What is UDP?

What is MPEG-TS?

What is DVR?

What is Bit Rate?

What is Transrating

What is adaptive bit rate?

What is RTCP

What is RTMPE

What is RTMPS

What is Helix Server?

What is SureStream?

What are HLS (HTTP Live Streaming), HDS (HTTP Dynamic Streaming), Smooth (Silverlight) Streaming?

What is Trick Play

What is a Keyframe

What is DRM?

What is Live Stream Record

What is MPEG-DASH?

What is Codec?

What is Embedded Player?

What is Encoding?

What is Flash?

What is H.263, H.264, H.265

What is Real Player?

What is Hotlinking?

What is HTTP Streaming?

What is IPTV?

What is Load Balancing?

What is Live Streaming?

What is a Manifest?

What is Multicast?

What is MetaData?

What is MPEG?

What is RTMP?

What is RTP?

What is RTSP?

What is RTMPT?

What is Smooth Streaming and what is Silverlight?

What is Streaming?

What are transcoding and transrating?

What is Transmuxing?

What is Unicast Streaming?

What is VOD?

What is a VSP?

What is a CDN?

What is AC-3?

What is AAC?

UDP (User Datagram Protocol) is a connectionless protocol that is widely used in streaming. It’s very efficient because it does not perform error checking as does TCP, but it’s therefore more prone to network issues; packets may be lost or may arrive out of order. Wowza Streaming Engine™ software supports re-streaming MPEG-TS and multicast streams over UDP, and Media Server software also supports the use of the Wowza Push Publish AddOn to publish MPEG-TS and multicast streams over UDP.

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MPEG-TS (MPEG Transport Stream) is a transport stream container format that’s used for streaming and storage of streams.

Wowza Streaming Engine™ software supports MPEG-TS live stream ingress, which can be re-streamed from live MPEG-TS encoders over UDP. Streaming Engine software supports using the Wowza Push Publishing AddOn to publish MPEG-TS.

The Streaming Engine software writes .ts files to support HLS (cupertino) playback and caching infrastructure of CDNs that support Wowza HTTP Origin features. These .ts files are kept in memory, not written to disk.

NOTE: These .ts files are not easily portable for other purposes if written to disk.

Wowza does not support .ts files for on-demand play.

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DVR (Digital Video Recorder) provides pause and rewind for live digital content. The Wowza nDVR AddOn brings DVR capabilities to live streaming. To do this, Wowza writes the live stream to disk in chunks that are similar to the segmented chunks Wowza creates for HTTP streaming. Clients play back from this recorded store, providing pause and rewind capability.

How to set up and run Wowza nDVR for live streaming

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Bitrate is a measure of the throughput of bits (or kilobits, megabits, gigabits, terabits) per second, written as bit/s or bps, kbit/s or kbps, Mbit/s or Mbps, Gbit/s or Gbps, and Tbit/s or Tbps.

The bitrate of a stream is a primary consideration in streaming. Higher-quality streams (with better resolution and larger frame sizes) have a higher bitrate than lower-quality streams. However, client bandwidth may limit the bitrate at which streams can be played back smoothly. 

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Transrating is the process of changing a video file from one bitrate to another. See Transcoding and Transrating

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Adaptive bitrate (ABR) streaming refers to a technology that lets playback clients switch between various bitrate versions of a stream on the fly to accommodate changing network conditions, CPU constraints, and display capabilities. This streaming method can provide optimal image and sound quality for the viewer. The client controls switching based on client-side factors, and Wowza Streaming Engine™ software performs the server-side switching, which is transparent to the user. 

 

ABR streaming requires multiple versions of a file or live stream. Each version is encoded with a different bitrate, and each file or live stream encoded for ABR streaming must be keyframe aligned with the corresponding files or streams. The Wowza Transcoder is used to transrate one high-quality stream into several bitrate versions that are always keyframe aligned and suitable for ABR streaming. For video on demand streaming, the encoding process must be able to produce keyframe-aligned sets.

 

Media Server software supports ABR for HTTP clients that use HLS (cupertino), HDS (sanjose), or Silverlight (smooth) streaming, and Flash RTMP clients that use Flash Dynamic Streaming.  Media Server software does not support ABR for RTP/RTSP or multicast play.

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RTCP (Real Time Transport Protocol Control Protocol) works together with RTP in RTSP streaming. While RTP carries audio and video streams, RTCP is the data channel in an RTSP stream. It’s used primarily to send quality of service (QoS) data to the source.

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RTMPE is a version of RTMP (Real Time Messaging Protocol) that uses Adobe's own security mechanism for encryption. Because RTMPE has proven to have security issues, other security options such as the RTMPS protocol should be used instead.

Created to enable low-level stream encryption for high-traffic sites, RTMPE uses the Anonymous Diffie-Hellman key exchange method which allows two parties that have no prior knowledge of each other to jointly establish a shared secret key over an insecure communications channel, but provides no verification of either party's identity. This opens vulnerabilities to “man-in-the-middle attacks” at session initialization.

