By the 1980s, video recording had successfully developed to the point where a VTR could be squeezed into a camera body, creating the camcorder. The requirements for a camcorder must have been challenging for early developers. The deck had to operate with a low power drain, be small, not be upset by motion and vibration, and work in extreme climatic conditions. The Betacam family of 1/2in decks and the 1/4in DV are a good example of just what can be achieved. These formats have even been adapted to support HD, with HDCAM, DVPRO HD and HDV. However, successful tape has proved to be, tape is still linear, and it stores video data. Broadcasters now want nonlinear file-based recording to fit better with their IT-based systems and to allow more flexible workflows.
Camcorders are a great example of the compromises that are inevitably part of engineering design. They must deliver superb pictures, but have a low power drain on the batteries and be light enough to carry around all day. Power is limited to about 40W by current battery technology, and weight to around 5kg (excluding the lens and battery).
Current videotape technology has reached a write speed of 440Mb/s for HDCAM-SR (880Mb/s at double speed), which sets a quality benchmark for acquisition. Camera operators have come to expect a record duration of around two hours from a single cassette, again setting an expectation for different media.
Currently available tapeless media, that is affordable and practical, is limited to around one hour (for HD) and a maximum data write speed of about 100Mb/s. That means compression is essential. Today, if you want 1080p50 4:4:4 recording, then a separate storage device must be used. No doubt in a few years it will be feasible to record a 3Gb/s stream to onboard storage.
It has been a long time waiting for other storage media to offer the features provided by tape. Cost and record duration were two obstacles. The broadcast environment, especially ENG, can be hazardous to technology. Reliability is essential.
Consumer technologies have been adapted to meet broadcast needs. One example is Blu-ray. A second is solid-state memory. A third, the hard drive, is forever decreasing in cost and increasing in capacity. All these technologies can now offer competition to conventional videotape, but with the major advantage of nonlinear access.
Making a choice
Choosing a camcorder used to be dictated by the type of tape: 1/2in or 1/4in, digital Betacam or DVCPRO. Now deciding on a camcorder starts with the media. Do you want an instant archive, or do you want to put off that decision?
Videotape is cheap enough to use once and keep on a shelf. When shooting to tape, that same tape can also be used to archive the production. As magnetic tape has a typical life of 25 years, any need to preserve the content long term can be put off well into the future.
Two tapeless formats are a similar cost to videotape: the optical Professional Disc and REV PRO. These can be employed in a similar way to tape, used once and stored away as a permanent archive of the production.
Currently, hard drives and solid-state drives (SSDs) are too expensive to use once and put away on the shelf. Instead the files must be copied to disk storage arrays for post production. The SSD can then be wiped and used for the next shoot. After post production, the show can be archived to a long-lasting and low-cost medium, such as data tape, to free space on the storage array.
Portable hard disk drives (HDDs) similarly should only be used for temporary storage. There are many stories of shows stored on portable drives that have been put away on a shelf. Five years later, the drive will not spin up and read back the data; drives like to spin continuously.
Your choice of acquisition medium is dictated by your workflow and by the program format. Sitcoms are long-lasting formats that can be sold way into the future. Other formats are transient and not worth the cost of archiving. News clips are short and are better stored in a managed archive, so the original camera media can be wiped and reused.
Once you have selected the media that best fits your budget and workflow, then it's down to the features and facilities. One big decision is whether to use a 2/3in or 1/2in lens. You may have a stock of lenses to reuse, or the program genre may dictate 2/3in. For programs shot on a smaller budget, 1/2in could be the ideal choice. It may even be appropriate to use a smaller sensor, perhaps a 1/3in camera with a fixed zoom.
Once you have chosen the recording media and lens-mount, you have probably narrowed down the selection of camcorders to one or two manufacturers and a handful of models. Other factors may modify those choices. Obviously there is cost, for both the camera and the removable media. You may have a good relationship with an existing supplier. The level of service and support is very important when buying cameras.
The current tapeless media have different features, each with pros and cons for a given application. What may be optimum for news may not suit drama.
The HDD has been popular for some years as an add-on to DV cameras. Sitting between the camera and its battery, a 1394 drive provides an alternative to recording to DV tape. This principle has since been developed to support the higher data rates of HD. A typical 2.5in drive for video applications has a 320GB capacity, which equates to more than five hours at 100Mb/s.
This route has the advantage that it can also be used with existing cameras for those who want a direct-to-edit file transfer without the need to ingest from tape.
Another option is optical. The Sony Professional Disc was developed with blue-violet laser technology to support the requirements of the XDCAM camcorder family. The technology is similar to Blu-ray, but is housed in a rugged caddy to survive the rigors of outdoor shooting. Disks are available with 23GB and 50GB capacity. Data rates up to 50Mb/s can be recorded, giving a record duration of 95 minutes for the higher capacity disk. Lower data rates can be used with a pro rata longer record time.
The initial product was SD, but the latest iteration supports HD with long-GOP MPEG-2 4:2:2P@HL compression. The XDCAM series supports a number of SD and HD codecs at bit rates from 18Mb/s to 50Mb/s.
