Something is not right with how the video processor handles envelopes...

[Fabian]

Something is not right with how the video processor handles envelopes.

Consider this scenario:
Two envelope points, one at the cursor and another at the next (right) snap point.

For audio, dragging the next envelope point up and down does not affect the audio. You can test this by putting the JS:Tone generator on a track and opening the envelope for the Fine tune parameter. Dragging the next envelope point up or down does not affect the tuning; as it should not.

With video, we are not so fortunate. Try the following: Put an image or video on a track. Put the Brightness/Contrast preset into the video processor on that track. Open the envelope for brightness, and add the two envelope points. Put the cursor on the first and observe the video output as you drag the second one up and down. The brightness at the first envelope point should not change when the second envelope point is dragged, but it does.

And this issue *is* important, since it makes it impossible to delicately adjust video constructs. In my current particular case, the Vignette preset draws unwanted artifacts to the right and to the bottom as the peephole is enveloped, and I cannot add fixes to erase those as the setting of the next envelope point ruins the fix at the previous envelope point.

(I tried to make a gif showing the problem, but neither LiceCap nor GifCam seem able to capture reaper's video window.)

[Fabian]

Is it just me, then...?

Since the enthusiasm for this strangeity seems low, I made the following video to illustrate what goes on. Strangely, none of the screen captures I have (LiceCap, GifCam, Irfanview) can grab what Reaper shows in the video window, so I had to record a movie with my phone. And of course it got all blurry and shaky and out of focus, but it still shows what goes on.



The cursor is at the first envelope point, and when I drag the second envelope point up and down, the cross hair moves. It should not. The cross hair should stay where it is, since the envelope point at the cursor remains fixed at 0.5.

Even if I move an envelope points six snaps away from the cursor, the cross hair moves, though not as much.

[bellerandre]

Just a quick guess: is your envelope point set to something besides "linear"? Perhaps "slow start" or "bezier" of some sort?

[Fabian]

Originally Posted by bellerandre

Just a quick guess: is your envelope point set to something besides "linear"? Perhaps "slow start" or "bezier" of some sort?

It maybe doesn't show clearly in the video, but it is set to linear.

But you are right. Changing the shape of the first envelope point changes how much the line moves in the video window when the second envelope point is moved. For Square shape it does not move at all, for Fast end it moves very little, for Fast start it moves a lot.

For Fast start, moving the second envelope point fully up, changes the position of the line as much as if I manually change xpos from 0.500 to 0.558. But, when the line is moved due to moving the second envelope point, the value of xpos in the video processor preset still shows 0.500. This is in itself an issue, I think.

But really, at the point where the cursor is positioned the envelope point should be fixed. No?

[juliansader]

I can confirm this. My impression is that the knob in the video processor displays some kind of average value of the envelope over the next frame. (Not necessarily the simple mathematical average.) Similarly, when rendering the video itself, each frame seems to be processed with the average value of the envelope over the entire frame -- not with the starting envelope value.

[ashcat_lt]

Not at all related to the actual but, but you mentioned not being able to capture the video. I was trying to take screenshots of the video window the other day and they all came out black. Then I forced the project to use RGBA colorspace and it worked fine. Might be the same issue you were having?

[Philbo King]

Is it possible the point you are moving is in the same video frame as the stationary point? Because that would make this behavior make sense.

[Fabian]

Originally Posted by Philbo King

Is it possible the point you are moving is in the same video frame as the stationary point? Because that would make this behavior make sense.

I think this is aimed at me, the OP, right?

No, even if I set the grid and snap to absolute frames I see the same behavior.

[Philbo King]

Originally Posted by Fabian

I think this is aimed at me, the OP, right?

No, even if I set the grid and snap to absolute frames I see the same behavior.

Ah, well... Just an idea.

[Justin]

The video processor takes the envelope value from the middle of the frame, so you'll find that the middle of the frame in question is well after the envelope point which is likely at the start of the frame.

[Justin]

Adding a project setting to evaluate automation at the start of frame vs end, too.

[Fabian]

Originally Posted by Justin

Adding a project setting to evaluate automation at the start of frame vs end, too.

Thanks, this will make it possible for people like me, who have distinct ideas about what is "correct", able to choose

[Justin]

Oops I meant "middle" rather than "end."

The reason for this is that when determining whether a video item is to be processed, we use the middle of the video frame, because that makes it all more predictable. But for automation I can see the appeal of using the start.