1], tex[2] }) {
 408                         glTextureStorage2D(num, num_levels(frame->chroma_width, frame->chroma_height), GL_R8, frame->chroma_width, frame->chroma_height);
 409                 }
 410         }
 411
 412         glBindBuffer(GL_PIXEL_UNPACK_BUFFER, frame->pbo);
 413
 414         if (frame->need_flush_len > 0) {
 415                 glFlushMappedNamedBufferRange(frame->pbo, 0, frame->need_flush_len);
 416                 frame->need_flush_len = 0;
 417         }
 418
 419         glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
 420         glTextureSubImage2D(tex[0], 0, 0, 0, frame->width, frame->height, GL_RED, GL_UNSIGNED_BYTE, BUFFER_OFFSET(0));
 421         glGenerateTextureMipmap(tex[0]);
 422
 423         glTextureSubImage2D(tex[1], 0, 0, 0, frame->chroma_width, frame->chroma_height, GL_RED, GL_UNSIGNED_BYTE, BUFFER_OFFSET(frame->width * frame->height));
 424         glGenerateTextureMipmap(tex[1]);
 425
 426         glTextureSubImage2D(tex[2], 0, 0, 0, frame->chroma_width, frame->chroma_height, GL_RED, GL_UNSIGNED_BYTE, BUFFER_OFFSET(frame->width * frame->height + frame->chroma_width * frame->chroma_height));
 427         glGenerateTextureMipmap(tex[2]);
 428
 429         glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
 430
 431         glBindTextureUnit(0, tex[0]);
 432         glBindTextureUnit(1, tex[1]);
 433         glBindTextureUnit(2, tex[2]);
 434         glBindSampler(0, bilinear_sampler);
 435         glBindSampler(1, bilinear_sampler);
 436         glBindSampler(2, bilinear_sampler);
 437         glProgramUniform1i(ycbcr_program, 0, 0);
 438         glProgramUniform1i(ycbcr_program, 1, 1);
 439         glProgramUniform1i(ycbcr_program, 2, 2);
 440         glProgramUniform2f(ycbcr_program, 3, cbcr_offset[0], -cbcr_offset[1]);
 441
 442         float tx1 = 0.0f;
 443         float tx2 = 1.0f;
 444         float ty1 = 0.0f;
 445         float ty2 = 1.0f;
 446
 447         double video_aspect = double(frame->width) / frame->height;
 448         if (display_aspect > video_aspect) {
 449                 double extra_width = frame->height * display_aspect - frame->width;
 450                 tx1 = -0.5 * extra_width / frame->width;
 451                 tx2 = 1.0 + 0.5 * extra_width / frame->width;
 452         } else if (display_aspect < video_aspect) {
 453                 double extra_height = frame->width / display_aspect - frame->height;
 454                 ty1 = -0.5 * extra_height / frame->height;
 455                 ty2 = 1.0 + 0.5 * extra_height / frame->height;
 456         }
 457
 458         glBegin(GL_QUADS);
 459
 460         // (0,0)
 461         glVertexAttrib2f(1, tx1, ty1);
 462         glVertex2f(zoom_matrix[2 * 3 + 0], zoom_matrix[2 * 3 + 1]);
 463
 464         // (0,1)
 465         glVertexAttrib2f(1, tx1, ty2);
 466         glVertex2f(zoom_matrix[1 * 3 + 0] + zoom_matrix[2 * 3 + 0], zoom_matrix[1 * 3 + 1] + zoom_matrix[2 * 3 + 1]);
 467
 468         // (1,1)
 469         glVertexAttrib2f(1, tx2, ty2);
 470         glVertex2f(zoom_matrix[0 * 3 + 0] + zoom_matrix[1 * 3 + 0] + zoom_matrix[2 * 3 + 0],
 471                    zoom_matrix[1 * 3 + 0] + zoom_matrix[1 * 3 + 1] + zoom_matrix[2 * 3 + 1]);
 472
 473         // (1,0)
 474         glVertexAttrib2f(1, tx2, ty1);
 475         glVertex2f(zoom_matrix[0 * 3 + 0] + zoom_matrix[2 * 3 + 0],
 476                    zoom_matrix[1 * 3 + 0] + zoom_matrix[2 * 3 + 1]);
 477
 478         glEnd();
 479 }
 480
 481 void VideoWindow::set_current_frame(shared_ptr<VideoWidget::Frame> new_frame)
 482 {
 483         {
 484                 lock_guard lock(current_frame_mu);
 485                 current_frame = std::move(new_frame);
 486         }
 487         update();
 488 }
 489
