Video: Image alteration filters

1.Foreword

    This set of filters deeply alter the source video : Resize, rotate, flip and crop.

2.Image Alteration Filters

Crop 

    This filter crops the video (for example to remove black border). The cropped value left/right/top/bottom must be even.

    You can preview the part that will be cropped using the Apply button.

    On a clean video (dvd), you can try the Autocrop button. It won't work very well on a noisy source (capture)

Resize / Mplayer resize 

    The resize filter is a port to YV12 of avisynth resize filter. Mplayer resize is a port of Michael Niedermayer resize filter, which is used in mplayer

    Avisynth resize is slightly more accurate, but mplayer resize is 3x faster without any perceptible difference.

    The filter dialog config box is the same for both filters :

    You can direcly enter the new width/height and the resize algorithm or use the slider and the menu. Three resize methods are proposed :

    • Bilinear : Smooth a bit but easier to encode
    • Bicubic : Keep sharpness, harder to encode (for example leads more easily to macroblocking in SVCD)
    • Lanczos : Hard to describe, very sharp.
    Source and destination are important. If you do DVD2Divx for example, source is 4/3 or 16/9 and destination is 1:1. The other way around for Divx2SVCD.

    It is important as 4/3 has non square pixel (different for PAL and NTSC) and if you do 1:1 -> 1:1 you will end up with distorted image.

Blacken Borders 

    This filter replaces border(s) of video by pure black. It may be useful to replace dirty border by clean one (VHS capture for example)

Add Black Borders 

    This filter *ADDS* black border (the previous one replaces). It is used internally by *VCD res to resize a video to a give size without altering the aspect ratio.

Flip vertical 

    This filter vertically flips the video. Usefull when using broken video capture card for example.

Rotate 

    This filter was written by Tracy (see file for more informations)

    It rotates the video by 90/180/270 degree. The author uses it with video from its camera in landscape mode.

Resample fps 

    Alter the fps by duplicating/blending images so that the duration is unchanged. A solution to do 12 fps to 25 fps for example

Whirl 

    Useless but funny to watch