ATC支持HLS/HDS热备

                        +----------+        +----------+
               +--ATC->-+  server  +--ATC->-+ packager +-+   +---------+
+----------+   | RTMP   +----------+ RTMP   +----------+ |   | Reverse |    +-------+
| encoder  +->-+                                         +->-+  Proxy  +-->-+  CDN  +
+----------+   |        +----------+        +----------+ |   | (nginx) |    +-------+
               +--ATC->-+  server  +--ATC->-+ packager +-+   +---------+
                 RTMP   +----------+ RTMP   +----------+

vhost __defaultVhost__ {
    # vhost for atc for hls/hds/rtmp backup.
    # generally, atc default to off, server delivery rtmp stream to client(flash) timestamp from 0.
    # when atc is on, server delivery rtmp stream by absolute time.
    # atc is used, for instance, encoder will copy stream to master and slave server,
    # server use atc to delivery stream to edge/client, where stream time from master/slave server
    # is always the same, client/tools can slice RTMP stream to HLS according to the same time,
    # if the time not the same, the HLS stream cannot slice to support system backup.
    # 
    # @see http://www.adobe.com/cn/devnet/adobe-media-server/articles/varnish-sample-for-failover.html
    # @see http://www.baidu.com/#wd=hds%20hls%20atc
    #
    # default: off
    atc             on;
}

vhost atc.srs.com {
    # whether enable the auto atc,
    # if enabled, detect the bravo_atc="true" in onMetaData packet,
    # set atc to on if matched.
    # always ignore the onMetaData if atc_auto is off.
    # default: on
    atc_auto        off;
}