FLAC to OPUS – Convert a folder of FLAC Lossless music to OPUS compressed versions and keep them in sync.

I have a large collection of FLAC losslessly encoded music (CD and Hi-Res) on my home server, this is great when listening at home, but I want to listen on my phone offline and when travelling, I use Foobar2000 for this purpose.

I have a 200GB MicroSD card in my phone, so I looked at ways to convert the FLAC files to OPUS.  Foobar2000 has a built in convert method, but if changes are made to the FLAC’s then work is involved to get them back in sync.


FLACtoOPUS, converting files so settings grayed out.

FLACtoOPUS converts a “FLAC” files folder to a “OPUS” folder by converting and syncing the files even though they have a different extension.  To save space the artwork can be removed from the OPUS files and if available the Folder.jpg is copied and converted to a max of 400×400.  The top image is one folder from my collection, the bottom is what it looks like after conversion and syncing.

FLAC Folder
FLAC Folder (C:\FLACtoOPUS\FLAC\Robot Koch\Sphere)
OPUS Folder
OPUS Synced Folder (C:\FLACtoOPUS\OPUS\Robot Koch\Sphere)


You will need to download:

FLACtoOPUS.zip (0.92 BETA)

0.91 Released as beta
0.92 Added 244, 288 and 352 in bitrates

** If any issues are found, please report in the comments **

Inside the zip there are 2 files, the FLACtoOPUS.exe and opusenc.exe this is version 1.3 from opustools.

  1. Run the FLACtoOPUS.exe program.
  2. Select the source folder of FLAC files.
  3. Select the destination folder of where you want to put the Opus file, make sure the folder is empty, and not with the source folder.
  4. Select the bitrate required, transparency is achieved at 144 for most people so 160 is a good choice. If you have good quality folder.jpg artwork tick remove images (this stops the program embedding the artwork in the Opus files, which uses a lot more space on a large collection).
  5. Select how many processor cores you want to use for conversion, if you are not working on the machine this can be set to the maximum available.
  6. Now press the convert button.


  1. Files that are not to be synced in the destination folder will be deleted, it is best to select an empty folder.
  2. Hidden folders and folders beginning with . ie .nomedia or .sync will not be deleted from the destination.
  3. If you press stop, files currently being processed will be finished.
  4. If the modified date of the source FLAC file is > the modified date of the OPUS file then the file is deleted and re-synced.


Foobar2000 is a good choice for Opus playback, both on desktop and mobile, I am using Android to play the Opus files.

Foobar2000 on Android 9 (Pie)

Getting the OPUS files on your phone


You could insert your SDCard into your computer and sync direct to it, this is probably the quickest way.

Resilio Sync

Resilio Sync can be used to sync the converted files folder to your phone, I am currently drafting a guide on how to set this up, this is the method I use as Resilio Sync runs in the background so it runs until finished and does not stop when phone sleeps.


One thought on “FLAC to OPUS – Convert a folder of FLAC Lossless music to OPUS compressed versions and keep them in sync.

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