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Flash Video

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Flash Video
FLV file Icon from Adobe Systems
Filename extension
.flv, .f4v, .f4p, .f4a, .f4b
Internet media type
video/x-flv, video/mp4, video/x-m4v, audio/mp4a-latm, video/3gpp, video/quicktime, audio/mp4
Developed byAdobe Systems (originally developed by Macromedia)
Type of formatmedia container

Flash Video is the name of a file format used to deliver video over the Internet using Adobe Flash Player (initially produced by Macromedia) versions 6–10. Until version 9 update 2 of the Flash Player, Flash Video referred to a proprietary file format, having the extension FLV. The most recent public release of Flash Player supports H.264 video and HE-AAC audio. Flash Video content may also be embedded within SWF files. Notable users of the Flash Video format include YouTube, Google Video, Yahoo! Video, Reuters.com, and many other news providers.

Flash Video is viewable on most operating systems, via the widely available Adobe Flash Player and web browser plugin, or one of several third-party programs such as MPlayer, VLC media player, Quicktime, or any player which uses DirectShow filters (such as Media Player Classic, Windows Media Player, and Windows Media Center) when the ffdshow filter is installed.

Though the container format itself is open, the codecs used with it are patented.

Flash Player

Main article: Adobe Flash Player

The Adobe Flash Player is a multimedia and application player originally developed by Macromedia and acquired by Adobe Systems. It plays SWF files which can be created by the Adobe Flash authoring tool, Adobe Flex, or a number of other Adobe Systems and third party tools.[citation needed] It has support for a scripting language called ActionScript, which can be used to display Flash Video from an SWF file. Because the Flash Player runs as a browser plug-in, it is possible to embed Flash Video in web pages and view the video within a web browser. The primary downside of Flash's FLV player is that it is very inefficient compared to a directly embedded video file, dropping frames when running on slow clients that run directly embedded video perfectly. [citation needed]

Format details

Commonly, Flash Video files contain video bit streams which are a variant of the H.263 video standard, under the name of Sorenson Spark. Flash Player 8 and newer revisions support the playback of On2 TrueMotion VP6 video bit streams. On2 VP6 can provide a higher visual quality than Sorenson Spark, especially when using lower bit rates. On the other hand it is computationally more complex and therefore will not run as well on certain older system configurations. Flash Player 9 Update 3 includes support for H.264 video standard (also known as MPEG-4 part 10, or AVC) which is even more computationally demanding, but offers significantly better quality/bitrate ratio.

The Flash Video file format supports two versions of a so called 'screenshare' codec which is an encoding format designed for screencasts.[citation needed] Both these formats are bitmap tile based, can be lossy by reducing color depths and are compressed using zlib. The second version is only playable in Flash Player 8 and newer.[citation needed]

Support for encoding Flash Video files is provided by an encoding tool included with Adobe's Macromedia Flash Professional 8 product, On2's Flix encoding tools, Sorenson Squeeze, FFmpeg and other third party tools.[citation needed]

Audio in Flash Video files is usually encoded as MP3.[citation needed] However, Flash Video files recorded from the user's microphone use the proprietary Nellymoser codec.[citation needed] FLV files also support uncompressed audio or ADPCM format audio.[citation needed] Recent versions of Flash Player 9 support AAC (HE-AAC/AAC SBR, AAC Main Profile, and AAC-LC).[1]

On August 20, 2007, Adobe announced on its blog that with Update 3 of the Flash Player 9 (released), Flash Video will also support the MPEG-4 international standard. [2] Specifically, Flash Player will have support for video compressed in H.264 (MPEG-4 Part 10), audio compressed using AAC (MPEG-4 Part 3), the MP4, M4V, M4A, 3GP and MOV multimedia container formats (MPEG-4 Part 14), 3GPP Timed Text specification (MPEG-4 Part 17) which is a standardized subtitle format and partial parsing support for the 'ilst' atom which is the ID3 equivalent iTunes uses to store metadata.[citation needed]

A Flash Player 9 update including a new MP4 H.264 component was released on December 3, 2007.[3]

File formats

Because of restrictions in the .flv format, Adobe Systems has created new file formats listed below. Flash player does not check the extension of the file, but rather looks inside the file to detect which format it is.[2]

File Extension Mime Type Description
.f4v video/mp4 Video for Adobe Flash Player
.f4p video/mp4 Protected Video for Adobe Flash Player
.f4a audio/mp4 Audio for Adobe Flash Player
.f4b audio/mp4 Audio Book for Adobe Flash Player

Codec support

FLV players

An FLV player is a type of media player that is used for playing flash video from PC as well as from Internet websites. An FLV player can be used standalone, without the need of the Adobe Flash authoring or developmental tools.

The following players support FLV files in their default installations:

Free Software

Desktop-based

Windows, Mac OS X, Linux-based
Windows, Linux-based
Linux-based

Web-based

Freeware

Desktop-based

Windows

If ffdshow DirectShow codecs are installed on a Windows system, other software applications may also be able to play flv files:

Mac OS X

Web and Desktop

Web-based

Recorders

Flash Video is often delivered via an embedded Flash file, though there are various stream recorders available.

Delivery options

Flash Video files can be delivered in several different ways:

  • As a standalone .FLV file. Although Flash Video files are normally delivered using a Flash player for control, the .FLV file itself is fully-functional on its own and can be played or converted to other formats from local storage such as a hard disk or a CD.
  • Embedded in an SWF file using the Flash authoring tool (supported in Flash Player 6 and later). The entire file must be transferred before playback can begin. Changing the video requires rebuilding the SWF file.
  • Progressive download via HTTP (supported in Flash Player 7 and later). This method uses ActionScript to include an externally hosted Flash Video file client-side for playback. Progressive download has several advantages, including buffering, use of generic HTTP servers, and the ability to reuse a single SWF player for multiple Flash Video sources. Flash Player 8 includes support for random access within video files using the partial download functionality of HTTP, sometimes this is referred to as streaming. However, unlike streaming using RTMP, HTTP "streaming" does not support real-time broadcasting. Streaming via HTTP requires a custom player and the injection of specific Flash Video metadata containing the exact starting position in bytes and timecode of each keyframe. Using this specific information, a custom Flash Video player can request any part of the Flash Video file starting at a specified keyframe. For example, Google Video and Youtube support progressive downloading and can seek to any part of the video before buffering is complete. The server-side part of this "HTTP pseudo-streaming" method is fairly simple to implement, for example in PHP, as an Apache HTTPD module, or a lighttpd module.
  • Streamed via RTMP to the Flash Player using the Flash Media Server (formerly called Flash Communication Server), VCS, ElectroServer, Wowza Pro, WebORB for .NET or the open source Red5 server. As of April 2008, there are stream recorders available for this protocol, re-encoding screencast software excluded.

See also

References

  1. ^ "Flash Video (FLV) Open Source Flash".
  2. ^ a b "What just happened to video on the web". Adobe.
  3. ^ "Adobe Flash Player 9 Downloads". Adobe. 2007-12-03. Retrieved 2008-01-31.
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