Brian's Brain

I've expressed my enthusiasm for the HDV (and related D-VHS) format numerous times in Brian's Brain over the past few months. And I'm still enthralled with it. But it admittedly suffers from (at least) two fundamental shortcomings.

First off....well, it's miniDV-sized tape. It's easily damaged. It eventually wears out and, unlike with VHS, when you drop a bit in the digital era, you've got big problems. It requires large, heavy, power-hungry motors, along with expensive precision transport mechanisms. And it's not random-access (that is, unless you have lots of patience).

HDV's other issue is its reliance on ancient MPEG-2 compression. 720-line resolution, progressive-scan video requires a 19 Mbps data rate, while 1440x1080 pixel interlaced video needs 25 Mbps. That bitrate translates to around 11 GBytes of storage capacity consumed per hour. Now you see why HDV uses inexpensive tape. Three quarters of an hour of HDV would overflow the biggest 1" HDD now available (8 GByte). Even the incrementally higher-capacity small form factor HDDs I expect to see launched at CES next month won't be able to hold an acceptably long HDV-based video recording. And an adequate amount of flash memory won't be able to hit a consumer-friendly price point for a while yet, although it's establishing a foothold in the professional ranks.

Enter Ambarella. The company's founders (CEO Fermi Wang, CTO Les Kohn and Executive Vice President Didier LeGall) all hail from C-Cube, a video compression pioneer that was later acquired by LSI Logic. Les was the chief architect of the DoMiNo architecture; prior to C-Cube he was a fellow at Sun Microsystems, where he was the chief architect of the Ultrasparc-1 and 2 CPUs, and before then an architect of the i860 RISC processor at Intel. And between C-Cube and Ambarella, he and Wang founded Afara Websystems, which was acquired by Sun in 2002 and whose Niagara processor became the foundation of the UltraSPARC T1 CPU that powers Sun's latest-announced servers. That's some pedigree!

Ambarella's first-generation codec implements MPEG-4 part 10 (also known as MPEG-4 AVC, and as H.264) main and high profile for video, JPEG for still images, and AAC for audio. Company officials claim that H.264 has, on average, 2.25 to 2.5 times better compression efficiency than MPEG-2 at the same frame rate, frame size and quality level, but that achievement comes at a price; typical MPEG-4 decoders and encoders (hardware- or software-based) are 4x the complexity of their MPEG-2 counterparts. Fortunately, deep submicron processes, combined with careful architecture work (Kohn points out that the company developed and analyzed compression algorithms for six months before they ever began defining their chip), now enable cost-effective H.264 codecs that, equally important for battery-operated applications, are power-thrifty.

The 'A1' chip's processing muscle combines an ARM925 with a 'massively parallel programmable video processing pipeline' (the company wouldn't be more specific, citing in-progress patent applications). It comes in three speed bin variants:

• The entry-level A100 runs at a 180 MHz clock rate, consumes 450 mW of power (including a digital image stabilization function), and supports D1 (480-line interlaced resolution, 60 fields per second) image compression rates. It can also capture 480-line progressive resolution, at 60 frames per second, although it will encode the video in an interlaced fashion
• The A150 runs at 216 MHz, consumes 700 mW of power (again, including DIS), and supports encoding of 720-line progressive scan, 30 frame-per-second and 480-line progressive scan, 60 frame-per-second material.
• The high-end A199 also runs at 216 MHz, but burns roughly 1W of power. This time DIS isn't included, but within that power envelope the chip is capable of doing video pre-processing when fed by a RGB image sensor. It's capable of supporting video resolutions up to 720p 60 (720-line progressive scan, 60 frames per second) and 1080i (HDV's 1440x1080 pixel resolution, interlaced, 60 fields per second).

The Ambarella A1 is highly integrated; the chip also includes such peripherals as a USB 2.0 transceiver, a glueless interface to numerous flash memory chip and module options, and four input ADCs. It also provides an LCD controller, three output video DACs and a video encoder to directly drive various display types. A complete camera design needs only also include an image sensor, lens and zoom control, mass storage (HDD, flash memory, and/or optical disc), a single DDR-2 SDRAM (chosen over DDR-1 predominantly for its low power, not its speed), and user interface LCD, LEDs, buttons, etc. And how much will the A1 cost? “The Ambarella platform can be used to support a wide range of products, from volume consumer products to professional encoding equipment. The pricing for each instance is a function of volume and feature set and will cover a range from $25 for SD-resolution devices in volume quantities to over $1000 for small quantity professional use.”

High resolution direct-view LCDs and plasma monitors, along with DLP- and LCoS-based rear-projection displays, are whetting consumers' tastes for high definition video. However, with no end to the blue laser optical disc storage impasse in near-term sight, and with red laser optical disc-based high resolution video still disappointingly immature, HDV doesn't yet have a format 'lock' beyond its existing beachhead of professional (and wanna-be professional) users. This is going to be an interesting market to watch develop and mature. Where are you placing your bets?