Merge commit '9c0e4b33'

* commit '9c0e4b33':
  ac3: update AC3PreferredStereoDownmixMode.
Merged-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/ac3.h

@@ -111,7 +111,7 @@ typedef enum AC3PreferredStereoDownmixMode {
     AC3_DMIXMOD_NOTINDICATED = 0,
     AC3_DMIXMOD_LTRT,
     AC3_DMIXMOD_LORO,
-    AC3_DMIXMOD_RESERVED
+    AC3_DMIXMOD_DPLII // reserved value in A/52, but used by encoders to indicate DPL2
 } AC3PreferredStereoDownmixMode;
 
 typedef struct AC3BitAllocParameters {