Dolby Vision is not a video codec in itself, but rather a sophisticated high-dynamic-range (HDR) and wide-color-gamut (WCG) format that works in conjunction with existing video codecs. It enhances the visual experience by adding dynamic metadata to video streams, allowing for scene-by-scene or even frame-by-frame optimization of brightness, contrast, and color.
The Underlying Codec for Dolby Vision
While Dolby Vision itself is a processing and metadata layer, it relies on a foundational video compression codec to deliver the actual video data. The most common and widely adopted underlying video codec used with Dolby Vision is HEVC (High Efficiency Video Coding), also known as H.265. HEVC is preferred due to its efficient compression capabilities, which are crucial for handling the higher resolutions (like 4K) and increased bit-depths (10-bit or 12-bit) typically associated with HDR content.
Dolby Vision can also be implemented over other codecs, such as H.264 (AVC), particularly in older or specific use cases, though HEVC is dominant for premium content.
Dolby Vision Profiles and Their Codec Identifiers
To distinguish different implementations and compatibility levels, Dolby Vision utilizes various "profiles." These profiles define how the Dolby Vision enhancement layer is integrated with the base video stream. When streamed, these profiles are identified by specific codec strings within the media container (often MP4).
Here's a breakdown of common Dolby Vision profiles and their associated codec identifiers:
| Dolby Vision Profile | MIME Type (codecs attribute) |
Description (Common Underlying Codec) |
|---|---|---|
| Dolby Vision Profile 8 | video/mp4 ; codecs="dvhe.08.07" |
Dolby Vision over HEVC (most common) |
| Dolby Vision Profile 9 | video/mp4 ; codecs="dvav.09.05" |
Dolby Vision over AVC (H.264) |
| Dolby Vision Profile 9 | video/mp4 ; codecs="dva1.09.05" |
Another variant of Dolby Vision over AVC (H.264) |
| HEVC/H.265 (Base) | video/mp4 ; codecs="hev1.1.6.L93.B0" |
Standard HEVC/H.265 (without Dolby Vision specifics in codec string) |
Understanding the Identifiers:
dvhe: Indicates Dolby Vision content layered on top of HEVC. This is widely used for streaming services, Blu-ray discs, and broadcast.dvav/dva1: Indicate Dolby Vision content layered on top of AVC (H.264). These are less common for new content but support broader device compatibility.- The numbers following (e.g.,
.08.07,.09.05) refer to specific profile and level versions within the Dolby Vision specification, detailing aspects like maximum luminance, bit depth, and how the enhancement layer is structured.
How Dolby Vision Works with Codecs
Dolby Vision content typically consists of a base layer (which can be standard dynamic range SDR, or HDR10) encoded with a standard video codec like HEVC, plus an additional enhancement layer and dynamic metadata. The Dolby Vision decoder in a compatible device reads this metadata and uses it to apply tone mapping and color transformations in real-time, optimizing the image for the specific display's capabilities. This ensures a consistent and high-quality visual experience across a wide range of devices.
