Stereoscopic movie editing is more difficult in comparison with 2-D movies, as the editor should work with two video rows and mind that the edges of the cuts coincided perfectly to avoid non-coincidence of the scenes, as well as violations of the human perception rules. The latter is based on the biological patterns of image perception of processing. Anaglyph viewing is regarded as the technology of the past, and contemporary editing is closely linked with polarized images.
Introduction
3D movie editing is one of the latest tendencies of the contemporary movie industry. These technologies help watchers to get involved in the atmosphere of any movie, hence, a horror becomes more terrific, action ‑ more thrilling, comedy – funnier, etc. However, movie making and editing also presuppose additional difficulties, as 3D signal processing requires a higher accuracy level, as well as computation capacities. The history of 3D editing is closely linked with the evolution of stereo images in general, however, the actual difficulty is closely linked with the necessity to synchronize at least two streams of signal. The contemporary software editing tools make 3D movie editing as simple as 2D signal processing, however, the key principles of stereoscopic image processing need to be analyzed. A historical overview of anaglyph stereo image editing will help realize the polarized stereo signal. Hence, the paper aims to review and analyze the key 3D signal editing techniques, as well as review editing software such as Avid Media Composer. The features of this video editor are closely linked with the values of traditional video signal editing, hence, the general aspects of movie editing will be represented from the perspectives of comfort and simplicity offered by the Avid Media Composer toolset.
Historic Overview
In general, the ways and methods of producing 3D movies are various, and they differ with the technology of creating the depth of perception. The popularity of various systems of 3D picture creation changed through the years, and the first attempt at 3D picture creation was made in 1948. All the watchers in a cinema were given anaglyph glasses. Red and cyan color filters “filtered” the picture, hence, making the eyes percept two different pictures. The shifted images made an illusion of a 3D picture. This is regarded as the golden era of 3D movies, though it ended in the 1950s when polarization systems were implemented. As it is stated in Pasqualotto and Hayward (832):
In the 21st century, polarization 3-D systems have continued to dominate the scene, though during the 60s and 70s some classic films which were converted to anaglyph for theaters not equipped for polarization and were even shown in 3-D on TV. In the years following the mid-80s, some movies were made with short segments in anaglyph 3D. The following are some of the technical details and methodologies employed in some of the more notable 3-D movie systems that have been developed.
In the light of this statement, it should be emphasized that the history of 3D movie editing originates from anaglyph images. Even though polarized and anaglyph video signals do not differ from the polarized from the perspective of digital video processing, however, anaglyph video processing became the basis of 3D movie editing, as the same principles are now used in polarized systems, where two video signals should be synchronized and have similar lighting and color parameters. Hence, the key principle of 3D signal editing is the calculation of the color rendering as well as lighting in order not to cause discomfort for the audience, and for creating a realistic picture. (Nowell-Smith, 310)
Human perception patterns and principles
In general, the stereoscopic motion picture is created by the means of showing the same image from various angles. The objects that we see looking at a screen are not a true 3D image, as these are two flat objects which are perceived as volumetric objects. Hence, two images are superimposed through polarizing filters, hence the human brain perceives two images, and combines them, and it makes the image deep and multidimensional. The details of this process are described by Zone (677):
As each filter passes only that light which is similarly polarized and blocks the light polarized differently, each eye sees a different image. This is used to produce a three-dimensional effect by projecting the same scene into both eyes but depicted from slightly different perspectives. Since no head tracking is involved, the entire audience can view the stereoscopic images at the same time.
Because this principle is the basis of 3D perception, the latest tendencies of 3D performances presuppose refuse from polarizing glasses, as the polarized image is projected on a screen, and so the image is perceived as multidimensional.
3-D Movie Parameters
In general, stereo image editing and shooting involve various factors and their combinations which form the visual image with the special depth perception. These are camera parameters, viewing location, projector-screen configuration, and psychological factors (Jorke, 46). Incorrect parameters may cause dissatisfaction and eyestrain, as incorrect exposure and large disparities of the image.
