The term, Source Aspect Ratio making many peoples confusing, is changed to Storage Aspect Ratio. It is not so intuitive word explaining what it really means, but there seems to be no good alternative other than this.
Aspect ratio refers generally to the ratio between the width and height of an object.
- Source Aspect Ratio (SAR) = Storage Aspect Ratio (SAR) = H.Res / V.Res , the relative number of pixels in each dimension as stored in the file.
- Display Aspect Ratio (DAR) = Picture Aspect Ratio (PAR), the relative dimensions of the video as display on-screen.
- Pixel(Pel) Aspect Ratio (PAR) = Sample Aspect Ratio (SAR), the relative dimensions of individual pixels.
As for the detailed infomation of Pixel Aspect Ratio, visit the following link.
How does it work, "Auto Select Aspect Ratio"?
The adjacent ratio will be selected among the standard aspect ratios defined in KMP (4:3 TV, 16:9 HDTV, 1.85:1 WideScreen, 2.35:1 CinemaScope) after deciding the aspect ratio to use (SAR < DAR) when starting the playback of video. The procedure of selecting AR automatically is the operation supposing that all video materials were encoded in the standard aspect ratio. In most cases, as most video encodings do not violate such a standard ratio, AR correction will be applied on the assumption of bad encoding if a ratio is not matched to one of the defined standards.
The priority of selecting aspect ratio is as follows: SAR < DAR < Auto AR.
These kind of information is accessible by pressing "TAB" with video playback starting.
The option of outputting as SAR (Storage Aspect Ratio) is originally designed for the bad xvid encodings containing the wrong AR information in its bitstream. Do not select the option if you do not encounter the situation described above.