RTMPE is not enabled in the Wowza Streaming Engine™ software by default, but a Wowza version of RTMPE is provided on request through an AddOn.

For more information about RTMPE, see: http://en.wikipedia.org/wiki/Real_Time_Messaging_Protocol#Encryption

© 2013 Wowza Media Systems, LLC. Wowza and related marks are registered trademarks of Wowza Media Systems, LLC. Flash and related marks are registered trademarks of Adobe Systems Incorporated. iPhone, iPad, and Apple TV are registered trademark of Apple, Inc. Silverlight is a registered trademark of Microsoft Corporation. All other trademarks are the property of their respective owners. Third party trademarks are used solely to identify and describe third party products as being compatible with Wowza products. Wowza is in no way sponsored, endorsed by or otherwise affiliated with any such third party trademark owners.

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RTMPS is RTMP (Real Time Messaging Protocol) that is transmitted over a TLS/SSL connection, encrypted during transmission from point A to point B. This prevents security breaches such as "man in the middle" from succeeding during transmission. RTMPS is recommended rather than RTMPE for stream encryption.

RTMPS requires an SSL certificate be installed on the Wowza® Media Systems sever, which can be done by using the Wowza StreamLock™ service or another SSL certificate authority.

StreamLock™ provides a free SSL certificate when useing RTMPS

 

© 2013 Wowza Media Systems, LLC. Wowza and related marks are registered trademarks of Wowza Media Systems, LLC. Flash and related marks are registered trademarks of Adobe Systems Incorporated. iPhone, iPad, and Apple TV are registered trademark of Apple, Inc. Silverlight is a registered trademark of Microsoft Corporation. All other trademarks are the property of their respective owners. Third party trademarks are used solely to identify and describe third party products as being compatible with Wowza products. Wowza is in no way sponsored, endorsed by or otherwise affiliated with any such third party trademark owners.

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See RealPlayer

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See RealPlayer

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HLS, HDS, and Smooth Streaming (also referred to in Wowza Streaming Engine™ software as “cupertino”, “sanjose,” and “smooth” streams) are used, respectively, by iOS, Flash, and Silverlight clients to play segmented video and audio files that have been downloaded to a player over HTTP. These stream types vary in detail but work similarly. Wowza Streaming Engine™ software segments live streams and multimedia files into small files (chunks) for delivery to requesting HTTP playback clients. HTTP clients use a manifest file generated by Wowza Streaming Engine software to order requests for the chunks of a stream. Streaming Engine software breaks chunks on keyframes, although not usually on every keyframe; however, each chunk will contain at least one keyframe.

HTTP Live Streaming avoids the network problems sometimes associated with RTMP streaming, which can be blocked in some networks and may require port configuration on the delivery side. On the positive side, HTTP streams are easier to cache and they work with proxy servers. (You cannot proxy RTMP).

Also, ABR streaming is better supported in HTTP clients than in Flash RTMP clients. ABR is built into the HTTP streaming protocols. HTTP clients are able to constantly measure client-side bandwidth calculated by chunk size and download time, whereas RTMP must employ a separate process to measure bandwidth and requires a custom player to implement ABR streaming.

The chunks Wowza creates for HTTP streaming are not written to disk; they are kept in memory.

Wowza does not support ingest of HLS, HDS, or Smooth Streams.

HLS  is a streaming media protocol developed for use in iOS devices by Apple, Inc. Despite the name, “HTTP Live Streaming,” both live and on-demand streaming is supported with HLS. Many set-top boxes, recent Android devices, VLC, and other players support HLS play.

HDS was developed by Adobe for use with Flash player applications. OSMF (Open Source Media Framework) is used in Flash players that play HDS streams.

Smooth Streaming was developed by Microsoft for use with Silverlight player applications.

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Trick Play enables fast forward and rewind of on-demand streams. Wowza Streaming Engine™ software supports Trick Play for Flash RTMP clients and for .flv files that contain SorensonSpark or VP6 video. It is not supported in Wowza Streaming Engine™ software for H.264 video or in other client types. 

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In video compression, a keyframe is the full frame of an image; it’s also known as an intra-frame or i-frame. In compressed video, the first frame is a full image. Subsequent frames—called p-frames—contain information about what has changed between each frame. Keyframes are placed at regular intervals throughout a video; these intervals are set in the encoder. In Wowza Streaming Engine™ software, keyframe frequency (keyframe interval / frames per second) is an important consideration. In HTTP, Wowza Streaming Engine™ software breaks chunks on keyframes. Wowza Streaming Engine software can then optimize HTTP streams and corresponding keyframe frequency settings made in the encoder. This article for HLS streaming shows how to make these types of settings. As an example of another type of keyframe setting, the Silverlight player requires a keyframe frequency between 1 and 4 seconds.

NOTE: Keyframe frequency affects seek precision; most players are only able to seek to the nearest keyframe.

