For a decade, streaming live video to a mobile device was hard to do. Bandwidth issues, firewalls and network infrastructure support all created problems. Streaming protocols weren’t firewall friendly. HTTP progressive download was invented partially to get past firewalls but didn’t offer true streaming capabilities. Now, the advent of adaptive streaming over HTTP has changed everything and is reshaping video delivery to mobile devices as well as devices such as IP set-top boxes (STBs).
There is a battle taking place over the adaptive streaming technology to reach those mobile devices. The three main adaptive streaming contenders are all industry heavyweights: Apple, Microsoft and Adobe. Last year Microsoft released its version of adaptive streaming called Smooth Streaming, part of its Silverlight web application framework. Shortly thereafter Apple introduced HTTP Live Streaming (HLS) as a proposed IETF standard and the draft is now on its fourth iteration. Not to be outdone, in late 2009 Adobe announced it too would play in the adaptive HTTP streaming space, with project Zeri. Aside from these three main contenders, 3GPP is standardizing its own version of HTTP streaming, and MPEG is also entering the fray.
What is the big deal with adaptive streaming?
Adaptive streaming does two main things for video that make it such a good choice for mobile delivery.
- Adaptive streaming segments video into small chunks. For example HLS usually uses 10 second chunks.
- The video is encoded at multiple bitrates and resolutions creating chunks of different sizes. This is the ‘adaptive’ part of adaptive streaming, as the mobile client can choose between different bitrates/resolutions and adapt to larger or smaller chunks automatically as network conditions change.
These two key features of adaptive streaming provide several benefits:
- Video chunks can be cached by proxies and easily distributed to CDNs or HTTP servers, which are simpler and cheaper than the special streaming servers required for ‘older’ video streaming technologies.
- Bitrate switching allows clients to dynamically adapt to network conditions.
- Eliminates the guesswork for content providers on what bitrates to encode for end devices.
- Works great with firewalls since the stream is sent over HTTP.
- Live and VoD workflows are almost identical. When a provider creates a live stream, the chunks can be kept for later VoD delivery.
Who will win the adaptive streaming battle? I’m looking for the person that can answer that for me. Leave a comment on this post with a compelling argument of who you think that will be and I’ll send you a free RGB Networks shirt.