[LG Sound Sync] Document and implement muting

doc/reverse-engineering-lg.md

@@ -87,18 +87,39 @@ Looks like this changes some status bits - cool :-)
 0xf62: 00 00 00 00 00 00 00 00 00 00 02 A0 00 00 00 13 5F 04 8A 60 02 00 8C 04
 ```
 
-## Update: Data from a LG OLED55C9 (with volume 53%)
+### Corresponding status when connected to a LG OLED55C9
 
 ```
 0xf61: 00 00 00 00 00 00 00 00 00 00 02 B0 00 00 00 03 5F 04 8A 60 02 00 0C 04
 0xf62: 00 00 00 00 00 00 00 00 00 00 02 B0 00 00 00 03 5F 04 8A 60 02 00 0C 04
 ```
 
+## Muting
+
+Pressing the mute button on the remote toggles two bits:
+
+```
+0xf61: 00 00 00 00 00 00 00 00 00 00 04 E0 00 00 00 05 0F 04 8A 60 02 00 0C 04
+                                      |              |
+0xf61: 00 00 00 00 00 00 00 00 00 00 0C E0 00 00 00 0D 0F 04 8A 60 02 00 0C 04
+```
+
+More visible at the bit level:
+
+```
+                                      4: 0100        5: 0101
+                                      |  |           |  |
+                                      C: 1100        D: 1101
+```
+
+(Data collected using a LG OLED55C9 with volume set to 80%.)
+
 ## Conclusions
 
 It seems the volume information is encoded multiple times.
 
-It might be the easiest way to use byte 16.5 (half of byte 16 and 17) that gives the volume as 0-100.
+It might be the easiest way to use byte 16.5 (half of byte 16 and 17) that gives the volume as 0-100 when unmuted.
+When muted, the first bit in that byte is set.
 
 Checking bytes 17.5/19 for 0xF048A seems to indicate that Sound Sync is active.
 

hifiberrydsp/lg/soundsync.py

@@ -27,11 +27,11 @@
 
 from threading import Thread
 
-from hifiberrydsp.hardware.adau145x import Adau145x
 from hifiberrydsp.filtering.volume import percent2amplification
 from hifiberrydsp import datatools
 
 try:
+    from hifiberrydsp.hardware.adau145x import Adau145x
     from hifiberrydsp.hardware.spi import SpiHandler
     # depends on spidev and is not required to run tests
 except:
@@ -86,29 +86,32 @@ def is_spdif_active(self):
 
     def try_read_volume(self):
         spdif_status_register = 0xf617
-        return self.parse_volume_from_status(self.spi.read(spdif_status_register, 6))
+        return self.parse_volume_from_status(self.spi.read(spdif_status_register, 5))
 
     # Volume    ~~~~~
-    #      0: 00f048a..$  This is what the SPDIF status registers look like with different volume levels set.
-    #      1: 01f048a..$
-    #      2: 02f048a..$  We check for f048a (SIGNATURE_VALUE) to see if LG Sound Sync is enabled.
-    #      3: 03f048a..$
-    #    100: 64f048a..$  The byte to the left is the volume we want to extract.
-    #         ~~
-    SIGNATURE_SHIFT = 2 * 4
+    #      0: 00f048a$  This is what the SPDIF status registers look like with different volume levels set.
+    #      1: 01f048a$
+    #      2: 02f048a$  We check for f048a (SIGNATURE_VALUE) to see if LG Sound Sync is enabled.
+    #      3: 03f048a$
+    #    100: 64f048a$  The byte to the left is the volume we want to extract.
+    #         ~~        The first bit is set to 1 when muted.
     SIGNATURE_MASK = 0xfffff
     SIGNATURE_VALUE = 0xf048a
-    VOLUME_SHIFT = 7 * 4
-    VOLUME_MASK = 0xff
+    SHIFT = 5 * 4
+    MUTE_MASK = 0b10000000
+    VOLUME_MASK = 0b01111111
 
     @staticmethod
     def parse_volume_from_status(data):
         bits = int.from_bytes(data, byteorder="big")
 
-        if bits >> SoundSync.SIGNATURE_SHIFT & SoundSync.SIGNATURE_MASK == SoundSync.SIGNATURE_VALUE:
-            return bits >> SoundSync.VOLUME_SHIFT & SoundSync.VOLUME_MASK
+        if bits & SoundSync.SIGNATURE_MASK != SoundSync.SIGNATURE_VALUE:
+            return None
 
-        return None
+        if bits >> SoundSync.SHIFT & SoundSync.MUTE_MASK:
+            return 0
+
+        return bits >> SoundSync.SHIFT & SoundSync.VOLUME_MASK
 
     def write_volume(self, volume):
         assert 0 <= volume <= 100

hifiberrydsp/lg/test_soundsync.py

@@ -4,22 +4,20 @@
 
 class TestSoundSync(TestCase):
     def test_parse_volume_with_missing_sound_sync_signature(self):
-        assert SoundSync.parse_volume_from_status(b'\xff\xff\xff\xff\xff\xff') is None
-
-    def test_parse_out_of_range_volume(self):
-        # The maximum value is 100, but we don't enforce that in the parser itself,
-        # but rather in later validation.
-        assert SoundSync.parse_volume_from_status(b'\x00\x1f\xff\x04\x8a\x62') == 255
+        assert SoundSync.parse_volume_from_status(b'\xff\xff\xff\xff\xff') is None
 
     def test_parse_volume_of_0(self):
-        assert SoundSync.parse_volume_from_status(b'\x00\x10\x0f\x04\x8a\x62') == 0
+        assert SoundSync.parse_volume_from_status(b'\x00\x10\x0f\x04\x8a') == 0
 
     def test_parse_volume_of_50(self):
-        assert SoundSync.parse_volume_from_status(b'\x00\x13\x2f\x04\x8a\x62') == 50
+        assert SoundSync.parse_volume_from_status(b'\x00\x13\x2f\x04\x8a') == 50
 
     def test_parse_volume_of_100(self):
-        assert SoundSync.parse_volume_from_status(b'\x00\x16\x4f\x04\x8a\x62') == 100
+        assert SoundSync.parse_volume_from_status(b'\x00\x16\x4f\x04\x8a') == 100
 
     def test_parse_volume_of_100_on_another_tv(self):
         # Data observed on a LG OLED55C9
-        assert SoundSync.parse_volume_from_status(b'\x00\x06\x4f\x04\x8a\x60') == 100
+        assert SoundSync.parse_volume_from_status(b'\x00\x06\x4f\x04\x8a') == 100
+
+    def test_parse_volume_of_muted_tv(self):
+        assert SoundSync.parse_volume_from_status(b'\x00\x0d\x0f\x04\x8a') == 0