 490 void matmul3x3(const double a[9], const double b[9], double res[9])
 491 {
 492         for (int i = 0; i < 3; ++i) {
 493                 for (int j = 0; j < 3; ++j) {
 494                         double sum = 0.0;
 495                         for (int k = 0; k < 3; ++k) {
 496                                 sum += a[i * 3 + k] * b[k * 3 + j];
 497                         }
 498                         res[i * 3 + j] = sum;
 499                 }
 500         }
 501 }
 502
 503 void VideoWidget::wheelEvent(QWheelEvent *event)
 504 {
 505         int delta = event->angleDelta().y();
 506         if (delta == 0) {
 507                 return;
 508         }
 509         double x = event->position().x() / width();
 510         double y = 1.0 - event->position().y() / height();
 511         double zoom = delta > 0 ? pow(1.005, delta) : pow(1/1.005, -delta);
 512
 513         const double inv_translation_matrix[9] = {
 514                 1.0, 0.0, 0.0,
 515                 0.0, 1.0, 0.0,
 516                 -x, -y, 1.0
 517         };
 518         const double scale_matrix[9] = {
 519                 zoom, 0.0, 0.0,
 520                 0.0, zoom, 0.0,
 521                 0.0, 0.0, 1.0
 522         };
 523         const double translation_matrix[9] = {
 524                 1.0, 0.0, 0.0,
 525                 0.0, 1.0, 0.0,
 526                 x, y, 1.0
 527         };
 528         double tmp1[9], tmp2[9];
 529         matmul3x3(zoom_matrix, inv_translation_matrix, tmp1);
 530         matmul3x3(tmp1, scale_matrix, tmp2);
 531         matmul3x3(tmp2, translation_matrix, zoom_matrix);
 532
 533         fixup_zoom_matrix();
 534         video_window->set_zoom_matrix(zoom_matrix);
 535         update();
 536 }
 537
 538 void VideoWidget::mousePressEvent(QMouseEvent *e)
 539 {
 540         if (e->button() == Qt::BackButton) {
 541                 emit mouse_back_clicked();
 542         } else if (e->button() == Qt::ForwardButton) {
 543                 emit mouse_forward_clicked();
 544         } else if (e->button() == Qt::LeftButton) {
 545                 dragging = true;
 546                 last_drag_x = e->position().x();
 547                 last_drag_y = e->position().y();
 548         }
 549 }
 550
 551 void VideoWidget::mouseReleaseEvent(QMouseEvent *e)
 552 {
 553         if (e->button() == Qt::LeftButton) {
 554                 dragging = false;
 555         }
 556 }
 557
 558 void VideoWidget::mouseMoveEvent(QMouseEvent *e)
 559 {
 560         if (!dragging) {
 561                 return;
 562         }
 563         float dx = (e->position().x() - last_drag_x) / width();
 564         float dy = (e->position().y() - last_drag_y) / height();
 565
 566         //zoom_matrix[6] += dx * zoom_matrix[0];
 567         //zoom_matrix[7] += dy * zoom_matrix[4];
 568         zoom_matrix[6] += dx;
 569         zoom_matrix[7] -= dy;
 570         fixup_zoom_matrix();
 571         video_window->set_zoom_matrix(zoom_matrix);
 572
 573         last_drag_x = e->position().x();
 574         last_drag_y = e->position().y();
 575
 576         update();
 577 }
 578
 579 // Normalize the matrix so that we never get skew or similar,
 580 // and also never can zoom or pan too far out.
 581 void VideoWidget::fixup_zoom_matrix()
 582 {
 583         // Correct for any numerical errors (we know the matrix must be orthogonal
 584         // and have zero rotation).
 585         zoom_matrix[4] = zoom_matrix[0];
 586         zoom_matrix[1] = zoom_matrix[2] = zoom_matrix[3] = zoom_matrix[5] = 0.0;
 587         zoom_matrix[8] = 1.0;
 588
 589         // We can't zoom further out than 1:1. (Perhaps it would be nice to
 590         // reuse the last zoom-in point to do this, but the center will have to do
 591         // for now.)
