lavc/dpx: Reset n_datum for every new line when decoding 12bit.

Fixes odd unpacked 12bit decoding.
Reported-by: Piotr Bandurski

libavcodec/dpx.c

@@ -234,10 +234,10 @@ static int decode_frame(AVCodecContext *avctx,
     case 12:
         if (!packing) {
             int tested = 0;
-            if (descriptor == 50 && endian && (avctx->width%8) == 0) { // Little endian and widths not a multiple of 8 need tests
+            if (descriptor == 50 && endian) { // Little endian needs tests
                 tested = 1;
             }
-            if (descriptor == 51 && endian && (avctx->width%2) == 0) { // Little endian and widths not a multiple of 2 need tests
+            if (descriptor == 51 && endian) { // Little endian needs tests
                 tested = 1;
             }
             if (!tested) {
@@ -422,6 +422,7 @@ static int decode_frame(AVCodecContext *avctx,
                                                &n_datum, endian);
                 }
             }
+            n_datum = 0;
             for (i = 0; i < elements; i++)
                 ptr[i] += p->linesize[i];
             // Jump to next aligned position

libavcodec/version.h

@@ -29,7 +29,7 @@
 
 #define LIBAVCODEC_VERSION_MAJOR  58
 #define LIBAVCODEC_VERSION_MINOR  20
-#define LIBAVCODEC_VERSION_MICRO 101
+#define LIBAVCODEC_VERSION_MICRO 102
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \