Dash playing (CMAF)

What Is CMAF (Common Media Application Format)?

The Common Media Application Format (CMAF) is essentially a new format to reduce HTTP delivery latency. It is a new standard that aims to reduce the cost, complexity, and latency of streaming (typically 3-5 seconds). CMAF can be used in DASH or HLS. Both LL-DASH (Low Latency Dash) and LL-HLS (Low Latency HLS) are supported by Ant Media Server in the CMAF format.

How to use CMAF

In Ant Media Server v2.4.3 and earlier, you must enable it in your application's configuration file, as shown below. It is now possible to enable it directly from the Ant Media dashboard starting with version 2.5.0.

1. Open the following file with your favorite editor

/usr/local/antmedia/webapps/WebRTCAppEE/WEB-INF/red5-web.properties

2. Enable DASH by adding the following property to the file above.

settings.dashMuxingEnabled=true

If you want to enable LL-HLS (an experimental feature), you also need to set the following properties:

settings.dash.llHlsEnabled=true

3. Restart the Ant Media Server

sudo service antmedia restart

4. Send the WebRTC stream to Ant Media Server via the WebRTC publisher page. Let’s assume your stream id is “stream1”

https://YOUR_DOMAIN:5443/WebRTCAppEE

5. Play the stream with CMAF using the following URL:

https://YOUR_DOMAIN:5443/WebRTCAppEE/play.html?id=stream1&playOrder=dash

There are a few more options for CMAF and their default values. You can assume that the following values are in use if they are not specified in the properties file:

#Duration of segments in mpd files.
settings.dashSegDuration=6
#Fragments are a property of fragmented MP4 files. Typically a fragment consists of moof + mdat.
settings.dashFragmentDuration=0.5

#Target latency
settings.dashTargetLatency=3.5

#DASH window size. Number of files in manifest
settings.dashWindowSize=5

#DASH extra window size. Number of segments kept outside of the manifest before removing from disk
settings.dashExtraWindowSize=5

#Enable low latency dash. This settings is effective if dash is enabled
settings.dash.llEnabled=true