HLS: SRS2 processes audio-only streams into HLS format, experiencing lag and static noise issues on Apple systems.

[lewang321]

When slicing the pure audio stream with srs_2.0 into HLS, if the configuration option hls_vcodec vn; hls_acodec aac; is selected, there will be no video information in the PMT of ts. However, when playing the audio using Apple iOS system, there will be stuttering and noise, while it plays normally on Android system.

hls.conf configuration file:

listen              1935;
max_connections     1000;
vhost __defaultVhost__ {
    hls {
        enabled         on;
        hls_fragment    5;
        hls_td_ratio    1.5;
        hls_aof_ratio  1.0;
        hls_on_error    ignore;
        hls_storage     disk;
#        hls_ts_floor    off;
        hls_acodec      aac;
        hls_vcodec      vn;
#        hls_cleanup     on;
#        hls_nb_notify   64;
#        hls_wait_keyframe       off;
        hls_window      60;
        hls_path        ./objs/nginx/html;
        hls_m3u8_file   [app]/[stream].m3u8;
        hls_ts_file     [app]/[stream]-[seq].ts;
    }

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[lewang321]

Topology is RTMP ----> SRS -----> IOS.

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[lewang321]

The RTMP stream is pushed to SRS through FMLE. It is in the pure audio AAC format.

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[winlinvip]

What is the sampling rate of the SRS logs and audio?

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[lewang321]

