QuickTime Animation format (also known as QuickTime RLE) is a
video compression format
A video coding format (or sometimes video compression format) is a content representation format for storage or transmission of digital video content (such as in a data file or bitstream). It typically uses a standardized video compression algor ...
and
codec
A codec is a device or computer program that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder.
In electronic communications, an endec is a device that acts as both an encoder and a decoder on a signal or da ...
created by
Apple Computer
Apple Inc. is an American multinational technology company headquartered in Cupertino, California, United States. Apple is the largest technology company by revenue (totaling in 2021) and, as of June 2022, is the world's biggest company b ...
to enable playback of
RGB
The RGB color model is an additive color model in which the red, green and blue primary colors of light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three addi ...
video in
real time
Real-time or real time describes various operations in computing or other processes that must guarantee response times within a specified time (deadline), usually a relatively short time. A real-time process is generally one that happens in defined ...
without expensive hardware.
It is generally found in the
QuickTime
QuickTime is an extensible multimedia framework developed by Apple Inc., capable of handling various formats of digital video, picture, sound, panoramic images, and interactivity. Created in 1991, the latest Mac version, QuickTime X, is avai ...
container
A container is any receptacle or enclosure for holding a product used in storage, packaging, and transportation, including shipping.
Things kept inside of a container are protected on several sides by being inside of its structure. The term ...
with the
FourCC
A FourCC ("four-character code") is a sequence of four bytes (typically ASCII) used to uniquely identify data formats. It originated from the OSType or ResType metadata system used in classic Mac OS and was adopted for the Amiga/Electronic Arts I ...
'rle '.
[Three letters followed by a space.] It can perform either
lossless
Lossless compression is a class of data compression that allows the original data to be perfectly reconstructed from the compressed data with no loss of information. Lossless compression is possible because most real-world data exhibits statistic ...
or
lossy
In information technology, lossy compression or irreversible compression is the class of data compression methods that uses inexact approximations and partial data discarding to represent the content. These techniques are used to reduce data size ...
compression and is one of the few video codecs that supports an
alpha channel
In computer graphics, alpha compositing or alpha blending is the process of combining one image with a background to create the appearance of partial or full transparency. It is often useful to render picture elements (pixels) in separate pas ...
. Supported
color depth
Color depth or colour depth (see spelling differences), also known as bit depth, is either the number of bits used to indicate the color of a single pixel, or the number of bits used for each color component of a single pixel. When referring to ...
s are 1-bit (monochrome), 15-bit RGB, 24-bit RGB, 32-bit
ARGB
RGBA stands for red green blue alpha. While it is sometimes described as a color space, it is actually a three-channel RGB color model supplemented with a fourth ''alpha channel''. Alpha indicates how opaque each pixel is and allows an image to ...
, as well as
palettized RGB. As a result of reverse-engineering of the format, a decoder is implemented in
XAnim as well as an encoder and decoder in
libavcodec
libavcodec is a free and open-source library of codecs for encoding and decoding video and audio data.
libavcodec is an integral part of many open-source multimedia applications and frameworks. The popular MPV, xine and VLC media players use ...
.
Technical Details
QuickTime Animation uses
run-length encoding
Run-length encoding (RLE) is a form of lossless data compression in which ''runs'' of data (sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original ...
and
conditional replenishment
Conditional (if then) may refer to:
* Causal conditional, if X then Y, where X is a cause of Y
*Conditional probability, the probability of an event A given that another event B has occurred
* Conditional proof, in logic: a proof that asserts a ...
for compression.
[ When encoding, the input frame is scanned pixel-wise in raster-scan order and processed line-wise.][ Within a line, pixels are segmented into runs, the length of which is variable and signaled in the bitstream. For each run, one of three coding modes is used: same color, skip, or PCM.][ In same color mode, a run of pixels is represented by a single color in a run-length encoding fashion. If pixels with different colors are joined into a run (of a single color) by the encoder, the coding process is lossy, otherwise it is lossless. The lossless mode is used at the 100% quality level. In skip mode, the run of pixels is left unchanged from the previous frame (conditional replenishment). In PCM mode, the color of each pixel is written to the bitstream, without any compression.][
Run-length encoding works well on content with large areas of constant color. Conditional replenishment works well if only small areas change from frame to frame. QuickTime Animation works well on content with both these properties, such as traditional 2-D animation and screencast content.]
See also
* List of lossless video codecs
Notes
References
External links
QuickTime Animation (RLE) Video Decoder - FFmpeg
Quicktime Animation (RLE) Video Encoder - FFmpeg
Animation
Animation is a method by which image, still figures are manipulated to appear as Motion picture, moving images. In traditional animation, images are drawn or painted by hand on transparent cel, celluloid sheets to be photographed and exhibited ...
Video codecs
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