VideoCore

Mobile multimedia devices require a lot of high-speed video processing, but at low power for long battery life. The ARM processor core has a high IPS per watt figure (and thus dominates the mobile phone market), but requires video acceleration coprocessors and display controllers for a complete system. The amount of data passing between these chips at high speed results in higher power consumption. Specialised co-processors may be optimised for throughput over latency (more cores and data parallelism, but at a lower clock speed), and have instruction-sets and memory architectures designed for media processing (e.g. saturation arithmetic, and handling of specialised data formats).

The VideoCoreIV-AG100-R found in the Raspberry Pi 1, 2 and 3, is documented to fully support OpenGL ES 2.0 and OpenVG 1.1.

The 3D engine is composed of various subsystems, the most abundant being the QPUs. A QPU is a 16-way single instruction, multiple data (SIMD) processor.

"Each processor has two vector floating-point ALUs which carry out multiply and non-multiply operations in parallel with single instruction cycle latency. Internally the QPU is a 4-way SIMD processor multiplexed 4× over four cycles, making it particularly suited to processing streams of quads of pixels," according to Broadcom's VideoCore® IV 3D Architecture Reference Guide.

"QPUs are organized into groups of up to four, termed slices, which share certain common resources," the document continues. cf. Vertex and shader.

These "slices" correspond roughly to AMD's Compute Units.

At least VC 4 (e.g. in the Raspberry Pi) does not support S3 Texture Compression (S3TC).[2] It probably also does not support Adaptive Scalable Texture Compression (ASTC).

Of video compression algorithms currently in wide use, such as H.263, H.264/MPEG-4 AVC, MPEG-4, MPEG-2, MPEG-1, H.265, Daala, Theora, VP8 and VP9, Broadcom's VideoCore products support hardware acceleration of some operations. In some cases only decompression, only compression or both up to a certain resolution (e.g. 720p or 1080p) and up to a certain frame rate (e.g. 30 or 60 frames per second).

(It should be understood that lack of hardware acceleration is not an absolute obstacle to obtaining some method of processing or transcoding such streams, using general-purpose CPU instructions, perhaps at a rate perceived slow levied against hardware acceleration, may overcome such an obstacle. Preventing such an obstacle by using a lower resolution decreases power use and redacts heat sinks as it aids the preservation of components.)

• Instruction set written with video processing in mind from the start. For example, saturation arithmetic so that the sum of two bright pixels does not 'wrap around' into dark values.
• An array of graphics processing units for parallel computing of video data at relatively low clock speed.
• Very high integration puts CPU, GPUs, memory and display circuitry on a single chip, removing the power burden of driving fast off-chip buses.

The VideoCore I-based VC01 provides video and multimedia capabilities to various Samsung phones, including SCH-V540, SCH-V4200, SCH-V490.[3]

The VideoCore II-based VC02 / BCM2722 processor provides video capabilities for Apple's 5th generation iPod.[4]

The VideoCore III-based BCM2727 processor provides video, still and 3D graphics capabilities for the Nokia N8.

The VideoCore IV BCM2763 processor improves on the VideoCore III with support for 1080p encode and decode, along with higher resolution camera support and faster 2D and 3D graphics, all at very low power. It is used in the Nokia 808 PureView,[5] some versions of Roku hardware and the Raspberry Pi (2835/2836 models for versions 1/2 accordingly).[6]

The VideoCore IV BCM28155 processor supports for 1080p encode and decode, improved 2D and 3D graphics with dual-core ARM Cortex-A9 CPU in BCM28155 chipset. It is used in the Samsung Galaxy S II Plus, Samsung Galaxy Grand and Amazon Fire TV Stick.

The VideoCore V BCM7251 processor supports 2160p60 decode and transcode or dual 1080p60 encode/decode, features improved codec support (H.265), DDR3 and DDR4 support, USB 3.0, PCIe, Gigabit Ethernet and 802.11ac on a dual-core ARM Cortex-A15 Brahma15 dual core CPU.