[SSN] Prep Reverse Batch

[SSN] Prep Reverse Batch takes an image batch and reverses the order of the frames. Frame 0 becomes the last frame, the last frame becomes first, and everything between flips. One IMAGE input, one IMAGE output, nothing else. It's the smallest node in this pack and it's also exactly as useful as it sounds.

The classic use is the reverse-playback loop. Take a generated animation, reverse a copy of it, and glue the two together with SsnPrepAppendBatch - the canonical "play it forwards, then play it backwards" ping-pong loop that makes a short clip feel like a seamless loop instead of a clip that restarts. That single trick is worth more than half the video polish tricks I see people ask about, and this node is the entire "backwards" half of it. It's also the natural answer when a model generated your frames in the wrong temporal order (some pipelines do, embarrassingly often), or when you want to preview a sequence from the end.

Mechanically it's a torch.flip on dimension zero - the batch axis - which is the correct, cheap way to reverse a sequence, and it doesn't touch the pixel data inside any frame. Each individual image is unmodified; only their order changes. It has no opinions about channels or resolution, which makes it the rare prep node that accepts RGB or RGBA alike.

The honest take: this is a tool you'll reach for once in a while and be very glad exists when you do, but it's not something to plan a workflow around. The ping-pong loop is the one pattern that elevates it from "niche" to "actually keep this installed." If your workflow never loops or reorders frames, you'll never touch it - and that's fine, it costs you nothing sitting in the menu.

Install

Part of smn_support_nodes by SummonTheCat. ComfyUI Manager → search smn_support_nodes → Install → restart, or:

cd ComfyUI/custom_nodes
git clone https://github.com/SummonTheCat/smn_support_nodes

Restart required. Dependencies (opencv-python, imageio-ffmpeg) auto-install; no models to download.

Troubleshooting

There is almost nothing to get wrong - the node accepts any image batch and reverses it. The one conceptual trap is confusing "reverse the batch order" with "flip each image horizontally"; this node does the former (temporal reversal) and does not mirror the pixels. If you wanted each frame mirrored left-to-right, you need a horizontal-flip node, which this pack doesn't provide.