... And a Few Words About MPEG-2 and AVC-Intra

Sony today disclosed new details of its newest generation of HDV camcorders, including a new form factor – it takes full-size DV cassettes – designed to win the hearts and minds of longtime DV users. "It has the sensitivity our SD customers were asking for," said Tatsuro Kurachi, marketing and business development manager for professional video products. "I would say it's the ultimate SD camcorder – it just happens to have HD imagers, too." Officials also responded directly for the first time to the drum-beating that’s been going on over the claimed higher efficiencies of AVC encoding versus MPEG-2. (In a nutshell: reports of MPEG-2’s death have been greatly exaggerated.)
The new HVR-S270U (the European version will be the S270E and the Japanese will be the S270J) is a shoulder-mounted HDV camcorder with an interchangeable lens that was showed as a mock-up under glass at IBC in September. It has three 1/3-inch CMOS chips that use Sony’s Clearvid configuration (to increase sensitivity) and Exmor technology, borrowed from the XDCAM EX (to reduce noise). The result, according to Kurachi, is an imager that doesn’t trade signal-to-noise-ration performance for increased sensitivity in low-light situations. The camera is rated for minimum illumination of 1.5 lux.

Even the viewfinder aims to please – at 1920×480, it packs a lot of pixels into a very small space.

The S270U is slated to ship in February for $10,500. That buys you a Zeiss Vario-Sonnar T* 12x zoom lens (32 to 384mm) and a 1/3-inch bayonet-type lens mount. With an adapter, the camera can also be used with 2/3-inch or ½-inch HD lenses, 12-pin ENG lenses, or even with the line-up of α (alpha) lenses for Sony’s new series of digital SLR cameras.

Like the EX, which is an XDCAM recorder that doesn’t record to XDCAM discs, the new S270U is an HDV recorder that doesn’t have to record to HDV tapes. Beyond capturing and recording images as 60i using 2:3 pulldown, the S270U’s native progressive recording mode lets it output 24p and 30p (25p on the European version) via iLink.

Other options to get your footage out of the camera include MiniDV and also standard-sized DV cassettes, which will hold 4.5 hours of HDV footage. A compact flash memory recording unit attaches to the side of the camera, and holds 72 minutes of HDV, DVCAM or DV footage on a 16 GB card. The camera will record simultaneously on tape and flash media; it can record HD to tape and SD to flash; or it can use a “relay mode” to seamlessly switch recording to the solid-state memory when a tape runs out.

Why is it a shoulder-mount camera? There’s still the obvious perception issue: a guy with a big camera on his shoulder looks more like a serious shooter to some people than the guy running around with the Handycam. But it also has to be a big piece of gear to support the oversized DV tapes. “In order to house that standard-sized cassette, this form factor was inevitable,” said Kurachi.

Have it Handheld
But if you don’t like to hoist a camera up on your shoulder, Sony has another deal for you to consider. The $6850 HVR-Z7U is the S270’s little brother – a handheld version of the same camera (also due next February). There are some differences: it supports only MiniDV tape; it has two XLR audio inputs rather than four; it has HDMI output instead of HD SDI; and it uses an infoLITHIUM series battery (just like the Z1U, the V1U, and the PD170). But the sensors are the same.
Both cameras are complemented by the new $5540 HVR-M35U deck, which plays full-size DV and MiniDV tapes. It features native progressive recording and plays back all HDV formats, including 720p (which is output via HDMI, not iLink).
Codec Controversy
On the subject of codecs, Sony has argued before that MPEG-2 is a better choice for video acquisition than the AVC-Intra format that Panasonic has introduced to dramatically expand the usability of flash media – which is still capacity-challenged compared to tape and optical disc – by doubling the effective recording time at equivalent bitrates. Previously, Sony had pointed to MPEG-2’s history in the market and the existing infrastructure supporting it as advantages over AVC, but VP Bob Ott this week started pushing back against aggressive claims made for AVC’s efficiency. “Although AVC is a part of the MPEG family, in order to have a successful product using AVC with pictures equal or close to MPEG-2 at 25 Mbps, they have to go long-GOP or use an extremely high data rate. And if they go long-GOP they face the same issues” as MPEG-2, Ott said.

Panasonic’s professional products use AVC-Intra, an intraframe codec designed to avoid some of the problems associated with interframe, or “long-GOP” compression. However, the intraframe variety of codec is significantly less efficient than the interframe version. Ott claims that AVC-Intra running at 50 Mbps is “not even close” to the quality of long-GOP MPEG-2. Sony’s Juan Martinez, senior manager of technology for Sony Electronics showed slides that appeared to demonstrate a dramatic difference in quality between MPEG-2 and AVC-Intra over five generations. Of course, Panasonic’s demos cut the other way, showing high-quality AVC-Intra footage that dusted the MPEG-2-encoded competition.

Sony responds, in turn, by noting that most Blu-ray Discs are being encoded using MPEG-2 long-GOP compression even though AVC is an option, as is Microsoft’s VC1 format. “MPEG-2 is a mainstay” in the compression-and-authoring business, where quality is paramount, Martinez said. And Ott acknowledged that raw picture quality is ultimately a question best answered in a test lab.

The other argument in MPEG-2’s favor is about the sheer complexity of AVC-encoded material. Ott estimated that editing AVC-Intra footage is seven to eight times more processor-intensive than editing MPEG-2. “From a workflow standpoint, it ain’t laptop-ready,” he said. “People are developing NLEs to support AVC-Intra – but we feel that picture quality, through multiple concatenations, is going to be a major issue.”