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Adaptive Bitrate

Adaptive bitrate improves the user experience by offering the best video quality available for the screen size and connection being used.  It is particularly beneficial when used in conjunction with large screens or high-resolution devices with lots of available bandwidth.   IVA doesn’t recommend adaptive bitrate for use with 3G or EDGE Network devices at the present time because of poor performance with the current bitrates we offer.

There are several versions of adaptive bitrate streaming in the marketplace and IVA is encoding videos in three of them: HDS, HSS, HLS.  We will soon be encoding in a fourth called DASH.  We are using High Profile for the encodes and are currently offering speeds ranging from 600kbps up to 2500kbps.

Here is a listing of the adaptive bitrate technologies that IVA is offering:

HDS
HDS stands for HTTP Dynamic Streaming and was developed by Adobe.  It delivers adaptive bitrate standards-based MP4 media over regular HTTP connections.   This format will work only on devices that support Flash.  Check out Adobe’s site for full details.

HSS
Microsoft has developed its own adaptive bitrate format called HTTP Smooth Streaming. It is a part of IIS Media Services and enables streaming media to Silverlight and other clients over HTTP.   HSS detects local bandwidth and CPU conditions to switch bitrates in near real time to offer the highest quality video that network and device conditions will allow.  The files are delivered in a fragmented MP4 format and are stored as ISMV files.   For more information view Microsoft’s website and download the technical specs and overview.

HLS
Apple’s solution to adaptive bitrate delivery is called HTTP Live Streaming.    The source files for this format are packaged in an MPEG-2 Transport Stream which is then broken up into a series of smaller chunks (.ts files) and referenced in a .M3U8 playlist file index.  Clients read the index file to request the chunks in the correct sequence.  Depending on the available bandwidth the client will choose a chunk from an appropriate bitrate allowing for seamless transitioning between bitrates.   This format is ideal for streaming video to iOS devices as it is supported natively on iOS 3.0 and later as well as on Safari 4.0 or later.

Supported devices include iPhone 3 and higher, all iPads, Mac OS-X; nearly all set top boxes (Xbox, PS3, Roku, Apple TV, Boxee), as well as Android devices running ICE Cream Sandwich.  IVA will be introducing HLS in a future version of our Flash Player Platform as a plugin which will bring HLS to all PCs supporting Flash.

DASH
Dynamic Adaptive Streaming over HTTP is the open source approach to adaptive bitrate now in development under the auspices of the international MPEG group.  The goal is to have a technology that is universally implemented compared to the more vendor-centric solutions listed above.  The proposed international standard was approved in November 2011.  DASH is audio/video codec agnostic, however the specification provides specific guidance and formats for use with two types of containers, the MPEG-4 file format or the MPEG-2 Transport Stream.  IVA is watching the emerging DASH technology closely and will make encodes available as the standard solidifies.

Adaptive Bitrate Comparison Chart

Adobe HDS Microsoft  HSS Apple HLS 3GPP/MPEG DASH
Source Video Codecs H.264, VP6 H.264, VC-1 H.264 H.264 + others(agnostic)
Source Audio Codecs AAC, MP3 AAC, WMA AAC, MP3 AAC + others(agnostic)
Package/Segment Format MP4 Fragments MP4 Fragments MPEG-2 TS MP4 Fragments + MPEG-2 TS
File storage on server Contiguous Contiguous Individual file per segment (pre iOS 5.0) Contiguous or individual files per segment
Audio/Video/Text packaging Multiplexed in 1 Segment Multiplexed in 1 segment Multiplexed in 1 segment( pre iOS 5.0) Multiplexed or separate segments for audio, video
Segmentation & Delivery Adobe Interactive Server (or Adobe tools + Apache module for on-demand MS IIS (+ few other vendors including Helix) Multiple vendors. Standard HTTP or Streaming servers (+ Helix Multiple vendors. Standard HTTP or Streaming servers (+ Helix)
Playback Flash, Air Silverlight Apple iOS, Quick Time X 3GPP-Rel 9 or MPEG clients
Protection Flash Access PlayReady AES-128 encryption Flexible (e.g., OMA or UV)
Typical Segment Duration 2-4sec 2-4sec 10 sec Flexible

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