YUV420 转 RGB 测试

逐像素浮点运算转换的，很慢，目测 1080p 只有 12fps 左右

sws_scale(img_convert_context, (const unsigned char *const *)p_frame->data, p_frame->linesize, 0, p_codec_context->height,
						  p_frame_yuv->data, p_frame_yuv->linesize);

// SDL_UpdateYUVTexture(sdl_texture, &sdl_rect,
// 					 p_frame_yuv->data[0], p_frame_yuv->linesize[0],
// 					 p_frame_yuv->data[1], p_frame_yuv->linesize[1],
// 					 p_frame_yuv->data[2], p_frame_yuv->linesize[2]);

size_t image_h = p_codec_context->height;
size_t image_w = p_codec_context->width;

Image image(image_w, image_h);

for (int y = 0; y < image_h; y++)
{
    for (int x = 0; x < image_w; x++)
    {
        int y2 = y / 2;
        int x2 = x / 2;

        uint8_t Y = p_frame_yuv->data[0][y * p_frame_yuv->linesize[0] + x];
        uint8_t Cb = p_frame_yuv->data[1][y2 * p_frame_yuv->linesize[1] + x2];
        uint8_t Cr = p_frame_yuv->data[2][y2 * p_frame_yuv->linesize[2] + x2];

        uint8_t R = Y + 1.402 * (Cr - 128);
        uint8_t G = Y - 0.34414 * (Cb - 128) - 0.71414 * (Cr - 128);
        uint8_t B = Y + 1.772 * (Cb - 128);

        image.Set(x, y, {R, G, B});
    }
}

uint8_t *pixels = new uint8_t[image_h * image_w * 4];
for (int y = 0; y < image_h; y++)
{
    for (int x = 0; x < image_w; x++)
    {
        vec3 vec = image.Get(x, y);

        uint8_t r = vec.x;
        uint8_t g = vec.y;
        uint8_t b = vec.z;

        pixels[y * image_w * 4 + x * 4 + 0] = 0;
        pixels[y * image_w * 4 + x * 4 + 1] = b;
        pixels[y * image_w * 4 + x * 4 + 2] = g;
        pixels[y * image_w * 4 + x * 4 + 3] = r;
    }
}

SDL_UpdateTexture(sdl_texture, &sdl_rect, pixels, image_w * 4);

delete[] pixels;

SDL_RenderClear(sdl_renderer);
SDL_RenderCopy(sdl_renderer, sdl_texture, NULL, &sdl_rect);
SDL_RenderPresent(sdl_renderer);
// SDL_Delay(10);