Create a boomerang / ping-pong effect from an MP4

Classic 2-second boomerang

Trim, reverse, merge. The whole thing is local and watermark-free.

1. Trim source.mp4 to 0.0–2.0 s  -> jump.mp4         (lossless-trimmer)
2. Reverse jump.mp4              -> jump_reversed.mp4 (this tool)
3. Merge in order:
     jump.mp4
     jump_reversed.mp4           -> boomerang.mp4 (4 s loop)

Loops seamlessly: forward 2 s, backward 2 s, repeat.

Why the reverser alone is not a boomerang

A common mistake: expecting the reverser to output a loop. It outputs ONLY the reversed clip. The bounce needs both halves joined.

Reverser output (one half only):
  jump_reversed.mp4  -> plays 2 s backward, then stops

Boomerang (both halves, via merger):
  jump.mp4 + jump_reversed.mp4 -> 4 s forward-then-back loop

Boomerang to a Telegram/Signal sticker

After building the loop, convert to animated WebP for a small, crisp sticker.

1. boomerang.mp4 (4 s)  ->  video-to-webp  ->  boomerang.webp
   (animated WebP is smaller than GIF at the same quality)
2. Upload as a sticker. Keep loops <=3 s so the file stays tiny.

Silent boomerang

If you do not want the reversed audio in the loop, strip sound from each half before merging — the reverser always reverses audio, it cannot mute.

1. Reverse jump.mp4 here       -> jump_reversed.mp4 (audio reversed)
2. Remove audio from both jump.mp4 and jump_reversed.mp4
   (audio-track-extractor remove-audio path)
3. Merge the two silent halves  -> silent boomerang.mp4

Longer source: trim first, then reverse

A 90-second source would trigger the chunked reverse path. For a boomerang you want a short loop anyway, so trim before reversing.

Source: clip.mp4 (90 s)  -- reversing this whole thing runs chunked
Better: trim to the 1.5 s moment  -> moment.mp4
        reverse moment.mp4         -> moment_reversed.mp4 (single pass)
        merge moment + moment_reversed -> 3 s boomerang

The reverser produces only the reversed clip — it does not loop forward-then-back on its own. A boomerang is two halves joined, so you always pair the reverser with the merger. This keeps each tool single-purpose and the merge fast.

The merger can stream-copy only when inputs share the same codec, resolution, and frame rate. The reverser always outputs H.264 MP4 at CRF 20, so if your original is also H.264 MP4 the concat is a fast copy. If the original is a different codec or resolution, the merger transcodes — slower, but still produces a correct boomerang.

The reversed half has reversed audio (areverse). Played as a loop, the soundtrack runs forward then backward. For music or speech this usually sounds odd, so most boomerangs are silent — strip audio from both halves before merging if you want no sound.

The bounce is seamless when the reversed half ends on the original's first frame. A hard seam usually means the trim points sit mid-motion. Re-trim so the start and end frames are visually close, then reverse and merge again.

Reversing a long source triggers the chunked pipeline and produces a long reversed half — not what you want for a boomerang. Trim to a 1–3 second moment with the lossless-trimmer first; the short clip then reverses in the fast single pass.

The reverser always writes MP4 because reversal is a full re-encode. The boomerang loop is therefore MP4. Re-package after merging if you specifically need a MOV container.

A 4-second 1080p MP4 can be a few MB; as a sticker it should be far smaller. Convert the loop with video-to-webp and keep the loop under 3 seconds — animated WebP beats GIF on size at equal quality.

Each step honours the video tier caps: 1 GB Free, 10 GB Pro, 100 GB Pro-media/Developer. Since boomerang sources are short, this is rarely hit — but a huge raw source is rejected before reversing. Trim or compress first.