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Jacob Gustafson 2016-08-04 22:47:29 -04:00
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This is a manual rotoscoping (frame by frame painting) application. Rotoscoping is the only accurate way to achieve effects such as manual object removal (such as removing wires for flying scenes), cartoons mixed with live action, correction of layer order errors (such as if the wrong fingers get in the way of a virtual object that is held), doing energy effects without 3D mockups of characters (3D mockups are normally needed in order to address situations where part or all of the energy effect goes behind a character or some of the character's fingers), or detailed junk matte tweaking (such as is needed when all or part of an actor appears in front of a studio wall instead of a green screen). Before the digital age, these issues were address by hand, and rotoscoping was considered an essential part of post effects to address a whole domain of issues. The fact that there are so few applications like this is a shame. Ideally this project will be used as a basis to create plugins (see Developer Notes) so that more video editing applications will include rotoscoping, however, RotoCanvas is being tested and compiled as standalone application so that the software can be used immediately.
### Why aren't there more rotoscoping applications?
Possibly, rotoscoping applications are not considered commercially viable since there is unavoidable lag situations that can't be reasonably blamed on developers but inevitably are (see "Caveats" below). Unavoidable lag and format complexity issues could be reasons for the discontinuation of such programs as Ulead ® VideoPaint ®. Another reason could be that rotoscoping is highly dependent on the source frame remaining the same, whereas MPEG (variants of which are used almost everywhere) has inherently inexact frame seeking. These issues may be partially or completely resolved by advanced caching (for the lag issue) and advanced frame seeking algorithms (for the accuracy issue), either of which are not easily achieved but both of which are needed in a professional video application (since video, which has slow seeking would be required, and MPEG, which is normally inaccurate would be required). Even if image sequences are used to resolve the seek lag and seek accuracy issues, seek lag normally remains simply because the edits have to be re-applied or re-loaded (basically, a multi-layer image project needs to be loaded each time seeking to a different frame). Leaving rotoscoping out entirely is often seen as the only way to avoid these issues. This program aims to implement rotoscoping regardless of the possibility of seek lag or requiring image sequences (to avoid seek accuracy issues), since in this project, rotoscoping is considered to be an essential feature.
Possibly, rotoscoping applications are not considered commercially viable since there is unavoidable lag situations that can't be reasonably blamed on developers but inevitably are (see "Caveats" below). Unavoidable lag and format complexity issues could be reasons for the discontinuation of such programs as Ulead ® VideoPaint ®. Another reason could be that rotoscoping is highly dependent on the source frame remaining the same, whereas MPEG (variants of which are used almost everywhere) has inherently inexact frame seeking. These issues may be partially or completely resolved by advanced caching (for the lag issue) and advanced frame seeking algorithms (for the accuracy issue), either of which are not easily achieved but both of which are needed in a professional video application (since video, which has slow seeking would be required, and MPEG, which is normally inaccurate would be required). Even if image sequences are used to resolve the seek lag and seek accuracy issues, seek lag normally remains simply because the edits have to be re-applied or re-loaded (basically, a multi-layer image project needs to be loaded each time seeking to a different frame). Leaving rotoscoping out entirely is often seen as the only way to avoid these issues. This program aims to implement rotoscoping regardless of the possibility of seek lag or requiring image sequences (to avoid seek accuracy issues). In this project, rotoscoping (the core feature) is considered to be an indispensable part of video editing, regardless of the fact that meeting the expectations of normal consumers (primarily expectations for speed and format support) may be impractical to be achieved by volunteer programmers, or may be impossible for technical reasons described here.
## Caveats
* Lag during frame loading cannot be avoided, since each video frame must be loaded at full quality, which at 1080p takes up an unavoidable 8100kb per layer. Maximum performance could be achieved when one or more frames in either direction of the current frame are cached, in their edited form. However, upon editing, the cache will have to be updated and the image, redrawn. To prevent further lag in that situation, the source frame (base layer) could be cached so that editing layers can be applied without reloading the frame from the source video file.