Initial Commit

src/librespot/audio/NormalizationData.py

@@ -0,0 +1,50 @@
+from __future__ import annotations
+from librespot.standard import BytesInputStream, DataInputStream, InputStream
+import logging
+import math
+
+
+class NormalizationData:
+    _LOGGER: logging = logging.getLogger(__name__)
+    track_gain_db: float
+    track_peak: float
+    album_gain_db: float
+    album_peak: float
+
+    def __init__(self, track_gain_db: float, track_peak: float,
+                 album_gain_db: float, album_peak: float):
+        self.track_gain_db = track_gain_db
+        self.track_peak = track_peak
+        self.album_gain_db = album_gain_db
+        self.album_peak = album_peak
+
+        self._LOGGER.debug(
+            "Loaded normalization data, track_gain: {}, track_peak: {}, album_gain: {}, album_peak: {}"
+            .format(track_gain_db, track_peak, album_gain_db, album_peak))
+
+    @staticmethod
+    def read(input_stream: InputStream) -> NormalizationData:
+        data_input = DataInputStream(input_stream)
+        data_input.mark(16)
+        skip_bytes = data_input.skip_bytes(144)
+        if skip_bytes != 144:
+            raise IOError()
+
+        data = bytearray(4 * 4)
+        data_input.read_fully(data)
+        data_input.reset()
+
+        buffer = BytesInputStream(data, "<")
+        return NormalizationData(buffer.read_float(), buffer.read_float(),
+                                 buffer.read_float(), buffer.read_float())
+
+    def get_factor(self, normalisation_pregain) -> float:
+        normalisation_factor = float(
+            math.pow(10, (self.track_gain_db + normalisation_pregain) / 20))
+        if normalisation_factor * self.track_peak > 1:
+            self._LOGGER.warning(
+                "Reducing normalisation factor to prevent clipping. Please add negative pregain to avoid."
+            )
+            normalisation_factor = 1 / self.track_peak
+
+        return normalisation_factor