Leitner's Cinematography Corner

11+ hours of 1920×1080 recording in my hand.
Photo by D.W. Leitner

Last week Sony announced its first professional AVCHD camcorder line, NXCAM, at InterBEE in Japan. It’s not Sony’s first brush with AVCHD.

In 2006 Sony and Panasonic jointly announced the Advanced Video Codec High Definition standard for consumer camcorders recording 8 cm MiniDVD discs. Remember them? So three years ago!

Then, in late 2008, Sony introduced a professional POV camera system, HXR-MC1, adapted from a consumer AVCHD camcorder. (Read my review. My experiments mounting an MC1 camera head at the end of a K-Tek audio boom pole led to K-Tek’s design of an adapter for the MC1, demonstrated at NAB 2009.)

Before we go further, what exactly is AVCHD? Why another low-end HD format?

Two Memory Stick PRO Duo slots to the left of the battery, HDMI and HD-SDI to the right, with a 128GB flash memory module (with indicator lights) to the far right.
Photo by D.W. Leitner

AVCHD is a Sony-Panasonic trademark for long-GOP (group of pictures) MPEG-4, specifically the MPEG-4 standard known as AVC/H.264, embraced since 2005 by Apple for Web streaming, incorporated into the Blu-ray standard, and often described as two times as efficient as MPEG-2 compression. In other words, perfect for today’s SDHC cards and Memory Sticks.

(Similarly, HDV is a trademark for long-GOP MPEG-2, the compression that made DVDs possible.)

Panasonic’s professional AVC line is named AVCCAM, exemplified by the innovative handheld AG-HMC150—a built-in waveform display!—introduced at NAB 2008. (Can Panasonic, with all due respect, persist any longer in their campaign to disparage long-GOP compression as deeply inferior to intraframe compression?)

Sony’s new professional AVC line, NXCAM, joins the bandwagon at an opportune time. Native AVC/H.264 editing demands two to four times the CPU processing power of native HDV editing, and the latest multi-core computers and graphics cards are increasingly up to the task. (Older computers are out of luck.) Sony Vegas, Adobe Premiere Pro, Pinnacle and others now offer native AVCHD editing, with Apple Final Cut Pro the notable exception. FCP’s work-around is to capture AVCHD to ProRes 422 via Log & Transfer, which works great but adds a step and consumes dramatically more disk space.

Both AVCCAM and NXCAM feature AVCHD’s highest bit rate of 24Mbps, for better quality than consumer AVCHD camcorders offering 17Mbps.

RCA-type connector for Timecode Link at the front of the handgrip.

Photo by D.W. Leitner

(AVCHD is variable bit-rate compression with a maximum video data bit rate of 21Mbps. The average video data bit rate is less, of course. The remaining 3Mbps carry audio and metadata. Marketers prefer the more impressive 24Mbps ceiling, hence Sony’s “up to� 24Mbps qualifier. Tape-based HDV, by comparison, has a constant video data bit rate of 25Mbps.)

AVCHD and HDV share the same 8 bits quantization, 4:2:0 chroma sampling, and 720p/1080p/1080i choices. However HDV is limited to recording 1440 x 1080 pixels, while AVCHD can record a full 1920 x 1080. And instead of 192kbps of compressed MPEG-1 Audio Layer II per channel, AVCHD records either superior Dolby AC-3 or, in the case of Sony’s upcoming NXCAM camcorder, uncompressed Linear PCM audio.

The inaugural Sony NXCAM, the model number and cost of which I’m not yet allowed to disclose—I can reveal only that it will be available early next year—will be a handheld model which, like Sony’s recent HVR-Z5, features 1/3in. Exmor 3CMOS sensors with ClearVid diagonal pixel sampling and a built-in 20x G-series zoom.

Entirely new will be a sleek new GUI on a touch-panel LCD to supplement the usual menu buttons and scroll wheels. New also will be SD recording to MPEG-2, both SDI and HD-SDI output, and an RCA-like connector to momentarily synchronize timecode with another NXCAM (no GenLock however).

And tellingly, no IEEE 1394. End of an era?

To the left of the battery well (same battery used by Z1, V1, Z7, Z5, etc.) are twin slots for Memory Stick PRO Duo media, Sony’s answer to SDHC.

I do wish the same data stream could be recorded to both slots at the same time for instant redundancy—like a little pair of mirrored RAID 1 drives. The desirability of instant backups seems so obvious to me, and someday someone will surely enable this functionality.

In the meantime this new camcorder offers the next best thing: redundant recording of the same data stream to both Memory Stick and—are you ready?—a 128GB flash memory module the size of a MiniDV cassette that docks to the side of the camcorder.

At the highest quality 24Mbps rate, this 128GB module records more than 11 hours of AVCHD! After recording several minutes of 1080/30p myself, I looked at the remaining media in the viewfinder and saw 686 minutes of recording time left. I almost dropped out of my chair.

(I can’t help but muse: if only this camcorder had been available when Alexandr Sukorov directed his brilliant 99-min. epic, Russian Ark, in a single, long, equally epic take. To shoot a narrative spanning 200 years, set entirely at the Russian State Hermitage Museum in St. Petersburg, in HD in the year 2002 required a heavy backpack stuffed with hard drives and strapped to some poor video-cable Sherpa trying to keep pace with German DP/Steadicam operator Tilman Büttner. So many spinning disks, in fact, the backpack resisted his movement with gyroscopic force!)

Anyway, to dump the contents of the 128GB flash module to a hard drive, you simply snap it off the side of the camcorder and attach it to your Mac or PC using a common USB cable. It even powers itself off the USB bus, no batteries necessary.

Of course you don’t have to record redundantly or simultaneously. You can record either to Memory Stick or 128GB flash module separately; or you can start and stop them in record mode at separate times. You can even back up the contents of your several 32GB Memory Sticks to the larger-capacity 128GB flash module later in the day, as desired.

One thing is certain: Sony’s upcoming NXCAM will accelerate the momentum towards solid-state recording. Owners may never buy media again.