[2015-10-27 10:08:08.715][trace][26340][0] srs checking config...
[2015-10-27 10:08:08.715][trace][26340][0] detect intranet address: 127.0.0.1, ifname=lo
[2015-10-27 10:08:08.715][trace][26340][0] retrieve local ipv4 ip=10.12.4.61, index=0
[2015-10-27 10:08:08.716][trace][26340][0] detect intranet address: 10.12.4.61, ifname=eth0
[2015-10-27 10:08:08.716][trace][26340][0] retrieve local ipv4 ip=172.17.42.1, index=1
[2015-10-27 10:08:08.716][trace][26340][0] detect intranet address: 172.17.42.1, ifname=docker0
[2015-10-27 10:08:08.716][warn][26340][0][0] stats network use index=0, ip=10.12.4.61
[2015-10-27 10:08:08.716][warn][26340][0][0] stats disk not configed, disk iops disabled.
[2015-10-27 10:08:08.716][trace][26340][0] write log to file ./objs/srs.log
[2015-10-27 10:08:08.716][trace][26340][0] you can: tailf ./objs/srs.log
[2015-10-27 10:08:08.716][trace][26340][0] @see: https://github.com/simple-rtmp-server/srs/wiki/v1_CN_SrsLog
[2015-10-27 10:08:08.716][trace][26340][0] srs(simple-rtmp-server) 2.0.195
[2015-10-27 10:08:08.716][trace][26340][0] license: The MIT License (MIT), Copyright (c) 2013-2015 SRS(simple-rtmp-server)
[2015-10-27 10:08:08.716][trace][26340][0] primary/master: SRS/1.0release
[2015-10-27 10:08:08.716][trace][26340][0] authors: winlin,wenjie.zhao
[2015-10-27 10:08:08.716][trace][26340][0] contributors: winlin<winlin@vip.126.com> wenjie.zhao<740936897@qq.com> xiangcheng.liu<liuxc0116@foxmail.com> naijia.liu<youngcow@youngcow.net> alcoholyi<alcoholyi@qq.com> byteman<wangchen2011@gmail.com> chad.wang<chad.wang.cn@gmail.com> suhetao<suhetao@gmail.com> Johnny<fengjihu@163.com> karthikeyan<keyanmca@gmail.com> StevenLiu<lq@chinaffmpeg.org> zhengfl<zhengfl_1989@126.com> tufang14<breadbean1449@gmail.com> allspace<allspace@gmail.com> niesongsong<nie950@gmail.com> rudeb0t<nimrod@themanxgroup.tw> 
[2015-10-27 10:08:08.716][trace][26340][0] uname: Linux MediaWiki 2.6.32-504.el6.x86_64 #1 SMP Wed Oct 15 04:27:16 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
[2015-10-27 10:08:08.716][trace][26340][0] build: 2015-10-26 16:49:02, little-endian
[2015-10-27 10:08:08.716][trace][26340][0] configure:  --disable-all --with-ssl --with-hls --with-nginx --with-ffmpeg --with-transcode
[2015-10-27 10:08:08.716][trace][26340][0] features: --prefix=/usr/local/srs --with-hls --without-hds --without-dvr --with-nginx --with-ssl --with-ffmpeg --with-transcode --without-ingest --without-stat --without-http-callback --without-http-server --without-stream-caster --without-http-api --without-librtmp --without-research --without-utest --without-gperf --without-gmc --without-gmp --without-gcp --without-gprof --without-arm-ubuntu12 --without-mips-ubuntu12 --log-trace
[2015-10-27 10:08:08.716][trace][26340][0] conf: conf/hls.conf, limit: 1000
[2015-10-27 10:08:08.716][trace][26340][0] writev limits write 1024 iovs a time
[2015-10-27 10:08:08.716][warn][26340][0][0] SRS 2.0.195 is not stable, please use stable branch 1.0release instead
[2015-10-27 10:08:08.716][trace][26340][0] cpu is amd64, glibc 2.12
[2015-10-27 10:08:08.716][trace][26340][0] cpu is x86_64, glibc 2.12
[2015-10-27 10:08:08.716][trace][26340][0] check feature rtmp handshake: on
[2015-10-27 10:08:08.716][trace][26340][0] check feature hls: on
[2015-10-27 10:08:08.716][warn][26340][0][0] check feature hds: off
[2015-10-27 10:08:08.716][warn][26340][0][0] check feature http callback: off
[2015-10-27 10:08:08.716][warn][26340][0][0] check feature http api: off
[2015-10-27 10:08:08.716][warn][26340][0][0] check feature http server: off
[2015-10-27 10:08:08.716][warn][26340][0][0] check feature http parser: off
[2015-10-27 10:08:08.716][warn][26340][0][0] check feature dvr: off
[2015-10-27 10:08:08.716][trace][26340][0] check feature transcode: on
[2015-10-27 10:08:08.716][warn][26340][0][0] check feature ingest: off
[2015-10-27 10:08:08.716][warn][26340][0][0] check feature system stat: off
[2015-10-27 10:08:08.716][trace][26340][0] check feature compile nginx: on
[2015-10-27 10:08:08.716][trace][26340][0] check feature compile ffmpeg: on
[2015-10-27 10:08:08.716][warn][26340][0][0] stream caster: off
[2015-10-27 10:08:08.716][trace][26340][0] MR(merged-read): on, @see https://github.com/simple-rtmp-server/srs/issues/241
[2015-10-27 10:08:08.716][trace][26340][0] MR(merged-read) default 0 sleep 350
[2015-10-27 10:08:08.716][trace][26340][0] MW(merged-write) default sleep 350
[2015-10-27 10:08:08.716][trace][26340][0] read chunk stream cache cid [0, 16)
[2015-10-27 10:08:08.716][trace][26340][0] default gop cache 1, play queue 30s
[2015-10-27 10:08:08.716][trace][26340][0] complex send algorithm enabled.
[2015-10-27 10:08:08.716][warn][26340][0][0] TCP_NODELAY enabled, may hurts performance.
[2015-10-27 10:08:08.716][trace][26340][0] auto guess socket send buffer by merged write
[2015-10-27 10:08:08.716][trace][26340][0] system default latency in ms: mw(0-350) + mr(0-350) + play-queue(0-30000)
[2015-10-27 10:08:08.716][trace][26340][0] start deamon mode...
[2015-10-27 10:08:08.716][trace][26341][0] father process exit. ret=0
[2015-10-27 10:08:08.716][trace][26342][0] son(deamon) process running.
[2015-10-27 10:08:08.716][trace][26342][0] st_set_eventsys to epoll
[2015-10-27 10:08:08.717][trace][26342][0] st_init success, use epoll
[2015-10-27 10:08:08.717][trace][26340][0] grandpa process exit.
[2015-10-27 10:08:08.717][trace][26342][100] server main cid=100
[2015-10-27 10:08:08.717][trace][26342][100] write pid=26342 to ./objs/srs.pid success!
[2015-10-27 10:08:08.727][trace][26342][100] RTMP listen at tcp://0.0.0.0:1935, fd=8
[2015-10-27 10:08:08.727][trace][26342][100] signal installed
[2015-10-27 10:08:10.605][trace][26342][104] RTMP client ip=10.16.0.3
[2015-10-27 10:08:10.605][trace][26342][104] srand initialized the random.
[2015-10-27 10:08:10.607][trace][26342][104] simple handshake success.
[2015-10-27 10:08:10.607][trace][26342][104] connect app, tcUrl=rtmp://10.12.4.61/live, pageUrl=, swfUrl=rtmp://10.12.4.61/live, schema=rtmp, vhost=__defaultVhost__, port=1935, app=live, args=null
[2015-10-27 10:08:10.607][trace][26342][104] out chunk size to 60000
[2015-10-27 10:08:10.845][trace][26342][104] client identified, type=fmle-publish, stream_name=mytest1, duration=-1.00
[2015-10-27 10:08:10.855][trace][26342][104] source url=/live/mytest1, ip=10.16.0.3, cache=1, is_edge=0, source_id=-1[-1]
[2015-10-27 10:08:11.041][trace][26342][104] hls: win=60.00, frag=5.00, prefix=, path=./objs/nginx/html, m3u8=[app]/[stream].m3u8, ts=[app]/[stream]-[seq].ts, aof=1.00, floor=0, clean=1, waitk=1, dispose=0
[2015-10-27 10:08:11.052][trace][26342][104] start publish mr=0/350, p1stpt=20000, pnt=20000, tcp_nodelay=0, rtcid=106
[2015-10-27 10:08:11.382][trace][26342][104] got metadata
[2015-10-27 10:08:11.382][trace][26342][104] 4B audio sh, codec(10, profile=LC, 2channels, 0kbps, 44100HZ), flv(16bits, 2channels, 44100HZ)
[2015-10-27 10:08:11.382][trace][26342][104] input chunk size to 366
[2015-10-27 10:08:11.386][trace][26342][104] input chunk size to 398
[2015-10-27 10:08:11.386][trace][26342][104] audio drop ts segment, sequence_no=0, uri=mytest1-0.ts, duration=59839.19, start=0
[2015-10-27 10:08:11.391][trace][26342][104] input chunk size to 410
[2015-10-27 10:08:11.396][trace][26342][104] input chunk size to 501
[2015-10-27 10:08:14.896][trace][26342][104] input chunk size to 505
[2015-10-27 10:08:15.399][trace][26342][104] input chunk size to 514
[2015-10-27 10:08:16.394][trace][26342][104] input chunk size to 528
[2015-10-27 10:08:22.397][trace][26342][104] input chunk size to 539
[2015-10-27 10:08:32.885][trace][26342][104] input chunk size to 545
[2015-10-27 10:08:51.052][trace][26342][104] <- CPB time=20001, okbps=0,0,0, ikbps=129,129,0, mr=0/350, p1stpt=20000, pnt=20000

