In 2016, CMAF standardization was just beginning, carrying the promise of simplified workflows and improved CDN caching efficiency. Where are we now .

DRM, Encoding, OTT, Players, Repackaging, Standards, Streaming, Workflow

It’s been almost five years since I published the last article on this blog – ten years since the first one – time flies quickly, and so do streaming technologies. In 2016, CMAF standardization was just beginning, carrying the promise of simplified workflows and improved CDN caching efficiency. The CBCS encryption scheme support was supposed to expand far out of the Apple ecosystem, and IMSC was poised to become the dominant subtitles standard. I thought I would fast forward to now and check how much of it did really happen, which other technologies did emerge as foundational for streaming workflows, and what could be the next important ones for the five years to come.

Current core technologies

Let’s start with the technologies which confirmed or revealed their first class OTT citizen status in the last five years.

The CMAF/CBCS/IMSC wave Since 2016, CMAF has become the de facto media container format. All video Standards Developing Organizations (SDOs) like DVB, ATSC, DASH-IF or 3GPP have adopted this MPEG standard as a baseline technology for their own standards. The Consumer Technology Association has launched its Web Application Video Ecosystem (WAVE) project to further drive interoperability between content producers and media player developers leveraging CMAF, and the CMAF Industry Forum to promote the use of CMAF across the video ecosystem. CTA-WAVE recently released the DASH-HLS interoperability Specification, which describes how DASH and HLS should leverage CMAF contents, and provides insights on mapping between DASH and HLS manifests. And MPEG has defined a CMAF profile for DASH (part of the core DASH spec 5th edition, in Final Draft International Standard stage). So yes, CMAF is now everywhere, and nothing can be done that is not CMAF compatible.

All modern video players do support CMAF media segments, so the footprint for TS segments use is now limited to pre-iOS 10 devices and other legacy hardware players which can’t be updated – a clearly shrinking ensemble due to hardware renewal cycles. Unlike LL-DASH players, Apple LL-HLS players don’t leverage CMAF chunks, as the heuristics on these platforms rely on full line speed transfer, but at least they are compatible with it and it makes it possible to share a single set of media segments between LL-HLS and LL-DASH manifests.

The success of CMAF was also conditioned by CBCS taking over the CTR encryption scheme, as this was the preliminary requirement to carry multiple DRMs in the same set of segments and have the CDN deliver with the best caching efficiency, compared to two sets of segments in CTR and CBCS modes. We need to acknowledge that this vision only half realized outside of the Apple ecosystem, as only 2020 and beyond non-Apple devices do actually support CBCS in hardware, which is limiting support for 1080p resolutions and beyond. Taking into account the standard hardware renewal cycle, this leads us to the 2025 to see CBCS universally supported. Even in environments like browsers, where you would expect CBCS to be a table stakes feature now, there is still a lot of interop work to see it behaving well with all DRMs and Clearkey encryption.

In the CMAF promise package, there was also the relief perspective of using a single subtitles TTML format across all devices, with the advent of IMSC1 in both text and image profiles (see section 4.4.1 of the CTA specification). While Apple introduced support for IMSC1 Text Profile in the 2017 draft-pantos-hls-rfc8216bis-00 spec, HLS still doesn’t officially support the Image Profile, and the domination of WebVTT in the HLS world has not really been challenged yet, leaving the subtitle ecosystem fractured. It probably relates to the fact that supporting even the IMSC1 text profile – a wide specifi...