Add target `dtype` argument to `save` function for sox backend (#1204)

test/torchaudio_unittest/sox_io_backend/save_test.py

 import io
 import itertools
 
+import torch
 from torchaudio.backend import sox_io_backend
 from parameterized import parameterized
 
@@ -24,7 +25,7 @@ class SaveTestBase(TempDirMixin, PytorchTestCase):
         """`sox_io_backend.save` can save wav format."""
         path = self.get_temp_path('data.wav')
         expected = get_wav_data(dtype, num_channels, num_frames=num_frames)
-        sox_io_backend.save(path, expected, sample_rate)
+        sox_io_backend.save(path, expected, sample_rate, dtype=None)
         found, sr = load_wav(path)
         assert sample_rate == sr
         self.assertEqual(found, expected)
@@ -68,7 +69,7 @@ class SaveTestBase(TempDirMixin, PytorchTestCase):
         save_wav(src_path, data, sample_rate)
         # 2.1. Convert the original wav to mp3 with torchaudio
         sox_io_backend.save(
-            mp3_path, load_wav(src_path)[0], sample_rate, compression=bit_rate)
+            mp3_path, load_wav(src_path)[0], sample_rate, compression=bit_rate, dtype=None)
         # 2.2. Convert the mp3 to wav with Sox
         sox_utils.convert_audio_file(mp3_path, wav_path)
         # 2.3. Load
@@ -99,7 +100,7 @@ class SaveTestBase(TempDirMixin, PytorchTestCase):
         save_wav(src_path, data, sample_rate)
         # 2.1. Convert the original wav to flac with torchaudio
         sox_io_backend.save(
-            flc_path, load_wav(src_path)[0], sample_rate, compression=compression_level)
+            flc_path, load_wav(src_path)[0], sample_rate, compression=compression_level, dtype=None)
         # 2.2. Convert the flac to wav with Sox
         # converting to 32 bit because flac file has 24 bit depth which scipy cannot handle.
         sox_utils.convert_audio_file(flc_path, wav_path, bit_depth=32)
@@ -132,7 +133,7 @@ class SaveTestBase(TempDirMixin, PytorchTestCase):
         save_wav(src_path, data, sample_rate)
         # 2.1. Convert the original wav to vorbis with torchaudio
         sox_io_backend.save(
-            vbs_path, load_wav(src_path)[0], sample_rate, compression=quality_level)
+            vbs_path, load_wav(src_path)[0], sample_rate, compression=quality_level, dtype=None)
         # 2.2. Convert the vorbis to wav with Sox
         sox_utils.convert_audio_file(vbs_path, wav_path)
         # 2.3. Load
@@ -184,7 +185,7 @@ class SaveTestBase(TempDirMixin, PytorchTestCase):
         data = get_wav_data('float32', num_channels, normalize=True, num_frames=duration * sample_rate)
         save_wav(src_path, data, sample_rate)
         # 2.1. Convert the original wav to sph with torchaudio
-        sox_io_backend.save(flc_path, load_wav(src_path)[0], sample_rate)
+        sox_io_backend.save(flc_path, load_wav(src_path)[0], sample_rate, dtype=None)
         # 2.2. Convert the sph to wav with Sox
         # converting to 32 bit because sph file has 24 bit depth which scipy cannot handle.
         sox_utils.convert_audio_file(flc_path, wav_path, bit_depth=32)
@@ -216,7 +217,7 @@ class SaveTestBase(TempDirMixin, PytorchTestCase):
         data = get_wav_data(dtype, num_channels, normalize=False, num_frames=duration * sample_rate)
         save_wav(src_path, data, sample_rate)
         # 2.1. Convert the original wav to amb with torchaudio
-        sox_io_backend.save(amb_path, load_wav(src_path, normalize=False)[0], sample_rate)
+        sox_io_backend.save(amb_path, load_wav(src_path, normalize=False)[0], sample_rate, dtype=None)
         # 2.2. Convert the amb to wav with Sox
         sox_utils.convert_audio_file(amb_path, wav_path)
         # 2.3. Load
@@ -248,7 +249,7 @@ class SaveTestBase(TempDirMixin, PytorchTestCase):
         data = get_wav_data('int16', num_channels, normalize=False, num_frames=duration * sample_rate)
         save_wav(src_path, data, sample_rate)
         # 2.1. Convert the original wav to amr_nb with torchaudio
-        sox_io_backend.save(amr_path, load_wav(src_path, normalize=False)[0], sample_rate)
+        sox_io_backend.save(amr_path, load_wav(src_path, normalize=False)[0], sample_rate, dtype=None)
         # 2.2. Convert the amr_nb to wav with Sox
         sox_utils.convert_audio_file(amr_path, wav_path)
         # 2.3. Load
@@ -389,7 +390,7 @@ class TestSaveParams(TempDirMixin, PytorchTestCase):
         path = self.get_temp_path('data.wav')
         data = get_wav_data('int32', 2, channels_first=channels_first)
         sox_io_backend.save(
-            path, data, 8000, channels_first=channels_first)
+            path, data, 8000, channels_first=channels_first, dtype=None)
         found = load_wav(path)[0]
         expected = data if channels_first else data.transpose(1, 0)
         self.assertEqual(found, expected)
@@ -402,7 +403,7 @@ class TestSaveParams(TempDirMixin, PytorchTestCase):
         path = self.get_temp_path('data.wav')
         expected = get_wav_data(dtype, 4)[::2, ::2]
         assert not expected.is_contiguous()
-        sox_io_backend.save(path, expected, 8000)
+        sox_io_backend.save(path, expected, 8000, dtype=None)
         found = load_wav(path)[0]
         self.assertEqual(found, expected)
 
