How to Configure FFmpeg Loop Filter Count

Configuring the loop count in the FFmpeg loop filter allows you to repeat a specific segment of a video or audio stream a set number of times. This article provides a quick and clear guide on how to define the loop count, specify the size of the loop, and set the starting frame using FFmpeg command-line arguments.

The Loop Filter Syntax

To configure the loop count, you must use the loop video filter (-vf "loop=...") or the aloop audio filter (-af "aloop=..."). The filter relies on three primary parameters:

• loop: The number of loops. Set this to -1 for an infinite loop, 0 for no loop, or any positive integer (e.g., 5) to repeat the segment that exact number of times.
• size: The number of frames (for video) or samples (for audio) to be kept in the loop buffer.
• start: The 0-based index of the first frame or sample where the loop begins.

Command Examples

1. Loop a Video Segment 5 Times

To loop a sequence of 100 frames, starting from the very first frame (index 0), a total of 5 times:

ffmpeg -i input.mp4 -vf "loop=loop=5:size=100:start=0" output.mp4

2. Infinite Video Looping

To loop a 150-frame segment starting at frame 50 infinitely, set the loop parameter to -1.

ffmpeg -i input.mp4 -vf "loop=loop=-1:size=150:start=50" output.mp4

Note: Infinite looping is typically used when outputting to formats that support infinite playback, like animated GIFs, or when streaming.

3. Loop an Audio Segment

For audio streams, use the aloop filter. Because audio uses samples instead of frames, the size and start values must be calculated in audio samples. For example, to loop 1 second of a 44.1kHz audio file 3 times from the beginning:

ffmpeg -i input.wav -af "aloop=loop=3:size=44100:start=0" output.wav