Flash Video is the name of a file format used to deliver video over the Internet using Adobe Flash Player (formerly known as Macromedia Flash Player) version 6, 7, 8, or 9. 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, Reuters.com, Yahoo! Video, MySpace, and many television news operations are also using Flash Video on their websites.
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.
Flash Player
The Adobe Flash Player is a multimedia and application player developed and distributed 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. It has support for a programming 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.
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. Recent beta versions of Flash Player 9 include 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.
An optional alpha channel which represents per pixel transparency is supported by including a second simultaneous video stream which encodes the alpha channel only, dropping any chromatic information. The implementation makes the assumption that the YUV data of the main On2 VP6 video stream is always converted to RGB by the client before compositing occurs as the resulting RGB values are alpha premultiplied and clamped accordingly. This option is only available for On2 VP6 encoded video streams.
The Flash Video file format supports two versions of a so called 'screenshare' codec which is an encoding format designed for screencasts. 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.
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.
Audio in Flash Video files is usually encoded as MP3. However, Flash Video files recorded from the user's microphone use the proprietary Nellymoser codec. FLV files also support uncompressed audio or ADPCM format audio. Recent beta versions of Flash Player 9 support AAC (HE-AAC/AAC SBR, AAC Main Profile, and AAC-LC).
On August 20, 2007, Adobe announced on its blog that with Update 3 of the Flash Player (currently in beta), Flash Video will also support the MPEG-4 international standard. [1] 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. Adobe also announced that they will be gradually moving away from the proprietary FLV format to the standard MP4 format owing to functional limits with the FLV structure when streaming H.264. The final release of the Flash Player supporting MPEG-4 is expected to be available in Fall 2007.[2]
FLV Player
Most media players based on the FFmpeg libraries should be able to play back Flash Video format video[3]. Listed below are some examples of media players supporting the Flash Video format:
VLC media player
MPlayer (uses FFmpeg)
xine (uses FFmpeg)
RealPlayer
Zoom Player
GOM Player
Any player which can use the ffdshow (based on FFmpeg) DirectShow codecs:
Media Player Classic
Windows Media Player
Windows Media Center (with registry hack)
Any player which uses QuickTime, after installation of the FLV component
