Only run container name detection upon ffmpeg parse failure.

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 1407 matching lines @@
 static const uint8_t kWtvSignature[] = {0xb7, 0xd8, 0x00, 0x20, 0x37, 0x49,
                                         0xda, 0x11, 0xa6, 0x4e, 0x00, 0x07,
                                         0xe9, 0x5e, 0xad, 0x8d};
 
 // Attempt to determine the container type from the buffer provided. This is
 // a simple pass, that uses the first 4 bytes of the buffer as an index to get
 // a rough idea of the container format.
 static MediaContainerName LookupContainerByFirst4(const uint8_t* buffer,
                                                   int buffer_size) {
   // Minimum size that the code expects to exist without checking size.
-  if (buffer_size < 12)
+  if (buffer_size < kMinimumContainerSize)
     return CONTAINER_UNKNOWN;
 
   uint32_t first4 = Read32(buffer);
   switch (first4) {
     case 0x1a45dfa3:
       if (CheckWebm(buffer, buffer_size))
         return CONTAINER_WEBM;
       break;
 
     case 0x3026b275:
@@ skipping 225 matching lines @@
     if (CheckEac3(buffer + offset, buffer_size - offset))
       return CONTAINER_EAC3;
   }
 
   return CONTAINER_UNKNOWN;
 }
 
 }  // namespace container_names
 
 }  // namespace media