Moving Picture Expert Group (MPEG) has been responsible for developing many multimedia standards, including MPEG-2, MPEG-4, MPEG-7, MPEG-21 and others. MPEG developed a standard for streaming multimedia over the Internet. The standard is known as MPEG-DASH.
MPEG developed the specification working with many specialists and other groups responsible for standards. The resulting standard is known as MPEG Dynamic Adaptive Streaming over HTTP (MPEG-DASH). Streaming platforms such as Apple’s HTTP Live Streaming, Microsoft’s Smooth Streaming, and Adobe’s HTTP Dynamic Streaming all use HTTP streaming as their fundamental delivery method.
To receive the content from each server, a device must support its proprietary client protocol, because each platform uses different segment format. A standard for HTTP streaming of multimedia content would allow a standard-based client to stream content from any standard-based server, allowing cooperation between servers and clients manufactured by different vendors.
In the past, it was difficult to transmit live video, because of the irregularity of broadband, adverse firewall settings, and the lack of support on the network infrastructure, all of which produced obstacles for live streaming. Consumers are now expecting content delivery to have the same high quality that they see on TV on every video enabled device that they own. Because of adaptive technology, the quality has been greatly improved for the delivery of video to computers, game consoles, smartphones, as well as televisions and set-top boxes with IP hybrid.
Multi-screen video has become a reality although problems still exist. Streaming protocols from Adobe, Apple and Microsoft are closed systems with their own format of different text file extensions, protocols and content formats. Because of this, content producers and equipment manufacturers had to create diverse versions of their products to cover the entire range of products for streaming video. This has caused costs to rise and hindered global market development.
To solve these problems, the MPEG-DASH was adopted as a standard for multimedia streaming over the Internet, which incorporates the best elements of the three proprietary solutions. By doing this, MPEG-DASH provides cooperation between different servers in the network and different consumer electronic devices.
The Internet has become an important channel for the delivery of multimedia; and since HTTP is comprehensively used on the Internet, it is widely used for the delivery of multimedia content.
MPEG-DASH is set apart from other streaming technologies on the Internet because it can actually divide a video file in to smaller components before it is set to play through a stream. As a stream is playing, each of these components can be integrated into the stream, without causing disruption. This is especially beneficial to users that are operating on a slower network, because MPEG-DASH was created to change up the bit rate delivery for these streams, giving users with a slower internet connection a higher speed rate.
MPEG-DASH is very storage efficient for streaming service providers like Netflix, which use a content delivery network to store and deliver their videos; but to accommodate different types of devices, these providers had to offer different video formats, which means that they had multiple copies of the same content in their CDN. Under the MPEG-DASH standard all content can be encoded and encapsulated one way, and stored on CDN servers just once, leading to cost savings for storage space in addition to improved streaming performance.
Since MPEG-DASH encoders generate video segments on demand for the client, the client may be able to utilize that live stream faster and in segment sizes that are suitable to the current bitrate with fewer skips during video playback and a live stream that's closer to real time. Years ago, Web video was easy, as a 2, 4 or 10 MB file was downloaded to a device and then played. This was actually scaling, not streaming. To keep a stream of video flowing smoothly, the servers need to send these smaller segments when the device can accommodate them.
The video lives on the server in several different bit-rates with 250 kbs being low quality, 500 kbs medium quality, and 1000 kbs high quality. The device determines and then commands the server to send the best quality given the current network conditions (see diagram).
Web video is encoded in common codec formats and stored in various streaming formats, depending on the media player. Video delivery companies have their own streaming format and their own method of streaming, while MPEG-DASH defines openly published profiles. A media player can easily support these various streaming profiles.
MPEG-DASH works seamlessly with various DRM solutions, thereby protecting the rights of movie and sports producers.
This standard is attractive to many companies because of key market benefits that results, such as an independent stable international standard, which is not owned by any single company, as MPEG-DASH is a finalized specification. It delivers the complex DVD or Blu-ray experience, with multiple synchronized video and audio options. Multiplexed and non-multiplexed video and audio tracks can be mixed, providing for dynamic bandwidth adaptation, and support for multiple audio options such as language selection, surround sound, and bandwidth efficiency by sending only the requested tracks, as well as reduced production, storage, maintenance and delivery costs.
One-time encryption and packaging of content allows for simultaneous use of multiple DRM technologies. MPEG-DASH is designed for fast start-up, and the segments accessed via byte-range requests can optionally be stored contiguously on the server.
The standard also allows for efficient server based ad insertion. MPEG-DASH avoids having to provide multiple streaming solutions, each of which requires a separate ad insertion flow, content protection, and a different closed captioning format. It also improves scalability and fault tolerance by defining multiple-base URL, while signaling content descriptions such as accessibility, rating, and audio channel configuration.
MPEG-DASH works on any HTTP server and most mainstream media servers, which means that service providers are not required to invest in specialized MPEG-DASH-specific infrastructure. There is a dedicated group of encoders, content packagers, delivery platforms, and player builders, which provide a wide range of MPEG-DASH solutions.
There are other aspects unique to the MPEG-DASH system, meaning that the system is very adaptable and can be utilized in a number of different formats. Developers are starting to think about the benefits of incorporating this system into other streaming sites, because it has the capability to work with a number of different file formats, with just a few modified component parts. Presently, it can work with MPEG-2 and MPEG-4 technologies because the MPEG-DASH program was created specifically to work with these file formats.
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Len Calderone – Contributing Editor
Len has contributed articles to several publications. He also writes opinion editorials for a local newspaper. He is now retired.