 592         if (zoom_matrix[0] < 1.0) {
 593                 const double zoom = 1.0 / zoom_matrix[0];
 594                 const double inv_translation_matrix[9] = {
 595                         1.0, 0.0, 0.0,
 596                         0.0, 1.0, 0.0,
 597                         -0.5, -0.5, 1.0
 598                 };
 599                 const double scale_matrix[9] = {
 600                         zoom, 0.0, 0.0,
 601                         0.0, zoom, 0.0,
 602                         0.0, 0.0, 1.0
 603                 };
 604                 const double translation_matrix[9] = {
 605                         1.0, 0.0, 0.0,
 606                         0.0, 1.0, 0.0,
 607                         0.5, 0.5, 1.0
 608                 };
 609                 double tmp1[9], tmp2[9];
 610                 matmul3x3(zoom_matrix, inv_translation_matrix, tmp1);
 611                 matmul3x3(tmp1, scale_matrix, tmp2);
 612                 matmul3x3(tmp2, translation_matrix, zoom_matrix);
 613         }
 614
 615         // Looking at the points we'll draw with glVertex2f(), make sure none of them are
 616         // inside the square (which would generally mean we've panned ourselves out-of-bounds).
 617         // We simply adjust the translation, which is possible because we fixed scaling above.
 618         zoom_matrix[6] = min(zoom_matrix[6], 0.0);  // Left side (x=0).
 619         zoom_matrix[7] = min(zoom_matrix[7], 0.0);  // Bottom side (y=0).
 620         zoom_matrix[6] = std::max(zoom_matrix[6], 1.0 - zoom_matrix[0]);  // Right side (x=1).
 621         zoom_matrix[7] = std::max(zoom_matrix[7], 1.0 - zoom_matrix[4]);  // Top side (y=1).
 622 }
 623
 624 bool VideoWidget::open(const string &filename)
 625 {
 626         stop();
 627         internal_rewind();
 628         pathname = filename;
 629         play();
 630
 631         while (running == STARTING) {
 632                 // Poor man's condition variable...
 633                 usleep(10000);
 634                 sched_yield();
 635         }
 636         return (running != VIDEO_FILE_ERROR);
 637 }
 638
 639 void VideoWidget::play()
 640 {
 641         if (running != NOT_RUNNING && running != VIDEO_FILE_ERROR) {
 642                 std::lock_guard<std::mutex> lock(queue_mu);
 643                 command_queue.push_back(QueuedCommand { QueuedCommand::RESUME });
 644                 producer_thread_should_quit.wakeup();
 645                 return;
 646         }
 647         running = STARTING;
 648         producer_thread_should_quit.unquit();
 649         if (producer_thread.joinable()) {
 650                 producer_thread.join();
 651         }
 652         producer_thread = std::thread(&VideoWidget::producer_thread_func, this);
 653 }
 654
 655 void VideoWidget::pause()
 656 {
 657         if (running == NOT_RUNNING || running == VIDEO_FILE_ERROR) {
 658                 return;
 659         }
 660         std::lock_guard<std::mutex> lock(queue_mu);
 661         command_queue.push_back(QueuedCommand { QueuedCommand::PAUSE });
 662         producer_thread_should_quit.wakeup();
 663 }
 664
 665 void VideoWidget::seek(int64_t relative_seek_ms)
 666 {
 667         if (running == NOT_RUNNING || running == VIDEO_FILE_ERROR) {
 668                 return;
 669         }
 670         std::lock_guard<std::mutex> lock(queue_mu);
 671         command_queue.push_back(QueuedCommand { QueuedCommand::SEEK, relative_seek_ms, 0, 0 });
 672         producer_thread_should_quit.wakeup();
 673 }
 674
 675 void VideoWidget::seek_frames(int64_t relative_seek_frames)
 676 {
 677         if (running == NOT_RUNNING || running == VIDEO_FILE_ERROR) {
 678                 return;
 679         }
 680         std::lock_guard<std::mutex> lock(queue_mu);
 681         command_queue.push_back(QueuedCommand { QueuedCommand::SEEK, 0, relative_seek_frames, 0 });
 682         producer_thread_should_quit.wakeup();
 683 }
 684
 685 void VideoWidget::seek_absolute(int64_t position_ms)
 686 {
 687         if (running == NOT_RUNNING || running == VIDEO_FILE_ERROR) {
 688                 return;
 689         }
 690         std::lock_guard<std::mutex> lock(queue_mu);
 691         command_queue.push_back(QueuedCommand { QueuedCommand::SEEK_ABSOLUTE, 0, 0, position_ms });
 692         producer_thread_should_quit.wakeup();
 693 }
 694
 695 void VideoWidget::stop()
 696 {
 697         if (running == NOT_RUNNING || running == VIDEO_FILE_ERROR) {
 698                 return;
 699         }
 700         producer_thread_should_quit.quit();
 701         producer_thread.join();
 702 }
 703
 704 void VideoWidget::producer_thread_func()
 705 {
 706         if (!producer_thread_should_quit.should_quit()) {
 707                 if (!play_video(pathname)) {
 708                         running = VIDEO_FILE_ERROR;
 709                 } else {
 710                         running = NOT_RUNNING;
 711                 }
 712         }
 713 }
 714
 715 void VideoWidget::internal_rewind()
 716 {
 717         pts_origin = last_pts = 0;
 718         last_position = 0;
 719         start = next_frame_start = steady_clock::now();
 720 }
 721
 722 template<AVHWDeviceType type>
 723 AVPixelFormat get_hw_format(AVCodecContext *ctx, const AVPixelFormat *fmt)
 724 {
 725         bool found_config_of_right_type = false;
 726         for (int i = 0;; ++i) {  // Termination condition inside loop.
