Layered coding is a type of
data compression
In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compressi ...
for
digital video or
digital audio where the result of compressing the source video data is not just one compressed
data stream
In connection-oriented communication, a data stream is the transmission of a sequence of digitally encoded coherent signals to convey information. Typically, the transmitted symbols are grouped into a series of packets.
Data streaming has ...
, as in other types of compression, but multiple streams, called ''layers'', allowing decompression even if some layers are missing.
Overview
With layered coding, multiple data streams or layers are created when compressing the original video stream. This is in contrast to other types of compression, where the result is typically a single data stream.
During decompression, all layers can be combined to recreate the original video stream. Additionally, the stream can be decoded even if some layers are missing (though usually a layer hierarchy has to be respected, with a base layer that must available). If layers are missing, the resulting stream will have reduced visual quality, but will still be usable.
Use cases
Layered coding is helpful when the same video stream needs to be available in different qualities, for example for
adaptive bitrate streaming. Without layered coding, the source video stream must be encoded multiple times to obtain compressed streams with different qualities and bitrates. Layered coding allows only encoding a single time, because streams with different qualities can be obtained by discarding layers.
Related technologies
Layered coding is similar to
multiple description coding in that both produce multiple compressed streams that can be combined.
However, with multiple description coding the different streams are independent of each other, so any subset can be decoded, providing additional flexibility.
Scalable Video Coding
Scalable Video Coding: (SVC) is the name for the Annex G extension of the H.264/MPEG-4 AVC video compression standard. SVC standardizes the encoding of a high-quality video bitstream that also contains one or more subset bitstreams (a form of l ...
is a video compression standard that makes use of layered coding.
See also
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MPEG-5 Part 2 / Low Complexity Enhancement Video Coding / LC EVC - technique of similar approach
*
Scalable Video Coding
Scalable Video Coding: (SVC) is the name for the Annex G extension of the H.264/MPEG-4 AVC video compression standard. SVC standardizes the encoding of a high-quality video bitstream that also contains one or more subset bitstreams (a form of l ...
-
MPEG-4
MPEG-4 is a group of international standards for the compression of digital audio and visual data, multimedia systems, and file storage formats. It was originally introduced in late 1998 as a group of audio and video coding formats and related ...
specific technique of similar approach
*
Bitrate peeling
*
Hierarchical modulation
*
AV1 Scalable video coding
*
HEVC Scalability Extensions
*
*
References
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Data compression