detecting black frames

[StainlessS]

i and j are clips not frames. (EDIT: The frame being worked on is current_frame)
It should work similarly to the previous script, you are just swapping apples for oranges.

Both AverageLuma() and AudioMax() are just functions returning a float used in the conditional part of WriteFileIf().


EDIT: Instead of this:

#This is the line that actually writes the frame number of the FIRST frame that falls below the threshold
WriteFileIf(last, filename,  "(AverageLuma(i)<blankthreshold)&&AverageLuma(j)>blankthreshold", "current_frame+1", append = false)

Something like:

#This is the line that actually writes the frame number of the FIRST frame that falls below the threshold
WriteFileIf(last, filename,  "(AudioMax(i,0) < -100) && AudioMax(j,0) > -100", "current_frame+1", append = false)

[Gavino]

However, I think johnmeyer's example is incorrect.

j=trim(i,1,0) #Previous frame

will make j correspond to the next frame, not the previous one. I believe it should be:

j = SelectEvery(i,-1)

[StainlessS]

Have to admit to a little head scratching when I saw that and the current_frame+1 bit.
(guess I just thought 'must be right' and moved on).
Would I be right in thinking that the output should then be on current_frame rather than current_frame+1. ?

EDIT: on looking again, looks to me like the JM example outputs the frame number of the 1st frame after black frames, perhaps just labeled wrongly.

EDIT: Below looks correct to me (not checked)

j = SelectEvery(i,-1) # Previous frame
#This is the line that actually writes the frame number of the FIRST frame that falls below the threshold
WriteFileIf(last, filename,  "(AverageLuma(i)<blankthreshold)&&AverageLuma(j)>blankthreshold", "current_frame", append = false)

and so the audio thing,

j = SelectEvery(i,-1) # Previous frame
#This is the line that actually writes the frame number of the FIRST frame that falls below the threshold
WriteFileIf(last, filename,  "(AudioMax(i,0) < -100) && AudioMax(j,0) > -100", "current_frame", append = false)

ie if current frame (i) < -100 && previous frame(j) > -100, then output current_frame, the silent one.

[Gavino]

Originally Posted by StainlessS

Have to admit to a little head scratching when I saw that and the current_frame+1 bit.
(guess I just thought 'must be right' and moved on).
Would I be right in thinking that the output should then be on current_frame rather than current_frame+1. ?

Yes, you're right.
(I was assuming he used current_frame+1 to get frames numbered from 1 instead of 0, but it may just be a mistake.)

[johnmeyer]

Have to admit to a little head scratching when I saw that and the current_frame+1 bit.
(guess I just thought 'must be right' and moved on).

Like many of you, I have hundreds of these scripts and script fragments. I use this one all the time, and the comments I made were for my own benefit. I usually work on the script until it gets the job done for whatever is at hand, and then I move on. The comments are there to remind me what I was doing. In general, they are correct, but they reflect the workflow I created. In this case, the frame number file was imported back into Vegas where the first frame is frame number 1 and not frame number 0. That will explain why some of the numbers may be off by one.

As for the trim function, my comment was an error, and I modified my post to add to that comment to explain the error.