 727                 const AVCodecHWConfig *config = avcodec_get_hw_config(ctx->codec, i);
 728                 if (config == nullptr) {  // End of list.
 729                         break;
 730                 }
 731                 if (!(config->methods & AV_CODEC_HW_CONFIG_METHOD_HW_DEVICE_CTX) ||
 732                     config->device_type != type) {
 733                         // Not interesting for us.
 734                         continue;
 735                 }
 736
 737                 // We have a config of the right type, but does it actually support
 738                 // the pixel format we want? (Seemingly, FFmpeg's way of signaling errors
 739                 // is to just replace the pixel format with a software-decoded one,
 740                 // such as yuv420p.)
 741                 found_config_of_right_type = true;
 742                 for (const AVPixelFormat *fmt_ptr = fmt; *fmt_ptr != -1; ++fmt_ptr) {
 743                         if (config->pix_fmt == *fmt_ptr) {
 744                                 fprintf(stderr, "Initialized '%s' hardware decoding for codec '%s'.\n",
 745                                         av_hwdevice_get_type_name(type), ctx->codec->name);
 746                                 if (ctx->profile == FF_PROFILE_H264_BASELINE) {
 747                                         fprintf(stderr, "WARNING: Stream claims to be H.264 Baseline, which is generally poorly supported in hardware decoders.\n");
 748                                         fprintf(stderr, "         Consider encoding it as Constrained Baseline, Main or High instead.\n");
 749                                         fprintf(stderr, "         Decoding might fail and fall back to software.\n");
 750                                 }
 751                                 return config->pix_fmt;
 752                         }
 753                 }
 754                 fprintf(stderr, "Decoder '%s' supports only these pixel formats:", ctx->codec->name);
 755                 unordered_set<AVPixelFormat> seen;
 756                 for (const AVPixelFormat *fmt_ptr = fmt; *fmt_ptr != -1; ++fmt_ptr) {
 757                         if (!seen.count(*fmt_ptr)) {
 758                                 fprintf(stderr, " %s", av_get_pix_fmt_name(*fmt_ptr));
 759                                 seen.insert(*fmt_ptr);
 760                         }
 761                 }
 762                 fprintf(stderr, " (wanted %s for hardware acceleration)\n", av_get_pix_fmt_name(config->pix_fmt));
 763
 764         }
 765
 766         if (!found_config_of_right_type) {
 767                 fprintf(stderr, "Decoder '%s' does not support device type '%s'.\n", ctx->codec->name, av_hwdevice_get_type_name(type));
 768         }
 769
 770         // We found no VA-API formats, so take the first software format.
 771         for (const AVPixelFormat *fmt_ptr = fmt; *fmt_ptr != -1; ++fmt_ptr) {
 772                 if ((av_pix_fmt_desc_get(*fmt_ptr)->flags & AV_PIX_FMT_FLAG_HWACCEL) == 0) {
 773                         fprintf(stderr, "Falling back to software format %s.\n", av_get_pix_fmt_name(*fmt_ptr));
 774                         return *fmt_ptr;
 775                 }
 776         }
 777
 778         // Fallback: Just return anything. (Should never really happen.)
