DVD cameras. I-frame only and a storage pig...............................
tvbeurope.com
Momentum builds towards disk cameras
by James King
Just as disks have taken over from tape for many studio and OB recording applications, they are also beginning to find their way into portable cameras. At present, only Avid/Ikegami's EditCam is in daily use, but they will be joined next year by NEC's optical disk system and within a few years a host of manufacturers could be offering DVD-based camcorders.
Because DVD is basically consumer technology, it will have the huge advantage of mass market prices, particularly for the recording media. Unfortunately, there are several standards issues to be resolved before DVD cameras will see broadcast action. However, Sony was showing a prototype DVD system off the show floor at IBC which proved that the technology does work and produces surprisingly good results for something so far from production. But the three or four year wait for the DVD disk camera is attributable to lack of standardisation.
Sony's prototype is based on a specification created by the Optical Disk Camera's user group (made up of Japanese broadcasters, the US network ABC, and the BBC and IRT in Europe), and is based on DVD-RAM Level 1, with storage of up to 2.6GB per side. However, the user group, which is adamant that the disk must be based on an international standard, wants to use DVD-RAM Level 2, because it should offer 4.7GB storage per side.
But, that won't be ratified as a standard until next year, at the earliest. "If it uses proprietary media it is no use, so we have to wait for the consumer specification to be ratified," says Richard Lewis, Sony's product manager for camcorders. It will then take some time to complete development and start producing the recordable disks.
However, the prototype does give a good indication of the type of system they are aiming for. It uses MPEG-2 4:2:2, at 31 Mbps, I-frame only, with two channels of uncompressed audio and gives more than 20 minutes of recording time on the existing 5.2GB disk. Being a random access disk, it can have nonlinear recording (like Ikegami's RetroLoop feature) and playback.
It will have flexible data transfer rates, to accommodate most types of networks. It can also record and play back at any rate, giving 80 minutes recording time at 8Mbps. Users can also change the GOP (group of pictures) from I-frame only to increase recording times further.
Users will be able to do some simple editing in the camera, but a non-destructive editing workstation will also be available. The eventual camera will be the same size and weight as the prototype (or possibly smaller), which was a little bigger than a DVCAM camcorder.
Besides being delayed by the wait for standardisation, the main problems which have to be overcome before the DVD Disk camera is launched include: developing its electrical shock proofing; and making the drive fast enough for editing (which will require a special drive with capabilities above those of the consumer models). "But, until the media is fixed, nobody can move," says Lewis.
The demonstration used mechanical shock proofing, which worked perfectly despite the cameraman jumping up and down. The final version will also include solid state buffer memory, which will improve its ability to withstand shocks further. "Because it is a non-contact recording medium, it is difficult to damage the disk," he adds. It will also be very easy to maintain, and long-lasting, as the disks should be rewritable more than 10,000 times.
In a spin
However, "DVD can't match the high speed playback and record," of NEC's new optical disk recorder, claims Tetsuya Yamamoto, Diskcam developer, NEC. He believes that the market for disk cameras won't take off until the media prices drop, and says that the Avid/Ikegami field packs, which use magnetic disks, are too expensive. However, the optical disks used in the Diskcam will only be about $60 each. With 4.1 GB of storage, they can record about 20 minutes of video and audio using MPEG-2 4:2:2P I-frame only compression at 25Mbps, which should give high quality pictures.
The Diskcam is due to be available from NAB, for about $23,000 for a dockable digital disk recorder, which weighs about 3.5 kg, consumes 16 watts of power, and can be used with any conventional camera.
There will also be a $28,000 SDI desktop player available at NAB, with an SDTI version, which will allow two to four times real-time transfers. This is likely to be ready by the end of 1999. As the SDTI model will have two optical heads, it will be able to offer continuous playback at the same time as high-speed random access.
However, the Avid/Ikegami system has the advantage of being available now, and has been in use long enough that the bugs have been ironed out. Although it has been slow to take off, John Turley, Ikegami's marketing manager, says he has seen a resurgence of interest in the EditCam, "as people realise the applications it can be used for, such as sport. The BBC uses it for rallying, where the gaps between the cars is unpredictable and you have to keep recording. Well, you can with the RetroLoop. It gives transparent editing between cars, and means you have less footage to upload to base."
He says the software is now complete "and is considered to be idiot proof." There is also a new field editor for the EditCam which takes two field packs. The field packs themselves already record up to 40 minutes, and a new disk with 8GB drives should be shipping now which will give up to about 70 minutes. The system currently uses 5:1 compression, but should be able to offer up to 2:1 soon.
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