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DRM (Digital Rights Management) is a technology that protects content from piracy. The Wowza DRM AddOn provides integration with third-party DRM key management systems: BuyDRM™ KeyOS™, EZDRM, and Verimatrix® VCAS™.  

The Wowza Streaming Engine™ software encrypts content dynamically by using Microsoft® PlayReady® or Verimatrix® VCAS™ for play in clients that support Apple® HTTP Live Streaming (HLS) and Microsoft Smooth Streaming. Third-party DRM key management systems (such as BuyDRM™, KeyOS™, and EZDRM) handle the keys used to decrypt content.

DRM AddOn overview

Click here to learn more about DRM and different DRM service options.

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Live Stream Record is a built-in Wowza® Media Systems AddOn that provides a number of features for simple and advanced recording of live streams. The Live Stream Record AddOn enables you to control live stream recording by using a web-based user interface, or programmatically through an API,  or by using HTTP URL query parameters (which allow for integration with other systems such as schedulers). The Live Stream Record AddOn supports splitting live streams into multiple on-demand MP4 (QuickTime® container) files or FLV (Flash® Video container) files based on video duration, clock time, or file size.

More information: http://www.wowza.com/forums/content.php?123

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The definition of MPEG-DASH (Moving Picture Experts Group Dynamic Adaptive Streaming over HTTP standard, better known as MPEG-DASH) also known as DASH (Dynamic Adaptive Streaming over HTTP) is part of the MPEG protocol and is enabling streaming media content at a high quality over the traditional HTTP web servers.  It works by breaking down the content into smaller HTTP file segments that have short intervals of playback time content on them.  The segments with the highest bit rate are selected and downloaded by the player. This allows the system to adjust bit rate in real time due to network conditions.  MPEG-DASH leverages the already widely deployed HTTP web server infrastructure that is used for delivery of essentially all Internet content. It allows devices such as Internet connected televisions, TV set-top boxes, desktop computers, smartphones, tablets, etc.

The need for MPEG_DASH is due to the number of protocols, incompatible streaming formats and fragmented device specifications that make accessing and viewing their content increasingly difficult across the growing range of mobile devices and playback screens. Vendor-centric solutions examples are: HLS by Apple, Smooth Streaming by Microsoft, or HDS by Adobe.

The Wowza® MPEG-DASH preview supports DASH264-compatible players. Wowza® is working with industry-leading player vendors to make sure our MPEG-DASH support is compatible as the standard evolves.

MPEG-DASH standard market benefits:

  • independent stable international standard – not owned by any single company.
  • multi-video and audio tracks – deliver the complexity of a DVD or Blu-ray experience, with multiple synchronized video and audio options.
  • mix of multiplexed and non-multiplexed video and audio tracks – provide for dynamic bandwidth adaptation, support for multiple audio options such as language selection and surround sound, bandwidth efficiency and reduced production, storage, maintenance and delivery costs.
  • common encryption – one-time encryption and packaging of content allowing simultaneous use of multiple DRM technologies.
  • templated manifests – for fast start-up.
  • non-segmented origin files – files can optionally be stored contiguously on the server.
  • efficient ad insertion – server-based and client-based targeted ad-insertion via periods.
  • support for multiple CDNs/caches with the same manifest – define multiple base URL in the manifest, thus improving scalability and fault tolerance.
  • accessibility, rating and other content descriptions – possibility of signaling content descriptions such as accessibility, rating, audio channel configuration in the manifest.
  • industry convergence for streaming delivery – avoid having to provide multiple streaming solutions, each of which requires a separate ad insertion flow, content protection scheme, and a different closed captioning format.
  • ease of integration – DASH will work on any HTTP server and most mainstream media servers, meaning service providers and broadcast operators are not required to buy into new vendor-specific ecosystems or invest in specialized DASH-specific infrastructure.

 

More resources

How to set up DASH with Wowza Media Server

First live public trial of MPEG-DASH during the London Olympics

DASH Industry Forum

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The definition of Codec (Compression- Decompression) is hardware or a software algorithm that encodes audio/video data into a file format that can be transmitted and received, stored, encrypted or played back efficiently.


There a many Codec formats some for different uses. As technology improves new codec are created. For example, raw uncompressed PCM audio (44.1 kHz, 16 bit stereo, as represented on an audio CD or in a .wav or .aiff file) has long been a standard across multiple platforms, but its transmission over networks is slow and expensive compared with more modern compressed formats, such as MP3.
There are advantages and disadvantages with transmitting data with a codec. For example:


Lossy codecs: Often used in transmission of video and audio data are the most popular codecs in the software world are lossy, meaning that they reduce quality of the video or audio or both but in most cases is not noticeable to the user. Because the data is compressed there are improvements in smaller file sizes and decreased bandwidth during transmission.

