摘录


Support for both MPEG-DASH and HLS
Where HLS is typically delivered with Transport Stream containers and MPEG-DASH with fragmented MP4 (fMP4), CMAF specifies an fMP4 compatible container format.
Utilising this fMP4 container, will allow content publishers to encode and store their media once and deliver it with both the HLS and MPEG-DASH segmented adaptive streaming protocol, reducing costs and simplifying their overall workflow.

It is a more efficient media format HLS’s Transport Stream (TS) containers are inefficient for segmented adaptive media delivery due to their high overhead and payload ratios in comparison with fragmented MP4 (fMP4). Moving away from TS containers towards fMP4 will increase the effective bandwidth of the stream. Furthermore, CMAF specifies a low latency streaming mode for cases where latency is of crucial importance and every millisecond counts.

It is fully compatible with the Common Encryption (CENC) standard Without CENC, content distributors have to DRM encode and store their content multiple times, once for each required DRM system. This brings forward a high cost and reduces the overall CDN delivery efficiency. With CENC, content can be DRM encrypted and stored once and decrypted with a wide range of CENC compatible DRM solutions, such as Google’s Widevine, Microsoft’s PlayReady or Apple’s own FairPlay.

It has support for modern and upcoming codecs Transport Stream containers are designed to carry H.264 and AAC payload. This is furthermore enforced within the HLS specification. CMAF and its fragmented MP4 container however have support for modern media codecs such as HEVC/H.265 and VP9 as well as for the upcoming Alliance for Open Media Video 1 (AV 1), making them future proof.

It has the backing of major industry players Apple announced to support CMAF in combination with HLS in iOS10, macOS and tvOS. Together with Microsoft’s participation in the CMAF standard, this instils confidence from the industry. The general expectation is that most browser, operating system and device manufacturers will quickly release updates to their products in order to be compatible with the CMAF standard.

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asked 18 Feb, 14:48

%E8%B7%AF%E4%BA%BA%E7%94%B2's gravatar image

路人甲
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