CMAF Livestreams with Subtitles and Audio Description

The Common Media Application Format (CMAF) aims at unifying the two currently leading adaptive streaming standards: MPEG-DASH and Apple’s HLS. The sample live streams presented here, demonstrate the potential benefit of CMAF for future OTT IP services. 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. This allows any DASH player on Windows or Android to playback the exact same media segments as recent Apple devices (iOS10, tvOS, MacOS).

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. Also Audio Description is contained in the sample streams; CMAF supports multiple audio tracks for video assets, without the need of duplication or repackaging the video.

The implementation resulted from a cooperation by IRT with the IPTV and OTT solutions provider Keepixo and the German public broadcaster Bayerischer Rundfunk.

IRT investigates alternative streaming methods to legacy HLS or MPEG-DASH to find more efficient and thus less expensive workflows while targeting broadcast-quality also for IP-based distribution over the open Internet (see:

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