How HD upconverter works?

Answer 1

The principle of an up converter is very simple: take a standard definition signal, examine each pixel of it and then calculate what each pixel on an HD signal would look like if the signal was HD. Making that simple process actually happen is rather more complicated. Very powerful signal processors are needed to study a block of pixels of the incoming signal. Typically, the block will be four or five pixels wide and high. The centre of the pixel block is the position of the new pixel to be created in the HD signal. The pixels of the original signal that are closest to the position of the new pixel have the most impact on the new pixel. The further away the original pixels are from the new pixel position, the less they affect the brightness and color of the new pixel. Once the original pixels are assessed and the new pixel has been defined and stored away, the process is then repeated for the next HD pixel. There is far more to the process than is described but that is the principle of up conversion. The additional processes are used to generate images without hard, ragged or jerky edges and mis-shaped detail in the new image. The techniques have been developed over several decades and were first used to convert North American signals to European and vice versa. Some thirty years on and the conversion quality has improved dramatically. Despite the advances, up conversion is not an exact science and is not a perfect process. It is important to remember that HD signals contain about 5 times as much information as SD signals. Putting an SD signal through an up converter does NOT increase the amount of detail in the image. In fact, an up converter will actually degrade the detail very slightly. Fortunately, when we watch an up converted signal, it is quite common that we get an impression of a better image than the SD original.