Note: Please read FAQ before file an issue, see #2716

Description

推流端使用srt，拉流端使用rtmp，延迟一直在1.5s左右，但是推流端和拉流端均使用rtmp时，延迟在700ms左右，通过打印日志发现：
srs接受到srt连接至转换为rtmp的过程耗时有700ms左右，不知是否有优化空间。

1. SRS Version: 4.0
2. SRS Log:
   1510037 [2023-01-31 17:05:01.538][Trace][82959][2c985289] srt connect construct streamid:live/9999_884002,m=publish, mode:2, subpath:live/9999_884002,m=publish, vhost:default_host
   1510038 [2023-01-31 17:05:01.538][Trace][82959][2c985289] new srt connection streamid:live/9999_884002,m=publish, fd:764895394, vhost:default_host
   1510039 [2023-01-31 17:05:01.538][Trace][82959][2c985289] srto SRTO_LATENCY=300
   1510040 [2023-01-31 17:05:01.538][Trace][82959][2c985289] srto SRTO_PEERLATENCY=300
   1510041 [2023-01-31 17:05:01.538][Trace][82959][2c985289] srto SRTO_RCVLATENCY=300
   1510042 [2023-01-31 17:05:01.538][Trace][82959][2c985289] srto SRTO_SNDBUF=12058624
   1510043 [2023-01-31 17:05:01.538][Trace][82959][2c985289] srto SRTO_RCVBUF=12058624
   1510044 [2023-01-31 17:05:01.538][Trace][82959][2c985289] srto SRTO_MAXBW=1000000000
   1510045 [2023-01-31 17:05:01.538][Trace][82959][2c985289] srt mix_correct is enable.
   1510046 [2023-01-31 17:05:01.538][Trace][82959][2c985289] srt h264 sei filter is enable.
   1510047 [2023-01-31 17:05:01.538][Trace][82959][2c985289] srt_handle add new pusher streamid:live/9999_884002,m=publish, subpath:live/9999_884002,m=publish
   1510048 [2023-01-31 17:05:01.538][Trace][82959][2c985289] new conn added fd:764895394, event:0x00000009
   1510049 [2023-01-31 17:05:02.302][Trace][82959][2c985289] new rtmp client for srt upstream, key_path:live/9999_884002,m=publish
   1510050 [2023-01-31 17:05:02.302][Trace][82959][2c985289] rtmp client construct url:rtmp://127.0.0.1:9302/live/9999_884002,m=publish
3. SRS Config:
   srt_server {
   enabled on;
   listen 9311;
   maxbw 1000000000;
   connect_timeout 4000;
   peerlatency 300;
   recvlatency 300;
   #passphrase "12345678901";
   }