2 files changed, 25 insertions, 6 deletions

diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index c193117deb..16fe4ed8f6 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -1305,6 +1305,25 @@ typedef struct AVPicture {
     int linesize[4];       ///< number of bytes per line
 } AVPicture;
 
+/**
+ * AVPaletteControl
+ * This structure defines a method for communicating palette changes
+ * between and demuxer and a decoder.
+ */
+typedef struct AVPaletteControl {
+
+    /* demuxer sets this to 1 to indicate the palette has changed;
+     * decoder resets to 0 */
+    int palette_changed;
+
+    /* 256 3-byte RGB palette entries; the components should be
+     * formatted in the buffer as "RGBRGB..." and should be scaled to
+     * 8 bits if they originally represented 6-bit VGA palette
+     * components */
+    unsigned char palette[256 * 3];
+
+} AVPaletteControl;
+
 extern AVCodec ac3_encoder;
 extern AVCodec mp2_encoder;
 extern AVCodec mp3lame_encoder;
diff --git a/libavcodec/xan.c b/libavcodec/xan.c
index fa41c1da9b..918048f45f 100644
--- a/libavcodec/xan.c
+++ b/libavcodec/xan.c
@@ -115,9 +115,9 @@ static int xan_decode_init(AVCodecContext *avctx)
     s->avctx = avctx;
 
     if ((avctx->codec->id == CODEC_ID_XAN_WC3) && 
-        (s->avctx->extradata_size != PALETTE_CONTROL_SIZE)) {
+        (s->avctx->extradata_size != sizeof(AVPaletteControl))) {
         printf (" WC3 Xan video: expected extradata_size of %d\n",
-            PALETTE_CONTROL_SIZE);
+            sizeof(AVPaletteControl));
         return -1;
     }
 
@@ -809,13 +809,13 @@ static int xan_decode_frame(AVCodecContext *avctx,
                             uint8_t *buf, int buf_size)
 {
     XanContext *s = avctx->priv_data;
-    unsigned char *palette_control = avctx->extradata;
+    AVPaletteControl *palette_control = (AVPaletteControl *)avctx->extradata;
     int keyframe = 0;
 
-    if (palette_control[0]) {
+    if (palette_control->palette_changed) {
         /* load the new palette and reset the palette control */
-        xan_wc3_build_palette(s, &palette_control[1]);
-        palette_control[0] = 0;
+        xan_wc3_build_palette(s, palette_control->palette);
+        palette_control->palette_changed = 0;
         keyframe = 1;
     }