Problem with Music Files on USB Drives

elcpu wrote:

I erased the drive using Disk Utility and then copied the mp3s to the drive using Finder. Lo and behold the car then started to "say" that every other file was unplayable. I tried the stick on a music system at home, same issue, every other file unplayable. I then tried a different USB drive, same issue. Long story but the problem is that macOS places a duplicate named copy of every file in the USB drive with the prefix ._ and the extension .mp3 (even though they are not mp3s) and to make matters worse the files are hidden in macOS.

The Finder sees that the external drive does not use a Mac filesystem. It is trying to preserve some extended attributes that a Mac filesystem would maintain, by creating

• FOO.MP3 – the main file
• ._FOO.MP3 – the extended attribute file

The idea being that if you ever copy files back to the Mac, it can transparently combine the data from these two files, to preserve the extended attributes.

macOS is based on Unix, and adding a leading '.' (s a standard Unix convention for hiding a file from regular directory listings. The ._FOO.MP3 name represents an attempt to create a hidden file with a unique name that is easy to associate with the main file.

Unfortunately, other systems don't know about the Finder's "._" games, and may not even know about the Unix convention for hiding a file by starting its name with a "." They see the .MP3 suffix, conclude that the extended attribute files are MP3 files, and of course, then discover that these "MP3" files are hopelessly corrupt.

The same issue happens with preparing thumb drives and memory cards for use with HDTVs and digital picture frames. The ._*.JPG files look like corrupt JPG photos to many third-party devices.

The solution is to go into Terminal just before you eject a memory card or USB flash drive.

1. Go to that volume. (E.g., type cd and a space, then drag-and-drop the memory card or USB flash drive icon.)
2. Do a rm ._*.* to get rid of all files with a leading ._
3. Do a ls -a to identify any remaining files that begin with a .
4. Do a rm on any such files other than . or .. (in Unix, . means the current directory and .. is the parent directory)
5. In the Finder, eject the memory card or flash drive without doing anything else first.

For a MP3 or JPG file, you don't lose all that much by trashing the extended attributes file – even if you do decide to later copy the file back to the Mac.

I'm not sure how you managed to not have this problem before. You may have installed BlueHarvest which would prevent writing them. If you don't write the files with Finder, I think you can avoid it, but I'm not certain.

Before ejecting, run this command replacing volumeName with the name of your usb stick. If it has spaces in the name, enclose the full path in double quotes

dot_clean -m /Volumes/volumeName

For my 3D Printer, I created a Shortcut that I use to Clean & Eject the USB stick.

The code in the shell script:

args = ("$@")
if [[ $# -eq 0 ]]
	then args=("/Volumes/Prusa_Mini");
fi
for v in "${args[@]}"
do
	dot_clean -m "$v"
	diskutil eject "$v"
done

You can add a Shortcuts menu to the Status Menu area in the Menubar. You can also, ctrl-click on the drive and choose the Shortcut to clean and eject. Just change the path in the args= line to match your volume.

You can probably add lines to remove .DS_Store, .Trashes, and .Spotlight-V100, but if they don't cause any problems, probably leave alone.

For the checking part, if you just open the window and show hidden files (cmd-shift-. ), it won't write .DS_Store or the metadata (._) files. The metadata files only get written when you write the file.

elcpu wrote:

Many thanks. I can follow your logic above except the drag and drop of the USB drive icon into Terminal. I have not done that before and I am not sure how.

The shortcut I already got deletes all the ._ files and that removes the problem. The shortcut is a Terminal script:

dot_clean -m "/Volumes/USB MUSIC"

diskutil eject "USB MUSIC”

You don't need to do it the long way. I probably should use dot_clean -m.

The drag-and-drop thing is a useful feature of Terminal that helps with the need to escape, or quote, special characters in file names and directory names. If you drag a file, folder, or volume icon from the Desktop or a Finder window to the Terminal window, and drop it there, Terminal will paste in the file, directory, or volume path name, at the current text insertion point. Complete with any characters needed to make the shell recognize the name as being a single argument.

For instance, if you had Finder { Preferences / Settings } configured to show flash drive icons on the Desktop, you could type dot_clean -m in the Terminal window, add a space after that, and drag your drive's icon to the window. I think the command line would then show something like

$ dot_clean -m /Volumes/USB\ MUSIC

As far as the shell is concerned, this would be equivalent to

$ dot_clean -m "/Volumes/USB MUSIC"

Double-quotes around the whole string, or escape (\) characters in front of particular characters that would pose an issue, serve the same purpose.

elcpu wrote:

Servant of Cats wrote:

For instance, if you had Finder { Preferences / Settings } configured to show flash drive icons on the Desktop, [I do]<< you could type dot_clean -m in the Terminal window, add a space after that, and drag your drive's icon to the window. I think the command line would then show something like

$ dot_clean -m /Volumes/USB\ MUSIC

It did just that but why the $ sign above? What does the $ mean?

That's just part of the prompt, to let you know that the shell is waiting for you to type in another command. The bash shell ("Bourne Again Shell"; the name is a pun) uses "$"; other shells like csh might use "%".

The part in front of the "$" or "%" where it shows you the name of your Mac, and the current directory, is done using stuff in the default shell initialization scripts that customizes the prompt.

Back in the days when text terminals ruled, many power users would have objected to having "John-Does-Mac" take up space on every command line. They might have gone with something as minimal as just the "$" or "%" (after all, you could always do a pwd to show the current directory).

For what it's worth, I've used this app to clean up thumb drives full of MP3s for use in the car.

It works well for me.

https://apps.apple.com/us/app/dotcleaner-ds-store-remover/id1113480556?mt=12

I can understand the Spotlight issue. It should not affect anything. It will fail because it cannot read inside the directory.

The pathname error sounds strange. You should get a directory not found error.

I'll try to see if I can replicate that and figure out what is wrong. I think it is just reporting an error trying to get into some other sub-directory.

With the space, the command would be:

dot_clean -m "/Volumes/MINI 64/"

I asked the moderators to delete my bad command post and they deleted a lot more.

To recursively delete the .DS_Store files, you have to use find with the -delete option.

find "/Volumes/USB Music/" -name '.DS_Store' -type f -delete