feat: add FLAC lossless format support and refactor quality pickers (while staying backward compatible)

- Add `FLAC_FLAC` (16), `FLAC_FLAC_24BIT` (22) format codes (based on librespot-org/librespot#796, librespot-org/librespot#1424)
- Regenerate Metadata_pb2.py with protoc 3.20.1
- Add enums: `SuperAudioFormat.FLAC`, `AudioQuality.LOSSLESS`
- Refactor to generic DRY `FormatOnlyAudioQuality` base class while maintaining existing `VorbisOnlyAudioQuality` as wrapper
- Remove `AAC_24_NORM` (replaced by `FLAC_FLAC` at code 16)

librespot/audio/decoders.py

@@ -12,13 +12,13 @@ class AudioQuality(enum.Enum):
     NORMAL = 0x00
     HIGH = 0x01
     VERY_HIGH = 0x02
+    LOSSLESS = 0x03
 
     @staticmethod
     def get_quality(audio_format: AudioFile.Format) -> AudioQuality:
         if audio_format in [
                 AudioFile.MP3_96,
                 AudioFile.OGG_VORBIS_96,
-                AudioFile.AAC_24_NORM,
         ]:
             return AudioQuality.NORMAL
         if audio_format in [
@@ -35,6 +35,11 @@ class AudioQuality(enum.Enum):
                 AudioFile.AAC_48,
         ]:
             return AudioQuality.VERY_HIGH
+        if audio_format in [
+                AudioFile.FLAC_FLAC,
+                AudioFile.FLAC_FLAC_24BIT,
+        ]:
+            return AudioQuality.LOSSLESS
         raise RuntimeError("Unknown format: {}".format(audio_format))
 
     def get_matches(self,
@@ -47,35 +52,71 @@ class AudioQuality(enum.Enum):
         return file_list
 
 
-class VorbisOnlyAudioQuality(AudioQualityPicker):
-    logger = logging.getLogger("Librespot:Player:VorbisOnlyAudioQuality")
-    preferred: AudioQuality
+class FormatOnlyAudioQuality(AudioQualityPicker):
+    # Generic quality picker; filters files by container format
 
-    def __init__(self, preferred: AudioQuality):
+    logger = logging.getLogger("Librespot:Player:FormatOnlyAudioQuality")
+    preferred: AudioQuality
+    format_filter: SuperAudioFormat
+
+    def __init__(self, preferred: AudioQuality, format_filter: SuperAudioFormat):
         self.preferred = preferred
+        self.format_filter = format_filter
 
     @staticmethod
-    def get_vorbis_file(files: typing.List[Metadata.AudioFile]):
+    def get_file_by_format(files: typing.List[Metadata.AudioFile],
+                           format_type: SuperAudioFormat) -> typing.Optional[Metadata.AudioFile]:
         for file in files:
             if file.HasField("format") and SuperAudioFormat.get(
-                    file.format) == SuperAudioFormat.VORBIS:
+                    file.format) == format_type:
                 return file
         return None
 
-    def get_file(self, files: typing.List[Metadata.AudioFile]):
-        matches: typing.List[Metadata.AudioFile] = self.preferred.get_matches(
-            files)
-        vorbis: Metadata.AudioFile = VorbisOnlyAudioQuality.get_vorbis_file(
-            matches)
-        if vorbis is None:
-            vorbis: Metadata.AudioFile = VorbisOnlyAudioQuality.get_vorbis_file(
-                files)
-            if vorbis is not None:
+    def get_file(self, files: typing.List[Metadata.AudioFile]) -> typing.Optional[Metadata.AudioFile]:
+        quality_matches: typing.List[Metadata.AudioFile] = self.preferred.get_matches(files)
+
+        selected_file = self.get_file_by_format(quality_matches, self.format_filter)
+
+        if selected_file is None:
+            # Try using any file matching the format, regardless of quality
+            selected_file = self.get_file_by_format(files, self.format_filter)
+
+            if selected_file is not None:
+                # Found format match (different quality than preferred)
                 self.logger.warning(
-                    "Using {} because preferred {} couldn't be found.".format(
-                        Metadata.AudioFile.Format.Name(vorbis.format),
-                        self.preferred))
+                    "Using {} format file with {} quality because preferred {} quality couldn't be found.".format(
+                        self.format_filter.name,
+                        AudioQuality.get_quality(selected_file.format).name,
+                        self.preferred.name))
             else:
+                available_formats = [SuperAudioFormat.get(f.format).name
+                                   for f in files if f.HasField("format")]
                 self.logger.fatal(
-                    "Couldn't find any Vorbis file, available: {}")
-        return vorbis
+                    "Couldn't find any {} file. Available formats: {}".format(
+                        self.format_filter.name,
+                        ", ".join(set(available_formats)) if available_formats else "none"))
+
+        return selected_file
+
+
+# Backward-compatible wrapper classes
+
+class VorbisOnlyAudioQuality(FormatOnlyAudioQuality):
+    logger = logging.getLogger("Librespot:Player:VorbisOnlyAudioQuality")
+
+    def __init__(self, preferred: AudioQuality):
+        super().__init__(preferred, SuperAudioFormat.VORBIS)
+
+    @staticmethod
+    def get_vorbis_file(files: typing.List[Metadata.AudioFile]) -> typing.Optional[Metadata.AudioFile]:
+        return FormatOnlyAudioQuality.get_file_by_format(files, SuperAudioFormat.VORBIS)
+
+class LosslessOnlyAudioQuality(FormatOnlyAudioQuality):
+    logger = logging.getLogger("Librespot:Player:LosslessOnlyAudioQuality")
+
+    def __init__(self, preferred: AudioQuality):
+        super().__init__(preferred, SuperAudioFormat.FLAC)
+
+    @staticmethod
+    def get_flac_file(files: typing.List[Metadata.AudioFile]) -> typing.Optional[Metadata.AudioFile]:
+        return FormatOnlyAudioQuality.get_file_by_format(files, SuperAudioFormat.FLAC)

librespot/audio/format.py

@@ -6,6 +6,7 @@ class SuperAudioFormat(enum.Enum):
     MP3 = 0x00
     VORBIS = 0x01
     AAC = 0x02
+    FLAC = 0x03
 
     @staticmethod
     def get(audio_format: Metadata.AudioFile.Format):
@@ -26,7 +27,11 @@ class SuperAudioFormat(enum.Enum):
         if audio_format in [
                 Metadata.AudioFile.Format.AAC_24,
                 Metadata.AudioFile.Format.AAC_48,
-                Metadata.AudioFile.Format.AAC_24_NORM,
         ]:
             return SuperAudioFormat.AAC
+        if audio_format in [
+                Metadata.AudioFile.Format.FLAC_FLAC,
+                Metadata.AudioFile.Format.FLAC_FLAC_24BIT,
+        ]:
+            return SuperAudioFormat.FLAC
         raise RuntimeError("Unknown audio format: {}".format(audio_format))