add software gain boost parameter for input signal amplification

AGENTS.md

@@ -7,5 +7,6 @@
 
 ## Application
 - this is a bluetooth Auracast transmitter application
+- if you add a new parameter for a stream make sure it is saved to the settings.json so it is persisted
 - it consists of multicast_frontend.py and multicast_server.py mainly which connect to each other via a rest api
-
+- after you implemented something the user will mainly test it and you should call the update_and_run_server_and_frontend.sh script if the server and frontend were already running.

src/auracast/auracast_config.py

@@ -55,6 +55,7 @@ class AuracastBigConfig(BaseModel):
     precode_wav: bool = False
     iso_que_len: int = 64
     num_bis: int = 1  # 1 = mono (FRONT_LEFT), 2 = stereo (FRONT_LEFT + FRONT_RIGHT)
+    input_gain_db: float = 0.0  # Software gain boost in dB applied before LC3 encoding (0 = off, max 20)
 
 class AuracastBigConfigDeu(AuracastBigConfig):
     id: int = 12

src/auracast/multicast.py

@@ -805,6 +805,13 @@ class Streamer():
                 big['encoder'] = encoders[0]
                 big['precoded'] = False
 
+            # Pre-compute software gain multiplier from dB config (0 dB = 1.0 = no change)
+            gain_db = getattr(big_config[i], 'input_gain_db', 0.0)
+            gain_db = max(0.0, min(20.0, float(gain_db)))
+            big['_gain_linear'] = 10.0 ** (gain_db / 20.0) if gain_db > 0 else 0.0
+            if big['_gain_linear'] > 0.0:
+                logging.info("Software gain for BIG %d: +%.1f dB (linear %.3f)", i, gain_db, big['_gain_linear'])
+
         logging.info("Streaming audio...")
         bigs = self.bigs
         self.is_streaming = True
@@ -852,6 +859,14 @@ class Streamer():
                         stream_finished[i] = True
                         continue
 
+                    # Apply software gain boost if configured (> 0 dB)
+                    gain_lin = big.get('_gain_linear', 0.0)
+                    if gain_lin > 0.0:
+                        pcm_arr = np.frombuffer(pcm_frame, dtype=np.int16).astype(np.float32)
+                        pcm_arr *= gain_lin
+                        np.clip(pcm_arr, -32768, 32767, out=pcm_arr)
+                        pcm_frame = pcm_arr.astype(np.int16).tobytes()
+
                     # Measure LC3 encoding time
                     t1 = time.perf_counter()
                     num_bis = big.get('num_bis', 1)

src/auracast/server/multicast_frontend.py

@@ -198,6 +198,7 @@ else:
 
 # Analog gain control (only for Analog mode, placed below start button)
 analog_gain_value = 50  # default
+software_boost_db = 0  # default
 if audio_mode == "Analog":
     saved_analog_gain = saved_settings.get('analog_gain', 50)
     analog_gain_value = st.slider(
@@ -209,6 +210,16 @@ if audio_mode == "Analog":
         disabled=is_streaming,
         help="ADC gain level for both analog inputs (10-60%). Default is 50%."
     )
+    saved_boost = saved_settings.get('software_boost_db', 0)
+    software_boost_db = st.slider(
+        "Software Boost (dB)",
+        min_value=0,
+        max_value=20,
+        value=min(int(saved_boost), 20),
+        step=1,
+        disabled=is_streaming,
+        help="Digital gain boost applied before encoding (0-20 dB). Use this when the line-level signal is too quiet even at max ADC gain. Higher values may cause clipping on loud signals."
+    )
 
 # Placeholder for validation errors (will be filled in later)
 validation_error_placeholder = st.empty()
@@ -617,6 +628,7 @@ else:
                     'presentation_delay_ms': presentation_delay_ms2,
                     'qos_preset': qos_preset2,
                     'analog_gain': analog_gain_value,
+                    'software_boost_db': software_boost_db,
                 }
 
         radio1_cfg = {
@@ -633,6 +645,7 @@ else:
             'qos_preset': qos_preset1,
             'stereo_mode': stereo_enabled,
             'analog_gain': analog_gain_value,
+            'software_boost_db': software_boost_db,
         }
 
     if audio_mode == "Network - Dante":
@@ -1529,6 +1542,7 @@ if start_stream:
                         sampling_frequency=q['rate'],
                         octets_per_frame=q['octets'],
                         num_bis=channels,  # 1=mono, 2=stereo - this determines the behavior
+                        input_gain_db=float(cfg.get('software_boost_db', 0)),
                     )
                 ],
             )

src/auracast/server/multicast_server.py

@@ -493,6 +493,7 @@ async def init_radio(transport: str, conf: auracast_config.AuracastConfigGroup,
             'assisted_listening_stream': getattr(conf, 'assisted_listening_stream', False),
             'analog_stereo_mode': getattr(conf.bigs[0], 'analog_stereo_mode', False) if conf.bigs else False,
             'analog_gain': getattr(conf, 'analog_gain', 50),
+            'software_boost_db': getattr(conf.bigs[0], 'input_gain_db', 0.0) if conf.bigs else 0.0,
             'stream_password': (conf.bigs[0].code if conf.bigs and getattr(conf.bigs[0], 'code', None) else None),
             'big_ids': [getattr(big, 'id', DEFAULT_BIG_ID) for big in conf.bigs],
             'big_random_addresses': [getattr(big, 'random_address', DEFAULT_RANDOM_ADDRESS) for big in conf.bigs],
@@ -736,6 +737,7 @@ async def _autostart_from_settings():
                         iso_que_len=1,
                         sampling_frequency=rate,
                         octets_per_frame=octets,
+                        input_gain_db=float(settings.get('software_boost_db', 0)),
                     )
                 ]
                 conf = auracast_config.AuracastConfigGroup(
@@ -890,6 +892,7 @@ async def _autostart_from_settings():
                         iso_que_len=1,
                         sampling_frequency=rate,
                         octets_per_frame=octets,
+                        input_gain_db=float(settings.get('software_boost_db', 0)),
                     )
                 ]
                 conf = auracast_config.AuracastConfigGroup(