By John Matarazzo - National Training Manager, Sony Media Services
When George Lucas shoots a Star Wars movie in Sony High Definition video, you know big changes are afoot in Hollywood. With its half-inch media, its mild compression and its film-friendly 24 frames per second progressive scanning, Sony's HDCAM® 24P equipment is changing the face of films production. And it's driving a huge increase in demand for Sony HDCAM tape. The rapid success of HDCAM 24P makes this a good time to review what the system is, how it's being used and what role HDCAM tape is playing.
Here, you'll find a review of how HDCAM 24P recording came to be and what sets it apart from earlier HDCAM recording at 60i. We'll also cover such basics as the difference between "progressive" and "interlace" scanning and the difference between video "field" and video "frames." And of course, we'll review the technical characteristics that make Sony tape and important part of the HDCAM system!
It's a solution to acquisition in the digital age. It's a powerful way to save money. It's a new medium with new creative possibilities in entertainment and information. It's HDCAM 24P recording, a new version of the Sony HDCAM format. And it's rapidly gaining acceptance in Hollywood.
When Sony launched the HDCAM format in 1997, it was the realization of a 16-year quest. Sony had created the world's first one-piece HD camcorder.
The HDCAM format leveraged the affordability, durability and familiar user interface of Sony half-inch recording. And thanks in part to the reduced size of HDCAM tape's Metal Particles, HDCAM equipment offered long recording times. The camcorder uses Small cassettes with up to 40 minutes of recording time. While the field and studio VTRs use Large cassettes with up to 124 minutes.
With all these advantages, HDCAM equipment rapidly gained greater acceptance than any previous HD format.
As the HDCAM format reached market success, discussions between Sony and a leading Hollywood postproduction house, LaserPacific Media Corporation, revealed a new opportunity. The Hollywood experts identified the 24 frames-per-second (fps) capture rate of 35mm film as a crucial imaging standard. They argued for an HD video system capable of image capture at the 24 fps film rate and using "progressive" scanning instead of conventional "interlace" scanning. This 24-frame progressive system is abbreviated "24P." It's also called 24PsF, for 24 Progressive segmented frame. This refers to athe way the signal is delivered from VTR to VTR and from VTR to monitor.
LaserPacific reasoned that 24P would be a valuable addition to the motion picture industry. The reasons were many:
Compared to conventional 60i recording, 24P has the additional benefit of offering 25% longer recording time on a given cassette. Maximum recording time for Small cassette goes from 40 minutes to 50. Maximum for the Large cassette goes from 124 minutes to 155.
After years of testing and evaluation, George Lucas chose the new Sony HDW-F900 HDCAM 24P camcorders adapted with Panavision® lenses and accessories, to shoot Star Wars: Episode II. And feature films are just the beginning. While most primetime dramas and sitcoms are shot on 35mm film, HDCAM 24P acquisition is already making substantial inroads. The cost savings and convenience are just too big to ignore. The picture quality is superlative. What's more, HDCAM acquisition and postproduction give the final result greater archival value for the coming world of High Definition TV broadcasting.
As Sony moved to commercialize HDCAM 24P products, the International Telecommunications Union (ITU) created a family of standards. The equipment, which includes camcorder, studio VTR, video switchers and digital effects systems, can be switched for 24P, 25P and 30P progressive scan capture, as well as 50i and 60i interlace. The 60i corresponds to the conventional, U.S television field rate.
In addition to fielding a full range of HDCAM 24P equipment, Sony has built bridges between the world of Standard Definition and the world of HDCAM. The HDW-M2100 HD Multi Player offers universal playback compatibility for the long list of previous Sony half-inch formats in addition to HDCAM tapes! This single machine unites 17 years of Sony half-inch history. The HDW-M2100 features built-in HD-to-SD downconversion , bringing HDCAM tapes into conventional infrastructures. And built-in SD-to-HD upconversion carries 150 million existing Sony half-inch tapes into the High Definition future!
Playback compatibility of Sony half-inch VTRs. A new generation Sony videotape players improves access to archival tapes in Sony half-inch formats and helps simplify facility design.
*plays on selected VTR models
When Sony introduced the world's first one-piece High Definition camcorder, the production community marveled at the hardware. But a key enabling technology was the recording media: Sony HDCAM tape.
Because HDCAM 24P recording is an extension of the original HDCAM format, and because HDCAM 24P equipment can be switched to other image capture rates, including 60i, there is no "dedicated" 24P media. All HDCAM products accept the same HDCAM media! However, the difference image capture rates do result in different recording times.
The terms progressive and interlace describe the capture and display of the picture's scanning lines.
US-standard video captures pictures at 30 separate pictures or frames per second. However, interlace scanning divides each of these video frames into two fields. Each interlaced field captures a distinct,1/60 second slice of time. The first field captures and displays every other horizontal scanning line (the odd-numbered lines).
The second field captures and displays the even numbered lines. At any given instant, only the total scanning lines appears on the television screen. While this limits vertical resolution, it was an ingenious way to get around bandwidth limitations in the early years of television.
In contrast, progressive scanning maintains the integrity of the frame and displays all the scanning lines in a single pass. When carefully executed, progressive scanning can yield breathtaking image detail one reason why progressive scanning is universally used for computer displays.
Most movies, TV dramas, sitcoms and national TV commercials are originally shot on 35mm film. This means that before they can be televised, they must be transferred from film to video. When film footage is transferred to video for U.S. broadcasting, the frame rate must be converted from the 24 frames per second of 35mm film to the 60 fields per second, interlaced scanning of video. This picture rate conversion is called 3:2 pull-down.
By simple arithmetic, the 60 field of video divided by the 24 frames of film equals 2-1/2. This means that each movie frame must convert to an average of 2-1/2 video fields. To achieve this average, 3:2 pull-down converts the first film frame to 3 video fields, the next frame to 2 fields, then 3 fields, then 2 fields, and so on. This alternation of 3-2-3-2-3-2-3-2 is 3:2 pull-down.
The system works extremely well and is essentially transparent in everyday use. However, 3:2 pull-down can create three specific problems.
While you might expect the fate of HDCAM production to be directly tied to the success of High Definition television broadcasting, the reality is quite different. Consumer acceptance of full High Definition TV receivers is off to a sluggish start, but HDCAM is already a success. Clearly, HDCAM equipment is going into applications that are not strictly dependent on HD broadcasting.
High Definition is just one option in the wider category of Digital television (DTV) broadcasting. The Federal Communications Commission (FCC) has encouraged DTV broadcasters to use the Advanced Television Systems Committee (ATSC) standards. These include 18 possible DTV picture formats, of which six are classified as HD.
Other broadcast options include simulcasting as many as four SD programs on a single 6MHz channel and broadcasting data alongside video programming.
According to industry sales figures, television capable of displaying High Definition have so far sold in the hundreds of thousands. However, televisions fully equipped to both receive and display the ATSC standard signal have so far sold in the tens of thousands.
There are 18 recommended formats for DTV broadcasting. Of these, six are designated High Definition. (See the top tow rows.)