When it comes to adaptive bitrate streaming over HTTP, file format really does matter. The fragmented MP4 (fMP4) file format, first used by Microsoft, is the basis of IIS Smooth Streaming, Adobe HTTP Dynamic Streaming, and two industry streaming standards. 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. On the other hand, the fMP4 file format was specifically designed to address the needs of modern streaming to computers, televisions, and mobile devices. fMP4 offers a number of key benefits over M2TS solutions, such as:
- Trickplay capabilities (e.g., fast-forward, pause, instant replay)
- Seamless stream adaptation to local conditions
- Reduced storage requirements
- Backwards compatibility with M2TS-based solutions
- Integrated digital rights management (DRM)
When Microsoft first developed IIS Smooth Streaming, we built the fMP4 format on Part 12 of the MPEG-4 standard, which defines the ISO Base Media File Format. We released the specification for the fMP4 format under the name "Protected Interoperable File Format" (PIFF). In addition to IIS Smooth Streaming, this format has become the basis for streaming for Netflix, Comcast XFINITY, and two industry standards: the UltraViolet digital-rights management and delivery standard, which based their Common File Format on PIFF; and the upcoming MPEG-DASH (Dynamic Adaptive Streaming over HTTP) standard.
Tim Siglin, a well-known digital media consultant and writer with Transitions, Inc., has just released an excellent white paper that explores the fMP4 file format and what it means for the future of streaming video. A unique aspect of this paper is that teams from Microsoft and Adobe worked together with Tim on it, a first-time collaboration that provides hope for a standardized media streaming format in the near future. To get the Adobe perspective on this, please refer to Kevin Towes' blog post.
To learn more about fMP4 and read the white paper, titled "Unifying Global Video Strategies - MP4 File Fragmentation for Broadcast, Mobile and Web Delivery," please see Tim's blog post.