Reject saving GSM when not compatible (#1384)

test/torchaudio_unittest/backend/sox_io/save_test.py

@@ -305,7 +305,15 @@ class SaveTest(SaveTestBase):
     )
     def test_save_gsm(self, test_mode):
         self.assert_save_consistency(
-            "gsm", test_mode=test_mode)
+            "gsm", num_channels=1, test_mode=test_mode)
+        with self.assertRaises(
+                RuntimeError, msg="gsm format only supports single channel audio."):
+            self.assert_save_consistency(
+                "gsm", num_channels=2, test_mode=test_mode)
+        with self.assertRaises(
+                RuntimeError, msg="gsm format only supports a sampling rate of 8kHz."):
+            self.assert_save_consistency(
+                "gsm", sample_rate=16000, test_mode=test_mode)
 
     @parameterized.expand([
         ("wav", "PCM_S", 16),

torchaudio/csrc/sox/io.cpp

@@ -101,6 +101,13 @@ void save_audio_file(
     const auto num_channels = tensor.size(channels_first ? 0 : 1);
     TORCH_CHECK(
         num_channels == 1, "htk format only supports single channel audio.");
+  } else if (filetype == "gsm") {
+    const auto num_channels = tensor.size(channels_first ? 0 : 1);
+    TORCH_CHECK(
+        num_channels == 1, "gsm format only supports single channel audio.");
+    TORCH_CHECK(
+        sample_rate == 8000,
+        "gsm format only supports a sampling rate of 8kHz.");
   }
   const auto signal_info =
       get_signalinfo(&tensor, sample_rate, filetype, channels_first);
@@ -243,6 +250,16 @@ void save_audio_fileobj(
       throw std::runtime_error(
           "htk format only supports single channel audio.");
     }
+  } else if (filetype == "gsm") {
+    const auto num_channels = tensor.size(channels_first ? 0 : 1);
+    if (num_channels != 1) {
+      throw std::runtime_error(
+          "gsm format only supports single channel audio.");
+    }
+    if (sample_rate != 8000) {
+      throw std::runtime_error(
+          "gsm format only supports a sampling rate of 8kHz.");
+    }
   }
   const auto signal_info =
       get_signalinfo(&tensor, sample_rate, filetype, channels_first);