Examples are: 
Audio: Dolby AC3, AAC, MP3, WMA
Video: H.264 / MPEG-4 AVC, H.263, H.261, Open AVS, WMV 


Lossless codecs: Often used in storage of video and audio data are typically used for archiving data in a compressed form while retaining all of the information present in the original stream. This allows future editing of the data at a higher resolution.

Examples are:
Audio: MPEG4-ALS, FFMPEG, QuickTime
Video: FFV1, JPEG 2000, H.264 Lossless, PNG

 

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An embedded player is a browser-based application such as a Flash or Silverlight application that uses a browser plug-in as its runtime environment. An HTML page will include <Embed> and/or <Object> tags that load a player file, an .swf file for a Flash application, or an .xap file for a Silverlight application. The browser loads these files asynchronously. That is, the HTML page loads in the browser first, and then the browser loads the embedded player. It is the embedded player running in the browser plug-in that streams from the Wowza Streaming Engine® software. 

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A codec (coder/decoder) is a program that uses a compression-decompression algorithm to encode and decode video and audio to formats that can be streamed, stored, encrypted, and played back. In streaming, video and audio codecs are used by live encoders, file encoders, playback clients, and by the Wowza Streaming Engine™ software to send and receive live streams or to write files for on-demand play.

Encoding is the process of converting digital audio and video media files into a different format, generally by using a codec to compress them.

Encoding reduces the size of audio and video files. Each audio and video file format has a corresponding codec that is used to code it into the appropriate format and then to decode it for play. The encoding details of a file or stream are defined in its video and audio codecs. Wowza® Media Systems supports a wide variety of playback client video and audio codecs, and these encoding details determine levels of support and constraint. A matrix of audio and video codec support by client type can be found in this Wowza Specifications chart 

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Adobe Flash is a multimedia platform that can play and stream rich media content, including animations. The Flash Player is a browser plug-in, a runtime environment for Flash applications. It is usually downloaded from Adobe and then installed on web browsers. It is often used for games, streaming video, animated presentations, and banner ads.

The term “Flash player” is also used to refer to Flash applications that have been designed to play video and audio streams. The Flash Player (the plug-in) plays Flash applications; a Flash player (an application or playback client) plays streams. Most Wowza® Media Systems documents use the term “Flash client” to refer to Flash applications involved in streaming.

In general, content producers supply Flash playback clients. These are usually files stored on the content producer’s web server (or hosted by a third party) that are requested by and served to a browser. A Flash application is usually compiled into an .swf file, stored on a web server, and then embedded in an HTML page that is loaded in a user’s browser. The Flash client running in the browser is what connects to the Wowza Streaming Engine™ software. The web server’s only role is to serve the player files to the browser. 

 

Wowza supports play and publishing of Flash RTMP streams and play only of HDS (Flash Dynamic Streaming) streams.

Streaming Engine software and Flash RTMP clients can interact and exchange data by using RPC (remote procedure call) commands. Streaming Engine software uses Flash RTMP applications for most interactive operations that involve streaming (such as video chat).

Many available third-party Flash players work with Streaming Engine software. <link>  And Streaming Engine software includes several Flash examples that are designed for testing and as starting or reference points for developers.


© 2012 Wowza Media Systems, LLC. Wowza and related marks are registered trademarks of Wowza Media Systems, LLC. Flash and related marks are registered trademarks of Adobe Systems Incorporated. iPhone, iPad, and Apple TV are registered trademarks of Apple, Inc. Silverlight is a registered trademark of Microsoft Corporation. All other trademarks are the property of their respective owners. Third-party trademarks are used solely to identify and describe third-party products as being compatible with Wowza products. Wowza is in no way sponsored, endorsed by, or otherwise affiliated with any such third-party trademark owners.

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H.263 is an older video compression format standard, or codec. It’s still widely employed by Internet applications such as Flash Video content (used on sites such as YouTube and Google Video), desktop video conferencing, video telephony, surveillance and monitoring, and 3GPP files for play on mobile phones. IP Multimedia Subsystem (IMS) and Multimedia Messaging Service (MMS) also require the use of H.263. The Wowza Transcoder supports transcoding to h.263.

 

H.264/AVC (Advanced Video Encoding) or MPEG-4 Part 10 is a video compression format that provides higher-quality video with lower bitrates than earlier formats. The terms H.264, AVC, and MPEG-4 Part 10 are equivalent and interchangeable. H.264 is the current standard for video streaming and is the most commonly used format for encoding live streams and multimedia files for on-demand streaming that are served by the Wowza Streaming Engine® software. Most of the clients that Wowza® Media Systems supports will play H.264 video, restricted by the various limitations for the Levels and Profiles of H.264. The Wowza Transcoder’s default video encoding format is H.264.

 

H.265, also called High Efficiency Video Coding (HEVC), is a draft video compression standard that delivers much higher-resolution video at the same bitrate as H.264. Its data compression ratio standard is double that of H.264.

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RealPlayer is a streaming media player by RealNetworks, Inc.

SureStream - A feature that was created by RealNetworks that allows RealAudio or RealVideo clips to stream at various bit rates.

