Torchaudio is not detecting FFmpeg

[ruliworst]

🐛 Describe the bug

Hi everyone,

I am trying to use torchaudio with FFmpeg but for some reason it is not being detected.

import torchaudio
print(torchaudio.list_audio_backends())

I added the path 'C:\Program Files\ffmpeg\bin' to the PATH environment variable. As you can see I can execute ffmpeg from cmd. However, when I execute torchaudio.list_audio_backends() only 'soundfile' is detected. I tested this in a Python PIP (I can't use conda) virtual environment with version 3.10 and in another one with version 3.12 but, it didn't work in both. Torchaudio and torch versions are 2.2.1. I don't know if it is a problem with version compatibility but in the official documentation I saw ffmpeg 6 is supported and I checked the code which tries to load the libraries.

I checked a lot of related issues but I couldn't find the right solution.

Any suggestions are welcome!
Thanks.

Versions

Collecting environment information...

PyTorch version: 2.2.1+cpu
Is debug build: False
CUDA used to build PyTorch: Could not collect
ROCM used to build PyTorch: N/A
OS: Microsoft Windows Server 2022 Standard
GCC version: Could not collect
Clang version: Could not collect
CMake version: Could not collect
Libc version: N/A

Python version: 3.10.7 (tags/v3.10.7:6cc6b13, Sep  5 2022, 14:08:36) [MSC v.1933 64 bit (AMD64)] (64-bit runtime)
Python platform: Windows-10-10.0.20348-SP0
Is CUDA available: False
CUDA runtime version: 12.3.103
CUDA_MODULE_LOADING set to: N/A
GPU models and configuration: GPU 0: NVIDIA A100-PCIE-40GB
Nvidia driver version: 546.12
cuDNN version: Could not collect
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: True

CPU:
'wmic' is not recognized as an internal or external command,
operable program or batch file.

Versions of relevant libraries:

[pip3] numpy==1.26.4
[pip3] pytorch-lightning==2.2.4
[pip3] pytorch-metric-learning==2.5.0
[pip3] torch==2.2.1
[pip3] torch-audiomentations==0.11.1
[pip3] torch-pitch-shift==1.2.4
[pip3] torchaudio==2.2.1
[pip3] torchmetrics==1.4.0
[conda] Could not collect

[ruliworst]

Loading manullay the binaries is working but, I would like it was automatic.

ctypes.CDLL('C:/Program Files/ffmpeg/bin/avcodec-60.dll')
ctypes.CDLL('C:/Program Files/ffmpeg/bin/avdevice-60.dll')
ctypes.CDLL('C:/Program Files/ffmpeg/bin/avfilter-9.dll')
ctypes.CDLL('C:/Program Files/ffmpeg/bin/avformat-60.dll')
ctypes.CDLL('C:/Program Files/ffmpeg/bin/avutil-58.dll')

I still don't know why it is not working without preloading libraries.

[ruliworst]

If I locate the libraries in the same folder of libtorio_ffmpeg6.pyd , they are detected while importing. That is, in Lib/site-packages/torio/lib

EDIT: I have been checking the internal code and in file torchaudio\_extension\__init__.py line 24 there is a code which is not being executed:

if os.name == "nt" and (3, 8) <= sys.version_info < (3, 9):
    _init_dll_path()

This code adds the paths from PATH environment variable to the DLL search path. However, I would like to know why it is only executed in Python 3.8 version.

Thank you.