This month Texas Instruments launched the DM355, the latest chip in its “DaVinci” family. The DM355 supports high-definition MPEG‑4 video encoding and decoding (but not both simultaneously) and is intended for low-cost imaging and video applications such as digital still cameras, IP video cameras, digital photo frames and video baby monitors.
Unlike other DaVinci chips, the DM355 does not include a ‘C64x+ DSP core. Instead, a specialized coprocessor handles MPEG‑4 and JPEG processing. Like many of the previously introduced DaVinci parts, the DM355 also features an ARM9E CPU core and additional coprocessors for pre- and post-processing tasks such as resizing, histogram generation, and on-screen display.
TI’s decision to use a specialized compression coprocessor in place of the ‘C64x+ DSP was likely intended to improve performance, price, and power consumption, at the cost of reduced flexibility in terms of supported algorithms. According to TI, the compression coprocessor provides 400 MHz of ‘C64x+-equivalent throughput (i.e. a ‘C64x+ would require 400 MHz to perform the MPEG‑4 and JPEG processing supported by the coprocessor). The two DM355 variants are priced at $12.60 and $14.95; in contrast, the cheapest DaVinci chip costs $10, and features a 300 MHz ‘C64x+ core but no CPU core. (All prices in this article, unless otherwise stated, are based on 10,000 unit quantities.) TI reports that the DM355 consumes less than 400 mW for high-definition MPEG‑4 encoding.
The two DM355 variants clock the ARM9E core at 216 MHz and 270 MHz. The compression coprocessor supports encoding and decoding at different resolutions: the highest supported is MPEG‑4 Simple Profile encoding or decoding at 720p, 30 fps; and JPEG encoding or decoding at 50 MPixels/second. DM355 programmers will use the ARM core as the host processor and access coprocessor functionality through APIs, like with previous ARM-based DaVinci chips.
To enable quick application prototyping, TI offers a DM355 Digital Video Evaluation Module (see BDTI’s analysis of another TI Evaluation Module), and optimized MPEG‑4, JPEG, and G.711 codecs.
While media processors often include specialized features to balance conflicting demands of efficiency and flexibility, the DM355 is very specialized: virtually all of its multimedia processing power is provided by fixed-function accelerators, and MPEG‑4 and JPEG are the only video/image compression algorithms supported. By severely limiting flexibility in compression algorithms, TI is able to deliver limited HD video compression capabilities at a low price point.
The DM355 will compete against a range of video processing solutions. A notable competitor is Freescale’s i.MX27 application processor, which features a 400 MHz ARM9E CPU core and accelerators for video and image processing. According to Freescale, the i.MX27 can perform MPEG‑4 or H.264 encoding or decoding at D1 resolution, 30 fps, and costs $15.89 in 1,000 unit quantities. (The 216 MHz DM355 costs $14.25 in 1,000 unit quantities.) Another competitor, Zoran’s Coach 10 family of digital camera processors, supports up to 720p H.264 encoding and decoding at 30 fps and over 40 MPixels/s of image capture processing, according to the company; the company also claims that over ten digital camera makers are using its Coach processors. Other competitors include media processors from Mobilygen and Broadcom; for instance, Mobilygen’s MG3500 is capable of encoding two H.264 streams at 720p resolution, 30 fps, and is priced $30 in volume.
The emergence of new high-volume video markets such as portable video players and video-enabled cell phones is driving a proliferation of video-oriented processors. It remains to be seen where the “sweet spots” lie in these markets with respect to trade-offs between performance, cost, power consumption, and flexibility. Undoubtedly, though, there will some applications where price is paramount, and devices like the DM355 will likely find traction in those markets.
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