[libtcas] A Brief Introduction to TCAS

milkyjing

TCAS (Ternary Color Animation Solution) is a solution to Mandipa (Massive Amount Of Nonlinear Dynamic Isolated Pixels Animation (海量非线性动态离散像素点动画解决方案)

The name just implies the usage of TCAS

1. Massive Amount, the amount of pixels is usually very large, millions of pixels
2. Nonlinear, the living duration of the pixels are nonlinear
3. Dynamic, pixels have their living duration
4. Isolated, pixels are isolated, they may not have any relation with each other
5. Pixels, the basic unit, such pixels are called DIPs in TCAS
6. Animation, our goal is to use such file to generate video frames


Though theoritically speaking, DIPs can be completely independent with each other, it is not practical. For practical use, the degree of non-linearity should be limited, that is to say, several DIPs share some common living duration, and locality issue should also be considered.

TCAS is not good at filling a whole video frame (a width * height image), but can be used to draw relatively small and discrete objects such as lines, texts, etc. So, one of the major practical use of TCAS is to make subtitle/karaoke effects!

While developing libtcas, performance is the biggest issue keeping in my mind, so rendering a TCAS file is always very fast, but TCAS files are usually a way too big. After bringing the zlib to libtcas, the size becomes half, which is a big progress.

milkyjing

    The original motivation for me to develop a new file format is that ASS has some defects when used to make FXs at the pixel level, such as pixelated texts, text textures, etc. So TCAS was born as a supplement to ASS. Nevertheless, during the development I found that what ASS is good at and not and why, that is, as an implementation of vector graphics drawing system, ASS can draw objects including texts efficiently, but this is not the case when it is required to draw a large amount of isolated points (pixels). Thus I know what actually I need to develop, an implementation of bitmap drawing system. After two years' non-continuous and slow development TCAS becomes more sophisticated and gradually gains the ability to be put in practical use.