About The Sorenson Spark Codec - MACROMEDIA FLASH MX 2004-USING FLASH Use Manual

By default, Flash imports and exports video using the Sorenson Spark codec. A codec is a
compression/decompression algorithm that controls how multimedia files are compressed and
decompressed during import and export. For information on the Sorenson Spark codec, see
"About the Sorenson Spark codec" on page 179.
If you attempt to import a file format that is not supported on your system, Flash shows a
warning message indicating that the operation cannot be completed. In some cases, Flash might
import the video but not the audio in a file. For example, audio is not supported in MPG/MPEG
files imported with QuickTime 4. In such cases, Flash shows a warning indicating that the audio
portion of the file cannot be imported. You can still import the video without sound.
Note: Imported audio is published or exported as streamed audio, using the global audio streaming
settings selected in the Publish Settings dialog box. For more information, see "Setting publish
options for the Flash SWF file format" on page 312.

About the Sorenson Spark codec

Sorenson Spark is a motion video codec included in Flash that lets you add embedded video
content to Flash. Spark is a high-quality video encoder and decoder that dramatically lowers the
bandwidth required to deliver video into Flash while simultaneously increasing the video quality.
By including Spark, Flash makes important progress in video capability. In Flash 5 or earlier, you
could only simulate video using sequential bitmap images.
Two versions of Sorenson Spark are available: Sorenson Spark Standard Edition is included in
Flash MX 2004 and Flash Player 7. The Spark Standard edition codec produces good-quality
video for low-motion content, such as a person speaking. The Spark video codec comprises an
encoder and a decoder. The encoder (or compressor) is the component in Spark that compresses
your content. The decoder (or decompressor) is the component that decompresses the compressed
content so that it can be viewed. The decoder is included in Flash Player.
There are two types of compression that can be applied to digital media: spatial and temporal.
Temporal compression identifies the differences between frames and stores only those differences,
so that frames are described based on their difference from the preceding frame. Unchanged areas
are simply repeated from the previous frame(s). A temporally compressed frame is often called an
interframe.
Spatial compression, however, is applied to a single frame of data, independent of any
surrounding frames. Spatial compression can be lossless (in which no data is discarded from the
image) or lossy (in which data is selectively discarded). A spatially compressed frame is often called
an intraframe.
Sorenson Spark is an interframe codec. Sorenson Spark's efficient interframe compression, among
other features, distinguishes it from other compression technologies, requiring a much lower data
rate than most other codecs to produce good-quality video. Many other codecs use intraframe
compression; for example, JPEG is an intraframe codec.
However, interframe codecs also use intraframes. The intraframes are used as the reference frames
(keyframes) for the interframes. Sorenson Spark always begins with a keyframe. Each keyframe
becomes the main reference frame for the following interframes. Whenever the next frame is
significantly different from the previous frame, the codec compresses a new keyframe.
About the Sorenson Spark codec 179