Append To Video (Soze)

If you're generating video in chunks - segment by segment out of a WAN or LTX-style pipeline, say - and want to reassemble a longer clip afterward rather than trying to do it mid-graph, this is the node for that: tack one video file onto the end of another and write the result as a single file, audio track intact.

How it works

Per the pack's own README, this "shells out to ffmpeg" using its concat approach, and it must be on PATH - that's stated plainly, not something you need to guess at. Give it a base_video, an append_video, and where to write the result, and it hands the joined file back.

One thing worth calling out for anyone expecting an in-graph VIDEO tensor socket: all three inputs here are plain STRING file paths, not ComfyUI's VIDEO type. This node works on files that already exist on disk, not on video data still living inside the graph - so if your clips are still in-memory outputs from another node, you need to save them to disk first before this node can touch them.

The inputs and outputs that matter

• base_video (required, STRING) - path to the first clip.
• append_video (required, STRING) - path to the clip tacked onto the end.
• save_filename_path (required, STRING) - where the joined result gets written.

Outputs: output_file (the path it wrote) and status.

How to install it

ComfyUI Manager → search "ComfyUI_Soze" → install → restart. Manual:

cd ComfyUI/custom_nodes
git clone https://github.com/SozeInc/ComfyUI_Soze.git
pip install -r ComfyUI_Soze/requirements.txt

Then, separately, install ffmpeg itself and confirm it's on PATH - this is the one node in the pack with a real system-level dependency beyond the pip requirements.txt. If you're running ComfyUI inside a container or a managed cloud environment without shell access to install system packages, check that ffmpeg is actually available in that exact environment before building a workflow around this node - a working ffmpeg in your regular terminal doesn't guarantee it's on the PATH the ComfyUI process itself sees.

Common issues & troubleshooting

"ffmpeg not found" or the node errors immediately. Install ffmpeg via your OS package manager and verify ffmpeg -version runs from the same environment ComfyUI is actually running in, not just your normal shell - a venv, a Docker container, or a remote worker can all have a different PATH than your terminal.

The join fails or the audio comes out wrong. ffmpeg's concat approach is sensitive to the two clips having matching codecs, resolutions, and sample rates. If base_video and append_video came from different sources (or different render settings), normalize both to the same codec and format first rather than assuming concat will paper over the mismatch.

Paths not resolving. Same rule as every other file-path node in this pack: prefer absolute paths over relative ones to rule out working-directory confusion as the cause of a file-not-found error.