diff --git a/testdata/ffmpeg.d/cmd/prune/main.go b/testdata/ffmpeg.d/cmd/prune/main.go
index 7c6b6cd..0262415 100644
--- a/testdata/ffmpeg.d/cmd/prune/main.go
+++ b/testdata/ffmpeg.d/cmd/prune/main.go
@@ -67,17 +67,29 @@ func Run(ctx context.Context, args []string) error {
 				if seriesHasMovement, err := seriesHasMovement(ctx, seriesFiles, movementInterval); err != nil {
 					return err
 				} else if seriesHasMovement {
-					log.Println("found movement in", series)
+					firstFileInfo, err := os.Stat(seriesFiles[0])
+					if err != nil {
+						return err
+					}
+					lastFileInfo, err := os.Stat(seriesFiles[len(seriesFiles)-1])
+					if err != nil {
+						return err
+					}
+					durationSeconds := lastFileInfo.ModTime().Sub(firstFileInfo.ModTime()).Seconds()
+					frames := len(seriesFiles)
+					fps := int(float64(frames) / durationSeconds)
+
+					log.Println("found movement in", series, "over", durationSeconds, "seconds at", fps, "fps")
+
 					outd := strings.ReplaceAll(cam, "record", "movement")
 					os.MkdirAll(outd, os.ModePerm)
 					cmd := exec.CommandContext(ctx,
 						"ffmpeg",
 						"-y",
-						"-framerate", "3",
+						"-framerate", strconv.Itoa(fps),
 						"-pattern_type", "glob",
 						"-i", path.Join(cam, series)+".*.jpg",
-						//"-filter_complex", "fps=3,scale=-1:-1:flags=lanczos[x];[x]split[x1][x2];[x1]palettegen[p];[x2][p]paletteuse",
-						"-r", "3",
+						"-r", strconv.Itoa(fps),
 						path.Join(outd, series+".mp4"),
 					)
 					if out, err := cmd.CombinedOutput(); err != nil {