Helix Server - is a streaming server developed by RealNetworks, Inc.

 

© 2013 Wowza Media Systems, LLC. Wowza and related marks are registered trademarks of Wowza Media Systems, LLC. Flash and related marks are registered trademarks of Adobe Systems Incorporated. iPhone, iPad, and Apple TV are registered trademark of Apple, Inc. Silverlight is a registered trademark of Microsoft Corporation. All other trademarks are the property of their respective owners. Third party trademarks are used solely to identify and describe third party products as being compatible with Wowza products. Wowza is in no way sponsored, endorsed by or otherwise affiliated with any such third party trademark owners.

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Hotlinking refers to web links that are embedded in a website for the purpose of displaying the content from another site. Showing these “borrowed” images, text, videos, etc. is illegal when the links display intellectual property that belongs to someone else.

The process of hotlinking is the same as embedding. Some web services encourage embedding and hotlinking. For instance, YouTube provides a code snippet to facilitate embedding videos from their site into your own site. The SWF Hotlinking Protection AddOn prevents other website owners from linking to assets of another web server, such as a Flash player. Without this kind of protection, users can look at the source code of your HTML page, copy the <Embed> or <Object> tag, and place that in an HTML page on their website.

More information: http://www.wowza.com/forums/content.php?114

More information: http://www.wowza.com/forums/content.php?114

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HTTP Streaming also known as HLS is a default protocol for streaming audio and/or video online developed by Apple Inc. and is used in QuickTime and iOS software. HTTP Streaming breaks up the video stream into a sequence of small HTTP-based files to be downloaded at different data rates. The client may select an appropriate data rate to keep the video stream flowing at an optimal performs adapting on the networks bandwidth and other factors at any given moment in time.

A m3u8 playlist also called a manifest downloads metadata defining what type of files and data rates are available. 

HTTP Streaming is capable of traversing any firewall or proxy server that lets through standard HTTP traffic, unlike UDP-based protocols such as RTP. This also allows content to be delivered over widely available CDNs.

HTTP Streaming is also capable of DRM encryption and HTTPS secure key content protection as well as Closed Captioning for subtitles and Trick Play for fast forward and rewind capabilities.

 

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IPTV (Internet Protocol television) comprises television services that are delivered by a video stream (encoded as a series of IP packets) instead of by more traditional television formats such as cable. This technology allows video and audio to be transmitted over the Internet by breaking the video and audio data up into packets. IPTV devices can be Wowza playback clients.

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Load Balancing is the distribution of workloads across computers and networks. In streaming, load balancing is used to distribute playback client connections among edge servers to scale live and on-demand streaming.

The Wowza Dynamic Load Balancing AddOn provides a method for dynamically distributing connection load among multiple Wowza edge servers. Load balancing is used in tandem with the Media Cache technology and a live stream repeater (origin/edge) configuration, which are used to scale live and on-demand streaming.

Overview of  Dynamic Load Balancing http://www.wowza.com/addons/dynamic-load-balancing-solution

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Live Streaming is an audio or video stream that is played back in real time, rather than from the beginning; it is always in progress. A live stream  does not support pause, seek, or rewind functions.

The source of a live stream can originate from a live encoder, but it can also come from a static file. The Wowza scheduling function allows files to be used as the source of a live stream.

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In streaming, a manifest is a file that lists the information that HTTP playback clients require to play a stream. When an HTTP playback client requests a stream, Wowza Streaming Engine™ software responds with a manifest. HTTP clients use a manifest file generated by Wowza to order requests for the chunks of a stream, and to get metadata, bitrate, and codec information.

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Multicast is a process that lets a server send a stream to multiple recipients simultaneously in a single transmission. In this one-to-many distribution architecture, a single IP router creates optimal one-to-many distribution paths to a multicast destination address. A multicast stream is published to a multicast address in a VLAN. A live encoder publishes one stream to the multicast address; then playback clients stream from the multicast address, not directly from the source. The VLAN replicates multicast streams for each playback client. Multicast is not supported over the public Internet.

 

Wowza Streaming Engine™ software can re-stream from a multicast address, allowing the stream to be played back in any supported client.

 

The Wowza Push Publishing AddOn includes a multicast publishing feature. In addition, Wowza® Media Systems provides a Silverlight player for playing multicast streams.  

 

When Streaming Engine software is used as a multicast source, it does not log play statistics of multicast playback clients. These statistics are not logged because they are not streamed directly from the Streaming Engine software; they are streamed from the multicast destination IP from which the stream is being published.

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The metadata of a file or stream describes its contents. In streaming, a live stream or a file encoder adds metadata to the stream or file during encoding. Playback clients use this metadata to display the stream properly. For example, a file will include duration information in the metadata that is used to configure a Seek bar for on-demand play. Metadata that contains width and height information is commonly used to determine and display the correct aspect ratio for live streams on playback clients. The Wowza Transcoder, a live encoder, adds metadata to transcoded renditions.

