What Are We Trying to Compress? 3
4.14 Digital Intermediate Processes
The traditional way of making movies was purely mechanical. Splices were done manu-ally and the color grading was done with filters and timed exposures. Although they are automated now, the processes have been fundamentally the same for many years.
Dust laden image Dust particle detail
Scratch detail Figure 4-26 Dust and scratches.
Tears and punctures after scanning damaged film
Figure 4-27 Examples of film damage.
Cintel International Ltd.: http://www.cintel.com/
Snell & Wilcox: http://www.snellwilcox.com/
If the film is digitized and the color correction is done digitally, it can then be printed back onto film for distribution. This digital intermediate (DI) introduces an opportunity to improve the workflow and provide additional tools to the filmmaker.
Scanning the film in at the earliest possible point enables the editing to be done elec-tronically. This is very beneficial. The integration of special effects or corrective “surgery”
other than just grading the film can then be used to easily add or remove elements, or perform sky replacement or compositional adjustment to frame the content more attrac-tively.
Shooting on HDCAM equipment eliminates the scanning process altogether at the expense of losing the organic quality of film grain. That quality can be reintroduced during the finishing phase. The process of shooting and editing a movie is shown in Figure 4-28. The top row of boxes is the traditional mechanical process and the bottom is Table 4-4 RACINE-S Project Participants
Company Expertise
Arri Developing a portable scanner for all available formats.
Pandora Developing the processing hardware required to run the restoration International processes.
FSSG Software to regenerate speech. They call this virtual dubbing. They are also looking at the acoustical enhancement of audio recording and reproduction systems.
Cineca User interface being developed using VR techniques.
University of Interpolation software to replace or repair damaged and missing
Glasgow imagery.
Androme Collaborating with the University of Glasgow on joint research projects to develop multimedia software and restoration techniques.
Limberg Collaborating with the University of Glasgow on joint software tool Univeritair development projects.
Centrum (LUC)
Cinecitta Integration and bench testing to establish whether the restoration algorithms work satisfactorily, and feeding back to the researchers.
RACINE-S: http://www.racine.eu.com/Arri: http://www.arri.com/
the all-digital workflow. You can see there are opportunities to move from the traditional workflow to the digital intermediate form whenever you need to.
The digital revolution is pervading and affecting every aspect of film and TV pro-duction, and video compression is critical to the success of the industry from one end to the other.
A significant advantage of the digital intermediate process is that an archival copy of the film is retained in a digital form. Since this was scanned from the original pristine footage, there is very little likelihood of damage, dust, scratches, or other artifacts being introduced.
The colors in the picture will not fade over time the way the film emulsion would. Archiving becomes easier and repurposing to other formats such as DVD is a much simpler process.
This also facilitates the migration to D-cinema and the electronic delivery of movies.
Archiving over hundreds of years is becoming an issue with digital content, and some current studies are examining the aging of storage media and the most reliable file formats to interface with systems that won’t even exist for several hundred years. This might seem an odd subject to be talking about in a book on video compression, but it is quite important that future generations be able to decode the material that we store today.
You should bear that in mind when choosing a codec for archival purposes.
4.15 Summary
This chapter has touched on a lot of different aspects of how filmed images work. There are, however, many film formats that have not been covered here. Studying this topic on the Internet reveals a large number and variety of Web sites that describe some very odd film formats. In addition, you will find some information in the appendices about frame sizes and formats.
As you work with archival film sources, keep in mind that the exact size and resolu-tion of film stock varies considerably and that the values quoted here for picture sizes are nominal guidelines only. The chapter on digital imaging revisits the commonly used 2K, 4K, and 6K resolutions for digital film work.
The caveat stated at the beginning of this chapter applies here too: The resolution chosen for calculating image sizes is based on quoted values from a variety of sources.
However, you may scan at a higher or lower resolution than the 115 pixels per mm used here. You will need to make adjustments to take that into account if you are doing any capacity planning. Your mileage may vary.
In the next two chapters, video and digital imaging are studied. A few minor issues having to do with film will come up again later on in the discussion of some of the more esoteric aspects of video compression.
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