Play a video backwards, or forward and then backward, at a speed that reaches the file. Reverse the sound, keep it running forwards, or drop it. The memory a reversal needs is worked out from your own clip.
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Turn or mirror a video in the pixels rather than in a container flag, so it is upright everywhere. Says where each edge of the source will end up, composes the turn and the mirror in a stated order, and always writes MP4.
Cut a clip out of a video, choosing whether the cut lands on the exact frame (re-encodes to MP4) or leaves the streams untouched (instant and lossless, but only at a keyframe). The result says which ran and reads the real length back off the file.
Convert a video between MP4, WebM, OGG, MOV, AVI and MKV, each naming the codecs it really writes and each producing a file that actually plays. One quality dial normalised into four different encoder scales.
You want a pour shot reversed and run at double speed for a social clip.
Input
pour.mp4, 2.000 s at 30 fps · backwards · 4x · keep the sound forwards
Output
A 0.500 s MP4 whose first frame is the source’s last, with the soundtrack still running the right way round
The frames really do come out 59, 58, 57 and so on, and the speed really does reach the encoder: the same clip at 1x and at 4x used to produce the same 43,285 bytes, because the speed was never passed to the helper. Reversed speech is unintelligible, so keeping the soundtrack forwards under a backwards picture is its own setting rather than something to work around.
Play any video backward, or forward and then backward, at a speed you choose. Every frame is reordered by the encoder rather than by the player, so the result is an ordinary MP4 that plays anywhere.
Create visually striking reverse-motion clips for music videos, social media posts, or artistic projects.
Watch sports plays, dance choreography, or mechanical movements in reverse to study technique.
Turn a short action into a loop that runs out and back, which needs no crossfade because the turning point is one frame.
The reverse filter cannot emit its first output frame until it has read its last input frame, so it holds the whole decoded clip in memory at once. That makes the real limit a number of PIXELS rather than a number of seconds: sixty seconds of 640 by 480 and four seconds of 4K come to the same problem. Measured in this WebAssembly build, reversing a 640 by 480 30 fps clip took 1.08 seconds for 8 seconds of video, 2.04 for 16, 4.30 for 32 and 8.41 for 64, which is 1,920 frames and about 885 MB of buffered picture. It scales linearly and 885 MB is comfortable. The page works the figure out from your own file and warns before it starts rather than failing part way.
That measurement replaced a much more cautious rule. Clips over ten seconds used to be split into five second chunks, each reversed separately and then concatenated in reverse order, which is slower, re-encodes at every boundary and was nowhere near the real limit. That path is gone.
The controls all reach the encoder now, which is the change most worth knowing about. The Output Speed setting and the creative presets used to drive only the on-screen preview: exporting at 1x and at 4x produced the same 43,285 bytes, because the speed was never passed to the helper. Speed is now applied with setpts on the picture, and on the soundtrack either as a time stretch that holds the pitch steady or as a sample rate change that lets the pitch follow, whichever you choose. When the speed is not 1 there is a second choice with real consequences: keep the source frame rate, which drops or repeats frames, or keep every frame and change the rate, which is what makes a genuine slow motion out of a high frame rate source.
Boomerang is a real mode rather than a preset name. It splits the stream, reverses one copy and joins them, so the output is twice as long and the joint is one frame meeting itself, which is the only join that cannot jump. The soundtrack has three settings of its own: reverse it, which is a deliberate effect for music and unintelligible for speech; keep it running forwards under a backwards picture, which is what a music video usually wants; or drop it. The output is always MP4 with H.264, because the whole clip is being re-encoded anyway and there is nothing to be gained by writing it into a container that cannot hold it.
MP4 with H.264 video and, when you keep the sound, AAC. The whole clip is re-encoded to reorder the frames, so there is nothing to be gained by writing it into the container it arrived in.
Yes. It applies setpts to the picture and either a time stretch or a sample rate change to the sound, and the result panel prints the real length of the finished file against the length that was asked for.
There is a memory limit rather than a length limit, because the filter holds every decoded frame at once. The page works out the figure from your frame size and frame count and warns above about 1 GB; 885 MB, which is 64 seconds of 640 by 480, was measured to finish in 8.4 seconds in this build.
Yes, and it is often what you want. Reversed speech is unintelligible, so there is a setting that reverses only the picture and leaves the soundtrack running normally.
Video is decoded and re-encoded on your own device. Large files never leave your machine.