 779         return fmt[0];
 780 }
 781
 782 AVFrameWithDeleter VideoWidget::decode_frame(AVFormatContext *format_ctx, AVCodecContext *video_codec_ctx,
 783         const std::string &pathname, int video_stream_index,
 784         bool *error)
 785 {
 786         *error = false;
 787
 788         if (!queued_frames.empty()) {
 789                 AVFrameWithDeleter frame = std::move(queued_frames.front());
 790                 queued_frames.pop_front();
 791                 return frame;
 792         }
 793
 794         // Read packets until we have a frame or there are none left.
 795         bool frame_finished = false;
 796         AVFrameWithDeleter video_avframe = av_frame_alloc_unique();
 797         bool eof = false;
 798         do {
 799                 AVPacket *pkt = av_packet_alloc();
 800                 unique_ptr<AVPacket, decltype(av_packet_unref)*> pkt_cleanup(
 801                         pkt, av_packet_unref);
 802                 pkt->data = nullptr;
 803                 pkt->size = 0;
 804                 if (av_read_frame(format_ctx, pkt) == 0) {
 805                         if (pkt->stream_index == video_stream_index) {
 806                                 if (avcodec_send_packet(video_codec_ctx, pkt) < 0) {
 807                                         fprintf(stderr, "%s: Cannot send packet to video codec.\n", pathname.c_str());
 808                                         *error = true;
 809                                         return AVFrameWithDeleter(nullptr);
 810                                 }
 811                         }
 812                 } else {
 813                         eof = true;  // Or error, but ignore that for the time being.
 814                 }
 815
 816                 // Decode video, if we have a frame.
 817                 int err = avcodec_receive_frame(video_codec_ctx, video_avframe.get());
 818                 if (err == 0) {
 819                         frame_finished = true;
 820                         break;
 821                 } else if (err != AVERROR(EAGAIN)) {
 822                         fprintf(stderr, "%s: Cannot receive frame from video codec.\n", pathname.c_str());
 823                         *error = true;
 824                         return AVFrameWithDeleter(nullptr);
 825                 }
 826         } while (!eof);
 827
 828         if (frame_finished)
 829                 return video_avframe;
 830         else
 831                 return AVFrameWithDeleter(nullptr);
 832 }
 833
 834 int find_stream_index(AVFormatContext *ctx, AVMediaType media_type)
 835 {
 836         for (unsigned i = 0; i < ctx->nb_streams; ++i) {
 837                 if (ctx->streams[i]->codecpar->codec_type == media_type) {
 838                         return i;
 839                 }
 840         }
 841         return -1;
 842 }
 843
 844 steady_clock::time_point compute_frame_start(int64_t frame_pts, int64_t pts_origin, const AVRational &video_timebase, const steady_clock::time_point &origin, double rate)
 845 {
 846         const duration<double> pts((frame_pts - pts_origin) * double(video_timebase.num) / double(video_timebase.den));
 847         return origin + duration_cast<steady_clock::duration>(pts / rate);
 848 }
 849
 850 bool VideoWidget::play_video(const string &pathname)
 851 {
 852         queued_frames.clear();
 853         AVFormatContextWithCloser format_ctx = avformat_open_input_unique(pathname.c_str(), /*fmt=*/nullptr,
 854                 /*options=*/nullptr);
 855         if (format_ctx == nullptr) {
 856                 fprintf(stderr, "%s: Error opening file\n", pathname.c_str());
 857                 return false;
 858         }
 859
 860         if (avformat_find_stream_info(format_ctx.get(), nullptr) < 0) {
 861                 fprintf(stderr, "%s: Error finding stream info\n", pathname.c_str());
 862                 return false;
 863         }
 864
 865         int video_stream_index = find_stream_index(format_ctx.get(), AVMEDIA_TYPE_VIDEO);
 866         if (video_stream_index == -1) {
 867                 fprintf(stderr, "%s: No video stream found\n", pathname.c_str());
 868                 return false;
 869         }
 870
 871         // Open video decoder.
