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Data from Excel file to text layer
I’ve got some data that was recorded at 200Hz (it’s a steering wheel angle from a car). It’s in a simple Excel file, with the first column being time in seconds and the second being the angle in degrees, like so:
0.005 -2.124202967
0.01 -2.114402294
0.015 -2.116824389
0.02 -2.133757114
0.025 -2.134076595
0.03 -2.105466366
0.035 -2.081091404
0.04 -2.083098412
0.045 -2.097907305
0.05 -2.098354816
I want to overlay the angle values as text on some video of the steering wheel (recorded at 29.97fps). I’m totally new to After Effects expressions, so I’m not sure how to go about both loading the data from an external file and then figuring out the time difference so only the appropriate line of data is displayed for each frame of video. Any help would be greatly appreciated.
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2 Replies
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After Effects keyframe data are text-based. You can copy and paste them in a text file.
For instance, the keyframe data for a Slider Effect looks like this (10 frames):
Adobe After Effects 8.0 Keyframe DataUnits Per Second 25
Source Width 100
Source Height 100
Source Pixel Aspect Ratio 1
Comp Pixel Aspect Ratio 1Effects Slider Control #1 Slider #2
Frame
0 0
1 0.0399893
2 0.0799147
3 0.119712
4 0.159318
5 0.198669
6 0.237703
7 0.276356
8 0.314567
9 0.352274
10 0.389418End of Keyframe Data
Thus, you can format your Excel to a suitable format, save it as a text file and copy and paste into AE. For two columns of information you could use two sliders, but probably a better option is to use the position keyframe data of a single 2D null.
Then you can extract the values of the keyframes to your text layer. You can simply pick-whip the position x or y for the text layer source text.
Then there is the matter of converting from 200 frames per second to your comp speed… valueAtTime expression will handle that. If I’m thinking straight at this hour, you’ll just have to divide 200 by your frame rate for the Time value.
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I wouldn’t try to tackle this with the text-file-reading expression hack. First, when you read a text file with an expression, the text file has to evaluate as legal JavaScript, so you’d have to encase everything in triple quotes:
“””
0.005 -2.124202967
0.01 -2.114402294
0.015 -2.116824389
0.02 -2.133757114
0.025 -2.134076595
0.03 -2.105466366
0.035 -2.081091404
0.04 -2.083098412
0.045 -2.097907305
0.05 -2.098354816
“””At each frame, your expression would have to read the data file, split it into lines at the carriage returns, ignore blank lines, split each data line at the tab characters, parse the time data to see if it’s greater than the current time, etc.
A script that reads the data file and sets keyframes would be a better choice for this.
Dan
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