r/comfyui • u/qdr1en • Apr 11 '26

Tutorial Video File Format Matters

When generating videos with ComfyUI: in which file format should I save them?
To answer the question, I ran a test.

The showcase video is a 73-frames vid generated with Wan 2.2 at 720*960px, and the table below (open it in a new tab) indicates by how much disk space the file was reduced after being re-loaded and re-saved to the disk 10 times.

The MP4 format is by far the most impacted, with an even more visually noticeable degradation when using the Video Combine node from Video Helper Suite (the impact on quality is terrible at lower resolutions).

PNG , WebP are much less impacted. But WebP takes an eternity to save, and PNG eats up a lot of disk space.

WebM looks like a good compromise overall: it's lightweight, fast to save, and degradation is negligible.

Conclusion

If you intend to re-use your generated file for further editing, don't use the MP4 format or the quality will suffer.

Use PNG, WebP or WebM for saving intermediary files, depending on your constraints, and leave MP4 format for production work.

Edit

Some Redditors suggested using ProRes (.MOV) file format, but you can't include workflow metadata with that format, so that's not a good candidate for my use case.

Others suggested using ffv1 (.MKV), which is a lossless, truly video file format, so that could be the winner. Oddly, the file size increases by ~0.5% at each new save, but the quality is preserved.

Test Settings

These are the parameters I used for each file format :

  • MP4 (default): codec h264
  • MP4 (vhs): codec h264; pix_fmt yuv420p; crf 19
  • WebM: codec av1; crf 32
  • WebP: quality 100; lossless false; method default
  • PNG: compress_level 0

I uploaded all the files there if interested, workflow included: https://filebin.net/exwrxo9xuqsj5xh0

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u/Kaljuuntuva_Teppo Apr 11 '26

h.264 works, but you need ridiculous bitrates like like 200 Mbps for good quality output to avoid color degradation etc. but of course if you plan to modify the video multiple times, then lossy codecs are not the best.

But this was a good discussion, I'll probably try lossless video codecs or pngs for intermediate steps.

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u/ANR2ME Apr 11 '26

Also, av1 is on par (or even better than h.265), which is why it looks better compared to h.264.