@@ -415,10 +416,24 @@ class TestSaveParams(TempDirMixin, PytorchTestCase):
         expected = get_wav_data(dtype, 4)[::2, ::2]
 
         data = expected.clone()
-        sox_io_backend.save(path, data, 8000)
+        sox_io_backend.save(path, data, 8000, dtype=None)
 
         self.assertEqual(data, expected)
 
+    @parameterized.expand([
+        ('float32', torch.tensor([-1.0, -0.5, 0, 0.5, 1.0]).to(torch.float32)),
+        ('int32', torch.tensor([-2147483648, -1073741824, 0, 1073741824, 2147483647]).to(torch.int32)),
+        ('int16', torch.tensor([-32768, -16384, 0, 16384, 32767]).to(torch.int16)),
+        ('uint8', torch.tensor([0, 64, 128, 192, 255]).to(torch.uint8)),
+    ])
+    def test_dtype_conversion(self, dtype, expected):
+        """`save` performs dtype conversion on float32 src tensors only."""
+        path = self.get_temp_path("data.wav")
+        data = torch.tensor([-1.0, -0.5, 0, 0.5, 1.0]).to(torch.float32).view(-1, 1)
+        sox_io_backend.save(path, data, 8000, dtype=dtype)
+        found = load_wav(path, normalize=False)[0]
+        self.assertEqual(found, expected.view(-1, 1))
+
 
 @skipIfNoExtension
 @skipIfNoExec('sox')
@@ -452,11 +467,11 @@ class TestFileObject(SaveTestBase):
         res_path = self.get_temp_path(f'test.{ext}')
         sox_io_backend.save(
             ref_path, data, channels_first=channels_first,
-            sample_rate=sample_rate, compression=compression)
+            sample_rate=sample_rate, compression=compression, dtype=None)
         with open(res_path, 'wb') as fileobj:
             sox_io_backend.save(
                 fileobj, data, channels_first=channels_first,
-                sample_rate=sample_rate, compression=compression, format=ext)
+                sample_rate=sample_rate, compression=compression, format=ext, dtype=None)
 
