Multi-language audio with IIS Smooth Streaming: An example from Radiovaticana Live Streaming

One of many useful features that comes with IIS Media Services 4.0 and Smooth Streaming is the ability to stream live and on-demand content with multiple language audio tracks that are selectable by the viewer.  An example of this capability is the recent schedule of events that Vatican Radio (http://www.radiovaticana.org/) delivered  during the last month. Vatican Radio delivered several events, such as Christmas night liturgical celebrations presided over by the Holy Father, World Day of Peace on January 1st, Jannuary 9 at 09.30 CET we have another event with the Pope,  and other events with multiple audio tracks (Natural Audio, Italian, English, French, German, Spanish, Portuguese and Arabic) was delivered during the last month. The player used for these events was based on the Silverlight Media Framework (SMF) and provides the viewer with the ability to select which audio track to listen to.

The first publishing point on the IIS MS origin server provided a client manifest (.ismc file) of all the available tracks and the actual content to Silverlight media players. The second origin server publishing point had the Apple Devices Adaptive Streaming feature selected.  This enabled the origin server to do on-the-fly trans-muxing (repackaging from one file format to another) from the fragmented MP4 streams used by the Smooth Streaming format to the Apple HTTP Live Adaptive Streaming (HLS) format compatible with iPhone and iPad. It also created and published an HLS-compatible client manifest (.m3u8 file).  An HTTP CDN (content delivery network) pulled the content from the origin publishing points and distributed it to viewers on their Silverlight or iPhone/iPad clients.

The Silverlight client player, based on SMF, read all tracks published in the manifest and transparently adapted the video quality as needed, based on the bandwidth available and video rendering capabilities of each client.  The player also offered the possibility to the viewer to choose the audio track.

Read more: Giuseppe Guerrasio

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