fix(audio): prevent empty session replay

ql-application/threadx/interface/custom_app/vad_det.c

@@ -423,12 +423,16 @@ void vad_audio_process(void) {
 						{
 							size_t first = (vad_preroll_next + VAD_PREROLL_FRAMES - vad_preroll_count) % VAD_PREROLL_FRAMES;
 							size_t n;
+							int preroll_queued = 0;
 							for (n = 0; n < vad_preroll_count; n++) {
 								size_t frame_index = (first + n) % VAD_PREROLL_FRAMES;
 								if (hal_os_rb_write(ring_sender, vad_preroll[frame_index], VAD_FRAME_BYTES, 25) > 0) {
-									ql_rtos_semaphore_release(sender_sem);
+									preroll_queued = 1;
 								}
 							}
+							if (preroll_queued) {
+								ql_rtos_semaphore_release(sender_sem);
+							}
 							vad_preroll_count = 0;
 						}
 	                        set_state(STATE_RECORDING_ACTIVE);

ql-application/threadx/interface/custom_app/ws_talkingq.c

@@ -1367,6 +1367,14 @@ sender_loop:
 
 			if(!app_get_data_call_net_status()) continue;
 
+			/* One recording can release the semaphore many times while the sender
+			 * drains the ring buffer.  A stale token must never create an empty
+			 * session after the previous encoder has already been closed. */
+			left = rb_get_space_used(ring_sender);
+			if(shine_init == 0 && left <= 0){
+				continue;
+			}
+
 			if(shine_init==0){
 				shine_set_config_mpeg_defaults(&(sh_config.mpeg)); //--init sh_config struct
 				sh_config.wave.channels=PCM_MONO; //PCM_STEREO;//PCM_MONO;
@@ -1420,6 +1428,9 @@ sender_loop:
 				shine_init = 0;
 
 				audio_packet_type = 0;
+				/* Discard semaphore tokens already represented by the PCM that this
+				 * session drained.  Recording has stopped, so no new frames race here. */
+				while(ql_rtos_semaphore_wait(sender_sem, 0) == 0) {}
 			}
 	}
 }