Fix a pretty bad JPEG decoding bug; VA-API expects its quantization matrix to be...

diff --git a/vaapi_jpeg_decoder.cpp b/vaapi_jpeg_decoder.cpp
index 5143a28e4792c158d01a9a4c9404c8c8b214e192..1a3b64eb326b0c05731f1f439b6dd9df15d539b7 100644 (file)
--- a/vaapi_jpeg_decoder.cpp
+++ b/vaapi_jpeg_decoder.cpp
@@ -49,6 +49,18 @@ static mutex va_resources_mutex;
         return nullptr;                                                 \
     }
 
+// From libjpeg (although it's of course identical between implementations).
+static const int jpeg_natural_order[DCTSIZE2] = {
+        0,  1,  8, 16,  9,  2,  3, 10,
+       17, 24, 32, 25, 18, 11,  4,  5,
+       12, 19, 26, 33, 40, 48, 41, 34,
+       27, 20, 13,  6,  7, 14, 21, 28,
+       35, 42, 49, 56, 57, 50, 43, 36,
+       29, 22, 15, 23, 30, 37, 44, 51,
+       58, 59, 52, 45, 38, 31, 39, 46,
+       53, 60, 61, 54, 47, 55, 62, 63,
+};
+
 VAResources get_va_resources(unsigned width, unsigned height)
 {
        {
@@ -396,7 +408,7 @@ shared_ptr<Frame> decode_jpeg_vaapi(const string &filename)
                                        fprintf(stderr, "Baseline JPEG only!\n");
                                        return nullptr;
                                }
-                               iq.quantiser_table[quant_tbl_idx][i] = qtbl->quantval[i];
+                               iq.quantiser_table[quant_tbl_idx][i] = qtbl->quantval[jpeg_natural_order[i]];
                        }
                }
        }