24p production

24p has come of age. With the release of Star Wars: Episode II — Attack of the Clones, electronic cinematography and 24p post production have attained blockbuster status.

Is film dead? Not by a long shot.

But the arsenal of tools available to Hollywood's best and those who aspire to join their ranks is growing rapidly, along with acceptance of digital cinema technology. Cinematographers can now choose to acquire their images on film, or a growing range of 24p cameras. Meanwhile, the workflow for all forms of imagery — film, digital video and computer-generated — is converging, allowing for natural and synthetic imagery to be combined seamlessly.

Beyond the application of the Sony's CineAlta 24p HD camera for image acquisition, Star Wars: Episode II is being screened at more than 100 theaters equipped for digital projection. Many reviewers are proclaiming the end-to-end digital experience to be better than the “film look” that 24p digital seeks to emulate, and someday surpass.

Figure 1. The Viper Filmstream camera from Thomson offers support for multiple spatial resolutions, frame rates and aspect ratios.

Perhaps no other product category at NAB inspired as much enthusiasm and debate as systems designed to acquire and process 24p images. A two-day Digital Cinema Summit provided an opportunity for the motion picture and television industries to assess the status of HDTV and digital cinema — to determine if the technologies are converging and how they will impact the disparate worlds of motion picture and television production. Perhaps the best way to summarize the conclusions reached is that both sides are talking to one another. Given the historic rifts between these creative communities, this is real progress.

One area where there seems to be growing consensus is the desirability of the “p” component of 24p. Hollywood has steadfastly refused to accept the use of interlace for the acquisition of imagery. While 24 fps is an important number for exhibition — a critical component of the “film look” — it is not always the shooting rate. Film cameras allow for adjustment of the frame rate, enabling cinematographers to undercrank or overcrank the frame rate to achieve a variety of motion effects. Frame-based acquisition systems deliver significantly higher image quality than interlaced systems when playback speed is changed. De-interlacing is still more of an art than science.

Panasonic has focused on this important aspect of the electronic cinematography process with their AJ-HDC27 Varicam HD Cinema camera. The 720p camera supports variable frame rates from 4 to 60 fps. At NAB Panasonic announced the Cine-Style Gamma option, which allows for adjustment of the frame rate in single-frame increments and improved dynamic range performance.

The option extends the camera's usable dynamic range, especially in traditionally limiting areas such as highlight handling, a limitation of both SD and HD video cameras. Cine Gamma provides the user with a closer approximation of film's ability to maintain smooth image tonality even when compressing extreme highlights.

Panasonic did not limit its efforts to popularize 24p to products targeted at Hollywood cinematographers. The company introduced two new standard-definition cameras that offer 24p acquisition capabilities for video professionals and aspiring independent producers.

The AJ-SDX900 DVCPRO Cinema camera features three newly developed 2/3" 520,000-pixel CCDs that capture high-sensitivity images at 60 fps 525 lines (480 interlace scan) and at 30 frames or 24 fps progressive. The DVCPRO recording system in this camcorder is switchable between classic DVCPRO and EFP-quality 50 Mbits/s 4:2:2 DVCPRO50 modes. It supports both 16:9 and 4:3 aspect ratios, and offers 24 fps progressive scan (24p).

Rounding out its 24p offerings, Panasonic introduced the AG-DVX100 24p DV Cinema camera, a mini-DV camcorder that captures cinema-style, 24-frame progressive-scanned images.

The palm-sized AG-DVX100 will be equipped with three, 1/3" 410,000-pixel progressive-scan CCDs, with a 4:3 aspect ratio. Support for 16:9 will be provided by letterbox extraction from the 4:3 images, or through the use of an anamorphic lens adapter.

Paralleling the 24p camera announcements at NAB, Panasonic and Apple announced they are collaborating on two important technologies for the professional video industry. Panasonic will be adding FireWire to upcoming DVCPRO50 and DVCPRO HD VTRs, making them the first tape decks to support full ITU-601 digital 4:2:2 quality video at 50 Mbits/s, and high-definition video at 100 Mbits/s data rates over FireWire. The addition of FireWire to the VTRs eliminates the need to add a specialized PCI capture card in the computer, as well as the need to decompress the video prior to transfer. Apple will develop new software DV codecs to support DVCPRO50 and DVCPRO HD, and add support for the AG-DVX100 camcorder to Final Cut Pro.

