fix(plip): mute earpiece during capture

plip_voice/main/conversation.c

@@ -311,11 +311,19 @@ static void conv_task(void *arg)
                         vTaskDelay(pdMS_TO_TICKS(50));
                     }
                     if (!s_offhook) break;
-                    vTaskDelay(pdMS_TO_TICKS(100));   /* line settle after playback (was 200) */
+                    vTaskDelay(pdMS_TO_TICKS(200));   /* let the I2S DMA tail drain */
 
-                    /* Capture player utterance — nothing is playing now. */
+                    /* Kill the earpiece amp during capture: at full volume + 24 dB
+                     * mic gain the playback couples into the handset mic at ~50 %
+                     * FS and swamps the caller's voice (capture transcribed empty).
+                     * PA off = no echo path; restored before the reply plays. */
+                    audio_pa_set(false);
+                    vTaskDelay(pdMS_TO_TICKS(60));   /* PA mute settle */
+
+                    /* Capture caller utterance — earpiece muted, nothing plays. */
                     int n = audio_capture_wav(cap_buf, cap_max,
                                               cap_ms, CAPTURE_SILENCE_MS);
+                    audio_pa_set(true);              /* restore for filler/reply */
                     if (!s_offhook) break;   /* hung up during capture */
 
                     if (n <= 44) {