7 Replies Latest reply: Jan 27, 2015 3:22 AM by epicaricacy
Jerimiah Baldwin Level 1 Level 1

Using finder to copy a folder and its files from SD card to mac desktop seems to cause *some* files to be corrupted, specifically a handful of MP4 files from a FAT32 SD card  which was used in a digital camera. Using a binary/hex comparison tool reveals that some segments of the files contents were modified when copied from the SD card. 



This error occurs when copying multiple files using Finder windows.  However, when copying the same files one at a time, the corruption does not occur.  This appears to be an OS level bug.  In reviewing past content, I found that dozens of MP4 files have been corrupted in the past 4 months by merely copying the files from the SD card to mac desktop using Finder copy/paste.


I am using OS X Mountain Lion 10.8.3

MacBook Pro, OS X Mountain Lion (10.8.3)
  • sig Level 8 Level 8

    When you say corrupted, modified exactly what do you mean?

  • Jerimiah Baldwin Level 1 Level 1

    The bytes of the source file do not match the bytes of the destination file (after copying), even though the byte count (size) does match.  As I stated, I used a hex comparison tool to compare the file on the SD card to the file that was copied to my mac desktop/HD after copying the entire DCIM folder to my desktop.  The size of the files was exactly the same, but the bit/byte data was different.  i.e. the source and destination files were not identical but were different/modified.

  • sig Level 8 Level 8

    Is that your criteria? Byte size? That'll change depending upon the size of the media the file resides in. It does not mean the file is corrupted nor an OS X bug. So the same file on a 750 GB drive will occupy a different space than on a 8 GB SD card.

  • Jerimiah Baldwin Level 1 Level 1

    Well, like I said, the byte size in fact did *not* change.  So I'm not even concerned about that.  What *did* change is the content of those bytes and it doesn't matter what operating system you are using, the content of those bytes is *not* supposed to change.


    Also, like I said before, if I copy the individual file (MP4) insead of the entire folder, and then do the binary/hex comparison, the byte data is identical. i.e.


    a) copying one file at a time produces an *identical* file on the HD, i.e. the byte count AND the byte content are precisely the same.

    b) copying a folder with multiple files produces a *different* file on the HD, i.e. the byte count is the same BUT the byte content differs from the original file.

  • Daniel Silber Level 1 Level 1

    Hi Jermiah,


    did you ever find the cause for this or solve it?


    I seem to ba having a similar problem.



  • Jerimiah Baldwin Level 1 Level 1

    No. I believe the issue persists. I suspect it has something to do with the NTFS reader/driver I had installed in OS X. Bascially, I installed that software so thay my Mac could read/write to NTFS formatted disks.

    The honest truth is I've been trying to get away from Apple products because of this difficulty. I take most of my movies with my mobile phone now (switched to Android) and have them synced to Google Drive. The I sync Google Drive to my Mac where I can do video editing.

  • epicaricacy Level 1 Level 1

    Similar issue here - whenever I copy mp4 files from one USB to another, they cease working, and wonlt open in quicktime or vlc, and I get error messages about unsuppoorted formats. Copying them to the desktop - no worries. But then even copying from USB > desktop > Other USB - doesnt work!!