 872         const AVCodecParameters *video_codecpar = format_ctx->streams[video_stream_index]->codecpar;
 873         const AVCodec *video_codec = avcodec_find_decoder(video_codecpar->codec_id);
 874
 875         video_timebase = format_ctx->streams[video_stream_index]->time_base;
 876         AVCodecContextWithDeleter video_codec_ctx = avcodec_alloc_context3_unique(nullptr);
 877         if (avcodec_parameters_to_context(video_codec_ctx.get(), video_codecpar) < 0) {
 878                 fprintf(stderr, "%s: Cannot fill video codec parameters\n", pathname.c_str());
 879                 return false;
 880         }
 881         if (video_codec == nullptr) {
 882                 fprintf(stderr, "%s: Cannot find video decoder\n", pathname.c_str());
 883                 return false;
 884         }
 885
 886         // Seemingly, it's not too easy to make something that just initializes
 887         // “whatever goes”, so we don't get CUDA or VULKAN or whatever here
 888         // without enumerating through several different types.
 889         // VA-API and VDPAU will do for now. We prioritize VDPAU for the
 890         // simple reason that there's a VA-API-via-VDPAU emulation for NVidia
 891         // cards that seems to work, but just hangs when trying to transfer the frame.
 892         //
 893         // Note that we don't actually check codec support beforehand,
 894         // so if you have a low-end VDPAU device but a high-end VA-API device,
 895         // you lose out on the extra codec support from the latter.
 896         AVBufferRef *hw_device_ctx = nullptr;
 897         if (av_hwdevice_ctx_create(&hw_device_ctx, AV_HWDEVICE_TYPE_VDPAU, nullptr, nullptr, 0) >= 0) {
 898                 video_codec_ctx->hw_device_ctx = av_buffer_ref(hw_device_ctx);
 899                 video_codec_ctx->get_format = get_hw_format<AV_HWDEVICE_TYPE_VDPAU>;
 900         } else if (av_hwdevice_ctx_create(&hw_device_ctx, AV_HWDEVICE_TYPE_VAAPI, nullptr, nullptr, 0) >= 0) {
 901                 video_codec_ctx->hw_device_ctx = av_buffer_ref(hw_device_ctx);
 902                 video_codec_ctx->get_format = get_hw_format<AV_HWDEVICE_TYPE_VAAPI>;
 903         } else {
 904                 fprintf(stderr, "Failed to initialize VA-API or VDPAU for FFmpeg acceleration. Decoding video in software.\n");
 905         }
 906
 907         if (avcodec_open2(video_codec_ctx.get(), video_codec, nullptr) < 0) {
 908                 fprintf(stderr, "%s: Cannot open video decoder\n", pathname.c_str());
 909                 return false;
 910         }
 911         unique_ptr<AVCodecContext, decltype(avcodec_close)*> video_codec_ctx_cleanup(
 912                 video_codec_ctx.get(), avcodec_close);
 913
 914         internal_rewind();
 915
 916         running = RUNNING;
 917
 918         // Main loop.
 919         int consecutive_errors = 0;
 920         double rate = 1.0;
 921         while (!producer_thread_should_quit.should_quit()) {
 922                 if (process_queued_commands(format_ctx.get(), video_codec_ctx.get(), video_stream_index, /*seeked=*/nullptr)) {
 923                         return true;
 924                 }
 925                 if (paused) {
 926                         producer_thread_should_quit.sleep_for(hours(1));
 927                         continue;
 928                 }
 929
 930                 bool error;
 931                 AVFrameWithDeleter frame = decode_frame(format_ctx.get(), video_codec_ctx.get(),
 932                         pathname, video_stream_index, &error);
 933                 if (error) {
 934                         if (++consecutive_errors >= 100) {
 935                                 fprintf(stderr, "More than 100 consecutive video frames, aborting playback.\n");
 936                                 return false;
 937                         } else {
 938                                 continue;
 939                         }
 940                 } else {
 941                         consecutive_errors = 0;
 942                 }
 943                 if (frame == nullptr) {
 944                         // EOF.
 945                         return false;
 946                 }
 947
 948                 // Sleep until it's time to present this frame.
 949                 for ( ;; ) {
 950                         if (last_pts == 0 && pts_origin == 0) {
 951                                 pts_origin = frame->pts;
 952                         }
 953                         steady_clock::time_point now = steady_clock::now();
 954                         next_frame_start = compute_frame_start(frame->pts, pts_origin, video_timebase, start, rate);
 955
 956                         if (duration<double>(now - next_frame_start).count() >= 0.1) {
 957                                 // If we don't have enough CPU to keep up, or if we have a live stream
 958                                 // where the initial origin was somehow wrong, we could be behind indefinitely.
