Better detection of MP4 files

media/base/container_names.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/base/container_names.h"
 
 #include <stddef.h>
 
 #include <cctype>
 #include <limits>
@@ skipping 938 matching lines @@
   }
 }
 
 // Additional checks for a MOV/QuickTime/MPEG4 container.
 static bool CheckMov(const uint8_t* buffer, int buffer_size) {
   // Reference: ISO/IEC 14496-12:2005(E).
   // (http://standards.iso.org/ittf/PubliclyAvailableStandards/c061988_ISO_IEC_14496-12_2012.zip)
   RCHECK(buffer_size > 8);
 
   int offset = 0;
+  int valid_top_level_boxes = 0;
   while (offset + 8 < buffer_size) {
     uint32_t atomsize = Read32(buffer + offset);
     uint32_t atomtype = Read32(buffer + offset + 4);
-    // Only need to check for ones that are valid at the top level.
+
+    // Only need to check for atoms that are valid at the top level. However,
+    // "Boxes with an unrecognized type shall be ignored and skipped." So
+    // simply make sure that at least two recognized top level boxes are found.
+    // This list matches BoxReader::IsValidTopLevelBox().
     switch (atomtype) {
-      case TAG('f','t','y','p'):
-      case TAG('p','d','i','n'):
-      case TAG('m','o','o','v'):
-      case TAG('m','o','o','f'):
-      case TAG('m','f','r','a'):
-      case TAG('m','d','a','t'):
-      case TAG('f','r','e','e'):
-      case TAG('s','k','i','p'):
-      case TAG('m','e','t','a'):
-      case TAG('m','e','c','o'):
-      case TAG('s','t','y','p'):
-      case TAG('s','i','d','x'):
-      case TAG('s','s','i','x'):
-      case TAG('p','r','f','t'):
-      case TAG('b','l','o','c'):
+      case TAG('f', 't', 'y', 'p'):
+      case TAG('p', 'd', 'i', 'n'):
+      case TAG('b', 'l', 'o', 'c'):
+      case TAG('m', 'o', 'o', 'v'):
+      case TAG('m', 'o', 'o', 'f'):
+      case TAG('m', 'f', 'r', 'a'):
+      case TAG('m', 'd', 'a', 't'):
+      case TAG('f', 'r', 'e', 'e'):
+      case TAG('s', 'k', 'i', 'p'):
+      case TAG('m', 'e', 't', 'a'):
+      case TAG('m', 'e', 'c', 'o'):
+      case TAG('s', 't', 'y', 'p'):
+      case TAG('s', 'i', 'd', 'x'):
+      case TAG('s', 's', 'i', 'x'):
+      case TAG('p', 'r', 'f', 't'):
+      case TAG('u', 'u', 'i', 'd'):
+      case TAG('e', 'm', 's', 'g'):
+        ++valid_top_level_boxes;
         break;
-      default:
-        return false;
     }
     if (atomsize == 1) {
       // Indicates that the length is the next 64bits.
       if (offset + 16 > buffer_size)
         break;
       if (Read32(buffer + offset + 8) != 0)
         break;  // Offset is way past buffer size.
       atomsize = Read32(buffer + offset + 12);
     }
     if (atomsize == 0 || atomsize > static_cast<size_t>(buffer_size))
       break;  // Indicates the last atom or length too big.
     offset += atomsize;
   }
-  return true;
+  return valid_top_level_boxes >= 2;
 }
 
 enum MPEGVersion {
   VERSION_25 = 0,
   VERSION_RESERVED,
   VERSION_2,
   VERSION_1
 };
 enum MPEGLayer {
   L_RESERVED = 0,
@@ skipping 666 matching lines @@
     if (CheckEac3(buffer + offset, buffer_size - offset))
       return CONTAINER_EAC3;
   }
 
   return CONTAINER_UNKNOWN;
 }
 
 }  // namespace container_names
 
 }  // namespace media