Adaptive bitrate streaming. Adaptive streaming overview Adaptive streaming in action Adaptive bitrate streaming is a technique used in streaming multimedia over computer networks. While in the past most video streaming technologies utilized streaming protocols such RTP with RTSP, today's adaptive streaming technologies are almost exclusively based on HTTP[1] and designed to work efficiently over large distributed HTTP networks such as the Internet. It works by detecting a user's bandwidth and CPU capacity in real time and adjusting the quality of a video stream accordingly. More specifically, and as the implementations in use today are, adaptive bitrate streaming is method of video streaming over HTTP where the source content is encoded at multiple bit rates, then each of the different bit rate streams are segmented into small multi-second parts.[5] The streaming client is made aware of the available streams at differing bit rates, and segments of the streams by a manifest file.
Current uses[edit] History[edit] Progressive scan. Progressive scanning (alternatively referred to as noninterlaced scanning) is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence. This is in contrast to interlaced video used in traditional analog television systems where only the odd lines, then the even lines of each frame (each image called a video field) are drawn alternately, so that only half the number of actual image frames are used to produce video.[1] The system was originally known as "sequential scanning" when it was used in the Baird 240 line television transmissions from Alexandra Palace, United Kingdom in 1936. It was also used in Baird's experimental transmissions using 30 lines in the 1920s.[2] Progressive scanning is universally used in computing.[3] Example of interline twitter[edit] This rough animation compares progressive scan with interlace scan, also demonstrating the interline twitter effect associated with interlacing.
See also[edit] Video on demand. Video on demand (VOD) or audio and video on demand (AVOD) are systems which allow users to select and watch/listen to video or audio content when they choose to, rather than having to watch at a specific broadcast time. IPTV technology is often used to bring video on demand to televisions and personal computers.[1] Television VOD systems can either stream content through a set-top box, a computer or other device, allowing viewing in real time, or download it to a device such as a computer, digital video recorder (also called a personal video recorder) or portable media player for viewing at any time.
The majority of cable- and telco-based television providers offer both VOD streaming, including pay-per-view and free content, whereby a user buys or selects a movie or television program and it begins to play on the television set almost instantaneously, or downloading to a DVR rented from the provider, or downloaded onto a PC, for viewing in the future. Early development[edit] IPTV. Internet Protocol television (IPTV) is a system through which television services are delivered using the Internet protocol suite over a packet-switched network such as a LAN or the Internet, instead of being delivered through traditional terrestrial, satellite signal, and cable television formats. Unlike downloaded media, IPTV offers the ability to stream the media in smaller batches, directly from the source. As a result, a client media player can begin playing the data (such as a movie) before the entire file has been transmitted.
This is known as Streaming media. IPTV services may be classified into three main groups: live television, with or without interactivity related to the current TV show;time-shifted television: catch-up TV (replays a TV show that was broadcast hours or days ago), start-over TV (replays the current TV show from its beginning);video on demand (VOD): browse a catalog of videos, not related to TV programming. Definition[edit] History[edit] Promise[edit] Markets[edit]
Streaming media. A typical webcast, streaming in an embedded media player A client media player can begin playing the data (such as a movie) before the entire file has been transmitted. Distinguishing delivery method from the media distributed applies specifically to telecommunications networks, as most of the delivery systems are either inherently streaming (e.g., radio, television) or inherently nonstreaming (e.g., books, video cassettes, audio CDs). For example, in the 1930s, elevator music was among the earliest popularly available streaming media; nowadays Internet television is a common form of streamed media. The term "streaming media" can apply to media other than video and audio such as live closed captioning, ticker tape, and real-time text, which are all considered "streaming text". History[edit] In the early 1920s, George O. Attempts to display media on computers date back to the earliest days of computing in the mid-20th century.
New technologies[edit] Business developments[edit] J. Video codec. A video codec is a device or software that enables compression or decompression of digital video. The compression is usually lossy. Historically, video was stored as an analog signal on magnetic tape. Around the time when the compact disc entered the market as a digital-format replacement for analog audio, it became feasible to also begin storing and using video in digital form, and a variety of such technologies began to emerge. Audio and video call for customized methods of compression. Engineers and mathematicians have tried a number of solutions for tackling this problem. There is a complex relationship between the video quality, the quantity of the data needed to represent it (also known as the bit rate), the complexity of the encoding and decoding algorithms, robustness to data losses and errors, ease of editing, random access, and end-to-end delay.
Applications[edit] Encoding media by the public has seen an upsurge with the availability of CD and DVD recorders. Microsoft codecs[edit] Video. Video is an electronic medium for the recording, copying and broadcasting of moving visual images. History[edit] Video technology was first[citation needed] developed for cathode ray tube (CRT) television systems, but several new technologies for video display devices have since been invented. Charles Ginsburg led an Ampex research team developing one of the first practical video tape recorder (VTR).
In 1951 the first video tape recorder captured live images from television cameras by converting the camera's electrical impulses and saving the information onto magnetic video tape. Video recorders were sold for $50,000 in 1956, and videotapes cost $300 per one-hour reel.[1] However, prices gradually dropped over the years; in 1971, Sony began selling videocassette recorder (VCR) decks and tapes to the public.[2] After the invention of the DVD in 1997 and Blu-ray Disc in 2006, sales of videotape and recording equipment plummeted. Characteristics of video streams[edit] Aspect ratio[edit] MPEG-4 AVC. H.264 or MPEG-4 Part 10, Advanced Video Coding (MPEG-4 AVC) is a block-oriented motion-compensation-based video compression standard. As of 2014[update], it is one of the most commonly used formats for the recording, compression, and distribution of video content.[1] It supports resolutions up to 8192×4320, including 8K UHD.[2] The intent of the H.264/AVC project was to create a standard capable of providing good video quality at substantially lower bit rates than previous standards (i.e., half or less the bit rate of MPEG-2, H.263, or MPEG-4 Part 2), without increasing the complexity of design so much that it would be impractical or excessively expensive to implement.
This was achieved with new features such as an improved discrete cosine transform (DCT) algorithm and multi-picture inter-picture prediction. H.264 was standardized by the ITU-T Video Coding Experts Group (VCEG) together with the ISO/IEC JTC1 Moving Picture Experts Group (MPEG). Naming[edit] History[edit] Versions[edit]