zoom: Zoom Video with Stepped Levels

In compost: Video Compositing via 'FFmpeg'

Zoom Video with Stepped Levels

Description

Apply a stepped zoom effect to a video, changing zoom level at STT line boundaries. Uses 3 levels (no zoom, single, double) with smooth transitions between them. The pattern randomly alternates between zoom-in, hold, and zoom-out phases.

Usage

zoom(input, output, stt, amount = 0.05, levels = 3, transition = 0.3,
     seed = NULL, width = NULL, height = NULL, overwrite = TRUE, dry_run = FALSE)

Arguments

input	Path to input video.
output	Path for output video file.
stt	A whisper_transcription object or data frame with from and to timestamp columns (HH:MM:SS.mmm format).
amount	Zoom per level (default 0.05). Level 1 = 1+amount, level 2 = 1+2*amount.
levels	Number of zoom levels (default 3: none, single, double).
transition	Transition duration in seconds between zoom levels (default 0.3).
seed	Random seed for reproducible zoom patterns.
width	Output width in pixels. If NULL, detected from input.
height	Output height in pixels. If NULL, detected from input.
overwrite	If TRUE (default), overwrite output file.
dry_run	If TRUE, return the FFmpeg command without executing.

Value

Invisibly returns the output path. If dry_run, returns command string.

Examples

## Not run: 
stt <- readRDS("srt_text.RDS")
zoom("talking_head.mp4", "zoomed.mp4", stt = stt)
zoom("head.mp4", "zoomed.mp4", stt = stt, amount = 0.05, seed = 42)

## End(Not run)

compost documentation built on Aug. 4, 2026, 5:11 p.m.