Understanding Media Streaming


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Understanding Media Streaming

  1. 1. Multimedia 101 Understanding What is media streaming? What is the Media Streaming difference between streaming a media file and playing it directly from disk? What is media streaming? 2 How is media streaming different from non-streaming playback? 2 Terminology 2 What makes streaming media choppy? 4 Media Servers 4 Media Streaming with the ScreenPlay Pro HD 5 March 31, 2009
  2. 2. What is media streaming? Media streaming allows you to play back an audio or video file from the internet (or from a network location) without having to first download the complete file to your computer. When a media file is streamed, it is delivered as a constant data stream to your computer or media player rather than as an intact file that you must save and decompress before you can play it. For example, a live television broadcast might be streamed over the internet and viewed on your computer while the broadcast is in process. How is media streaming different from non-streaming playback? Media streaming developed as a means of delivering audio and video via the internet without having to first download and decompress a large file on your computer. Because media files (especially video) tend to be very large, it typically takes a very long time to download a file that might provide only a few minutes (or even seconds) of video. Media streaming makes it possible to start playback of a media file from the internet almost immediately with only a brief delay needed to buffer the data stream. Media streaming also means that a file you want to play doesn’t have to reside on your personal computer. Rather it is stored on a server that delivers the data stream ‘on demand’ when you want to view or listen to it. A multimedia file can be streamed or not streamed, depending on how it’s delivered to your media player. A good example of the difference between streaming and non- streaming media is viewing a video file on YouTube versus downloading the video as a file to your computer then viewing it. When the video is delivered over the internet as you view it (YouTube), it is streaming media. When you play the video as a file saved on your computer, it is non-streaming. Terminology Discussions of media streaming often use technical terms that are unfamiliar to many users. Here are some of the more common terms. Bit rate (bitrate or data rate) This is a measure of how fast data is being streamed. It most often refers to the number of bits that are conveyed or processed per second. Examples: • kbps or kbit/s = kilobits per second • Mbps or Mbit/s = megabits per second • Gbps or Gbit/s = gigabits per second Buffering Buffering is the process of collecting a small backlog of data on the end-user system. This supports continuous playback in case of delays or interruptions in the data stream (for example, due to network congestion). The media player reads from the buffer while the buffer refills from the media streaming provider. Buffer underrun (buffer underflow) Buffer underrun occurs when a buffer used to communicate between two devices or processes is fed with data at a lower speed than the data is being read from it. This requires the program or device reading from the buffer to pause its processing while the buffer refills. This can cause undesired and sometimes serious side effects, since the data being buffered is generally not suited to stop-start access of this kind. Understanding Media Streaming 2
  3. 3. Bandwidth A measure of available or consumed data communication resources, usually expressed in bits per second or a multiple of it (kbps, Mbps, Gbps). Bandwidth capacity or available bandwidth usually refers to the maximum throughput in a digital communication system. Consumed bandwidth generally refers to the average data rate of successful data transfer through a communication path. Compression Data compression or source coding is the process of encoding information using fewer bits (or other information-bearing units) than an unencoded representation would use through use of specific encoding schemes. As with any communication, compressed data communication only works when both the sender and receiver of the information understand the encoding scheme. For example, this text makes sense only if the receiver understands that it is intended to be interpreted as characters representing the English language. Similarly, compressed data can only be understood if the decoding method is known by the receiver. See Understanding Codecs in this white paper series for more information on this topic. CPU power CPU stands for central processing unit (or processor, for short) and refers to an electronic circuit that can execute computer programs. The CPU is the ‘brains’ of a computer system. CPU power is how fast a processor is capable of executing. Higher CPU power boosts the processing speed for streaming media. Dropout In the context of media streaming, dropout refers to a momentary loss of signal, usually caused by noise, propagation anomalies, or system malfunctions. For digital signals, dropouts can be sudden and complete. Error correction Refers to algorithms or computer programs that are applied to detect and fix errors in the data stream. This has great practical importance in maintaining data integrity across noisy channels and less-than-reliable storage media. LAN A local area network (LAN) is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport. Low latency Low latency allows human-unnoticeable delays between an input being processed and the corresponding output providing real time characteristics. In the context of media streaming, low latency interrupt paths are critical for preventing buffer underruns. Peer-to-peer (P2P) This refers to protocols that arrange for prerecorded streams to be sent between computers. This prevents the server and its network connections from becoming a bottleneck. In general, the data feed will come from multiple clients or peers rather than a single server. Protocols A protocol is a standard by which communication takes place between network devices. HTTP, TCP/IP, FTP, UPnP, and DNLA are all examples of commonly used network protocols. See Understanding Network Protocols in the “Networking 101” white paper series for more information on this topic. Understanding Media Streaming 3
