Streaming media refers to the simultaneous transmission and playback of video and audio data over a computer network . The process of data transmission itself is called streaming and transmitted ( "streamed") programs as a live stream or just stream called. Streaming media that was triggered via the WWW or HTML is also called web radio or web TV . In contrast to downloading (“ download ”), the goal of streaming is not to create a copy of the media for the user, but to output the media directly, after which the data is discarded.
The reproduction of programs via a live stream usually differs from classic broadcasting . While broadcasts are sent to an unlimited number of recipients at the same time ( broadcast ), streaming is usually a direct connection between the sender's server and the client of each individual user. The distribution often takes place via streaming portals and internet-based media libraries .
Streaming video is responsible for 80% of the growth in global data traffic, according to estimates in 2019, and consumes enormous amounts of energy.
Streaming media has been around since the middle of the 20th century. Little progress was made during the first few decades because the technology was expensive and the capabilities of the computer hardware were limited.
At the end of the 1980s, PCs became powerful enough to display a wide variety of media . The primary requirements for receiving streams were a strong CPU and sufficient bus (network) bandwidth for the required data rates.
In the late 1990s, higher data rates were available and access to the Internet was made easier. There were also standard protocols and formats , such as the Internet protocol family and HTML . The internet was commercialized . These advances in computer networks, combined with powerful PCs and modern operating systems , made streaming media possible for ordinary users. For the first time, on-demand services such as YouTube or "media libraries" from individual television stations were available to a broad audience, live streaming ( Internet radio and television ) established itself , and, especially in the corporate sector, other areas of application emerged with video conferences and video telephony .
There are now more and more offers and new streaming protocols such as Microsoft Media Server Protocol (MMS) and Real-Time Streaming Protocol (RTSP), and picture and sound quality have also been improved.
In order to be able to use streaming media offers, special software is required on the receiving end . This can be a plug-in that is integrated into a web browser , but it can also be a stand-alone playback program. The former is called up automatically as soon as a requested page contains streaming media data. These plug-ins and players are usually offered free of charge, in contrast to the streaming servers that send the data.
A variety of different competing streaming media technologies exist . The most famous representatives are:
Audio and video container formats
- Flash video streaming
- Advanced Streaming Format (ASF)
- Audio Video Interleave (AVI)
- Flash Video (FLV)
- MPEG transport stream
- Nullsoft Streaming Video
- Ogg ( Vorbis , Theora )
- Windows Media
Streaming software and servers
- Catra Streaming Platform
- dyne: bolic
- Helix server
- Icecast ( open source , audio only)
- Icecast 2 ( free software )
- Jinzora Broadcast Server Software ( Free Software )
- Logitech Media Server
- LSCube / Feng ( free software ), RTSP-capable, also masters newer free audio and video formats
- Microsoft Internet Information Services 10 , part of the Windows Server 2016 and Windows 10 operating system.
- No23Live ( Freeware , audio only)
- Open Broadcaster Software (OBS)
- PS3 Media Server Dedicated software for streaming videos, music and photos from Windows PCs to a PlayStation 3 in many different formats
- QuickTime Broadcaster
- QuickTime Streaming Server
- Red5 for the Real Time Messaging Protocol (RTMP).
- VideoLAN Server ( free software )
Data transfer rate
- Audio : mostly in the two- to three-digit kbit / s range
- Video : a few hundred kbit / s to a few Mbit / s (with triple play offers)
Typical available data transfer rates are:
- analog modem : up to 56 kbit / s
- ISDN : 64 or 128 kbit / s
- DSL and cable modems : 0.4–400 Mbit / s
- FTTH : 10 Mbit / s to 1 Gbit / s
- Ethernet : 10 Mbit / s, 100 Mbit / s, 1 Gbit / s or 10 Gbit / s
Since the data is to be reproduced at the same time as it is received, a sufficient data transmission rate must be available. It is necessary that the data transfer rate available for transmission is greater than the data transfer rate used for streaming. The audio and video data to be sent are therefore compressed before transmission . In most cases, lossy compression is used, as this is the only way to achieve a transferable amount of data per unit of time .