         expected_data, _ = sox_io_backend.load(ref_path)
         data, sr = sox_io_backend.load(res_path)
@@ -489,11 +504,11 @@ class TestFileObject(SaveTestBase):
         res_path = self.get_temp_path(f'test.{ext}')
         sox_io_backend.save(
             ref_path, data, channels_first=channels_first,
-            sample_rate=sample_rate, compression=compression)
+            sample_rate=sample_rate, compression=compression, dtype=None)
         fileobj = io.BytesIO()
         sox_io_backend.save(
             fileobj, data, channels_first=channels_first,
-            sample_rate=sample_rate, compression=compression, format=ext)
+            sample_rate=sample_rate, compression=compression, format=ext, dtype=None)
         fileobj.seek(0)
         with open(res_path, 'wb') as file_:
             file_.write(fileobj.read())

torchaudio/backend/sox_io_backend.py

 import os
+import warnings
 from typing import Tuple, Optional
 
 import torch
@@ -178,15 +179,16 @@ def _save(
         channels_first: bool = True,
         compression: Optional[float] = None,
         format: Optional[str] = None,
+        dtype: Optional[str] = None,
 ):
     if hasattr(filepath, 'write'):
         if format is None:
             raise RuntimeError('`format` is required when saving to file object.')
         torchaudio._torchaudio.save_audio_fileobj(
-            filepath, src, sample_rate, channels_first, compression, format)
+            filepath, src, sample_rate, channels_first, compression, format, dtype)
     else:
         torch.ops.torchaudio.sox_io_save_audio_file(
-            os.fspath(filepath), src, sample_rate, channels_first, compression, format)
+            os.fspath(filepath), src, sample_rate, channels_first, compression, format, dtype)
 
 
 @_mod_utils.requires_module('torchaudio._torchaudio')
@@ -197,6 +199,7 @@ def save(
         channels_first: bool = True,
         compression: Optional[float] = None,
         format: Optional[str] = None,
+        dtype: Optional[str] = None,
 ):
     """Save audio data to file.
 
@@ -243,12 +246,22 @@ def save(
         format (str, optional):
             Output audio format. This is required when the output audio format cannot be infered from
             ``filepath``, (such as file extension or ``name`` attribute of the given file object).
+        dtype (str, optional)
+            Output tensor dtype.
+            Valid values: ``"uint8", "int16", "int32", "float32", "float64", None``
+            ``dtype=None`` means no conversion is performed.
+            ``dtype`` parameter is only effective for ``float32`` Tensor.
     """
+    if src.dtype == torch.float32 and dtype is None:
+        warnings.warn(
+            '`dtype` default value will be changed to `int16` in 0.9 release.'
+            'Specify `dtype` to suppress this warning.'
+        )
     if not torch.jit.is_scripting():
-        _save(filepath, src, sample_rate, channels_first, compression, format)
+        _save(filepath, src, sample_rate, channels_first, compression, format, dtype)
         return
     torch.ops.torchaudio.sox_io_save_audio_file(
-        filepath, src, sample_rate, channels_first, compression, format)
+        filepath, src, sample_rate, channels_first, compression, format, dtype)
 
 
 @_mod_utils.requires_module('torchaudio._torchaudio')

torchaudio/csrc/sox/io.cpp

@@ -107,10 +107,19 @@ void save_audio_file(
     int64_t sample_rate,
     bool channels_first,
     c10::optional<double> compression,
-    c10::optional<std::string> format) {
+    c10::optional<std::string> format,
+    c10::optional<std::string> dtype) {
   validate_input_tensor(tensor);
 
   auto signal = TensorSignal(tensor, sample_rate, channels_first);
+  if (tensor.dtype() != torch::kFloat32 && dtype.has_value()) {
+    throw std::runtime_error(
+        "dtype conversion only supported for float32 tensors");
+  }
+  const auto tgt_dtype =
+      (tensor.dtype() == torch::kFloat32 && dtype.has_value())
+      ? get_dtype_from_str(dtype.value())
+      : tensor.dtype();
 
   const auto filetype = [&]() {
     if (format.has_value())
@@ -124,8 +133,7 @@ void save_audio_file(
     tensor = (unnormalize_wav(tensor) / 65536).to(torch::kInt16);
   }
   const auto signal_info = get_signalinfo(&signal, filetype);
-  const auto encoding_info =
-      get_encodinginfo(filetype, tensor.dtype(), compression);
+  const auto encoding_info = get_encodinginfo(filetype, tgt_dtype, compression);
 