The SSD storage uses Flash memory to store the video and audio data. Flash memory has become ubiquitous from the USB stick to video servers for playout and VOD. Some of its advantages include high data transfer rates and a rugged nature, which is ideal for handheld cameras.
Conventional Flash memory has a lifespan of between 10,000 and 100,000 rewrites. Eventually the 10nm-thick insulating layer inside the memory cells wears out from the erase operation. A new development of ferroelectric NAND promises improvements to more than 100 million times, which could easily outlast the camera. Compared with the wear of videotape after 1000 times, these numbers look very high, but SSDs are used as temporary caches to transfer data from camera to content store, and then erased and reused. In contrast, videotape is usually only recorded once and then stored in the production archive.
Many cameramen are familiar with tape and reluctant to move to solid-state memory. But younger folks are familiar with SSD in consumer devices (i.e. CompactFlash, SD). For them, it is a natural way to store video.
The cost of the SSD can be a surprise to those used to the cost of tape. This is the wrong way to look at the media. Rather than thinking of it as the archive format for the footage, it should be thought of as an integral part of the camera and only removed to move to more permanent storage. The SSD should be priced as a capital expense, not part of the operating budget.
Two broadcast formats have been developed, the Panasonic P2 and the Sony SxS. Consumer formats, CompactFlash and Secure Digital, are popular with low-cost camcorders and for storage of set-ups on professional cameras. Another development is the SSD in the form-factor of a hard drive. A typical HDD replacement has a 2.5in form-factor with an SATA interface so it can be directly substituted for a regular hard drive.
SSDs and HHDs can potentially record at much higher rates than 100Mb/s, especially when striped across several memory devices. However, high data rates would lead to very short record durations. SSDs must be affordable, and HDDs are limited by size, weight and power drain. The actual specifications are chosen to meet broadcast requirements, so they are inevitably a compromise. (See Table 1 below.)
To ingest a videotape shoot to an NLE, either the tape could be played back in a VTR and video captured as an SDI stream, or with the DV format, the video could be transferred over a 1394 link to the NLE.
A simple file transfer is used with IT-based media. But that does not mean that the NLE will support the codec. Just about all NLEs can handle DV25, and most can handle the common MPEG formats. If you opt to use a camera with AVC-I or JPEG2000 encoding, check that your favored editor supports the codec. If not, then your only option is to decode to SDI and ingest conventionally. That will exclude editing in the native camera format and can introduce an additional decode/encode step with attendant increase in artifacts.
Tape-based recording is generally 8 bit, which limits the opportunity for color grading in post. Where 10-bit HD video is needed for SFX or high-quality cinematography, the choice is to record to a separate tape deck like the Sony SRW-1 field recorder or Panasonic HD-D5, or to use racks of hard drives.
The tapeless camcorders that use DV or MPEG compression continue the 8-bit performance of videotape. However, products are emerging that support 10-bit codecs. Examples include the AVC-Intra compression used by Panasonic with the P2 card and JPEG2000 used by the Grass Valley Infinity.
If 10-bit recording is a must, then this will narrow your choices of make and model, unless you want to use separate record devices linked to the camera.
Broadcasters look for many things when making a purchasing decision. Sensitivity, noise levels and highlight handling are performance considerations. And flexibility may be important. If a crew has to travel internationally, can it shoot in 50Hz and 60Hz formats? Does a drama production need to be shot at film rate? Is one resolution sufficient, or does it need to be SD and HD, 720 and 1080, progressive and interlace?
Current technology limits recording to around 100Mb/s, so the use of compression is obligatory. However, with advances in storage technology, we will one day see camcorders that can record uncompressed 1080 50/60p to onboard media.
Aside from the specification and performance, what about the vendor? What is the track record of its cameras? How reliable is the company? How about its service and support?
For the owner/camera operator, there may be other more subtle aspects like style. Does the camera look professional? When you turn up on set, you need to look the part.
Users no longer need to purchase expensive tape decks. This has dramatically changed the economics of shooting and editing for the independent operator. For news editing in the field, this is a real plus. It is one less piece of equipment to carry around.
The new generation of tapeless cameras offers users more choices. With a videotape camcorder, the decision to purchase could be on specification and relationship with the vendor. Now a broadcaster must also decide what media it wants to use. For tape-style shooting, the Professional Disc or REV PRO offers a comparable media cost to tape, so it can be used to archive the shoot. For the IT-centric operation, SSDs provide fast and efficient workflows without the need for conventional video playback hardware. Some cameras even offer a choice of media formats for greater flexibility. Getting your future workflow resolved is probably the best place to start, before all the other testing and evaluation.
Table 1. Comparison of tapeless onboard storage formats. Note: The capacity of the media is constantly increasing, so the figures here were representative in December 2008. Media Technology Suppliers Capacity Typical data rate Record duration CompactFlash Flash Many 32GB 100Mb/s 32min GFPAK Flash Ikegami/Toshiba 64GB 100Mb/s 60min P2 Flash Panasonic 32GB 100Mb/s 32min Professional Disc Optical Sony/TDK 50GB 50Mb/s 95min REV PRO HDD Thomson Grass Valley/Iomega 65GB 100Mb/s 60min S×S Flash Sony/SanDisk 32GB 35Mb/s 100min
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