A buffer is used in the media player in order to compensate for different transit times of the data packets in the network and to prevent the associated blockages . Therefore, the playback is also slightly delayed, typically by 2 to 6 seconds. If this buffer is insufficient, some media players will dynamically increase it.
Since video data usually has a higher data rate than audio data, a much stronger compression is required here.
With the same type of compression, the quality decreases with the data transmission rate to which the data stream is to be reduced. The visible and audible quality of a stream therefore depends largely on the following factors:
- the type and quality of the raw material
- the compression method used
- the data transfer rate that can be used for transmission, which is usually limited by the Internet access .
- Data is transmitted from the server to the client via the network.
- Playback takes place during the transfer.
- Intermediate buffering for uninterrupted playback is necessary.
- In principle, it is possible to fast-forward, rewind and pause.
- Protocols: HTTP , FTP
- Provision of the offer in real time
- Protocols: RTP , RTCP , RTSP , SIP
- Special form: Phonecast (distribution via telephone server)
- Fast forward to the current live position is possible; Pausing and rewinding is ok. A. possible as in the on-demand stream.
Streaming Media in Education
In recent years, lecture recording systems have become increasingly popular in Europe. In Delft , for example, all lectures are recorded so that they can be made available to students at home. Since the student protests in 2009 in particular, many universities have started to develop their own systems or set up systems that already exist (Sonic Foundry, Camtasia, Lecture2Go and others).
There are two different types of recordings:
- Hardware recording (Sonic Foundry): There is a hardware streamer via which sources are connected and recorded. This option is simple but expensive.
- Software solutions (Camtasia, Lecturnity, etc.): Software is installed on the presentation computer and the presentation is recorded in this way. This option is inexpensive, but post-processing is necessary.
User numbers in Germany
According to a survey from 2019, 79 percent of all German Internet users aged 16 and over watch videos via stream at least occasionally. 42 percent use paid video-on-demand services.
According to a survey from 2020, 76 percent of Internet users aged 16 and over in Germany listen to music via streaming services at least occasionally. One in four (24 percent) uses paid streaming offers. This enabled audio streaming to gain further popularity: in 2019, only 72 percent of Internet users aged 16 and over in Germany listened to music via streaming services, two thirds of them daily. In 2019, one in five not only used free offers, but also paid for music streaming.
Traffic and network capacity
While traditional radio services ( radio , television , etc.) strive for the largest possible range with the least possible expenditure of energy and other resources (on the part of the broadcaster) and the current, specific number of viewers for the broadcaster has no (direct) influence on the costs, streaming -Media offers with a growing number of subscribers for the sender (directly) more expensive, because the data must be sent to each recipient individually. In network technology , the multicast mode is known, in which a data stream from the streaming server can be sent to different recipients at the same time with a low network load, but this is still practically not used because many routers on the Internet do not support it. Instead, so-called overlay networks are used for streaming offers with a mass audience ( e.g. broadcasts of the Bundesliga or pop concerts) , which make the data to be transmitted available in many locations at the same time from a network topological perspective - thus as close as possible to the respective recipient.
The picture and sound quality can often be rather low. B. mobile devices to ensure a smooth transfer. From this perspective, the use of streaming technology for content that does not depend on real-time transmission ( e.g. trailers ) appears rather questionable.
The high volume of data can lead to a high utilization of the network capacity at peak times. In the course of the COVID-19 pandemic , the high level of video streaming threatens to overload the data networks, so that governments, but also Internet providers, are calling for economical use and, if necessary, threatening to limit the services. The providers Netflix and Youtube then agreed to temporarily reduce the bit rates of their videos, while accepting a reduction in image quality.
