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Level 1

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writing JPG files to FAT32 thumbdrive for TV slideshow

This has me a little stumped. Macs can read/write FAT and FAT32 formatted drives. I wanted to do a picture slideshow on a VISIO smart TV (E-Series) in another town using its built in slideshow feature from .jpg files on a USB thumbdrive. Visio manual states the USB thumbdrive must be formated FAT32 (my own Samsung TV will also take FAT and NTFS). The thumbdrives I bought, SanDisk 16 GB, came formated FAT32 (according to Get Info) so I just copied my .jpg images over, no folders. Plugging the thumbdrive into a VISIO smart TV (slightly different model than on at location) here at Costco (with thier help) for testing before leaving, and later into the VISIO TV at location, and neither recognized it, playing around with menus showed an empty drive. No problem on my Samsung TV. On location, Visio owner just copied files on thumbdrive over to another thumbdrive using a Windows computer and the Visio TVs then had no problem, so it wasn't any part of the filename or extension. I thought if one device could see files on a FAT32 thumbdrive, all devices could. Is the Mac doing something not quite standard in writing the .jpg files so Visio TVs just can't read/see them? I did eject thumbdrive before phyically removing. Is this just a problem with Visio TV having a very rudimentary OS?

iPhone 6, iOS 11.1

Posted on Apr 22, 2018 12:55 PM

Best reply

Kurt Lang

Level 9

57,822 points

Posted on Apr 22, 2018 1:23 PM

When you write files to a FAT32 drive, the OS creates two files. One is the data fork (typically the actual data file) and another file to hold the resource fork data, which would normally be lost on the FAT32 drive's single fork file system. So, you end up with things like this:

puppy.jpg

._puppy.jpg

The second is the AppleDouble file of the saved resource fork. You don't see it from your Mac because it begins with a period, and any such file is automatically hidden.

However, the type of system you're referring to doesn't know anything about that and tries to display the ._puppy.jpg file because as far as it's concerned, it ends with .jpg, so it must be an image. That causes it to hang.

The Terminal command dot_clean will will remove these AppleDouble files.

Using an MS-DOS formatted USB flash drive as an example. Have the drive plugged in so its icon is available on the desktop. In Terminal, type:

dot_clean -mn

Put a space after the -mn. Don't hit Enter yet. Now drag and drop your USB drive's icon from the desktop into the Terminal window. It will fill out the correct path for you, similar to this:

dot_clean -mn /Volumes/FLASH\ DRIVE

I happened to use a flash drive that has the name "FLASH DRIVE". That's why the \(space) between the two words in Terminal.

What you've done is:

1) Entered the basic command

2) Added the command argument m, which means "Always delete dot underbar files." This is automatically done recursively (all folders and subfolders on the drive).

3) Added the command argument n, which means "Delete dot underbar file if there is no matching native file." Without it, Mac files on the DOS formatted drive such as ._Trash would be left behind.

4) Told it what drive to run this command on.

Now press Enter. It's done when Terminal goes to the next prompt. Dismount the drive and insert it in a Windows computer to confirm all ._ prefix files are gone. They should be. All .DS_Store files, I believe, still get left behind.

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writing JPG files to FAT32 thumbdrive for TV slideshow

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