app, mp3player: Hook up playlists 'offset' persist mode

Signed-off-by: Matthias Blankertz <matthias@blankertz.org>

software/src/app.py

@@ -48,7 +48,10 @@ class PlayerApp:
         if self.current_tag is not None:
             print('Tag gone, stopping playback')
             self.current_tag = None
-            self.player.stop()
+            if self.playlist is not None:
+                pos = self.player.stop()
+                if pos is not None:
+                    self.playlist.setPlaybackOffset(pos)
 
     def onButtonPressed(self, what):
         assert self.buttons is not None
@@ -69,7 +72,8 @@ class PlayerApp:
 
     def _set_playlist(self, tag: bytes):
         self.playlist = self.playlist_db.getPlaylistForTag(tag)
-        self._play(self.playlist.getCurrentPath() if self.playlist is not None else None)
+        self._play(self.playlist.getCurrentPath() if self.playlist is not None else None,
+                   self.playlist.getPlaybackOffset() if self.playlist is not None else 0)
 
     def _play_next(self):
         if self.playlist is None:
@@ -79,7 +83,7 @@ class PlayerApp:
         if filename is None:
             self.playlist = None
 
-    def _play(self, filename: bytes | None):
+    def _play(self, filename: bytes | None, offset=0):
         if self.mp3file is not None:
             self.player.stop()
             self.mp3file.close()
@@ -87,4 +91,4 @@ class PlayerApp:
         if filename is not None:
             print(f'Playing {filename!r}')
             self.mp3file = open(filename, 'rb')
-            self.player.play(self.mp3file)
+            self.player.play(self.mp3file, offset)

software/src/mp3player.py

@@ -21,14 +21,19 @@ class MP3Player:
         self.mp3task = None
         self.volume = 128
         self.cb = cb
+        self.pos = 0
 
-    def play(self, stream):
+    def play(self, stream, offset=0):
         """
         Play from byte stream.
+        If offset > 0, discard the first offset bytes
         """
         if self.mp3task is not None:
             self.mp3task.cancel()
             self.mp3task = None
+        if offset > 0:
+            stream.seek(offset, 1)
+        self.pos = offset
         self.mp3task = asyncio.create_task(self._play_task(stream))
 
     def stop(self):
@@ -38,6 +43,8 @@ class MP3Player:
         if self.mp3task is not None:
             self.mp3task.cancel()
             self.mp3task = None
+            return self.pos
+        return None
 
     def set_volume(self, volume: int):
         """
@@ -60,6 +67,7 @@ class MP3Player:
                     # End of file
                     break
                 _, _, underruns = await self.audiocore.async_put(data[:bytes_read])
+                self.pos += bytes_read
                 if underruns > known_underruns:
                     print(f"{underruns:x}")
                     known_underruns = underruns

software/tests/test_playerapp.py

@@ -35,7 +35,7 @@ class FakeMp3Player:
     def set_volume(self, vol: int):
         self.volume = vol
 
-    def play(self, track: FakeFile):
+    def play(self, track: FakeFile, offset: int):
         self.track = track
 
 
@@ -67,6 +67,9 @@ class FakePlaylistDb:
                 return None
             return self.parent.tracklist[self.pos]
 
+        def getPlaybackOffset(self):
+            return 0
+
     def __init__(self, tracklist=[b'test/path.mp3']):
         self.tracklist = tracklist