HD Camcorder Technologies - October 2007

In early October 2007, a friend asked me about buying an HD (High-Definition) camcorder to replace their family DV camcorder. His primary application is shooting his son's football games for post-game analysis. He's an engineer, and our discussions reflect that.

CURRENT HD CAMCORDER RECORDING TECHNOLOGIES

• Tape - We still like this. The consumer HDV tape format uses the old MiniDV tape format, and records MPEG-2 data at exactly the same 25Mbps (megaBITS per second) as standard definition DV. When you run out of tape while on vacation, you go to the store (even a grocery store, these days) or the photo booth at Disneyland to buy more. When you shoot to tape, it's a $5/hour archive of what represents 13GB of data. Camcorders can duplicate these digital tapes perfectly to each other over a FireWire cable, and footage edited on a computer can be written back to tape losslessly. Downsides: transferring footage to a computer for editing or transcoding ( i.e., for uploading to YouTube, putting on your cell phone) can only occur in real time. Also, tape is pretty mechanical, and may wear out in time easier than optical media (CD-R/RW, DVD-R/RW). Of course, optical media might fail eventually, too.
  
• Hard Drive - Perhaps handy and tempting because you can shoot several hours of footage without managing tapes, but when it's full, you'd better have a computer with lots of hard drive space handy, and some time to transfer the data. (On that African safari, you'd better have a laptop and a couple of external hard drives and batteries to transfer footage while bouncing across the veldt in a Land Rover.) HD camcorders shooting to HD use MPEG-4 H.264 "AVC" codec, just like DirecTV's new transmissions. The AVCHD standard provides for potentially greater fidelity than HDV. However, current implementations do not yet match the quality of HDV. Unlike HDV, AVCHD camera offer user-selectable bitrates to balance quality and capacity. This is a new paradigm for computer editing, so we're in the first generations of editing software which handle AVC. Unlike tape, footage can be potentially transferred to a computer in a fraction of the recording time. Obviously, footage must be archived elsewhere, but I'm assuming that you can simply use existing computer data management concepts to copy and "burn" data to DVD-Rs. I don't know if any HD camcorders allow using the drive as a mountable hard drive on the computer - that could potentially save even more time (though you really want your footage archived in another location for safe-keeping).
  
• Recordable DVD - This product may appear promising, but is pretty awkward in reality. Using either 12cm or 8cm optical recordable DVDs, these camcorders can produce discs which will play in a consumer DVD player without the need of a computer at any point. DVDs are inexpensive and as with tape, the camera creates a physical archive of the data. However, some mechanisms are slow to respond and ejecting a disc requires a several-minute "finalization" of the media - pretty unwelcome when they call your kid off the bench for the first time and you've just filled up your disc. I think all the HD camcorders recording to DVD-R are using AVCHD.
• Memory Cards - Astonishingly, Japanese giant Panasonic has been promoting solid-state broadcast HD camcorders for three years (I attend media production trade shows regularly). These shoot to " P2" cards, which are basically the old "PC Card/CardBus/PCMCIA" form-factor containing a RAID-array of four, matched, high-speed Secure Digital High-Capacity (SDHC) cards inside. These are very expensive, but provide many interesting technical benefits to professional video production. Knowing about that has lessened the impact of seeing the recent growth of consumer SD and HD camcorders which shoot to single SDHC cards. Again using AVCHD compression, this promises faster-than-realtime transfer of footage to a computer for editing. As with hard drives, the expense of memory cards means having to archive to another media form. You also have to consider buying multiple $80 8GB cards which might each hold an hour or two of footage.
  

BACKING UP

A wonderful thing digital technology has brought us is the ability to make perfect duplicates of our video footage. In the past, we could only make lower-quality copies of originals, and copies of copies were nearly unplayable. Today, your consumer video footage can be copied infinitely without any loss whatsoever. So if your parents make a copy of a DVD you sent them to your uncle, and he makes copies for your cousins, everyone's copies are identical. I find this particularly appropriate for protecting the family legacy of photographs and video recordings - if every family member gave every other family member a copy of their precious archives in digital form, then the chances of them surviving into the future are very high.

As with all data, even chemical-based photography, if you don't have duplicates, you risk the loss of irreplaceable of any information. So even if you haven't practiced it before, there's no time like the present to practice "safe data handling." Make duplicates of anything you wouldn't want to lose, and store the duplicates "off-site" in the event of a disaster at your primary storage site.

Actually making duplicates of video data is pretty time-intensive, because video takes up a lot of data space, and most methods take at least as long as the duration of the video. Here are some examples of how you might back up video data from the various digital forms:

• Tape-to-tape: High-definition HDV, standard-definition MiniDV, and Digital-8 camcorders can "dub" digitally between camcorders and VCRs if both recorders are equipped with FireWire interfaces (Sony calls this "i.Link" and the technical standard is known as "IEEE-1394"). Typically, a "4 pin to 4 pin" FireWire cable is connected between the two camcorders, one is played and the other is placed into record (typcially in "VCR" mode, rather than "camera" mode). The resulting copy represents the quality of the original perfectly.
• It's pretty awkward and impractical for most people to back up their videotapes while traveling, but if it's really a once-in-a-lifetime trip, you might consider packing along a spare camcorder or a couple of external hard drives for your laptop - never trust having all your data in one place.
  