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MPEG (Moving Pictures Expert Group) is a body of industry experts that sets standards in the field of audio and video. Working together since 1988, they have defined many of the codec and container formats that are used in video production and the streaming products and processes that Wowza® Media Systems supports. Examples include H.264 (MPEG-4 Part 10), MPEG-TS, and more recently the H.265 and the MPEG-DASH standards.
 

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RTMP (Real Time Messaging Protocol) is a protocol used by Flash Player to play on demand and live streams. The Flash player can stream on-demand content from a web server (as a progressive download) or both live and on-demand streams by using a streaming media server, such as Wowza Streaming Engine™ software. RTMP can contain multiple channels of video, audio, and data. RTMP provides low-latency streaming.

RTMP is also used for server-to-server streaming between Wowza live stream repeater edge servers and an origin server.

RTMP is a TCP-based stateful protocol; it maintains persistent connections. This means that audio, video, and data can move in both directions in an RTMP connection. For example, media content can move between a Streaming Engine software client and a Flash client, and either client can play or publish audio and video and send and receive commands and data. Using a Flash RTMP application as a client enables a wide variety of applications, including audio/video/text chat, ad insertion (pre-roll), pay-per-view and pay-per-minute (PPV,PPM), and rich user experience applications synchronized with stream content.

By default, RTMP uses TCP port number 1935.

RTMP defines several virtual channels, or tracks, on which packets may be sent and received, and which operate independently of each other. These tracks may contain audio, video, or data. There is typically at least one audio, video, and data track in an RTMP stream. The data track may contain cue points, also called timed text; RTMP clients can be designed with callback functions that listen for cue points. These client-side callback functions might display captions, subscribe to new streams, or change the user interface.

During a typical RTMP session, several channels are active simultaneously. RTMP packets are interleaved and multiplexed across several different active channels to ensure that each channel meets its bandwidth, latency, and other quality of service (QoS) requirements.

There are a number of RTMP protocol sub types:

  • RTMPS is RTMP encrypted over a TLS/SSL connection.
  • RTMPE is a version of RTMP that uses Adobe's own security mechanism for encryption.
    NOTE: RTMPE has proven to have security issues.
  • RTMPT is encapsulated within HTTP requests and can traverse firewalls.

For more information about RTMP, see: http://en.wikipedia.org/wiki/Real_Time_Messaging_Protocol#Encryption

 

 

© 2013 Wowza Media Systems, LLC. Wowza and related marks are registered trademarks of Wowza Media Systems, LLC. Flash and related marks are registered trademarks of Adobe Systems Incorporated. iPhone, iPad, and Apple TV are registered trademark of Apple, Inc. Silverlight is a registered trademark of Microsoft Corporation. All other trademarks are the property of their respective owners. Third party trademarks are used solely to identify and describe third party products as being compatible with Wowza products. Wowza is in no way sponsored, endorsed by or otherwise affiliated with any such third party trademark owners.

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RTP (Real Time Transport Protocol) is a streaming protocol that defines a standardized packet format for delivering audio and video over IP networks. RTP is used with RTCP (Real Time Transport Protocol Control Protocol) in RTSP streaming.

RTP protocol provides:

  • Jitter compensation and detection of out-of-sequence arrival in data that are common during transmissions on an IP network. 
  • Data transfer to multiple destinations through IP multicast.
  • Audio smoothing: packet loss that results in less than a second of lost audio data can be made unnoticeable with suitable error-concealment algorithms.
     

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RTSP (Real Time Streaming Protocol) is a network protocol created to control streaming media servers.  It  is used to establish and maintain streaming sessions between a stream source or playback client and a media server. RTSP uses RTP and RTCP for the delivery of the media.

RTSP maintains session state by using control sequences. These are commands that are sent over RTCP with session identifiers used to track concurrent sessions. Most RTSP control messages are sent by the client to the server, but some RTSP commands are initiated by the server and sent to the client. The default RTSP transport layer port number is 554.

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RTMPT (HTTP Tunneling) is a version of RTMP (Real Time Messaging Protocol) that is encapsulated within HTTP requests. This allows RTMPT packets to traverse firewalls. RTMPT often uses cleartext requests on TCP ports 80 and 443; this allows it to bypass most corporate traffic filtering. Such an encapsulated session can pass RTMP, RTMPS, or RTMPE packets within the HTTP tunnel.

 

 

© 2013 Wowza Media Systems, LLC. Wowza and related marks are registered trademarks of Wowza Media Systems, LLC. Flash and related marks are registered trademarks of Adobe Systems Incorporated. iPhone, iPad, and Apple TV are registered trademark of Apple, Inc. Silverlight is a registered trademark of Microsoft Corporation. All other trademarks are the property of their respective owners. Third party trademarks are used solely to identify and describe third party products as being compatible with Wowza products. Wowza is in no way sponsored, endorsed by or otherwise affiliated with any such third party trademark owners.

