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10th September 2006, 12:44
Hi, quick question, is it possible to delay the chroma of a video by one frame, or advance the luma by one? I can't see any way to do this with inbuilt functions, but am in the dark in terms of external fuctions to do something like this. A quick and dirty solution is fine as I'm just hoping for nice playback rather than a re-encode.
I've been thinking a little and I figure because there are conversions between YUV and RGB you could do it with some ShowRed/Green/Blue and merging, but I've been unable to get very far before my heat starts steaming :).
What I'm thinking so far:
o use the Show* to pull out the three channels to three variables
o merge the channels into three new variables as per these eqtns:
Y = (0.257 * R) + (0.504 * G) + (0.098 * B) + 16
Cr = V = (0.439 * R) - (0.368 * G) - (0.071 * B) + 128
Cb = U = -(0.148 * R) - (0.291 * G) + (0.439 * B) + 128
o trim the first frame from the Y variable and copy into three new variables as per these equations:
B = 1.164(Y - 16) + 2.018(U - 128)
G = 1.164(Y - 16) - 0.813(V - 128) - 0.391(U - 128)
R = 1.164(Y - 16) + 1.596(V - 128)
o merge the final three channels and enjoy!
Which leads to an avs script like so:
Ri = last.ShowRed
Gi = last.ShowGreen
Bi = last.ShowBlue
Y = (0.257 * Ri) + (0.504 * Gi) + (0.098 * Bi) + 16
U = (0.439 * R) - (0.368 * G) - (0.071 * B) + 128
V = -(0.148 * R) - (0.291 * G) + (0.439 * B) + 128
Y = trim(1,0)
Ro = 1.164(Y - 16) + 1.596(V - 128)
Go = 1.164(Y - 16) - 0.813(V - 128) - 0.391(U - 128)
Bo = 1.164(Y - 16) + 2.018(U - 128)
The part I'm stuck on is of course blending the clips together. Can anyone enlighten me and/or correct mistakes in my thinking?
I've been thinking a little and I figure because there are conversions between YUV and RGB you could do it with some ShowRed/Green/Blue and merging, but I've been unable to get very far before my heat starts steaming :).
What I'm thinking so far:
o use the Show* to pull out the three channels to three variables
o merge the channels into three new variables as per these eqtns:
Y = (0.257 * R) + (0.504 * G) + (0.098 * B) + 16
Cr = V = (0.439 * R) - (0.368 * G) - (0.071 * B) + 128
Cb = U = -(0.148 * R) - (0.291 * G) + (0.439 * B) + 128
o trim the first frame from the Y variable and copy into three new variables as per these equations:
B = 1.164(Y - 16) + 2.018(U - 128)
G = 1.164(Y - 16) - 0.813(V - 128) - 0.391(U - 128)
R = 1.164(Y - 16) + 1.596(V - 128)
o merge the final three channels and enjoy!
Which leads to an avs script like so:
Ri = last.ShowRed
Gi = last.ShowGreen
Bi = last.ShowBlue
Y = (0.257 * Ri) + (0.504 * Gi) + (0.098 * Bi) + 16
U = (0.439 * R) - (0.368 * G) - (0.071 * B) + 128
V = -(0.148 * R) - (0.291 * G) + (0.439 * B) + 128
Y = trim(1,0)
Ro = 1.164(Y - 16) + 1.596(V - 128)
Go = 1.164(Y - 16) - 0.813(V - 128) - 0.391(U - 128)
Bo = 1.164(Y - 16) + 2.018(U - 128)
The part I'm stuck on is of course blending the clips together. Can anyone enlighten me and/or correct mistakes in my thinking?