Movie editing is a form of art itself. Because 3D image involves a greater amount of parameters, it is a separate art form, as manipulating these parameters requires high qualification and experience. From the perspective of various technologies of 3D image creation, it should be emphasized that video signal presupposes the synchronized projection of two images, however, while an anaglyph picture could be on the single tape, the polarized video signal is created with at least two cameras, that shoot the scene from two slightly differing angles (similar to human eye angle difference). 3D movie editing presupposes manipulation of the timeline, as this is the key feature that differentiates movies from other types of visual art. Additionally, the important aspect of movie editing is the adjustment of proper transitions between cuts (hence, in 3D video signal these cuts are relevant for two images that should coincide by the editing timeline). Transitions between clips have increased since the early days of cinema, and movies may have several transitions and cuts per second. Consequently, all the parameters of timeline synchronization should be considered while editing.
Another aspect of a 3D movie is proper lighting (exposure). Dynamic scenes may be featured with complex lighting, as while one camera receives more light, the other may be shadowed. Hence, the final image will be confused, as if one eye gets the lighter image, the brain will process the entire image to equal the lighting. Hence, light rendering should be performed while processing the video signal. However, to avoid mistakes of light rendering, it is recommended to avoid shooting when one of the lenses is lighted better than the other.
Editing
Considering the values and patterns of human visual perception, it should be stated that shooting a 3D image is rather difficult, as directors and cameramen need to imagine how the audience will see the image in advance. Movie editing is aimed at making the proper timeline of the cuts and scenes, and, also removing the possible shooting mistakes and artifacts. Avid Media Composer is regarded as one of the most suitable and effective 3D video editors. It is suitable for all types of video signals whether it is anaglyph or polarized, as it is aimed at working with all types of 3D images. By the classification by Sorensen and Borre (34), the following aspect should be emphasized:
Many formats exist to simultaneously display the two stereo images to our eyes. The stereo pair is multiplexed either in time (using fast projectors and displays), in space (with alternate rows or columns belonging to different images), or in wavelength (through the red, green and blue color channels). While the need to distribute our content requires us to downgrade to anaglyph, we wish to remind the reader that this format may contain compression artifacts, such as bleeding between colors, which were not present either during development or in the user studies.
These parameters are generally considered while editing a 3D image, hence, Avid Media Composer will be regarded from the perspectives of image perception, principles of 3D image creation, and digital video signal parameters. 3D images may be created from a 2D signal by applying special tools. Hence, numerous stereoscopic multiplexers multiplex signal from two webcams, DV camcorders or professional cameras, stereo broadcasts, and 3D shootings. These multiplexers are used for creating 3D images if there is no 3D shooting equipment available.
Software Review (Avid Media Composer 5)
The software overview should be started by enlisting the video formats that may be processed by AMC.
NSC
PAL
HD – 720
HD – 1080
23.976p
24p
30i
24p
25i
25p
720p/23.976
720p/25
720p/50
720p/59.94
1080p/23.976
1080p/24
1080p/25
1080p/29.97
1080i/59.94
1080i/50
Because this is the line of professional video editing tools, the developers have offered an opportunity to editors to communicate with other editors all over the world. Numerous educational and adaptation programs are created by numerous requirements and needs of beginners and professionals. The key aim of these programs is to simplify the user to work with the system. News, comments, and maintenance may be accessed by every user of the AMC tool all over the world.
In general, this software is regarded as the most multi-functional media tool for professional video editing. It is suitable for editing movies, TV programs, or commercial videos, and it is aimed at widening the set of tools for a video editor by combining standard media composer with new hardware block Avid Nitris DX, which makes it particularly operative and highly productive. Additionally, various codecs SD and HD are maintained. Considering the hardware and system requirements, it should be stated that AMC may be used in movie production studios of any size and scale, and it is the best choice for multifunctional video editing. The key technical features that are aimed to improve 3D video editing are as follows:
- Real-time video output of all the HD and SD formats
- Acceleration of effect visualization by the means of involving the opportunities of multi-core processors, graphic adapter and PCI express
- Improved maintenance of numerous input formats including AVC-I, DVCPRO HD, XDCAM HD
- Maintenance of Mac Leopard OS and Windows Vista 32 and 64-bit
- SubCap tool for adding subtitles
- Innovative MetaFuze tool for quick joining of media files that entail a common file (type DPX and TIF) which are got by film scanning or from CGI systems
- Multistream processing in real-time
- Improved timeline functionality
- Improved effect architecture with optimized CPU / GPU acceleration
- Improved computation opportunities
- Toolset for displaying various time codes in real-time
The key parameters of 3D video editing are speed, flexibility, and intuition. The improved editing tools for controlling media data of the processed file help to regulate the parameters of 3D signal, as the Avid Media Composer allows a video editor to forget about the particularities of 3D editing, as it is intended to make editing simple and 2D like. It allows the assembly of SD and HD formats simultaneously in a real-time regime. There is no need to reformat the input data, as maintenance of various video camera hardware provides the opportunity to save resources, high quality of editing materials displaying as well as the required speed of work.
