A research centre, broadcaster and supplier partnership has provided sample live internet streams demonstrating the potential benefit of the emerging Common Media Application Format (CMAF).

IRT, the research and competence centre for audio-visual technologies of the public broadcasters in Germany, Austria and Switzerland, in  co-operation with IPTV and OTT solutions provider Keepixo and German public broadcaster Bayerischer Rundfunk (BR) provided sample live streams showing the potential of the Common Media Application Format. (CMAF) 

CMAF aims at unifying the two leading adaptive streaming standards, MPEG-DASH and Apple’s HLS.

Technically, with CMAF, both HLS playlists and DASH manifests are allowed to reference the same fragmented MP4 (fMP4) chunks, whereas currently these chunks must be duplicated for each streaming mechanism.

Br live service as recorded loop

BR live service as recorded loop

Source: IRT

The stream shows content from the TV programme of Bayerischer Rundfunk (BR). The programme was recorded and is played back in a loop but the encoding itself is done live.

This allows any DASH player on Windows or Android to playback the exact same media segments as recent Apple devices (iOS10, tvOS, MacOS).

Smart TVs based on HbbTV 1.5 and onwards support DASH-based streaming; therefore, CMAF also provides an important step towards the harmonisation of HbbTV and HLS platforms.

Benefits for broadcasters

For broadcasters the benefit of using CMAF for future OTT IP services lies in its efficiency: only one packaging system is required and only one set of media chunks needs to be built. Consequently, also less storage space is needed for non-linear services such as catch-up TV, leading to lower storage costs.

The viewer benefits as well, because HTTP caches in the delivery network become much more efficient, thus decreasing the risk of network congestion.

’CMAF provides promising options’

Dr. Klaus Illgner-Fehns

The implementation shows how future multiplatform access to adaptive streams can be realised. For the showcased streams prepared and live broadcast content has been encoded and packaged conform the CMAF specification.

The demo streams are publicly available for anyone interested, specifically to demonstrate the potential of CMAF to service providers and to the industry.

Accessibility

CMAF also facilitates a better deployment of accessibility services.

The sample streams contain deaf and hard of hearing subtitles in the IMSC1 format and can be extended by the alternative web caption format WebVTT. This flexibility results in a better cross-platform support on mobile devices and Smart TVs.

Audio Description, an accessibility service for the blind and visually impaired, is also contained in the sample streams; CMAF supports multiple audio tracks for video assets, without the need of duplication or repackaging the video.

“IRT is investigating alternative streaming methods to HLS-delivery or MPEG-DASH-delivery to find more efficient and thus less expensive workflows for IP-based distribution” said Dr. Klaus Illgner-Fehns, CEO of IRT. “Besides mechanisms for adaptive media transport, also the joined carriage of programme-associated data like subtitles is evaluated. In this context CMAF provides promising options.”

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