diff --git a/libavformat/mov.c b/libavformat/mov.c
index 9db6abac61..5923fb7f82 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -1372,9 +1372,9 @@ int ff_mov_read_stsd_entries(MOVContext *c, AVIOContext *pb, int entries)
                 val = avio_rb32(pb); /* flags */
                 if (val & 1)
                     st->codec->flags2 |= CODEC_FLAG2_DROP_FRAME_TIMECODE;
-                avio_rb32(pb);
-                avio_rb32(pb);
-                st->codec->time_base.den = avio_r8(pb);
+                avio_rb32(pb); /* time scale */
+                avio_rb32(pb); /* frame duration */
+                st->codec->time_base.den = avio_r8(pb); /* number of frame */
                 st->codec->time_base.num = 1;
             }
             /* other codec type, just skip (rtp, mp4s, ...) */