Sorenson codec may refer to either of three proprietary video codecs: Sorenson Video, Sorenson Video 3 or Sorenson Spark. Sorenson Video is also known as Sorenson Video Codec, Sorenson Video Quantizer or SVQ. Sorenson Spark is also known as Sorenson H.263 or FLV1 (and it is sometimes incorrectly named as Flash Video (FLV), which is the name of Adobe Flash container format).
Both codecs were devised by Sorenson Media Inc. (formerly Sorenson Vision Inc.). Sorenson Video is used in Apple's QuickTime and Sorenson Spark in Adobe Flash (formerly Macromedia Flash).
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The Sorenson Video codec first appeared with the release of QuickTime 3 on March 30, 1998. It was available in two versions: the Basic Edition encoder/decoder built into QuickTime 3 and Developer Edition which enabled advanced encoding features and two-pass variable bitrate.[1] With QuickTime 4, it was given wide exposure for the release of the teaser trailer for Star Wars Episode I: The Phantom Menace on March 11, 1999.
Sorenson Video 2 was released in March 1999; however, it mainly included minor improvements and optimizations to the Developer Edition of the encoder, as movies encoded with it were backwards compatible with the Sorenson Video decoder.
An improved Sorenson Video 3 codec debuted with the release of QuickTime 5.0.2 on July 1, 2001. It was available exclusively for QuickTime.[2][3] Apple QuickTime later focused on other compression formats and moved Sorenson Video 3 to a separate group called "legacy encoders".[4]
The Sorenson Video 3 (SV3) Pro Codec for QuickTime video is offered as a separate software product, but comes standard with the commercial encoding software Sorenson Squeeze.[5]
As Apple began to embrace MPEG-4 and move away from other proprietary codecs, Sorenson Media licensed a new video codec to Macromedia as Sorenson Spark (Sorenson H.263), released with Macromedia Flash 6/MX on March 4, 2002.[6][7] Sorenson Spark is the required video compression format for Flash Player 6 and 7.
Macromedia later tried to find a better video codec. Starting with Flash Player 8 (released in September 2005), the preferred video codec is VP6.[8][9] The Sorenson Spark can be still used in the Adobe Flash CS4 Professional (2008) for Flash Video FLV files as one of three video compression formats (alongside H.264 and On2 VP6).[8] Sorenson Spark is an older codec but it is also a widely available and compatible one, when used in Flash Video.[10] According to an Adobe engineer Tinic Uro, it is considered as an incomplete implementation of H.263.[9][11]
The Sorenson Media, Inc. offers Sorenson Squeeze, which can encode video to proprietary Sorenson formats, but also to standardized video compression formats, such as H.264, MPEG-4 Part 2, MPEG-2 and others.[12] There is also Sorenson H.264 and Sorenson MPEG-4 codec, which are one of many existing implementations of international standards and should not be confused with Sorenson proprietary codecs.
The official specifications of the codec are not public.
For a long time the only way to play back Sorenson Video was to use Apple's QuickTime player, or the MPlayer for Unix/Linux, which in turn piggy-backed DLL-files extracted from Apple's player for Microsoft Windows.
According to an anonymous developer[13] of FFmpeg, reverse engineering of the SVQ3 codec (Sorenson Video 3) revealed it as a tweaked version of H.264.[14] (It is considered as based on an early H.264 draft.[15]) The same developer also added support for this codec to FFmpeg, making native playback possible on all platforms supported by FFmpeg. FFmpeg supports decoding of "Sorenson Vector Quantizer 3" (fourcc SVQ3) and Sorenson Vector Quantizer 1 (fourcc SVQ1) starting with version 0.4.7, released in 2003.[16]
The next version of FFmpeg in 2003 also added encoding/decoding of Sorenson H.263 used in Flash (fourcc FLV1).[17] Encoding of SVQ1 was added in 0.4.9-pre1.[18]
The Sorenson Spark is sometimes defined as "almost H.263" or as "an incomplete implementation of H.263".[9][11] These compression formats differ mostly in header structure and ranges of the coefficients.[14]
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