Description
Scalable High efficiency Video Coding (SHVC) is a sophisticated video coding architecture standardized by MPEG and formally adopted by 3GPP in TS 26.948. It is an extension of the High Efficiency Video Coding (HEVC/H.265) standard that introduces scalable coding capabilities. The core principle of SHVC is layered coding. A video source is encoded not as a single monolithic bitstream, but as multiple interdependent layers: a mandatory base layer and one or more optional enhancement layers. The base layer provides a basic quality video representation at a lower resolution and/or bitrate. Each subsequent enhancement layer, when decoded in conjunction with the base layer and any lower enhancement layers, progressively improves the video quality, increasing spatial resolution (e.g., from SD to HD to 4K), temporal resolution (frame rate), or signal-to-noise ratio (quality).
The technical operation relies on inter-layer prediction. When encoding an enhancement layer, the encoder can use the reconstructed pictures from the lower layer (base or a previous enhancement layer) as a reference, in addition to the references within the same layer. This prediction significantly improves compression efficiency compared to simulcasting (independently encoding multiple versions). The bitstream is structured with clear markers, such as layer identifiers and Network Abstraction Layer (NAL) unit types, defined in the HEVC specification, which allow a media-aware network element or the client player to easily extract a subset of layers.
Within a 3GPP multimedia service architecture, SHVC integrates with the Dynamic Adaptive Streaming over HTTP (DASH) framework. A DASH Media Presentation Description (MPD) can describe a SHVC-encoded content as a single adaptation set containing multiple representations that correspond to different layer combinations (e.g., Base, Base+Enh1, Base+Enh1+Enh2). During streaming, the DASH client can dynamically request segments containing only the layers suitable for the current device capabilities (screen size, decoder performance) and network throughput. This eliminates the need to store and manage multiple independent encodes of the same content, reducing storage and delivery complexity while ensuring optimal quality of experience (QoE) across a diverse range of user conditions.
Purpose & Motivation
SHVC was developed to address the growing fragmentation in the video ecosystem, characterized by a vast array of end-user devices with different display resolutions, processing powers, and network connectivity profiles (from mobile 3G to fiber broadband). The traditional approach of transcoding and storing multiple independent versions (simulcast) of the same content for each target profile is highly inefficient in terms of storage and bandwidth, as it does not exploit the redundancy between different quality versions.
The primary problem SHVC solves is the need for a single, efficient, and flexible video representation that can be seamlessly adapted. Its creation was motivated by the explosion of adaptive bitrate streaming (ABR) and the need for a coding standard native to scalability. While earlier standards like H.264/SVC offered scalability, they did not achieve the same base efficiency as HEVC. SHVC builds on the superior compression of HEVC, adding scalability with minimal coding loss. This allows content providers and network operators to store one high-efficiency scalable bitstream, from which an optimal version for any user can be derived dynamically by simply truncating or extracting layers, dramatically simplifying content preparation, storage logistics, and delivery network caching strategies for multi-screen services.
Key Features
- Layered coding architecture with base and enhancement layers
- Built upon HEVC/H.265 for high base compression efficiency
- Supports spatial, temporal, and quality (SNR) scalability
- Uses inter-layer prediction to minimize bitrate overhead
- Seamlessly integrates with HTTP Adaptive Streaming (DASH)
- Enables single-encode storage for delivery to heterogeneous devices
Evolution Across Releases
3GPP first adopted Scalable High efficiency Video Coding (SHVC) by referencing the MPEG standard in TS 26.948. This initial adoption defined the codec profiles and levels for use in 3GPP services and established its integration with the DASH streaming framework for efficient adaptive delivery of video to devices with varying capabilities.
Defining Specifications
| Specification | Title |
|---|---|
| TS 26.948 | 3GPP TS 26.948 |