CMAF (Common Media Application Format, MPEG ISO/IEC 23000-19) is a standardized container of fragmented-MP4 segments that can serve both HLS and DASH from one set of files. Before CMAF, supporting Apple devices (HLS) and everything else (DASH) often meant packaging and storing two separate copies of every rendition; CMAF lets one set of segments be referenced by both an HLS playlist and a DASH MPD.
The practical wins are large: roughly half the packaging, storage, and — critically — CDN cache footprint, because a CMAF segment requested by an Apple device and the same segment requested by an Android device are the same object with the same cache key. CMAF also underpins low-latency streaming through its chunked-transfer mode (CMAF-CTE), the basis of LL-HLS and LL-DASH.
The main caveat is encryption: HLS/FairPlay historically required the cbcs scheme while older DASH used cenc/ctr, so true single-copy CMAF depends on standardizing on cbcs across all DRM systems.
