Analysis: Tensilica's D1 Video Engine

Tensilica is now offering a high-performance licensable video engine capable of MPEG-4 ASP encoding at D1 resolution. The processor is called the Diamond 388VDO, and it's one of four new dual-core "VDO" video engines from Tensilica. The 388VDO is the highest-performance member of the quartet and supports a variety of video codec standards at resolutions up to D1 (i.e., standard definition television). Target applications include chips for mobile handsets and personal media players.

The 388VDO incorporates two heterogeneous processor cores, each of which is configured to support different types of processing. One core supports 16- and 8-way SIMD operations and is optimized for the highly data-parallel processing that's characteristic of tasks like motion compensation and transforms; this core is called the "pixel processor." The other is optimized for the sequential processing needed for decision-making and bitstream unpacking; this core is called the "stream processor." A block diagram of a 388VDO-based SoC is shown in Figure 1.

Figure 1. Block diagram of Diamond 388VDO-based SoC (graphic courtesy of Tensilica).

Tensilica customized both cores with specialized hardware and instructions to accelerate common video codecs; for example, the 388VDO supports custom instructions for accelerating the computationally demanding CABAC entropy decoding algorithm used in H.264.

Tensilica's use of heterogeneous processor cores is sensible. High-end video requires a mixture of parallelizable and sequential processing capabilities, and using two different cores enables a more efficient mapping between tasks and processors. The cores' programmability is an advantage in video applications, which often need to support multiple existing or emerging standards, and may require custom processing.

According to Tensilica, the 388VDO consumes roughly 11 mm² in a TSMC 130G process and 6.6 mm² in 90G (these figures are post-layout and include memory). The company says that a 200 MHz 388VDO can run the following codecs at D1 resolution (720 x 480 @ 30 fps for NTSC; 720 x 576 @ 25 fps for PAL):

• H.264 main profile @ L3 (decode)
• MPEG-4 ASP (no GMC) @ L5 (decode)
• MPEG-2 MP @ ML (decode)
• WMV9/VC1 main profile (decode)
• MPEG-4 ASP (encode)

For more analysis of Tensilica's Diamond 388VDO, see InsideDSP.