The energy required for streaming consists of the server farm, transmission in the network and end device. The associated share of global warming depends on the energy mix used to generate electricity. According to studies from 2019, depending on the device (and stream quality), between 80 and 220 watts of electrical power should be used for streaming . These values coincide with a study from 2020. According to it, one hour of video streaming over the landline network in SD resolution on a 65-inch television set requires around 280 watt hours of energy, and 370 watt hours on the same device in HD resolution. Video streaming on the smartphone or tablet, on the other hand, only requires 65 or 75 watt hours of energy in SD resolution.
Limited user functions
Various content providers also use streaming technology with the aim of preventing even technically savvy end users from permanently saving the received data. Saving the stream transmitted via HTTP may be possible with special software (such as MPlayer ), but it can be made more difficult by other measures, such as DRM. As a result, the content has to be reloaded each time it is consumed again, which causes unnecessary repeated data transfer from the server to the user.
The competition in the market sometimes also leads to disadvantages for customers. Since 2015, Amazon has stopped selling Google Chromecast or Apple TV products. On the other hand, the Google Chromecast cannot establish a streaming connection with Amazon Prime - but it is not known whether this is due to Google or Amazon. In Germany, a connection with Amazon Prime between Chromecast and TV can only be established indirectly.
When streaming, the data is not permanently stored on the end user's device, so no permanent copy is created and the data object is never completely available, such as when downloading to a file. This is the only way to view media streamed on end devices that do not have enough storage space to completely download the file, e.g. B. many smartphones or simple tablets . If there is enough storage space available, this can in some cases be bypassed by the user with the help of additional software; many providers try to make this storage of data more difficult or to prevent it. Whether this obstacle or, on the other hand, the storage represents an "abuse" of the streaming technology is disputed: If the data consists of GEMA music repertoire, the provider is even obliged to prevent storage as far as possible. From the perspective of the author, streaming can be seen as a means to present his works and still technically retain the ability to control the exploitation and earn money from the use of his works ( digital rights management DRM).
Traditionally, the publishing rights for the content are often sold with a restricted distribution area by the content creators to the streaming services, for example only for a certain country. Due to the worldwide connectivity of the Internet, however, it is in principle possible for a user to access content from any other location. It is difficult to check whether, for example, a music channel distributed over the Internet is only used in the country in which the operator bought the rights. The resulting legal problems have hardly been discussed, and there are hardly any empirical values in the form of judgments or laws.
In December 2005, GEMA did not yet have a remuneration model for web TV (streaming TV). A lump sum of 30 euros per month was therefore provisionally charged.
In the meantime, GEMA has adopted a remuneration model for "web TV providers" which stipulates a staggering depending on the music content. As described in the form, from GEMA's point of view, web TV is the transmission of moving images in a sequence compiled by the operator over which the user has no influence. This means that almost all web TV stations fall out of the area covered by this agreement, as an archive for retrieving “Videos on Demand” maneuvers the station out of the GEMA definition.
In June 2014 the ECJ ruled that streaming was exempt from the European Copyright Directive , because the data loaded onto the computer were "temporary, volatile or accompanying and an integral and essential part of a technical process". The mere viewing of copyrighted works in the web browser or via a streaming client does not constitute a legal violation. However, the ECJ also ruled that a legal violation could exist if the stream is fed from an obviously illegal source. The mere viewing is therefore only not a legal violation if the person setting the stream does not violate copyright himself or if this is at least not visible to the viewer.
With a new regulation of the European Parliament and the European Council that will come into force in 2018, streaming subscriptions should be able to be used throughout the European Union. A subscription in one EU country must also be available from other EU countries - but only for "temporary" stays abroad. In order not to be considered a local provider in the respective foreign country, streaming service providers can choose as a control mechanism and specify whether customers must provide their payment and tax data, postal and IP address of their EU country of residence, for example to use video-on-demand -Offers.
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