+extern QGLWidget *global_share_widget;
+extern atomic<bool> should_quit;
+
+shared_ptr<Frame> decode_jpeg(const string &filename)
+{
+ shared_ptr<Frame> frame;
+ if (vaapi_jpeg_decoding_usable) {
+ frame = decode_jpeg_vaapi(filename);
+ if (frame != nullptr) {
+ return frame;
+ }
+ fprintf(stderr, "VA-API hardware decoding failed; falling back to software.\n");
+ }
+
+ frame.reset(new Frame);
+
+ jpeg_decompress_struct dinfo;
+ jpeg_error_mgr jerr;
+ dinfo.err = jpeg_std_error(&jerr);
+ jpeg_create_decompress(&dinfo);
+ JPEGDestroyer destroy_dinfo(&dinfo);
+
+ FILE *fp = fopen(filename.c_str(), "rb");
+ if (fp == nullptr) {
+ perror(filename.c_str());
+ exit(1);
+ }
+ jpeg_stdio_src(&dinfo, fp);
+
+ jpeg_read_header(&dinfo, true);
+
+ if (dinfo.num_components != 3) {
+ fprintf(stderr, "Not a color JPEG. (%d components, Y=%dx%d, Cb=%dx%d, Cr=%dx%d)\n",
+ dinfo.num_components,
+ dinfo.comp_info[0].h_samp_factor, dinfo.comp_info[0].v_samp_factor,
+ dinfo.comp_info[1].h_samp_factor, dinfo.comp_info[1].v_samp_factor,
+ dinfo.comp_info[2].h_samp_factor, dinfo.comp_info[2].v_samp_factor);
+ exit(1);
+ }
+ if (dinfo.comp_info[0].h_samp_factor != dinfo.max_h_samp_factor ||
+ dinfo.comp_info[0].v_samp_factor != dinfo.max_v_samp_factor || // Y' must not be subsampled.
+ dinfo.comp_info[1].h_samp_factor != dinfo.comp_info[2].h_samp_factor ||
+ dinfo.comp_info[1].v_samp_factor != dinfo.comp_info[2].v_samp_factor || // Cb and Cr must be identically subsampled.
+ (dinfo.max_h_samp_factor % dinfo.comp_info[1].h_samp_factor) != 0 ||
+ (dinfo.max_v_samp_factor % dinfo.comp_info[1].v_samp_factor) != 0) { // No 2:3 subsampling or other weirdness.
+ fprintf(stderr, "Unsupported subsampling scheme. (Y=%dx%d, Cb=%dx%d, Cr=%dx%d)\n",
+ dinfo.comp_info[0].h_samp_factor, dinfo.comp_info[0].v_samp_factor,
+ dinfo.comp_info[1].h_samp_factor, dinfo.comp_info[1].v_samp_factor,
+ dinfo.comp_info[2].h_samp_factor, dinfo.comp_info[2].v_samp_factor);
+ exit(1);
+ }
+ dinfo.raw_data_out = true;
+
+ jpeg_start_decompress(&dinfo);
+
+ frame->width = dinfo.output_width;
+ frame->height = dinfo.output_height;
+ frame->chroma_subsampling_x = dinfo.max_h_samp_factor / dinfo.comp_info[1].h_samp_factor;
+ frame->chroma_subsampling_y = dinfo.max_v_samp_factor / dinfo.comp_info[1].v_samp_factor;
+
+ unsigned h_mcu_size = DCTSIZE * dinfo.max_h_samp_factor;
+ unsigned v_mcu_size = DCTSIZE * dinfo.max_v_samp_factor;
+ unsigned mcu_width_blocks = (dinfo.output_width + h_mcu_size - 1) / h_mcu_size;
+ unsigned mcu_height_blocks = (dinfo.output_height + v_mcu_size - 1) / v_mcu_size;
+
+ unsigned luma_width_blocks = mcu_width_blocks * dinfo.comp_info[0].h_samp_factor;
+ unsigned chroma_width_blocks = mcu_width_blocks * dinfo.comp_info[1].h_samp_factor;
+ unsigned luma_height_blocks = mcu_height_blocks * dinfo.comp_info[0].v_samp_factor;
+ unsigned chroma_height_blocks = mcu_height_blocks * dinfo.comp_info[1].v_samp_factor;
+
+ // TODO: Decode into a PBO.
+ frame->y.reset(new uint8_t[luma_width_blocks * luma_height_blocks * DCTSIZE2]);
+ frame->cb.reset(new uint8_t[chroma_width_blocks * chroma_height_blocks * DCTSIZE2]);
+ frame->cr.reset(new uint8_t[chroma_width_blocks * chroma_height_blocks * DCTSIZE2]);
+ frame->pitch_y = luma_width_blocks * DCTSIZE;
+ frame->pitch_chroma = chroma_width_blocks * DCTSIZE;
+
+ JSAMPROW yptr[v_mcu_size], cbptr[v_mcu_size], crptr[v_mcu_size];
+ JSAMPARRAY data[3] = { yptr, cbptr, crptr };
+ for (unsigned y = 0; y < mcu_height_blocks; ++y) {
+ // NOTE: The last elements of cbptr/crptr will be unused for vertically subsampled chroma.
+ for (unsigned yy = 0; yy < v_mcu_size; ++yy) {
+ yptr[yy] = frame->y.get() + (y * DCTSIZE * dinfo.max_v_samp_factor + yy) * frame->pitch_y;
+ cbptr[yy] = frame->cb.get() + (y * DCTSIZE * dinfo.comp_info[1].v_samp_factor + yy) * frame->pitch_chroma;
+ crptr[yy] = frame->cr.get() + (y * DCTSIZE * dinfo.comp_info[1].v_samp_factor + yy) * frame->pitch_chroma;
+ }
+
+ jpeg_read_raw_data(&dinfo, data, v_mcu_size);
+ }
+
+ (void)jpeg_finish_decompress(&dinfo);
+ fclose(fp);
+
+ return frame;
+}