Moving forward with Live Stream Video Delivery

Allan Lei
Allan Lei
Dec 9, 2018 · 4 min read

Many popular apps offer live stream as a feature integration like Twitch and Youtube Live. With the ever increasing users drawn towards video based services, as seen with the trending race to top Youtube subscribed, the technology behind video delivery is equally increasing in importance. While most service will integrate video as a VOD like much of Youtube or DouYin, the challenge lies with live video delivery.

So what’s available?

There are many solutions available and is dependent on use case, but there are mainly 2 options, RTMP and DASH/HLS. While HLS is an option and having the much larger market share compared to DASH, DASH is vastly superior in terms of feature offering with DASH being able to support the majority of features of HLS. Many workflows are also switching to or dual supporting DASH with HLS.

What’s the difference?

RMTP

DASH

Roadblocks

RTMP, being a proprietary protocol developed by Adobe(Macromedia) which uses FLV, requires Flash to be usable on web browsers. With Flash being long gone, there is no straightforward way to support RMTP in browsers. Instead, support in modern browsers is via FLV over HTTP (via flv.js) resulting in increased management overhead. Technology momentum is also very important. Like with any technology, it should improve over time, but advancements to RMTP are nearly non-existent and has lost momentum over the years to other protocols like DASH, HLS and WebRTC.

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2018 Encoding.com Video Developer Report

DASH also has areas that need to be addressed with latency being one of the biggest. For applications that require near realtime/ultra low latency, DASH is not quite there yet. CMAF aims to improve this by introducing a specification on the encoding and transfer process.

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https://bitmovin.com/cmaf-low-latency-streaming

Paving the Road Ahead

HTTP/2.0 Server Push
While Server Push being relatively unused, in terms of video delivery, it can help move DASH even closer to RMTP in terms of latency by pushing segments immediately after encoding has finished.

QUIC (aka HTTP/3.0)
As mentioned above, being HTTP is a huge plus. With QUIC being standardized as HTTP/3.0, this mean DASH will in-essence receive free UDP support in addition to better network switching and a more efficient TLS connection.

To be fair, there have been some work done by QiNiu (a China based RTMP CDN) to integrate RTMP over QUIC.

CMAF Low Latency
Common Media Application Format for Low Latency is a encoding and transfer specification aimed to reduce latency by essentially sending IDRs as soon as they are encoded without waiting for the entire segment to encode.

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Thoughts

While RMTP still have clear use cases in publishing and low latency viewing, it is quickly being replaced. Without a clear roadmap for RTMP and with DASH closing the gap on low latency, it seems very likely that DASH will come out the solution of choice in the coming years.

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