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Smooth Streaming, an IIS Media Services extension, enables adaptive streaming of media to Silverlight and other clients over HTTP. Smooth Streaming provides a high-quality viewing experience that scales on content distribution networks.

Microsoft Silverlight is an application framework for writing and running rich Internet applications. The run-time environment for Silverlight is available as a plug-in for web browsers that run under Microsoft Windows and Apple’s OS X. 

 

 

© 2013 Wowza Media Systems, LLC. Wowza and related marks are registered trademarks of Wowza Media Systems, LLC. Flash and related marks are registered trademarks of Adobe Systems Incorporated. iPhone, iPad, and Apple TV are registered trademark of Apple, Inc. Silverlight is a registered trademark of Microsoft Corporation. All other trademarks are the property of their respective owners. Third party trademarks are used solely to identify and describe third party products as being compatible with Wowza products. Wowza is in no way sponsored, endorsed by or otherwise affiliated with any such third party trademark owners.

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Streaming is the process of sending compressed media files or live streams from computer to computer across a network without downloading the stream. Playback clients display the stream as it is received or from a small client-side buffer. The stream is not saved to disk client-side, as is the case with progressive download. Streaming provides several key advantages compared to progressive download:

  • Live streaming enabled – A media server such as one running Wowza Streaming Engine™ software is required to handle live stream ingress, replication, and packetization for different client types.
  • Content security – Media Server software provides many options for enhancing security because content is not downloaded to clients.
  • Random Seek in video on demand – In streaming, a file does not have to download to seek forward to a keyframe.
  • Streaming of large on-demand files – In progressive download, very large media files are impractical because they need to download sequentially. A user can only see what has downloaded.
  • Bandwidth savings – In streaming, only the parts of a media file that are played back are sent to the client.

With the exception of the benefits offered by live streaming, the advantages provided by streaming are all aspects of the fact that content is not downloaded in the client.

Wowza Streaming Engine™ software supports a variety of encoders and playback clients for live streaming. Live encoders with built-in H.264 video and AAC or MP3 audio are supported directly. Other encoding formats are supported for transcoding by using the Wowza Transcoder.

A number of technologies are used to  provide a continuous, uninterrupted stream, such as RTMP streaming, HTTP Streaming, H.264 encoding, and Adaptive bitrate (ABR) techniques.

 

Wowza Specifications

Wowza Transcoder Transcoding for live streaming

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Transcoding is the process of converting one analog-to-analog or digital-to-digital file to another file format. Frequently, video and audio files are transcoded when the original file formats are not supported in a system or then may be transcoded because newer formats have become available.

Transcoding is often a lossy process, introducing a loss in quality each time a file is transcoded. Transcoding can be lossless if the input is losslessly compressed and the output is either losslessly compressed or uncompressed.

As Wowza Streaming Engine™ software only reflects streams and does not typically transcode video and audio codecs unless the Wowza Transcoder is involved, the encoding of a live stream or file for on-demand play is determined by and set in the encoder.

Transcoding is not to be confused with packetizing. Wowza Streaming Engine software packetizes streams for each playback client differently, but in this process the video and audio codecs are unchanged from the source.

Using the Wowza Transcoder, video and audio tracks can be transcoded to formats supported by Wowza playback clients. The transcoder is also used to transrate, that is, to encode to lower bitrate versions of the source stream. This is a process that is commonly used to encode keyframe-aligned sets of live streams to support ABR streaming. Refer to the Wowza Transcoder documentation for a current list of video and audio codecs that are supported for decode (incoming live streams) and encode (play).
 
Transrating is the process of changing a video file from one bitrate to another. This is often done for adaptive bitrate systems via an encoder to create the different versions of the video. Transrating converts a file to a different bitrate, but does not change the video or audio encoding  format.

The Wowza Transcoder is used to transcode audio and video codecs that are not supported by the clients that the Wowza Streaming Engine™ software supports, and/or to transrate several renditions at different bitrates for ABR (Adaptive bitrate) streaming. The key advantage to using the transcoder to transcode server-side for ABR streaming is the guarantee of keyframe alignment of each rendition, which is necessary for switching during play. Moreover, not having to produce each rendition on the encoder side saves uplink bandwidth. This provides support for a higher-quality source stream where bandwidth is limited.

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Transmux (Transcode-Multiplexing) is a process that changes the format file of an audio or video file while keeping some or all of the streams containing information from the original. Transmuxing converts to a different container format without changing the file contents.

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In Unicast Streaming, each playback client is served its own stream. Unicast streams are the most common live and on-demand streaming types provided by Wowza Streaming Engine™ software. Media Server software creates a stream for each playback client; Media Server software then reflects a copy of the file or live stream to each client. For this reason, server and especially network utilization increases linearly as play load increases, so it’s critical in streaming to be aware of the stream bitrate, the peak concurrent load, and the server-side network capacity.