• NOTE: To dub from HDV to standard-def MiniDV or Digital-8, your HDV camcorder must be able to "downsample" or "convert" the HDV to DV during the dub. You can also dub from DV to some HDV camcorders, but the resulting dub will NOT be HDV.
• Archive to hard drive: This might seem a bit expensive as a long-term archive solution, but hard drive prices continue to fall. At the time of this writing in October 2007 I just noticed a fairly compact 500GB external FireWire hard drive for $150 at my local "warehouse" store - that's over 35 hours of DV/HDV storage, and even more AVCHD. On the road, you could copy from tape to external hard drive in your hotel room at night, if for no other purpose than as a temporary backup until you archived back to tape later, or to optical media.
• Archive to optical media: This process is typically performed by connecting a camcorder to computer via FireWire/IEEE-1394 cable and a video-editing program, then using a DVD-authoring program to "burn" the edited video to inexpensive recordable DVDs. Current technology encodes home videos as MPEG-2 video on recordable DVDs. This does NOT preserve the original fidelity of standard-definition DV, and so is certainly incapable of maintaining HD recordings. DVDs are "good enough" for most standard-def consumer applications. New-generation consumer HD camcorders that record HD video using the AVCHD/H.264 codec make files small enough to fit a little over an hour of their highest quality HD video on an existing DVD-R (4.7GB). At this time, AVCHD camcorders don't quite have the fidelity of HDV, but will likely change with time. In the next few years, we will probably transition to higher-capacity Blu-ray and HD-DVD recordable drives in our personal computers, and archiving to these may be able to preserve full fidelity of the original camera recordings.
• Duplicating DVDs - If your camcorder records directly to recordable DVDs, then these DVDs (and any DVDs you make from tape, hard drive-based, or memory-card-based camcorders) can be duplicated in a personal computer with a DVD-burning drive.
  

VIEWING HD HOME MOVIES

Until recently, the only way you could view consumer HD footage on your HDTV was to play back on your camcorder directly connected to the HDTV via HDMI/DVI, analog component video cables, or (if your HDTV supports it) even 1080i over FireWire cable. Of course, you can watch HD footage in full resolution on a computer, provided it's powerful enough and you have a display capable of displaying 1280x720 or 1920x1080 pixels.

NEW HD VIEWING ALTERNATIVES?

I recently realized that it might be possible to put the files from an AVCHD camcorder (or converted from another HD format to AVCHD/H.264 files) on existing DVD-recordable media and play it back in a Blu-ray or HD-DVD player (which support H.264 as one of their codecs), but only if that player could read recordable DVDs, and if it recognized AVCHD files as being valid. I'd sort of automatically put out of my mind worrying about producing high-definition DVDs until we owned a Blu-ray or HD-DVD burner - but it's possible to make hour-long high-def DVDs now, provided you have a Blu-ray or HD-DVD player with these qualities. I found a couple of posts on Sony Playstation 3 forums where users had reported playing 8cm DVDs recorded in a Sony HDR-UX7 HD camcorder on their PS3 game consoles (which have Blu-ray drives and can play commerical Blu-ray movies). Here is a YouTube video of a user demonstrating this (we'll assume this is not a hoax). This blogger says that you can place H.264 files into a folder named "VIDEO" on a data DVD and the PS3 will recognize and play those files. Using this technique, it's possible to make and existing DVD-recordable which plays around an hour of HD content.

STREAMS VS. FILES

I had not really considered this until now - I have just sort of assumed we'd eventually have to bite the bullet and purchase a Blu-ray or HD-DVD burner for a computer (or buy a computer with a burner) *and* decide which of the HD DVD standards we'd buy into to match it. This is also a nice consequence of a rather obtuse concept I first became aware of over a decade ago - with the new tapeless camcorders, we're transitioning from "streaming" data forms (as with tape or live video and audio broadcasts, you have to be able to join in progress) to "file-based" data forms. To get footage from a tape to play on a DVD, you have to create a file from data captured from the tape. With AVCHD, there's the promise of using familiar computer file paradigms and just copying files from the camera media (RAM, HD, DVD) to some other place and having a piece of hardware decode it. This is pretty exciting to us, because until now getting footage from a camcorder to a (SD) DVD is a pretty painful process, including having to "transcode" from however the video was compressed by the camera to another way the DVD player recognized. Having cameras that record files that can be played directly by set-top high-def DVD players (if indeed they can) really makes the path short (provided you're not editing).

EDITING COMPLEXITIES FOR CONSUMER HD

Having said that, the algorithms used to store all that HD data in *less* space (some current AVCHD camcorder record up to 1920x1080 pixels@30fps at a data rate of only 15Mbps, while standard-def DV records 720x480@30fps at 25Mbps) have to resort to some devious strategies - namely using inter-frame as well as intra-frame compression. This means that unlike the old DV standard, these cameras don't record every frame. They record periodic full frames followed by the differences between the full frames and the current one. This makes editing pretty tricky, since trying to go forward (or worse, backward) one frame will likely land you on a frame that doesn't actually exist. Early HDV editing solutions (from just 2 years ago) required capturing all the footage at real-time, then waiting hours while the computer created temporary files of intra-frame compressed frames. At the end of editing, if you wished to record back to HDV tape, you waited for hours again while software re-created the long-GOP (Group Of Frames) stream to put back on tape.

MAYBE DVD-BURNING CAMCORDERS AIN'T SO BAD

There is some argument for using a DVD-burning camcorder if all you want to do is, say, review football plays without editing. As long as you strategized disc-changes at non-critical times (assuming the tales of long DVD-finalizing waits are true), you'd be able to pop these in a [compatible HDTV player or personal computer with AVCHD decoding software] without any intermediate steps. Plus, you get archival media right from the camera (which you can duplicate in a computer with a DVD burner).

MORE CAMCORDER INFO

Camcorderinfo.com is a site which attempts to provide objective reviews of available products through scientific process. Founder Robin Liss was 12 years old when she founded the site a decade ago.