ComfyUI-FastImageSequence

ComfyUI-FastImageSequence

A fast PNG image-sequence saver for ComfyUI.

The built-in Save Image (Advanced) node encodes each frame of a batch one at a time. For long sequences (video / frame dumps) that's slow — almost all the time goes into single-threaded zlib PNG compression, not metadata.

This node encodes the frames of a batch in parallel. PyAV releases the GIL during compression, so encoding scales with your CPU cores. The output bytes are identical to the built-in node — same pixels, same compression, same file size — it's just much faster.

It also embeds the prompt/workflow metadata in only the first frame by default, so the workflow is still recoverable from the sequence without bloating every single frame.

Node

Save Image Sequence (Fast 16-bit) (category: image)

| Input | Default | Notes | |---|---|---| | images | — | The image batch to save. | | filename_prefix | ComfyUI | Supports the usual tokens (%date:yyyy-MM-dd%, etc.). | | bit_depth | 16-bit | 8-bit or 16-bit PNG. | | metadata (advanced) | first_frame | first_frame / all / none. | | threads (advanced) | 0 (auto) | Encoder threads. 0 = min(8, CPU count). |

Drop it in wherever you'd use Save Image (Advanced). It handles the whole batch itself, including the first-frame metadata, so wire the entire sequence into this one node (don't split it across two save nodes — that would collide on the sequential file numbering).

Performance

Measured on a 16-core CPU, 457 frames at 1920×1088, 16-bit RGB (worst-case noisy content; real frames are faster):

| threads | ms/frame | 457 frames | |---|---:|---:| | 1 (built-in, serial) | 372 | ~170 s | | 4 | 101 | ~46 s | | 8 (auto default) | 60 | ~27 s | | 16 | 43 | ~20 s | | 24 | 44 | ~20 s (no gain) |

Scaling flattens at your core count — there's no benefit to setting threads higher than the number of CPU cores. 0 (auto = 8) already captures most of the win; set it to your core count for the last few seconds.

For reference, metadata injection costs ~0.9 ms/frame (~0.2% of the total), so the metadata option is about file size / cleanliness, not speed.

Installation

Clone into your ComfyUI custom_nodes directory and restart:

cd ComfyUI/custom_nodes
git clone https://github.com/dreevelle/ComfyUI-FastImageSequence.git

av, numpy and torch ship with ComfyUI, so there are no extra dependencies to install.

Notes

• Output is byte-identical to Save Image (Advanced) for the same input — this node only changes how fast the frames are written, not the result.
• True 16-bit PNGs (IHDR bit depth 16). Note that Pillow downsamples 16-bit color PNGs to 8-bit when reading them, so a PIL.Image.open(...).mode check will report RGB even though the file on disk is genuinely 16-bit.
• Self-contained: it copies the small PNG encode/metadata helpers rather than importing from ComfyUI internals, so a core update won't break it.

License

MIT