 959                                 fprintf(stderr, "%s: Playback %.0f ms behind, resetting time scale\n",
 960                                         pathname.c_str(),
 961                                         1e3 * duration<double>(now - next_frame_start).count());
 962                                 pts_origin = frame->pts;
 963                                 start = next_frame_start = now;
 964                         }
 965                         bool finished_wakeup;
 966                         finished_wakeup = producer_thread_should_quit.sleep_until(next_frame_start);
 967                         if (finished_wakeup) {
 968                                 video_window->set_current_frame(make_video_frame(frame.get()));
 969                                 last_frame = steady_clock::now();
 970                                 update();
 971                                 break;
 972                         } else {
 973                                 if (producer_thread_should_quit.should_quit()) break;
 974
 975                                 bool seeked = false;
 976                                 if (process_queued_commands(format_ctx.get(), video_codec_ctx.get(), video_stream_index, &seeked)) {
 977                                         return true;
 978                                 }
 979
 980                                 if (paused) {
 981                                         // Just paused, so present the frame immediately and then go into deep sleep.
 982                                         video_window->set_current_frame(make_video_frame(frame.get()));
 983                                         last_frame = steady_clock::now();
 984                                         update();
 985                                         break;
 986                                 }
 987
 988                                 // If we just seeked, drop this frame on the floor and be done.
 989                                 if (seeked) {
 990                                         break;
 991                                 }
 992                         }
 993                 }
 994                 store_pts(frame->pts);
 995         }
 996         return true;
 997 }
 998
 999 void VideoWidget::store_pts(int64_t pts)
1000 {
1001         last_pts = pts;
1002         last_position = lrint(pts * double(video_timebase.num) / double(video_timebase.den) * 1000);
1003         post_to_main_thread([this, last_position{last_position.load()}] {
1004                 emit position_changed(last_position);
1005         });
1006 }
1007
1008 // Taken from Movit (see the comment there for explanation)
1009 float compute_chroma_offset(float pos, unsigned subsampling_factor, unsigned resolution)
1010 {
1011         float local_chroma_pos = (0.5 + pos * (subsampling_factor - 1)) / subsampling_factor;
1012         if (fabs(local_chroma_pos - 0.5) < 1e-10) {
1013                 // x + (-0) can be optimized away freely, as opposed to x + 0.
1014                 return -0.0;
1015         } else {
1016                 return (0.5 - local_chroma_pos) / resolution;
1017         }
1018 }
1019
1020 shared_ptr<VideoWidget::Frame> VideoWidget::alloc_frame(unsigned width, unsigned height, unsigned chroma_width, unsigned chroma_height)
1021 {
1022         lock_guard lock(freelist_mu);
1023         for (auto it = frame_freelist.begin(); it != frame_freelist.end(); ++it) {
1024                 if ((*it)->width == width &&
1025                     (*it)->height == height &&
1026                     (*it)->chroma_width == chroma_width &&
1027                     (*it)->chroma_height == chroma_height) {
1028                         Frame *frame = *it;
1029                         frame_freelist.erase(it);
1030                         return shared_ptr<Frame>{frame, free_frame};
1031                 }
1032         }
1033
1034         Frame *frame = new Frame;
1035         frame->owner = this;
1036         frame->width = width;
1037         frame->height = height;
1038         frame->chroma_width = chroma_width;
1039         frame->chroma_height = chroma_height;
1040
1041         size_t len = frame->width * frame->height + 2 * frame->chroma_width * frame->chroma_height;
1042
1043         while (!video_window->isValid()) {
1044                 usleep(100000);
1045         }
1046
1047         // Augh :-)
1048         mutex mu;
1049         condition_variable done_cv;
1050         bool done = false;
1051
1052         post_to_main_thread([this, &frame, len, &done, &mu, &done_cv]{
1053                 video_window->makeCurrent();
1054                 glCreateBuffers(1, &frame->pbo);
1055                 glNamedBufferStorage(frame->pbo, len, nullptr, GL_MAP_WRITE_BIT | GL_MAP_PERSISTENT_BIT);
