On Windows, FFmpeg can't be found by TorchAudio for Python > 3.8 - workaround available until TorchAudio addresses it

[DanMakingWithAI]

Though it wasn't causing any issues in usage, on Windows (10) I was finding my output logs to be full of (handled) exceptions from torch audio like:

DEBUG:torio._extension.utils:Loading FFmpeg6
DEBUG:torio._extension.utils:Failed to load FFmpeg6 extension.
Traceback (most recent call last):
  File "C:\Users\XXXXXX\.venv\gijiroku\Lib\site-packages\torio\_extension\utils.py", line 116, in _find_ffmpeg_extension
    ext = _find_versionsed_ffmpeg_extension(ffmpeg_ver)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\XXXXXX\.venv\gijiroku\Lib\site-packages\torio\_extension\utils.py", line 108, in _find_versionsed_ffmpeg_extension
    _load_lib(lib)
  File "C:\Users\XXXXXX\.venv\gijiroku\Lib\site-packages\torio\_extension\utils.py", line 94, in _load_lib
    torch.ops.load_library(path)
  File "C:\Users\XXXXXX\.venv\gijiroku\Lib\site-packages\torch\_ops.py", line 1032, in load_library
    ctypes.CDLL(path)
  File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.12_3.12.1008.0_x64__qbz5n2kfra8p0\Lib\ctypes\__init__.py", line 379, in __init__  
    self._handle = _dlopen(self._name, mode)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: Could not find module 'C:\Users\XXXXXX\.venv\gijiroku\Lib\site-packages\torio\lib\libtorio_ffmpeg6.pyd' (or one of its dependencies). Try using the full path with constructor syntax.

and so on as it carried on trying lower and lower version numbers.

I thought it odd as I have ffmpeg installed and accessible in my PATH.

Long story short, it looks like it's a bug with the current version of torch audio - open issue at pytorch/audio#3789 - whereby the path is not checked for DLLs on Windows if Python version is > 3.8)

I followed the first part of the advice given at pytorch/audio#3789 (comment) - as that can be done in client code (they also dipped into torchaudio code to fix it there but I'd rather not) and so have added this code to my imports:

import sys
if sys.platform == 'win32':
    from torchaudio._extension.utils import _init_dll_path

and called it just before initialising anything in the library (e.g. get_engine() or TextToAudioStream()):

if sys.platform == 'win32':
    _init_dll_path()

Probably an imperfect solution, but those exceptions no longer occur for me at least and I thought it worth sharing.

[KoljaB]

Thanks a lot, good insights I haven't been aware of.