Added never_convert_lossy_files option to convert plugin

When set to true, this config option chooses copying over converting when the
source file is in a lossy format. At the moment, everything except ape, flac,
alac and wav is considered lossy.

beetsplug/convert.py

@@ -37,6 +37,8 @@ ALIASES = {
     u'vorbis': u'ogg',
 }
 
+LOSSLESS_FORMATS = ['ape', 'flac', 'alac', 'wav']
+
 
 def replace_ext(path, ext):
     """Return the path with its extension replaced by `ext`.
@@ -128,6 +130,8 @@ def should_transcode(item, format):
     """Determine whether the item should be transcoded as part of
     conversion (i.e., its bitrate is high or it has the wrong format).
     """
+    if config['convert']['never_convert_lossy_files'] and not (item.format.lower() in LOSSLESS_FORMATS):
+            return False
     maxbr = config['convert']['max_bitrate'].get(int)
     return format.lower() != item.format.lower() or \
         item.bitrate >= 1000 * maxbr
@@ -308,6 +312,7 @@ class ConvertPlugin(BeetsPlugin):
             u'quiet': False,
             u'embed': True,
             u'paths': {},
+            u'never_convert_lossy_files': False,
         })
         self.import_stages = [self.auto_convert]
 

docs/plugins/convert.rst

@@ -67,6 +67,10 @@ The plugin offers several configuration options, all of which live under the
   adding them to your library.
 * ``quiet`` mode prevents the plugin from announcing every file it processes.
   Default: false.
+* ``never_convert_lossy_files`` means that lossy codecs, such as mp3, ogg vorbis,
+  etc, are never converted, as converting lossy files to other lossy codecs will
+  decrease quality further. If set to true, lossy files are always copied.
+  Default: false
 * ``paths`` lets you specify the directory structure and naming scheme for the
   converted files. Use the same format as the top-level ``paths`` section (see
   :ref:`path-format-config`). By default, the plugin reuses your top-level

test/test_convert.py

@@ -124,6 +124,44 @@ class ConvertCliTest(unittest.TestCase, TestHelper):
         mediafile = MediaFile(converted)
         self.assertEqual(mediafile.images[0].data, image_data)
 
+class NeverConvertLossyFilesTest(unittest.TestCase, TestHelper):
+
+    def setUp(self):
+        self.setup_beets(disk=True)  # Converter is threaded
+        self.album_ogg = self.add_album_fixture(ext='ogg')
+        self.album_flac = self.add_album_fixture(ext='flac')
+        self.load_plugins('convert')
+
+        self.convert_dest = os.path.join(self.temp_dir, 'convert_dest')
+        self.config['convert'] = {
+            'dest': self.convert_dest,
+            'paths': {'default': 'converted'},
+            'never_convert_lossy_files': False,
+            'format': 'mp3',
+            'formats': {
+                'mp3': 'cp $source $dest',
+                'opus': {
+                    'command': 'cp $source $dest',
+                    'extension': 'ops',
+                }
+            }
+        }
+
+    def tearDown(self):
+        self.unload_plugins()
+        self.teardown_beets()
+
+    def test_convert_flac_to_mp3_works(self):
+        with control_stdin('y'):
+            self.run_command('convert', self.album_flac.items()[0].path)
+        converted = os.path.join(self.convert_dest, 'converted.mp3')
+        self.assertTrue(os.path.isfile(converted))
+
+    def test_convert_ogg_to_mp3_prevented(self):
+        with control_stdin('y'):
+            self.run_command('convert', self.album_ogg.items()[0].path)
+        converted = os.path.join(self.convert_dest, 'converted.mp3')
+        self.assertTrue(os.path.isfile(converted))
 
 def suite():
     return unittest.TestLoader().loadTestsFromName(__name__)