Video Streaming Format — Part 3: Smooth Streaming
Here it is, the third part of our “Streaming Format” series. We kicked off TV Apps 101 a set of articles talking about Dynamic Adaptive Streaming HTTP and HTTP Live Streaming. If you wish to catch up on those two formats before continuing reading this, you can find the first two write-ups here and here.
Today, we will talk about HSS, or HTTP Smooth Streaming, or simply SS. It was introduced by Microsoft in October of 2008. Smooth Streaming runs on Microsoft’s Internet Information Services (IIS) server and Silverlight Player. Do not be surprised if you haven’t dealt with Silverlight lately. It was announced in 2012 that its development was over. Silverlight might still be used by Amazon Video on Firefox, Safari, and previous versions of Internet Explorer; however, Netflix already made a move away from Smooth Streaming and went to HTML5 in 2013.
Anyway, we should get back to the main topic of this post and share more details about Smooth Streaming.
These are some of the prominent features of the SS media delivery platform:
- It permits easy and cheap caching along the edge of the network. An edge is an entry point into enterprise on a network of a service provider. Router is one of the examples of a network service provider. A multiplexer, a data selector that chooses between analog and digital signals to forward into a single line of data, would be another example.
- SS allows seamless and dynamic switching between bit rates depending on network conditions and CPU power, and as a result viewers have smooth and more consistent feedback.
If you already caught up on the first two articles (DASH And HLS), you know that there are some similarities between Smooth Streaming and DASH.
- Both streaming formats require that media chunks, i.e. their boundaries, are aligned across different qualities, and each chunk should start with a keyframe.
- SS and DASH support fMP4 container format. fMP4 files have some distinct advantages over adaptive streaming solutions based on MPEG-2 Transport Streams, such as the proprietary HTTP Live Streaming (HLS) format developed by Apple. HLS is based on a derivative of the MPEG-2 Transport Stream (M2TS), which was developed nearly two decades ago for broadcast TV.
- Similar to DASH, SS format was developed with Internet streaming in mind. The main focus is delivering the content to the end-user continuously, without any downloading time spent during the viewing experience.
- One more feature of SS that resembles DASH is ISO (International Organization for Standardization) base media file format segments, better known as MP4 (a digital media file that stores not only video and audio, but also subtitles, and still images)
- Just like DASH, content in SS format can be repackaged into HLS format, and distributed to Apple devices, to reach a bigger audience and more screens.
Speaking of HLS, smooth streaming shares some features with that format too:
- All three formats allow fast channel switching. Chunks of content are transferred at a different bitrate, and it means that fragments of content will be downloaded, before being played. It reduces chances of missing out on quality, when there is a change in bit rates during streaming. This is also made possible due to dividing media into small chunks. Switching between different qualities happens along with the changes in bandwidth availability.
- Support for non-multiplexed content.
Smooth Streaming is simply another type of streaming format that we wanted for you to get familiar with. While a lot of devices and services have moved away from it, Microsoft’s Xbox still supports Smooth Streaming format. If you are planning to work on launching a video application that will run on Xbox, this will definitely be of use.
TV Apps 101 is a regular series where Odd digs a little deeper into streaming technologies, video app development, and why it should even matter to you. Interested in taking the next step in media distribution? Let Odd Networks connect your fans with your content by delivering your videos to multiple screens. The future is Odd.
