Live streaming with simultaneous translation into several languages using vMix and Wowza Streaming Engine.
The new version of the software live encoder vMix v26 has the ability to generate a transport stream used for transmission via the SRT protocol, with several audio tracks multiplexed into separate audio programs - audio PIDs. This, in turn, allows you to publish a video broadcast with simultaneous translation into several languages with one SRT stream. Our article will discuss the methodology for conducting multi-language broadcasts using vMix v18.104.22.168 and Wowza Streaming Engine v4.8.22. A video file and two additional audio files will be used to emulate the live broadcast.
After opening vMix, we need to create three broadcast sources. The video file MainStream.mp4 is used to create a video/audio source (operator camera emulation). Audio files Language1.mp3 and Language2.mp3 are specified when creating audio sources (emulation of simultaneous translation into 2 additional languages).
In the main vMix settings menu, select Audio Outputs, turn on tracks A and B.
In the audio mixer settings, in the INPUTS block, you must turn on the sound for all 3 audio sources and specify to use tracks M, A and B, respectively (by default, track M is selected for all sources). In the OUTPUTS block you need to turn on the sound for all 3 tracks.
Settings for stream publishing parameters are located in the main settings menu on the Outputs/NDI/SRT tab. In our example, we will use the output stream Output 1. The stream parameters settings menu opens by clicking on the “gear” icon.
In the Audio Channels list, you must select the publication of 3 tracks: MAB.
And the most important setting is located in the Quality menu - this is the Split Stereo Pairs into Separate Tracks checkbox.
After selecting these options, you can check the Enable SRT checkbox and publishing the stream to the server will start.
On Wowza server side, you need to receive your SRT stream by starting to receive .stream file with SRT type. This is described in more detail in our article: Publish SRT stream to Wowza. But Wowza accepts SRT stream with the single audio track only. And unlike MediaCaster with RTP type, it is not possible to start receiving the same SRT stream several times (by specifying the PID number of the audio track in the options of the .stream file).
The module developed by our company will allow you to overcome this limitation PWI Multilingual streaming Addon for Wowza Streaming Engine. When using this module, the input SRT stream with several language tracks will be converted into an HLS stream with the ability to select the translation language in any HLS player.