Hello community, how are you all?
So, We have a working live stream, working fine now even in Chromecast.
We have however the know issue with latency.
We run the live streams in 2x 8 core with 16Gb ram each. These are dedicated.
What we have noticed is that although we manage to start the stream with a latency of about 6 seconds, this latency keeps creeping up, no matter what, until reaching between 15 to 18 seconds (measured!).
No matter how idle or busy the servers are, no matter if we through more CPU or memory, it will always have some extra latency.
I would say that 5 seconds could be acceptable, but it seems to be impossible to reduce as things are.
Another effect that we have notice is that for come consumers, the stream seems to start playing from the very beginning. This seems to be eased with reducing drastically the hls_playlist_length parameter.
These are the rtmp settings we are using:
# RTMP configuration
rtmp {
server {
listen 1935; # Listen on standard RTMP port
chunk_size 3000;
buflen 100ms;
# This application is to accept incoming stream
application kLive {
live on; # Allows live input from above
# ADAPTIVE BITRATE SUPPORT
# Once the stream is alive, transcode for adaptive streaming
# This single ffmpeg command takes the input and transforms
# the source into 4 different streams with different bitrate
# and quality. The scaling done here respects the aspect
# ratio of the input.
# This is commented by default as it is CPU and RAM intensive
# If you opt to enable it, ensure you have sufficient resources.
exec /opt/kaltura/bin/ffmpeg -i rtmp://vod.xxxx.com:1935/$app/$name -async 1 -vsync -1
-preset veryfast -crf 23 -f flv rtmp://vod.xxxxx.com:1935/kLive/$name_high
-c:v libx264 -b:v 1920k -b:a 128k -vf "scale=1280:trunc(ow/a/2)*2" -tune zerolatency -preset veryfast -crf 23 -f flv rtmp://vod.xxxxx.com:1935/kLive/$name_hd720
-c copy -f flv rtmp://vod.xxxxx.com:1935/kLive/$name_src;
dash on;
#dash_path /var/tmp/dashme;
dash_path /opt/kaltura/web/content/tmp/dashme/;
hls on; # Enable HTTP Live Streaming
# Needed for Chromecast to be able to cast live streams
hls_base_url https://vod.xxxxxxxxx.com:8443/hlsme/;
# Instruct clients to adjust resolution according to bandwidth
hls_variant _low BANDWIDTH=288000; # Low bitrate, sub-SD resolution
hls_variant _mid BANDWIDTH=448000; # Medium bitrate, SD resolution
hls_variant _high BANDWIDTH=1152000; # High bitrate, higher-than-SD resolution
hls_variant _hd720 BANDWIDTH=2048000; # High bitrate, HD 720p resolution
hls_variant _src BANDWIDTH=4096000; # Source bitrate, source resolution
hls_cleanup on;
hls_sync 100ms;
hls_fragment 2s;
hls_playlist_length 5s;
hls_path /opt/kaltura/web/content/tmp/hlsme/;
# Define the two scripts that will run when recording starts and when it finishes
exec_publish /opt/kaltura/bin/create_live_entry.php $args;
exec_record_done /opt/kaltura/bin/upload_live_recording.php $args $path;
}
}
Does anyone have a good recommendation to lover the latency time to something close to 5 seconds?
Is there any supported WebRTC that currently works or is implementable?
Many thanks in advance.