--resolve FS-5243 improve mod_unimrcp audio buffering

src/mod/asr_tts/mod_unimrcp/mod_unimrcp.c

@@ -273,7 +273,8 @@ static switch_status_t audio_queue_destroy(audio_queue_t *queue);
  * SPEECH_CHANNEL : speech functions common to recognizer and synthesizer
  */
 
-#define SPEECH_CHANNEL_TIMEOUT_USEC (5 * 1000000)
+#define SPEECH_CHANNEL_TIMEOUT_USEC (5000 * 1000)
+#define AUDIO_TIMEOUT_USEC (SWITCH_MAX_INTERVAL * 1000)
 
 /**
  * Type of MRCP channel
@@ -725,11 +726,18 @@ static switch_status_t audio_queue_read(audio_queue_t *queue, void *data, switch
 #endif
 	switch_mutex_lock(queue->mutex);
 
+	/* allow the initial frame to buffer */
+	if (!queue->read_bytes && switch_buffer_inuse(queue->buffer) < requested) {
+		*data_len = 0;
+		status = SWITCH_STATUS_SUCCESS;
+		goto done;
+	}
+
 	/* wait for data, if allowed */
 	if (block) {
 		while (switch_buffer_inuse(queue->buffer) < requested) {
 			queue->waiting = requested;
-			if (switch_thread_cond_timedwait(queue->cond, queue->mutex, SPEECH_CHANNEL_TIMEOUT_USEC) == SWITCH_STATUS_TIMEOUT) {
+			if (switch_thread_cond_timedwait(queue->cond, queue->mutex, AUDIO_TIMEOUT_USEC) == SWITCH_STATUS_TIMEOUT) {
 				break;
 			}
 		}
@@ -774,6 +782,9 @@ static switch_status_t audio_queue_clear(audio_queue_t *queue)
 	switch_buffer_zero(queue->buffer);
 	switch_thread_cond_signal(queue->cond);
 	switch_mutex_unlock(queue->mutex);
+	queue->read_bytes = 0;
+	queue->write_bytes = 0;
+	queue->waiting = 0;
 	return SWITCH_STATUS_SUCCESS;
 }