   SoxFormat sf(sox_open_write(
       path.c_str(),
@@ -239,10 +247,19 @@ void save_audio_fileobj(
     int64_t sample_rate,
     bool channels_first,
     c10::optional<double> compression,
-    std::string filetype) {
+    std::string filetype,
+    c10::optional<std::string> dtype) {
   validate_input_tensor(tensor);
 
   auto signal = TensorSignal(tensor, sample_rate, channels_first);
+  if (tensor.dtype() != torch::kFloat32 && dtype.has_value()) {
+    throw std::runtime_error(
+        "dtype conversion only supported for float32 tensors");
+  }
+  const auto tgt_dtype =
+      (tensor.dtype() == torch::kFloat32 && dtype.has_value())
+      ? get_dtype_from_str(dtype.value())
+      : tensor.dtype();
 
   if (filetype == "amr-nb") {
     const auto num_channels = tensor.size(channels_first ? 0 : 1);
@@ -253,8 +270,7 @@ void save_audio_fileobj(
     tensor = (unnormalize_wav(tensor) / 65536).to(torch::kInt16);
   }
   const auto signal_info = get_signalinfo(&signal, filetype);
-  const auto encoding_info =
-      get_encodinginfo(filetype, tensor.dtype(), compression);
+  const auto encoding_info = get_encodinginfo(filetype, tgt_dtype, compression);
 
   AutoReleaseBuffer buffer;
 

torchaudio/csrc/sox/io.h

@@ -46,7 +46,8 @@ void save_audio_file(
     int64_t sample_rate,
     bool channels_first,
     c10::optional<double> compression,
-    c10::optional<std::string> format);
+    c10::optional<std::string> format,
+    c10::optional<std::string> dtype);
 
 #ifdef TORCH_API_INCLUDE_EXTENSION_H
 
@@ -68,7 +69,8 @@ void save_audio_fileobj(
     int64_t sample_rate,
     bool channels_first,
     c10::optional<double> compression,
-    std::string filetype);
+    std::string filetype,
+    c10::optional<std::string> dtype);
 
 #endif // TORCH_API_INCLUDE_EXTENSION_H
 

torchaudio/csrc/sox/utils.cpp

@@ -156,6 +156,24 @@ caffe2::TypeMeta get_dtype(
   return c10::scalarTypeToTypeMeta(dtype);
 }
 
+caffe2::TypeMeta get_dtype_from_str(const std::string dtype) {
+  const auto tgt_dtype = [&]() {
+    if (dtype == "uint8")
+      return torch::kUInt8;
+    else if (dtype == "int16")
+      return torch::kInt16;
+    else if (dtype == "int32")
+      return torch::kInt32;
+    else if (dtype == "float32")
+      return torch::kFloat32;
+    else if (dtype == "float64")
+      return torch::kFloat64;
+    else
+      throw std::runtime_error("Unsupported dtype");
+  }();
+  return c10::scalarTypeToTypeMeta(tgt_dtype);
+}
+
 torch::Tensor convert_to_tensor(
     sox_sample_t* buffer,
     const int32_t num_samples,

torchaudio/csrc/sox/utils.h

@@ -85,6 +85,8 @@ caffe2::TypeMeta get_dtype(
     const sox_encoding_t encoding,
     const unsigned precision);
 
+caffe2::TypeMeta get_dtype_from_str(const std::string dtype);
+
 ///
 /// Convert sox_sample_t buffer to uint8/int16/int32/float32 Tensor
 /// NOTE: This function might modify the values in the input buffer to