H264SVC

H264SVC, also known as H.264 Scalable Video Coding and defined in ITU-T H.264 Annex G, is an extension of the H.264/AVC video compression standard that enables scalable coding. It allows a single bitstream to be decoded at multiple resolutions, frame rates, and quality levels by using a base layer plus one or more enhancement layers. This design supports adaptation to varying network conditions and device capabilities without sending separate streams.

In a typical SVC bitstream, the base layer provides a basic representation of the video, while enhancement layers add spatial detail (higher resolution), temporal detail (higher frame rate), or improved SNR/quality. Decoders may choose to decode only the base layer or include one or more enhancement layers depending on bandwidth and processing power. The layers are designed to enable features such as random access, error resilience, and dynamic switching between layers in scalable streaming.

H.264 SVC supports temporal, spatial, and quality (SNR) scalability, and supports mixed scalability where two or more dimensions are extended simultaneously. It also preserves compatibility with AVC decoders by providing a decodable base layer, though not all AVC decoders can exploit the enhancement layers.

Applications and status: SVC has been used in professional and broadcast contexts, especially in video conferencing, streaming with fluctuating bandwidth, and gateways that perform bandwidth adaptation. While influential in the development of scalable coding, widespread consumer hardware support remains limited, in part due to licensing considerations and complexity. SVC influenced later scalable coding extensions in HEVC (SHVC).