Media composer is directly integrated with the video manufacturing blocks due to the technology of single disc arrays Avid Unity, and non-linear system of video-editing process maintenance Avid Interplay. Hence, numerous users may be maintained in real-time, performing various tasks of editing and arrangement.
Avid Media Composer provides the standard toolset of color correction, hence, the frames may be combined quickly and easily. Avid DNxHD codec ensures resource-saving and high-quality work in HD format. The work with SpectraMatte masks allows adding various effects, and the Fluid Motion tool provides the opportunity to change the movement speed. Additionally, the project presupposes adding various plug-ins for extending the set of tools.
Interface
The editing process and interface are common for everyone who has ever tried to edit movies and video content. Nevertheless, the AMC provides an opportunity to adjust the interface to the needs and requirements of a user. In general, there are three regimes of working with video, which are:
- Side-by-side. This presupposes storing left and right eye images, while one is located beside the other in a vertical split frame. A full-frame 1920 x 1080 image displays the left eye in the left half of the image, using half of the horizontal resolution. The right eye occupies the right half – or 960 x 1080 each. (Cable, 5).
- Interlaced regime takes half the resolution from each source by alternating lines of horizontal pixels from each eye, from top to bottom, to make up a full-frame comprised of both images. (Cable, 6)
- Over/under the regime is not intended for 3D video editing, however, it may be used for working with one of the 3D streams. This involves both the left eye view and the right eye view together, storing the left and right eye images, one above the other, in a horizontal split frame. (Cable, 5)
Editing Particularities
Some 3D videos include text information such as subtitles. Improper synchronization of text with the 3D image may cause eye strain. Avid Media Composer is featured with flexible opportunities for adjusting subtitles. Additionally, the editor may adjust the font size of the interface to avoid discomfort for the eyes.
As most images are edited in side-by-side mode, at half resolution, the blend effects may be performed by incorporating dissolving, fades, and supers. However, as it is stated by v (22): “Transform effects such as wipes, resize, and compositing that requires the image to carry both eyes in the same frame, will lose the stereo effect and the entire image will no longer appear in 3D”
As for the demerits of the editing system, it should be emphasized that most of them are purely subjective, as Avid is regarded as one of the best media tools for professionals. However, the only may be enlisted. AMC does not involve the depth grading tool. As it is expected that all the corrections are made before the dailies, and the editing process is made in an offline regime, the 3D finishing process is needed. Sync alterations require specific tools for stereoscopic finishing.
Conclusion
3D editing is regarded as one of the most demanding processes in the movie industry. Editing software had been developing for years considering 3D perception patterns and principles, however, few tools may be regarded suitable for professional editing. Avid Media Composer is one of the most capable for editing, as it is created for professionals and by professionals.
Works Cited
Cable, Trevor. Avid Stereoscopic 3D Editing Guide. Laika, Portland, Oregon. 2010.
Jorke, Helmut. Stereo projection using interference filters. Stereoscopic Displays and Applications. 2006.
Nowell-Smith, Geoffrey, ed. The Oxford History of World Cinema. Oxford: Oxford University Press, 1997.
Pasqualotto, Achille, and William G. Hayward. “A Stereo Disadvantage for Recognizing Rotated Familiar Objects.” Psychonomic Bulletin & Review 16.5 (2009): 832.
Sorensen, Svend Erik Borre; Sorensen, Nils Lykke. Method for recording and viewing stereoscopic images in color using multichrome filters. United States Patent 6687003. Free Patents Online. 2001.
Zone, Ray. Stereoscopic Cinema & the Origins of 3-D Film, 1838-1952. University Press of Kentucky, 2007.