# Get Video frame number

**URL:** <https://psychtoolbox.discourse.group/t/get-video-frame-number/5179>\
**Category:** Programming Help\
**Created:** [November 20, 2023, 10:59pm UTC](https://psychtoolbox.discourse.group/t/get-video-frame-number/5179 "2023-11-20T22:59:48Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![dgraetz](https://avatars.discourse-cdn.com/v4/letter/d/ec9cab/32.png) [@dgraetz](https://psychtoolbox.discourse.group/u/dgraetz)\
**Post date:** [November 20, 2023, 10:59pm UTC](https://psychtoolbox.discourse.group/t/get-video-frame-number/5179/1 "2023-11-20T22:59:48Z")

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Hello,

I am trying to present videos and would like to know the frame number that I am drawing so that I can later correlate frame content with behavior. How can I get the frame number from Screen(‘GetMovieImage’)?

Thanks!

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**Author:** ![mariokleiner](https://avatars.discourse-cdn.com/v4/letter/m/13edae/32.png) [@mariokleiner](https://psychtoolbox.discourse.group/u/mariokleiner)\
**Post date:** [November 21, 2023, 7:42am UTC](https://psychtoolbox.discourse.group/t/get-video-frame-number/5179/2 "2023-11-21T07:42:08Z")

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You can’t get a frame number, but you can get a timeIndex / presentation timestamp in movie time as 2nd return argument. Ie. essentially the same purpose, but in seconds since start of movie instead of frames since start of movie.

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**Author:** ![dgraetz](https://avatars.discourse-cdn.com/v4/letter/d/ec9cab/32.png) [@dgraetz](https://psychtoolbox.discourse.group/u/dgraetz)\
**Post date:** [November 21, 2023, 7:55am UTC](https://psychtoolbox.discourse.group/t/get-video-frame-number/5179/3 "2023-11-21T07:55:00Z")

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Thank you. I guess then my question is: Can the timeindex take any other values than multiples of (1/fps)?

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**Author:** ![dcnieho](https://avatars.discourse-cdn.com/v4/letter/d/779978/32.png) [@dcnieho](https://psychtoolbox.discourse.group/u/dcnieho)\
**Post date:** [November 21, 2023, 8:24am UTC](https://psychtoolbox.discourse.group/t/get-video-frame-number/5179/4 "2023-11-21T08:24:55Z")

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The general answer to that would be that it depends on your video file, and whether its constant framerate or variable frame rate. Constant framerate should be 1/sample rate yes

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**Author:** ![dgraetz](https://avatars.discourse-cdn.com/v4/letter/d/ec9cab/32.png) [@dgraetz](https://psychtoolbox.discourse.group/u/dgraetz)\
**Post date:** [November 21, 2023, 8:38am UTC](https://psychtoolbox.discourse.group/t/get-video-frame-number/5179/5 "2023-11-21T08:38:51Z")

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Thanks. So what would be the solution in case I have a variable framework but I still want to know which frame was on the screen?

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**Author:** ![mariokleiner](https://avatars.discourse-cdn.com/v4/letter/m/13edae/32.png) [@mariokleiner](https://psychtoolbox.discourse.group/u/mariokleiner)\
**Post date:** [November 21, 2023, 8:38pm UTC](https://psychtoolbox.discourse.group/t/get-video-frame-number/5179/6 "2023-11-21T20:38:58Z")

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The returned `timeindex` timestamps, defining the “position” of the frame within the movie, starting at 0 seconds at the beginning of the movie, should be unique for each frame, so they are a unique identifier for each frame. `DetectionRTInVideoDemo.m` demo may contain some useful bits wrt. this topic. Hasn’t been in ages though.

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<div class="post-metadata">

**Author:** ![dgraetz](https://avatars.discourse-cdn.com/v4/letter/d/ec9cab/32.png) [@dgraetz](https://psychtoolbox.discourse.group/u/dgraetz)\
**Post date:** [December 1, 2023, 1:37am UTC](https://psychtoolbox.discourse.group/t/get-video-frame-number/5179/7 "2023-12-01T01:37:10Z")

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The time method works for me, thank you!