Turn
- std.Turn90(vnode clip)
- std.Turn180(vnode clip)
- std.Turn270(vnode clip)
Turns the frames in a clip by the given number of degrees clockwise, which means that Turn90 turns them to the right, Turn270 to the left and Turn180 upside down.
Turn90 and Turn270 swap the output width and height, and with them the chroma subsampling, so a 4:2:2 clip becomes 4:4:0 and the other way around. Turn180 leaves the dimensions and the format alone.
A quarter turn is a transpose with one of the two axes reversed, so Turn90 and Turn270 do the same amount of work as Transpose. Combining Transpose with FlipVertical or FlipHorizontal produces the same result but needs an extra pass over the frame.
Turning a clip twice in the same direction is the same as Turn180, and turning it once in each direction returns the original clip.
Here is a picture to illustrate what the filters do:
55 5 0 0 1 1 2 3 89 8 1 5 8 13 21 34 Turn90 => 144 13 1 55 89 144 233 377 233 21 2 377 34 3 0 1 1 2 3 377 233 144 89 55 5 8 13 21 34 Turn180 => 34 21 13 8 5 55 89 144 233 377 3 2 1 1 0 3 34 377 0 1 1 2 3 2 21 233 5 8 13 21 34 Turn270 => 1 13 144 55 89 144 233 377 1 8 89 0 5 55