Category:Microsoft Windows software
Category:Pixar applications
Category:Windows-only softwareOne of the most common techniques to achieve an effect in a video signal is to utilize the sub-sampling (or downsampling) of one of the color components of a picture, or the temporal compression (or compressing) of the same picture, with the aim of resulting in a video sequence of the same overall bit rate or number of pixels, but of which a significant part of the image, namely a reduced number of pixels, is visible only with difficulty.
This is a problem that is well known in television, which is generally the case in videocards at the present time.
For example, the PAL standard has a horizontal and vertical resolution of 625 and 608 pixels respectively. In this case, it is possible to achieve a 4:3 format, of which the visible part is 312 pixels by 216 pixels. It is also possible to obtain a format of 4:3:2, of which the visible part is 432 pixels by 288 pixels, or a format of 16:9, of which the visible part is 432 pixels by 216 pixels.
These formats are represented in FIG. 1, in which the top part represents the four possible PAL formats (shown in the bottom part of FIG. 1) and the bottom part represents the two possible NTSC formats. In the left-hand part of FIG. 1, the part between the dotted lines represents the vertical and horizontal resolution of the PAL format, while the right-hand part of FIG. 1 represents the horizontal and vertical resolution of the NTSC format.
These different formats have a specific impact on the image in terms of perceived image quality. For example, the formats 4:3:2 and 4:3 are usually perceived as having a more clear image than the formats 16:9 and 16:10.
In the case of video compression, such as MPEG 2, the so-called MPEG-2 bitstream, the filtering is more complex, since the images must be filtered in real time and in addition, the quality of the representation of the images must be maintained, so as not to lose the initial image. The quality of the representation of the images is measured according to the CQ of the filtered image, this quality being computed on the basis of the DCT coefficients of the image.
The coefficients computed using the DCT technique represent the spatial information of the image, while the quantization of these coefficients is in effect a spatial compression that ac619d1d87
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