[lewang321]

FMLE configuration is as follows: format: AAC, Channels: Stereo, Sample Rate: 44100 Hz, Bit Rate: 128 Kbps.

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[winlinvip]

Try reducing the bitrate to 64. Also, please send me the slices and m3u8 file so that I can package and transfer them to the cloud storage.

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[lewang321]

http://pan.baidu.com/s/1eQDGevo

[lewang321]

After adjustment, modify the FMLE configuration to:

Format: AAC
Channels: Stereo
Sample Rate: 44100 Hz
Bit Rate: 48 Kbps

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[lewang321]

There is still a regular noise 'pupu' when playing pure audio on Apple systems.

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[winlinvip]

RTMP to TS audio explosion, the reason is because the TBN of RTMP is 1/1000, which is in milliseconds, but TS is 1/90000, which is in 1/90 milliseconds. Therefore, TS has a higher resolution.
To convert from lower resolution to higher resolution, the timestamps need to be recalculated. This is available in SRS1/nginx-rtmp, but the calculation seems to be incomplete. SRS2 does not calculate it and directly uses the RTMP timestamps.
This may cause audio explosion issues, typically occurring once per slice. Therefore, if the slice can be increased to 10 or 30 seconds, the impact will be minimal.

However, I will fix it and see how to solve it most effectively. You can increase the size of the slice to confirm if this is the issue.

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[winlinvip]

I listened carefully, and there is a slight pause every 5 seconds, but the static noise from the microphone is constant.
Can you also record the RTMP stream and send me both the RTMP and corresponding TS files?

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[winlinvip]

I found out that there has been too much emphasis on PCR, actually it is not necessary.

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[winlinvip]

Every PCR causes a timestamp error between RTMP and TS, resulting in crackling sound and significant gaps between segments.

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