Over the years European video equipment vendors have focused on the needs of the film industry, developing a range of tools that have become part of the new digital workflow in Hollywood, New York, London and other centers of film production around the world. Through a series of mergers and acquisitions, a comprehensive workflow solution for the film industry is now being developed by Thomson multimedia Broadcast Solutions. The film imaging product line includes the Spirit DataCine, Specter Virtual DataCine, VooDoo media recorder, and digital image processing tools including the Scream and Shout, a new application for film restoration.

At NAB Thomson also entered the electronic cinematography arena with the introduction of the Viper FilmStream camera, based on HD sensor and camera technology acquired from Philips.

Viper extends creative control into the post-production process, providing many of the benefits of working with film negative. The film acquisition/production process is optimized to provide latitude in post production. Film offers excellent dynamic range, with up to eight F-stops of exposure latitude; this results in good detail in shadows and highlights and good linearity through the mid tonal range. And film does not subsample color detail like most video recording systems.

Cinematography involves is a two-step process: shooting, and then grading and processing the images to achieve the desired look. While shooting the cinematographer need only select any desired optical filters, set an appropriate light exposure (F-stop) and the shutter angle. The cinematographer concentrates on focus and framing while shooting; critical image adjustments are deferred to the post-production process.

Figure 2. The Viper uses a technique called Dynamic Pixel management (DPM) to support multiple spatial resolutions.

Typically, the RGB outputs of a video camera are heavily processed. The processing steps, many of which are irreversible, include: gamma, knee (several parameters), matrix, gain, white/black balance, contours (many parameters) and black stretch.

The Viper FilmStream camera emulates film, in that the only critical decisions for the cinematographer are exposure and shutter angle. The uncompressed RGB outputs of the sensors are sampled using a 12-bit A/D process, then converted to 10-bit logarithmic values for data storage. The logarithmic quantization curve is the Cineon log curve, which is now in the standardization process in SMPTE. Using logarithmic values places more quantization steps in the black and shadow areas of the image, closely matching the way the human visual system perceives brightness (aka luminance).

The uncompressed RGB data is transferred to storage via dual HD-SDI links using the 4:4:4 RGB 10-bit mapping that conforms to SMPTE proposed standard 372 M, now in the final phases of standardization. Viper can also output YUV 4:2:2 via a single 1.5 Gbits/s HD-SDI link, and it can be upgraded to a version with full support for HD video processing techniques.

Another feature of the Viper is support for multiple spatial resolutions, frame rates and aspect ratios (see Figure 1). The ability to support multiple spatial resolutions comes by virtue of a technique called Dynamic Pixel management (DPM). (See Figure 2.)

For the 1920×1080 formats, vertical samples are combined in varying proportions to support both 16:9 and 2.37:1 aspect ratios. Both horizontal and vertical samples are combined to produce the 1280×720 raster. Because of the reduced raster size 720 lines at 24/25/30/60 fps are supported, while for 1080 lines 24/25/30 fps are supported along with 60 fps.

How do you deal with the ˜3 Gbits/s FilmStream output? In a facility with a Specter or other high-bit-rate data recorder, the camera output can be streamed directly to the storage that will be used during post production. To deal with location shooting, Thomson has partnered with Director's Friend, a German company specializing in tools to support digital cinematography.

The df-cineFS is a field image processing, editing and display console optimized to capture and process the FilmStream outputs. Another version, the df-cineHD works with 24p cameras that provide a 1.5 Gbits/s HD-SDI output. Integrated color correction tools make it possible to view a high-resolution preview of the acquired image data.

HDreel is a portable hard disk storage unit suitable for DC operation. The 576 GByte total capacity supports about 96 minutes recording time at 24p (YUV/8-bit) and 48 minutes at 24p (RGB/10-bit).

