libv4lconvert: Fix interpretation of bit 7 of the Pixart JPEG marker

Signed-off-by: Hans de Goede <hdegoede@redhat.com>

diff --git a/lib/libv4lconvert/tinyjpeg.c b/lib/libv4lconvert/tinyjpeg.c
index d227c79..01bd409 100644 (file)
--- a/lib/libv4lconvert/tinyjpeg.c
+++ b/lib/libv4lconvert/tinyjpeg.c
@@ -1404,7 +1404,7 @@ static void pixart_decode_MCU_2x1_3planes(struct jdec_private *priv)
           different quantization table per MCU. So if the marker changes we
           need to rebuild the quantization tables. */
        if (marker != priv->marker) {
-               int i, j, comp, lumi, chroma;
+               int i, j, comp, lumi;
                unsigned char qt[64];
                /* These values have been found by trial and error and seem to
                   work reasonably. Markers with index 0 - 7 are never
@@ -1457,8 +1457,7 @@ static void pixart_decode_MCU_2x1_3planes(struct jdec_private *priv)
                i = (marker & 0x7c) >> 2; /* Bits 0 and 1 are always 0 */
                comp = qfactor[i];
                lumi = (marker & 0x40) ? 1 : 0;
-               chroma = (marker & 0x80) ? 2 : 3;
-               /* printf("marker %02x comp %d lumi %d chroma %d\n", marker, comp, lumi, chroma); */
+               /* printf("marker %02x comp %d lumi %d\n", marker, comp, lumi); */
 
                /* Note the DC quantization factor is fixed! */
                qt[0] = pixart_q[lumi][0]; 
@@ -1468,10 +1467,14 @@ static void pixart_decode_MCU_2x1_3planes(struct jdec_private *priv)
                }
                build_quantization_table(priv->Q_tables[0], qt);
 
-               qt[0] = pixart_q[chroma][0]; 
-               for (i = 1; i < 64; i++) {
-                       j = (pixart_q[chroma][i] * comp + 50) / 100;
-                       qt[i] = (j < 255) ? j : 255;
+               /* If bit 7 of the marker is set chrominance uses the
+                  luminance quantization table */
+               if (!(marker & 0x80)) {
+                       qt[0] = pixart_q[3][0];
+                       for (i = 1; i < 64; i++) {
+                               j = (pixart_q[3][i] * comp + 50) / 100;
+                               qt[i] = (j < 255) ? j : 255;
+                       }
                }
                build_quantization_table(priv->Q_tables[1], qt);