Bugfix: -o m4a would fail [Fixes #720]

In FFmpeg, a given encoding may not always point to the same format
string.

spotdl/encode/encode_base.py

@@ -21,6 +21,13 @@ from spotdl.encode.exceptions import EncoderNotFoundError
 
 """
 
+_TARGET_FORMATS_FROM_ENCODING = {
+    "m4a": "mp4",
+    "mp3": "mp3",
+    "opus": "opus",
+    "flac": "flac"
+}
+
 
 class EncoderBase(ABC):
     """
@@ -44,6 +51,7 @@ class EncoderBase(ABC):
         self.encoder_path = encoder_path
         self._loglevel = loglevel
         self._additional_arguments = additional_arguments
+        self._target_formats_from_encoding = _TARGET_FORMATS_FROM_ENCODING
 
     def set_argument(self, argument):
         """
@@ -94,6 +102,14 @@ class EncoderBase(ABC):
         """
         pass
 
+    def target_format_from_encoding(self, encoding):
+        """
+        This method generates the target stream format from given
+        input encoding.
+        """
+        target_format = self._target_formats_from_encoding[encoding]
+        return target_format
+
     def re_encode_from_stdin(self, input_encoding, target_path):
         """
         This method must invoke the encoder to encode stdin to a

spotdl/encode/encoders/ffmpeg.py

@@ -76,7 +76,7 @@ class EncoderFFmpeg(EncoderBase):
             + ["-i", input_path] \
             + arguments.split() \
             + self._additional_arguments \
-            + ["-f", target_encoding] \
+            + ["-f", self.target_format_from_encoding(target_encoding)] \
             + [target_file]
 
         return command

spotdl/encode/encoders/tests/test_ffmpeg.py

@@ -48,7 +48,7 @@ class TestEncodingDefaults:
             '-acodec', 'copy',
             '-b:a', '192k',
             '-vn',
-            '-f', 'm4a',
+            '-f', 'mp4',
              target_path
         ]
         return command
@@ -112,7 +112,7 @@ class TestEncodingInDebugMode:
             '-acodec', 'copy',
             '-b:a', '192k',
             '-vn',
-            '-f', 'm4a',
+            '-f', 'mp4',
              target_path
         ]
         return command
@@ -180,7 +180,7 @@ class TestEncodingAndTrimSilence:
             '-b:a', '192k',
             '-vn',
             '-af', 'silenceremove=start_periods=1',
-            '-f', 'm4a',
+            '-f', 'mp4',
             target_path
         ]
         return command

spotdl/encode/tests/test_encode_base.py

@@ -86,3 +86,12 @@ class TestMethods:
     def test_encoder_not_found_error(self):
         with pytest.raises(EncoderNotFoundError):
             self.EncoderKid("/a/nonexistent/path", "0", [])
+
+    @pytest.mark.parametrize("encoding, target_format", [
+        ("m4a", "mp4"),
+        ("mp3", "mp3"),
+        ("opus", "opus"),
+        ("flac", "flac"),
+    ])
+    def test_target_format_from_encoding(self, encoderkid, encoding, target_format):
+        assert encoderkid.target_format_from_encoding(encoding) == target_format