Thomson will be working with a variety of industry experts, both cinematographers and those who will work with the FilmStream images, to explore and refine the capabilities enabled with this approach to digital cinematography. Gary Demos of DemoGraFx, has spent much of the past decade developing image processing and compression technology for digital cinema and Digital TV. Demos has long advocated the use of logarithmic coding for high resolution images.

“The use of a logarithmic representation in an electronic camera is a real step forward. In our experiments, LOG coding provides a better representation for compression that the traditional gamma corrected video representation.”

To be fair, Thomson is not alone in pushing for an extended gamut when working with digital cinema images. For Star Wars: Episode II, Industrial Light and Magic utilized direct RGB links from the Sony CineAlta HDCam for capturing all of the model imagery use in this effects intensive motion picture. Virtually every frame in the picture was processed in some way.

Equipment from Snell and Wilcox played key role in the production of Attack of the Clones, which used a 2.37:1 “scope” extraction (1920×818) from the 16:9 source. 4:4:4 10-bit disk stores were employed to capture RGB data from the cameras. The movie was graded on using the Snell & Wilcox Picasso tool suite, which has a Pandora color corrector at its core. And in the private showings the final scaling to the Texas Instruments DLP-cinema projector head was through a Snell & Wilcox HD6200 interformat converter.

Anticipating the increased interest digital film and HD video production, vendors of digital post-production systems announced upgrades and new products at NAB to meet the growing demand for 24p production tools.

Avid Technology announced new versions of the Avid|DS family, featuring a new Media Composer-style interface, enhanced conform capabilities and support for key HD formats and frame rates, including 24p for mastering. The Avid|DS HD v6.0 system integrates paint, animation, character generation, special effects, compositing and HD finishing capabilities, with Avid's familiar editorial environment. In addition, more than 80 percent of the titles, effects, and graphics commonly created in an offline session can be automatically transferred to the Avid|DS HD v6.0 system for high-resolution finishing.

At NAB, Discreet Logic announced mixed resolution support for flint, flame and inferno. These products will now support all resolutions from film and video to DTV/HDTV — all with universal 24p mastering capabilities. Mixed resolution support gives artists the ability to create and manage intricate effects by freely combining, mixing and matching images of different size, aspect ratio and color depth in one unified environment.

Pinnacle Systems continues to offer one of the most cost effective solutions for 24p film and HD production, CinéWave HD. The CinéWave hardware and bundled software work seamlessly together to address the full range of post-production requirements via the Apple Power Mac G4. CinéWave HD supports uncompressed SD and HD formats; it includes a full version of Apple's Final Cut Pro and Pinnacle's Commotion Pro and Knoll Light Factory. At NAB Pinnacle announced support for Apple's OS-X operating system; the upgrade will be free for all CinéWave owners when it ships in July.

Just before NAB, Quantel made a somewhat belated announcement of peaceful coexistence with the world of “open systems” - software-based image and video processing tools that run on popular computing platforms. The company, which once dominated the market for video paint systems and DVEs, was the last holdout from the era of dedicated video processing gear. Following ownership changes and the evolution of the marketplace, the company announced a bold new initiative just before NAB - Generation Q.

Generation Q products will offer scalable solutions from Windows-based desktops to lightning-fast high-end Quantel hardware. Each product like will offer “resolution co-existence,” spanning the full range of video resolutions from the Web to film and HD. Resolution coexistence means storing all media in its original format, editing this native media on the timeline, then outputting in a choice of spatial/temporal resolutions and aspect ratios.

The Quantel iQ post-production system can support real-time 24p production with rasters of up to 2048×1556. A fully configured system offers 7 TBytes of storage, enough to accommodate 16 hours of 1920×1080 at 24p digital images. At NAB Quantel also announce the availability of eQ, a cost reduced version of iQ for facilities that work primarily with SD, but have the occasional need to offer HD production capabilities.

The period of anticipation appears to be coming to an end. The gala premiere of 24p Digital Cinema has been well received. The marketplace is responding with a wide range of tools to fit virtually every budget. Now the process of collaboration to refine the tools begins.

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