lavc/proresdec2: Fix slice_count for very high resolutions.

QT ignores the value written in the frame header.
Issue reported by forum user Koracas.

libavcodec/proresdec2.c

@@ -180,7 +180,10 @@ static int decode_picture_header(AVCodecContext *avctx, const uint8_t *buf, cons
     else
         ctx->mb_height = (avctx->height + 15) >> 4;
 
-    slice_count = AV_RB16(buf + 5);
+    // QT ignores the written value
+    // slice_count = AV_RB16(buf + 5);
+    slice_count = ctx->mb_height * ((ctx->mb_width >> log2_slice_mb_width) +
+                                    av_popcount(ctx->mb_width & (1 << log2_slice_mb_width) - 1));
 
     if (ctx->slice_count != slice_count || !ctx->slices) {
         av_freep(&ctx->slices);

libavcodec/version.h

@@ -30,7 +30,7 @@
 
 #define LIBAVCODEC_VERSION_MAJOR  57
 #define LIBAVCODEC_VERSION_MINOR  13
-#define LIBAVCODEC_VERSION_MICRO 101
+#define LIBAVCODEC_VERSION_MICRO 102
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \