Live stream audio delay

Hi,

We have problem about RTP over RTSP streaming video.

I have set up Wowza&ffmpeg and have created an stream, which is a consistent audio delay(2sec),
when accessing the stream with VLC(RTSP).

However when I access the same stream with Smartclient, there is a 20 - 30 sec delay. ( xProtect Smartclient 2018 R2 )
The delay increases with the passage of time.

Is there an issue with Wowza&ffmpeg setting the audio?

1)System configuration

iphone(Gogoder is installed)→(RTMP※1)→ Wowza Streaming engine&ffmpeg →(RTP/RTSP※2) → xProtect Professional+( recorder)
※1 RTMP:H.264、AAC_LW
※2 RTP/RTSP:H.264、G711

2) codec

Video codec H.264

Audio codec G711 mulaw ( We transcode from AAC_LW 44100Hz to G711 8000Hz with ffmpeg(audio codec pcm_mulaw))

  1. ffmpeg

ffmpeg -rtsp_transport tcp -i “rtsp://:1935/live/myStream” -rtsp_transport tcp -i “rtsp://:1935/live/myStream” -vsync 1 -vcodec libx264 -r 29.97 -acodec pcm_mulaw -async 1000 -ac 1 -ar 8000 -map 0:0 -map 1:1 -f rtsp -rtsp_transport tcp rtsp://:1935/live/testRTSP

※IP’s are same.

Thanks.