To scale unicast delivery of on-demand streams for large audiences, Wowza server software includes Media Cache technology (for Wowza Streaming Engine™ software, this technology is provided by the MediaCache AddOn). To scale unicast delivery of live streams for large audiences, Wowza server software is set up in a live stream repeater (origin/edge) configuration. When using these architectures, playback clients stream from edge servers that either repeat live streams from an origin server or cache on-demand assets that are stored  on a web server or network drive (NAS, NFS).

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VOD (video on demand) streaming uses a multimedia file as the source; it is always accessible; it always plays from the beginning or other specified start point, and it has a duration (which is usually included in the file’s metadata). By comparison, a live stream is always playing in progress, is only available while it is live, and has an unknown duration.

For all playback client types, Wowza Streaming Engine™ software supports on-demand play of .mp4 and other QuickTime container files (.mov, f4m, .3gpp, etc.) that contain H.264 video and AAC or MP3 audio. For Flash RTMP and Flash HTTP clients, Wowza supports play of .flv files that contain SorensonSpark or VP6 video and NellyMoser or Speex audio.

It is important in streaming to know the bitrate of a file used for on-demand streaming. The approximate average bitrate of a file can be calculated by using this formula: size in bytes * 8 / duration = bits per second (bps).

For ABR (Adaptive bitrate) on-demand streaming, multiple renditions of a multimedia file are encoded in different bitrates

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A VSP (Video Service Provider) is a provider that focuses on the storage and transmission of streaming media. VSP services are designed to handle the high bandwidth and server capacity requirements of streaming. Some VSP services are listed on the Wowza Partners Page.

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A CDN (Content Delivery Network) is a distribution system designed to scale the delivery of web pages, audio, video, and other Internet-based content. A CDN replicates content in caching servers located in geographically dispersed datacenters. A CDN service should route clients to a server in the nearest datacenter.

A CDN can be used to deliver Wowza Streaming Engine® software streams rapidly and cost effectively. There are two common ways to use a CDN with Streaming Engine software, and an additional method that’s less frequently used.

The first CDN distribution method uses the Wowza Push Publishing feature to push a live stream from  Streaming Engine software to a CDN. Using this feature and RTMP, a stream is pushed from the Streaming Engine software to the CDN. The CDN then passes the stream through to its network for Flash RTMP client play and/or packetizes the stream for HTTP clients. This method supports only live streams.

The second way to employ a CDN is to use Wowza HTTP Origin, a feature in the Streaming Engine software. Using this method, the Streaming Engine software packetizes the stream for HTTP clients. The CDN pulls the “chunks” into its cache and replicates in its network for client play. This method supports both on demand and live streaming to HTTP playback clients. Flash RTMP and RTSP playback clients are not supported.

Some CDN operators may be willing to set up a Wowza live stream repeater edge cluster in their network and use an external (to the CDN) Wowza Streaming Engine server as an origin server. However, this is an unusual situation.

In all cases, playback clients stream from the CDN, not directly from the Wowza Streaming Engine. Therefore, there is no logging of client playback in the Wowza Streaming Engine™ manager and advanced play features that involve the manager directly do not work when using a CDN.

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Dolby® Digital AC-3 (Audio Codec 3) and Dolby Digital Plus (Enhanced AC-3) are audio codecs that can contain up to six channels of sound. AC-3 is a version of the Dolby® Digital audio compression technology that supports up to 48 kHz sample rates. It’s used in many popular forms of entertainment including DVDs, Blu-ray Discs, cable, broadcast, satellite TV programming, PCs, and video games. With its advanced encoding/decoding technology and multichannel audio, Dolby Digital can deliver a cinematic audio experience.

Wowza Streaming Engine™ 3.6 allows AC-3 audio from an MPEG-TS source to pass through unaltered for Apple HLS and Microsoft Smooth Streaming play. This allows users to experience immersive surround-sound audio when using  playback clients such as Apple TV®, Xbox 360®, Sony PlayStation® 3 (PS3), hybrid set-top boxes, and smart TVs. 

 

© 2013 Wowza Media Systems, LLC. Wowza and related marks are registered trademarks of Wowza Media Systems, LLC. Flash and related marks are registered trademarks of Adobe Systems Incorporated. iPhone, iPad, and Apple TV are registered trademark of Apple, Inc. Silverlight is a registered trademark of Microsoft Corporation. All other trademarks are the property of their respective owners. Third party trademarks are used solely to identify and describe third party products as being compatible with Wowza products. Wowza is in no way sponsored, endorsed by or otherwise affiliated with any such third party trademark owners.

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AAC (Advanced Audio Coding) is a compressed audio format similar to MP3. AAC is used as the audio track in live streams and multimedia files that are recorded to an MP4 container for files that use .mp4, .f4v, .mov, .m4v, .mp4a, .3gp, and .3g2 filename extensions. Compared to MP3 files, AAC audio generally delivers better quality at the same bitrate and has wider support among playback clients supported by Wowza Streaming Engine™ software.

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