MovieMaker: number of frames or frames-per-second

Core Library Questions

amnon.owed

MovieMaker: number of frames or frames-per-second

in Core Library Questions • 3 years ago

I've checked out the javadocs and the source code.

The only information you can get of a movie is: mov.duration() (float movie duration in seconds)

Which is useful, but I also need either one of these:

total number of frames in a video (int)

frames-per-second (float)

Right now I just look it up beforehand in (regular) Quicktime, but ideally this would be automatic in Processing.

Anybody have or can figure out a method to get this?

Thanks!

Replies(5)

davbol

Re: MovieMaker: number of frames or frames-per-second

3 years ago

Quicktime doesn't think in terms of fps, all it cares about is how much time occurs between frames, so fps isn't a value you can directly retrieve from a movie. There are two general approaches:

To derive the average fps you can take total frames / total seconds. Unfortunately, Quicktime also doesn't care about the total number of frames, so you can't retrieve that directly either. The most reliable way to get the total number of frames is to step through the movie one frame at a time and count them yourself.

The other approach is to assume that every frame in the movie has exactly the same duration, then divide the time scale by the time between successive frames (the number of media samples) to get fps. (then you only need to read one frame instead of all of them) This approach can actually be more accurate for some frame rates (like NTSC where timescale=30000, samples=1001, fps~=29.970029...; sometimes approximated as timescale=2997, samples=100, fps=29.97)

There's some code in here that you could (with some minimal effort on your part) repurpose for either approach, hth.

amnon.owed

Re: MovieMaker: number of frames or frames-per-second

3 years ago

Good stuff. Will have a go at it with this one.

Thank you!

tiffany_fr

Re: MovieMaker: number of frames or frames-per-second

2 years ago

Hi,

I'm a Little bit curious about this code but link to .zip is dead…
Up ?

amnon.owed

Re: MovieMaker: number of frames or frames-per-second

2 years ago

For what it's worth, here is a code snippet I made back then, based on davbol's code and suggestions. However I quickly found that it works on some videos, but not on all. Note that GSVideo (and presumably Processing 2.0's video library) now has functions such as getSourceFrameRate() and length() to get this kind of info. Although they perhaps face the same problem, that it won't work on all videos.

Code Snippet

import processing.video.*;
InfoMovie myInfoMovie;
void setup() {
myInfoMovie = new InfoMovie(this, "input.mov");
myInfoMovie.printInfo();
exit();
}
class InfoMovie extends Movie {
InfoMovie(PApplet parent, String filename) {
super(parent,filename);
}
void printInfo() {
try {
int timeScale = movie.getTimeScale();
println("1. TimeScale: " + timeScale);
int durationSamples = movie.getDuration();
println( "2. Duration (Samples): " + durationSamples);
float durationTime = (float) durationSamples / timeScale;
println( "3. Duration (Time): " + durationTime);
int interestingTimeFlags = quicktime.std.StdQTConstants.nextTimeStep;
int [] mediaTypes = new int[] {quicktime.std.StdQTConstants.videoMediaType};
quicktime.std.movies.TimeInfo timeInfo = movie.getNextInterestingTime(interestingTimeFlags, mediaTypes, 0, 1);
float sampleTime = timeInfo.time;
float fpsSampleTime = timeScale / sampleTime;
println("4. Sample (Time): " + sampleTime + " => FPS: " + fpsSampleTime);
float sampleDuration = timeInfo.duration;
float fpsSampleDuration = timeScale / sampleDuration;
println("5. Sample (Duration): " + sampleDuration + " => FPS: " + fpsSampleDuration);
float sampleAverage = (timeInfo.duration + timeInfo.time)/2;
float fpsSampleAverage = timeScale / sampleAverage;
println("6. Sample (Average): " + sampleAverage+ " => FPS: " + fpsSampleAverage);
} catch (quicktime.QTException ex) { }
}
}

tiffany_fr

Re: MovieMaker: number of frames or frames-per-second

2 years ago

println("thanks");

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