Can We Unify HLS and DASH in 2020?
Now that we have CMAF, a common file format that can unify both DASH and HLS, it is time to see how it will be implemented practically. The first hurdle to overcome is the encryption, and there is currently unified support for the CBCS encryption scheme by all of the major DRM systems such as Apple FairPlay for HLS, and Google Widevine and Microsoft PlayReady for DASH. With this approach a single media file can be encrypted in the CBCS format and distributed to any player, no matter what DRM system is in use. This fulfills the initial promise of CMAF.
The second hurdle is low latency, especially with the newly published Apple LL-HLS protocol, which diverges from the chunk transfer encoding mode defined by MPEG DASH in 2018. Apple has realized that, even using CMAF, unifying the two systems would require effort on its side. There are positive signs DASH and HLS can come up with a single cacheable media file format to make the promise of CMAF become a reality and enable low latency. The third hurdle that needs to be resolved is ad insertion. The balls are up in the air on both HLS and DASH, so convergence might take more time.
In 2020, all signs point toward the industry developing a unified CMAF-based, live OTT streaming system that supports common encryption with CBCS, along with ad insertion and low latency for both HLS and DASH delivery formats. Under this approach, media files are only stored once, which saves processing, storage and delivery costs. This will create an optimized delivery scheme that will enable all of the key features OTT service providers are looking for. Accomplishing this will resolve fragmentation issues, make OTT live streaming more profitable and speed up its development.
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