mokuro hangs without any page progress while maxxing out CPU core

[ElnuDev]

Hello! I have previously run mokuro with no issues prior to 0.2.0 with CUDA on my main system that has a dedicated GPU. I'm now running mokuro 0.2.2 on NixOS on my other system that doesn't have a GPU, so I have to run it on CPU. It has been running over an hour while maxxing out one of my cores. I figured it would take a while without acceleration, but it seems to be just hanging since it doesn't show any page progress.

[elnu@pang13:~/Nextcloud/Manga/DLraw.net-Yotsubato  vol 01-15/Yotsubato v01-05/[あずまきよひこ] よつばと! 第01巻]$ mokuro . --legacy-html=False
/nix/store/nsfn3qcz4w7w158yawk8sq3fqjvbysaz-mokuro-0.2.2/lib/python3.13/site-packages/comic_text_detector/utils/yolov5_utils.py:4: UserWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html. The pkg_resources package is slated for removal as early as 2025-11-30. Refrain from using this package or pin to Setuptools<81.
  import pkg_resources as pkg
2025-12-03 14:20:51.391 | INFO     | mokuro.run:run:63 - Scanning paths...

Found 1 volumes:

/home/elnu/Nextcloud/Manga/DLraw.net-Yotsubato  vol 01-15/Yotsubato v01-05/[あずまきよひこ] よつばと! 第01巻 (unprocessed)

Each of the paths above will be treated as one volume.


Continue? [yes/no]yes
2025-12-03 14:20:56.726 | INFO     | mokuro.run:run:133 - Processing 1/1: /home/elnu/Nextcloud/Manga/DLraw.net-Yotsubato  vol 01-15/Yotsubato v01-05/[あずまきよひこ] よつばと! 第01巻
Processing pages...:   0%|                                                                                                                                             | 0/231 [00:00<?, ?it/s]2025-12-03 14:20:56.749 | INFO     | mokuro.manga_page_ocr:__init__:41 - Initializing text detector, using device cpu
2025-12-03 14:20:56.749 | INFO     | mokuro.cache:_download_if_needed:22 - Downloading https://github.com/zyddnys/manga-image-translator/releases/download/beta-0.2.1/comictextdetector.pt
2025-12-03 14:20:59.223 | INFO     | mokuro.cache:_download_if_needed:30 - Finished downloading https://github.com/zyddnys/manga-image-translator/releases/download/beta-0.2.1/comictextdetector.pt

Any ideas what's going on? Thanks in advance.

It's also worth mentioning that it's completely unresponsive to ^C. No issues on a Windows 11 VM either.

[GalladeGuy]

I'm having the same issue on NixOS, though I have a GPU available which I guess it isn't using. Did you find a fix for this?

[fd63]

I've also been having mokuro issues on NixOS.

From what I can tell, mokuro broke when nixpkgs updated opencv from 4.11.0 to 4.12.0 (here).

I'm not sure whether this affects non-nix mokuro users who have this opencv version.

For me, with opencv-4.12.0, most of the time mokuro will hang indefinitely before processing any pages (after printing "Initializing text detector, using device cpu"). Other times it will successfully process a handful of pages before hanging.

My workaround is to use mokuro from an older nixpkgs revision, before the opencv update. This can be done by running mokuro inside an ephemeral shell created like this:

$ nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/751890b33476e0a9311b3534bccb60b13286ce9d.tar.gz -p mokuro

Or by replacing mokuro in your environment.systemPackages like this:

environment.systemPackages = [
    (import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/751890b33476e0a9311b3534bccb60b13286ce9d.tar.gz") {}).mokuro
];