subclip: Extract a Time Range from a Media File

In compost: Video Compositing via 'FFmpeg'

Extract a Time Range from a Media File

Description

Cut [start, start + duration] (or [start, end]) out of an audio or video file via ffmpeg. Re-encodes by default for frame-accurate cuts; set reencode = FALSE for a fast stream copy (cuts land on keyframes).

Usage

subclip(input, output, start = 0, duration = NULL, end = NULL, reencode = TRUE,
        overwrite = TRUE, dry_run = FALSE)

Arguments

input	Path to input media.
output	Path for the extracted output; extension selects the format.
start	Start time in seconds (default 0).
duration	Length in seconds, or NULL to use end or run to the end of the file.
end	End time in seconds (ignored when duration is set).
reencode	If TRUE (default), re-encode for accurate cuts; if FALSE, stream-copy (fast, keyframe-aligned).
overwrite	If TRUE (default), overwrite the output file.
dry_run	If TRUE, return the ffmpeg command without executing.

Value

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

Examples

## Not run: 
subclip("audio.mp3", "chunk.mp3", start = 2.14, duration = 5.0)
subclip("clip.mp4", "head.mp4", start = 0, end = 3, reencode = FALSE)

## End(Not run)

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