How Netflix Is Deploying AV1 with CMAF
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Learn more about AV1 and CMAF at Streaming Media West 2021.
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Cyril Concolato: In our pipeline, our AV1 encoder is producing an elementary stream. And in the context of AV1, the stream is decomposed into Open Bitstream Units (OBUs). If you're familiar with AVC or HEVC, they have nine units. So AV1 has a similar concept. And in our packager, the role here is to parse this elementary stream and produce CMAF segments. But to do that, it first detects what's called temporal units--the time boundaries between frames--and determines the timing. And here I would highlight that AV1 is really simplified compared to other codecs in the sense that we don't have the complexities around frame reordering or the nasty leading pictures that you have in other codecs, and you don't need in the packaging things like edit lists, which are always very, very difficult to handle in implementations.
Similarly, there's another simplification done in CMAF for AV1 around the sequence header OBU, which are equivalent to--if you're familiar with AVC and HEVC parameter sets like VPS, PPS, and SPS. And CMAF for AV1 recommends a way to do in-band and out-of-band signaling. So where for other codecs, you have to maintain two pipelines--you have your out-of-band pipeline and your in-band pipeline , for AV1, there's just one pipeline, one specification.
Same thing for encryption. AV1 recommends the encryption using cbcs with a 1:9 encryption pattern. So, for AV1, you don't need to maintain two encryption pipelines. No dichotomy between CTR and CBC, just one.
And finally, in our system, we use the typical structure or constraints of CMAF, but with the on-demand approach. For example, we use segment indexing or sub-segment indexing. So, that is really the first format that we've deployed with with CMAF. And it was really, I would say, an easy deployment due to all these certifications.
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