Read mov files where the moov atom is hidden within a free atom.

Fixes ticket #1551 / issue 2226.

libavformat/isom.h

@@ -169,6 +169,7 @@ typedef struct MOVContext {
     int64_t next_root_atom; ///< offset of the next root atom
     int *bitrates;          ///< bitrates read before streams creation
     int bitrates_count;
+    int moov_retry;
 } MOVContext;
 
 int ff_mp4_read_descr_len(AVIOContext *pb);

libavformat/mov.c

@@ -3120,6 +3120,19 @@ static int mov_read_default(MOVContext *c, AVIOContext *pb, MOVAtom atom)
         if (atom.size >= 8) {
             a.size = avio_rb32(pb);
             a.type = avio_rl32(pb);
+            if (a.type == MKTAG('f','r','e','e') &&
+                a.size >= 8 &&
+                c->moov_retry) {
+                uint8_t buf[8];
+                uint32_t *type = (uint32_t *)buf + 1;
+                avio_read(pb, buf, 8);
+                avio_seek(pb, -8, SEEK_CUR);
+                if (*type == MKTAG('m','v','h','d') ||
+                    *type == MKTAG('c','m','o','v')) {
+                    av_log(c->fc, AV_LOG_ERROR, "Detected moov in a free atom.\n");
+                    a.type = MKTAG('m','o','o','v');
+                }
+            }
             if (atom.type != MKTAG('r','o','o','t') &&
                 atom.type != MKTAG('m','o','o','v'))
             {
@@ -3486,11 +3499,15 @@ static int mov_read_header(AVFormatContext *s)
         atom.size = INT64_MAX;
 
     /* check MOV header */
+    do {
+    if (mov->moov_retry)
+        avio_seek(pb, 0, SEEK_SET);
     if ((err = mov_read_default(mov, pb, atom)) < 0) {
         av_log(s, AV_LOG_ERROR, "error reading header: %d\n", err);
         mov_read_close(s);
         return err;
     }
+    } while (pb->seekable && !mov->found_moov && !mov->moov_retry++);
     if (!mov->found_moov) {
         av_log(s, AV_LOG_ERROR, "moov atom not found\n");
         mov_read_close(s);