How to Find the Exact Timestamp of an Extracted Frame

You have extracted a batch of frames, and frame_0042.jpg is the one that matters. Now you need to know where it came from: to quote the time in a report, to watch that part again with sound, or to pull out more frames around it.

The filenames do not include timestamps, which keeps them short and makes them sort correctly everywhere. The timestamp is not lost, though. Frames are taken at fixed, predictable moments, so you can work out exactly where any of them came from.

The formula

You need three numbers: the video’s duration in seconds (D), how many frames you asked for (N), and the frame’s number from its filename (n, starting at 1).

The frame was taken at (D ÷ N) × (n − 0.5) seconds.

D ÷ N is the gap between frames. The 0.5 is there because each frame comes from the middle of its slice of the video rather than the start, which keeps the first frame away from the black or title frame at 0:00.

A worked example: a 10-minute video (600 seconds) with 120 frames has a gap of 5 seconds. Frame 42 was taken at 5 × 41.5 = 207.5 seconds, which is 3:27.5.

A quick lookup table

For two common intervals, this is where some frame numbers land:

Doing it in a spreadsheet

If you are logging a lot of frames, a spreadsheet saves the arithmetic. Put the duration in seconds in B1, the frame count in B2, and frame numbers down column A starting at A4. The first formula gives each timestamp in seconds; the second shows it as minutes and seconds.

=($B$1/$B$2)*(A4-0.5)

=TEXT(($B$1/$B$2)*(A4-0.5)/86400, "[m]:ss.0")

Where to find the duration and the count

FrameRipper shows both before you extract. The line above the controls reads something like "1920×1080 · 600.0s · 120 frames every 5.0s". If you expect to look up timestamps later, note it down or take a screenshot of it.

If you did not, the duration is in your video player or the file’s properties, and the count is usually the number of files in the ZIP.

Jumping back to that moment

• VLC: Playback, Jump to Specific Time (Ctrl+T on Windows and Linux), then type the time.
• YouTube, for a video you uploaded: add &t=207s to the end of a youtube.com/watch link, or ?t=207 to a youtu.be link, to start at 207 seconds.
• Video editors: most let you type a time straight into the timecode display to move the playhead there.
• FFmpeg: the command below saves that exact moment as a lossless image.

ffmpeg -ss 207.5 -i input.mp4 -frames:v 1 frame.png

Extracting more frames around a moment

Once you know roughly where something happens, the best way to get more detail is to cut out a short clip around it and extract from that. Asking for thousands of frames across the whole video gets there too, but most of them will come from parts you do not need.

On iPhone, drag the trim handles in the Photos editor and save it as a new clip. On a Mac, QuickTime Player’s Edit, Trim does the same. With FFmpeg, this copies 15 seconds starting at 3:20 without re-encoding:

ffmpeg -ss 200 -i input.mp4 -t 15 -c copy clip.mp4

How precise this is

The formula gives the moment the tool asked for. The picture you get is the frame on screen at that moment, so the real precision is set by the frame rate: within about 33 milliseconds for 30 fps video. Frames per second explained covers why that is the limit.

Once you have cut a short clip, extract densely from it. The single-frame page has a table of frame counts for half-second and one-second spacing.