Add backend module and isolate backend-related functionalities (#700)

test/common_utils.py

@@ -10,7 +10,7 @@ from torch.testing._internal.common_utils import TestCase
 import torchaudio
 
 _TEST_DIR_PATH = os.path.dirname(os.path.realpath(__file__))
-BACKENDS = torchaudio._backend._BACKENDS
+BACKENDS = torchaudio.list_audio_backends()
 
 
 def get_asset_path(*paths):

torchaudio/__init__.py

@@ -9,20 +9,20 @@ from torchaudio import (
     sox_effects,
     transforms
 )
-from torchaudio._backend import (
+from torchaudio.backend import (
     _get_audio_backend_module,
+    list_audio_backends,
     get_audio_backend,
     set_audio_backend,
-)
-from torchaudio._sox_backend import (
     save_encinfo,
     sox_signalinfo_t,
     sox_encodinginfo_t,
     get_sox_option_t,
     get_sox_encoding_t,
     get_sox_bool,
+    SignalInfo,
+    EncodingInfo,
 )
-from torchaudio._soundfile_backend import SignalInfo, EncodingInfo
 from torchaudio._internal import (
     module_utils as _mod_utils,
     misc_ops as _misc_ops,

torchaudio/backend/__init__.py

+from .utils import (
+    _get_audio_backend_module,
+    list_audio_backends,
+    get_audio_backend,
+    set_audio_backend,
+)
+from .sox_backend import (
+    save_encinfo,
+    sox_signalinfo_t,
+    sox_encodinginfo_t,
+    get_sox_option_t,
+    get_sox_encoding_t,
+    get_sox_bool,
+)
+from .soundfile_backend import (
+    SignalInfo,
+    EncodingInfo,
+)

torchaudio/_sox_backend.py → torchaudio/backend/sox_backend.py

@@ -8,10 +8,10 @@ from torchaudio._internal import (
     module_utils as _mod_utils,
     misc_ops as _misc_ops,
 )
-from torchaudio._soundfile_backend import SignalInfo, EncodingInfo
+from .soundfile_backend import SignalInfo, EncodingInfo
 
 if _mod_utils.is_module_available('torchaudio._torchaudio'):
-    from . import _torchaudio
+    from torchaudio import _torchaudio
 
 
 @_mod_utils.requires_module('torchaudio._torchaudio')

torchaudio/_backend.py → torchaudio/backend/utils.py

 from typing import Any, Optional
 
 from torchaudio._internal import module_utils as _mod_utils
-from . import _soundfile_backend, _sox_backend
+from . import soundfile_backend, sox_backend
 
 _BACKEND = None
 _BACKENDS = {}
 
 if _mod_utils.is_module_available('soundfile'):
-    _BACKENDS['soundfile'] = _soundfile_backend
+    _BACKENDS['soundfile'] = soundfile_backend
 if _mod_utils.is_module_available('torchaudio._torchaudio'):
-    _BACKENDS['sox'] = _sox_backend
+    _BACKENDS['sox'] = sox_backend
 
 if 'sox' in _BACKENDS:
     _BACKEND = 'sox'