Arm has just announced Mali-D71 display processor optimized for 4K120 displays used for virtual reality, Assertive Display 5 display management core which adds support for high dynamic range (HDR10 / HLG), as well as CoreLink MMU-600 system memory management unit to handle data feed to Mali-D71, with the integration leading to a 55% area saving for the combined solution and a 50% latency improvement.
The main advantages of D71 display processor include:
- 30% system power savings by fully offloading GPU workloads before output such as composition, rotation, high-quality scaling, and other imaging processing in fixed function hardware.
- 2x area efficiency compared to Mali-DP650. When driving a single display, it can re-use the resources of a secondary display, doubling the performance.
- 4x latency tolerance – Mali-D71 can sustain up to 4x the delay on the system bus for the same throughput, helping maintaining high refresh rates up to 120 fps.
- 2x pixel throughput
Mali D71 will also improve multi-window display support with up to 8 Android composition layers in single display mode.
As mentioned in the introduction, Assertive Display 5 adds support for HDR content (HDR10 or HLG), and it can do so to any characteristic of display (any dynamic range and gamut), also delivering an HDR experience on an SDR display.
Assertive Display 5 utilizes iridix8 HDR local tone-mapping engine to handle HDR, combines with other blocks as shown in the diagram above. Since not all displays are capable of the 100,000:1 contrast ratio enabled by HDR, tone mapping maps one set of colors to another, approximating the appearance of high dynamic range images on devices with a more limited dynamic range.
HDR also has a wider color gamut with Rec.2020, or WCG (wide color gamut), but again HDR displays are not yet capable of showing the full gamut of Rec.2020, and instead achieve P3 gamut, right between Rec.709 (normally associated with SDR) and Rec.2020. So this also needs to be mapped as best as possible, and AD-5 relies on an hardware implementation of 3D LUT (Three-dimensional look-up tables) to perform gamut and color mapping.
AD-5 and Mali-D71 also support the handling of both HDR and SDR windows within the same composition scene.