Microsoft Smooth Streaming

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Smooth Streaming, an IIS Media Services extension, enables adaptive streaming of media to Silverlight and other clients over HTTP. Smooth Streaming provides a high-quality viewing experience that scales massively on content distribution networks, making true HD 1080p media experiences a reality.

Smooth Streaming is the productized version of technology first used by Microsoft to deliver on-demand video of the 2008 Summer Olympics for NBCOlympics.com. By dynamically monitoring both local bandwidth and video rendering performance, Smooth Streaming optimizes playback of content by switching video quality in real-time.

Viewers with high bandwidth connections and modern computers can experience full HD 1080p quality streaming, while others with lower bandwidth or older computers receive the appropriate stream for their capabilities. The end result is simple: viewers across the board enjoy a compelling, uninterrupted streaming experience, which leads to extended audience engagement and increased revenue opportunities.


Smooth Streaming uses the simple but powerful concept of delivering small content fragments (typically two seconds worth of video) and verifying that each has arrived within the appropriate time and played back at the expected quality level. If one fragment does not meet these requirements, the next fragment delivered will be at a somewhat lower quality level. Conversely, when conditions allow it, the quality of subsequent fragments will be at a higher level.

To create Smooth Streaming presentations, the same source content is encoded at several quality levels, typically with each level in its own complete file, using a compression tool such as Expression Encoder 3 or a product from one of our many partners. Content is delivered using a Smooth Streaming-enabled IIS origin server. Once the IIS origin server receives a request for media, it will dynamically create cacheable virtual fragments from the video files and deliver the best content possible to each end user. The benefit of this virtual fragment approach is that the content owner only needs to manage complete files rather than thousands of pre-segmented content files.

Smooth Streaming provides media companies with a better way to make full HD on the Web a reality. It offers code-free deployment and simplified content management for content creators and content delivery networks. For end users, the improved video viewing experience will bring the reliability and quality of HD television to their favorite video Web sites.

To see Smooth Streaming in action, check out the Experience Smooth Streaming page on the IIS web-site, where you can simulate different bandwidths and see how Smooth Streaming responds. To learn more, download Smooth Streaming from and read the Smooth Streaming Technical Overview or the Smooth Streaming Deployment Guide.


Each chunk has a unique URL, and all requests for that chunk get the same URL from any client. Each chunk is small enough to fit in a cache proxy. They'll get automatically cached by the existing proxy cache infrastructure, including squid. "Smooth Streaming adapts streaming to the web instead of trying to adapt the web to streaming." That includes proxy caches inside a CDN, at corporate firewalls, at ISPs, ecetera.


Smooth Streaming media asset therefore consists of the following files:

• MP4 files containing video/audio
  • *.ismv – contains video and audio, or only video
    1 ISMV file per encoded video bitrate
  • *.isma - contains only audio
    In videos with audio, the audio track can be muxed into an ISMV file instead of a separate ISMA file
• Server manifest file
  • *.ism
    Describes the relationships between media tracks, bitrates and files on disk
    Only used by the IIS Smooth Streaming server – not by client
• Client manifest file
  • *.ismc
    Describes to the client the available streams, codecs used, bitrates encoded, video resolutions, markers, captions, etc.
    It’s the first file delivered to the client

Both manifest file formats are based on XML. The server manifest file format is based specifically on the SMIL 2.0 XML format specification.



Smooth Streaming format specification supports:

• VC-1, WMA, H.264 and AAC codecs
• Text streams
• Multi-language audio tracks
• Alternate video and audio tracks (i.e. multiple camera angles, director’s commentary, etc.)
• Multiple hardware profiles (i.e. same bitrates targeted at different playback devices)
• Script commands, markers/chapters, captions
• Client manifest Gzip compression
• URL obfuscation
• Live encoding and streaming

How to download/rip/capture/save/record Smooth Streaming
Streaming video recording/downloading software supporting Microsoft Smooth Streaming