  4. 4. Throughput Throughput is the average rate of successful data delivery. Throughput for delivery of streaming media depends on the capabilities of the media server, the protocol used for transmission, network bandwidth, and client (end-user) CPU power. Unicast – Multicast Unicast transmission is the sending of information packets to a single destination. Unicast servers provide a stream to a single user at a time, while multicast servers can support a larger audience by serving content simultaneously to multiple users. Video on demand (VOD) A media stream can be ‘on demand’ or ‘live’. On demand streams are stored on a server for a long period of time, and are available to be transmitted at a user’s request. Live streams are only available at one particular time, as in a video stream of a live sporting event. What makes streaming media choppy? Interruptions in streaming media playback are far from uncommon, especially for video streamed from the internet. Stop-and-start “rebuffering” delays result when the throughput of the delivered data stream is lower than the playback bitrate. In less technical terms, if your media player is playing a file faster than the media server is delivering the data stream, your player frequently has to stop to let the media data stream catch up. The opposite problem can also occur. If the media server transmits a data stream faster than your system can receive or process it, some information packets will be lost. This can result in poor video quality and possibly even jumps in playback. Media Servers Media servers are specialized for optimized delivery of audio and video content to a media player. With a media server connected to a home network, you can use the media server to consolidate media files from individual computers on the network, so you can access all of your media content from any media networked device. Several Iomega products include media server capabilities and can stream audio and video files over a home network. For example, the Iomega® Home Media Network Hard Drive can be configured to share media files with iTunes or DLNA clients for playback on your computer, TV, or Stereo. You can use this feature to set up the iTunes libraries stored on computers throughout your home network so they are accessible by all users on the network. The Iomega® StorCenter™ ix2 and StorCenter ix4 series NAS Servers include a built-in media server that scans for media files in specified Shared Folder directories. Any media content contained in these directories will be scanned by the Iomega StorCenter media server and accessible to any user on your network with a media player. The Media Server supports playback of videos, music and pictures from any UPnP AV (Universal Plug and Play Audio Visual) network media players, such as iTunes®, Windows Media Player®, or Xbox 360®. The Iomega® ScreenPlay™ Pro HD is a specialized media player that is capable of streaming audio and video files across a network to play on your TV. You can use this capability to tie your home network into your home entertainment system. See the next section for detailed instructions. Understanding Media Streaming 4
  5. 5. Media Streaming with the ScreenPlay Pro HD Here’s how to stream your videos, music, and photos directly to your TV from any volume on your home network: 1. Connect the ScreenPlay Pro HD to your home network. If you have a wireless network, see the white paper on Setting Up Your ScreenPlay Pro HD in a Wireless Network for detailed setup instructions. 2. Connect the ScreenPlay Pro HD to video and audio inputs on your TV set. See the white paper on Installing Your ScreenPlay Pro HD for complete instructions. 3. Connect the ScreenPlay Pro HD to power. 4. Turn on your TV and change the input setting as needed to receive input from the ScreenPlay Pro HD. Refer to the manual that came with the TV if you are uncertain how to do this. 5. Point the remote control at the front of the ScreenPlay Pro HD and press the STANDBY button, or press the Standby/Power button on the front of the drive. 6. During activation, the blue LED will blink brightly for several seconds. When the blue LED glows steadily, the ScreenPlay Pro HD is ready to use for playback. NOTE: Pressing the STANDBY button again will return the ScreenPlay Pro HD to Standby mode and turn off the blue LED. While in Standby mode, the ScreenPlay Pro HD will not respond to other navigation or command buttons. 7. From the main ScreenPlay menu, select Network and press the ENTER key on the remote control. 8. The Network menu will show volumes available on your network. Use the cursor keys on the remote control or front of the ScreenPlay Pro HD to browse to and select the media files you want to play. NOTE: If you need to enter a username and password to login to a network volume, press the ENTER key on the remote control to bring up the ScreenPlay virtual keyboard. Use the remote control and the ENTER key to select the necessary characters. 9. Once you have highlighted the file you want to play, press the ENTER key. For information on using the remote control while playing media files, refer to the ScreenPlay Pro HD User’s Manual. In addition to streaming media files from the network to the TV set, you can use the ScreenPlay Pro HD to store a multimedia library that is accessible from individual computers on your home network. See Best Practices in Setting Up a Multimedia Library in the white paper series on Making the Most of Your ScreenPlay Pro HD. Copyright © 2009 Iomega Corporation. All rights reserved. Iomega, StorCenter, ScreenPlay, and the stylized “i” logo are registered trademarks of Iomega Corporation in the United States and/or other countries. Microsoft and Windows are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries. Certain other product names, brand names, and company names may be trademarks or designations of their respective owners. 033009b Understanding Media Streaming 5