Error loading MP3 files from CommonVoice
State: closed

### Describe the bug

When loading a CommonVoice dataset with `datasets==2.9.0` and `torchaudio>=0.12.0`, I get an error reading the audio arrays: 

```python
---------------------------------------------------------------------------
LibsndfileError                           Traceback (most recent call last)
~/.local/lib/python3.8/site-packages/datasets/features/audio.py in _decode_mp3(self, path_or_file)
    310             try:  # try torchaudio anyway because sometimes it works (depending on the os and os packages installed)
--> 311                 array, sampling_rate = self._decode_mp3_torchaudio(path_or_file)
    312             except RuntimeError:

~/.local/lib/python3.8/site-packages/datasets/features/audio.py in _decode_mp3_torchaudio(self, path_or_file)
    351 
--> 352         array, sampling_rate = torchaudio.load(path_or_file, format="mp3")
    353         if self.sampling_rate and self.sampling_rate != sampling_rate:

~/.local/lib/python3.8/site-packages/torchaudio/backend/soundfile_backend.py in load(filepath, frame_offset, num_frames, normalize, channels_first, format)
    204     """
--> 205     with soundfile.SoundFile(filepath, "r") as file_:
    206         if file_.format != "WAV" or normalize:

~/.local/lib/python3.8/site-packages/soundfile.py in __init__(self, file, mode, samplerate, channels, subtype, endian, format, closefd)
    654                                          format, subtype, endian)
--> 655         self._file = self._open(file, mode_int, closefd)
    656         if set(mode).issuperset('r+') and self.seekable():

~/.local/lib/python3.8/site-packages/soundfile.py in _open(self, file, mode_int, closefd)
   1212             err = _snd.sf_error(file_ptr)
-> 1213             raise LibsndfileError(err, prefix="Error opening {0!r}: ".format(self.name))
   1214         if mode_int == _snd.SFM_WRITE:

LibsndfileError: Error opening <_io.BytesIO object at 0x7fa539462090>: File contains data in an unknown format.

```

I assume this is because there's some issue with the mp3 decoding process. I've verified that I have `ffmpeg>=4` (on a Linux distro), which appears to be the fallback backend for `torchaudio,` (at least according to #4889).

### Steps to reproduce the bug

```python
dataset = load_dataset("mozilla-foundation/common_voice_11_0", "be", split="train")
dataset[0]
```

### Expected behavior

Similar behavior to `torchaudio<0.12.0`, which doesn't result in a `LibsndfileError`

### Environment info

- `datasets` version: 2.9.0
- Platform: Linux-5.15.0-52-generic-x86_64-with-glibc2.29
- Python version: 3.8.10
- PyArrow version: 10.0.1
- Pandas version: 1.5.1

Comments:
Hi @kradonneoh, thanks for reporting.

Please note that to work with audio datasets (and specifically with MP3 files) we have detailed installation instructions in our docs: https://huggingface.co/docs/datasets/installation#audio
- one of the requirements is torchaudio<0.12.0

Let us know if the problem persists after having followed them.

I saw that and have followed it (hence the Expected Behavior section of the bug report). 

Is there no intention of updating to the latest version? It does limit the version of `torch` I can use, which isn’t ideal.

@kradonneoh hey! actually with `ffmpeg4` loading of mp3 files should work, so this is a not expected behavior and we need to investigate it. It works on my side with `torchaudio==0.13` and `ffmpeg==4.2.7`. Which `torchaudio` version do you use?

`datasets` should support decoding of mp3 files with `torchaudio` when its version is `>0.12` but as you noted it requires `ffmpeg>4`, we need to fix this in the documentation, thank you for pointing to this! 

But according to your traceback it seems that it tries to use [`libsndfile`](https://github.com/libsndfile/libsndfile) backend for mp3 decoding. And `libsndfile` library supports mp3 decoding starting from version 1.1.0 which on Linux has to be compiled from source for now afaik. 

fyi - we are aiming at getting rid of `torchaudio` dependency at all by the next major library release in favor of `libsndfile` too.

We now decode MP3 with `soundfile`, so I'm closing this issue