1056                 frame->data = (uint8_t *)glMapNamedBufferRange(frame->pbo, 0, len, GL_MAP_WRITE_BIT | GL_MAP_FLUSH_EXPLICIT_BIT | GL_MAP_PERSISTENT_BIT);
1057                 video_window->doneCurrent();
1058
1059                 lock_guard lock(mu);
1060                 done = true;
1061                 done_cv.notify_all();
1062         });
1063         {
1064                 unique_lock lock(mu);
1065                 done_cv.wait(lock, [&done]{ return done; });
1066         }
1067
1068         return shared_ptr<Frame>{frame, free_frame};
1069 }
1070
1071 void VideoWidget::free_frame(VideoWidget::Frame *frame)
1072 {
1073         VideoWidget *self = frame->owner;
1074         lock_guard lock(self->freelist_mu);
1075         if (self->frame_freelist.size() >= 16) {
1076                 GLuint pbo = frame->pbo;
1077                 post_to_main_thread([self, pbo]{
1078                         self->video_window->makeCurrent();
1079                         glUnmapNamedBuffer(pbo);
1080                         glDeleteBuffers(1, &pbo);
1081                         self->video_window->doneCurrent();
1082                 });
1083                 delete self->frame_freelist.front();
1084                 self->frame_freelist.pop_front();
1085         }
1086         self->frame_freelist.push_back(frame);
1087 }
1088
1089 shared_ptr<VideoWidget::Frame> VideoWidget::make_video_frame(const AVFrame *frame)
1090 {
1091         AVFrameWithDeleter sw_frame;
1092
1093         if (frame->format == AV_PIX_FMT_VAAPI ||
1094             frame->format == AV_PIX_FMT_VDPAU) {
1095                 // Get the frame down to the CPU. (TODO: See if we can keep it
1096                 // on the GPU all the way, since it will be going up again later.
1097                 // However, this only works if the OpenGL GPU is the same one.)
1098                 sw_frame = av_frame_alloc_unique();
1099                 int err = av_hwframe_transfer_data(sw_frame.get(), frame, 0);
1100                 if (err != 0) {
1101                         fprintf(stderr, "%s: Cannot transfer hardware video frame to software.\n", pathname.c_str());
1102                 } else {
1103                         sw_frame->pts = frame->pts;
1104                         sw_frame->pkt_duration = frame->pkt_duration;
1105                         frame = sw_frame.get();
1106                 }
1107         }
1108
1109         if (sws_ctx == nullptr ||
1110             sws_last_width != frame->width ||
1111             sws_last_height != frame->height ||
1112             sws_last_src_format != frame->format) {
1113                 sws_dst_format = decide_dst_format(AVPixelFormat(frame->format));
1114                 sws_ctx.reset(
1115                         sws_getContext(frame->width, frame->height, AVPixelFormat(frame->format),
1116                                 frame->width, frame->height, sws_dst_format,
1117                                 SWS_BICUBIC, nullptr, nullptr, nullptr));
1118                 sws_last_width = frame->width;
1119                 sws_last_height = frame->height;
1120                 sws_last_src_format = frame->format;
1121         }
1122         if (sws_ctx == nullptr) {
1123                 fprintf(stderr, "Could not create scaler context\n");
1124                 abort();
1125         }
1126
1127         uint8_t *pic_data[4] = { nullptr, nullptr, nullptr, nullptr };
1128         int linesizes[4] = { 0, 0, 0, 0 };
1129         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(sws_dst_format);
1130
1131         shared_ptr<Frame> video_frame = alloc_frame(
1132                 frame->width,
1133                 frame->height,
1134                 AV_CEIL_RSHIFT(int(frame->width), desc->log2_chroma_w),
1135                 AV_CEIL_RSHIFT(int(frame->height), desc->log2_chroma_h));
1136
1137         // We always assume left chroma placement for now.
1138         video_window->set_cbcr_offset(
1139                 compute_chroma_offset(0.0f, 1 << desc->log2_chroma_w, video_frame->chroma_width),
1140                 compute_chroma_offset(0.5f, 1 << desc->log2_chroma_h, video_frame->chroma_height)
1141         );
1142
1143         pic_data[0] = video_frame->data;
1144         linesizes[0] = frame->width;
1145
1146         pic_data[1] = pic_data[0] + frame->width * frame->height;
1147         linesizes[1] = video_frame->chroma_width;
1148
1149         pic_data[2] = pic_data[1] + video_frame->chroma_width * video_frame->chroma_height;
1150         linesizes[2] = video_frame->chroma_width;
1151
1152         sws_scale(sws_ctx.get(), frame->data, frame->linesize, 0, frame->height, pic_data, linesizes);
1153
1154         video_frame->need_flush_len = video_frame->width * video_frame->height + 2 * video_frame->chroma_width * video_frame->chroma_height;
1155
1156         return video_frame;
1157 }
1158