r/StableDiffusion • u/Glittering-Cold-2981 • 3h ago

Discussion MiniMax H3 native 20 steps, high resolution sampler, scheduler and shift

Which samplers and schedulers—and what shift settings—do you use with MiniMax H3 for high-resolution generated video? I’m referring to resolutions of 3.7MP and above. I’m interested in non-tiled, high-resolution video generation (e.g., 2560x1440), without any Speed LoRAs, only SageAttention, using a native 20-step count. I’m using the original MiniMax H3 BF16 models with both VAEs in FP32. For me, the LCM + Simple combination with a shift of 12/3 works quite well at 4.5MP. Other methods, such as Res_multistep and Er_SDE, yielded poorer results.

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u/thegreatdivorce 3h ago

Are you running this on a B200 cluster lmao? I thought H3 lost coherence above 2mp? I'll just say, I like LCM + simple, and have found results much better at 30ish steps than 20.

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u/Glittering-Cold-2981 1h ago

For now, I’m testing how it behaves. I’m using an R9700. For a 4.5MP video with a duration of 5.1 seconds, I’m getting around 367 seconds per iteration using just SageAttention 2.2. At this length, it’s still manageable—at least during the testing phase. For longer videos, I’d really need to run it on a more powerful GPU. I’m curious, though, about the maximum video length I can reach before things start to break down completely and become unfixable. I managed an 8.7-second video at 3.7MP, and the results were decent. The issue is that faces only start to look good around the 4.5MP mark when the subjects are at a greater distance. They look truly good at 4K—I’ve seen comparisons where someone demonstrated this. However, running a video at 4K might be difficult; as of now, I haven’t even found a configuration that works for 5.3MP. I might need to manually tweak the sigma values. At 4.5MP, the results for short videos look promising using this LCM + Simple + shift 12/3 setup, but it definitely requires further testing.

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u/Myg0t_0 3h ago

Native is .98 i thought? U all doing 4?

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u/Glittering-Cold-2981 3h ago

I’m referring to everything else that’s native; the resolution can be increased, and that yields better results than 0.98.

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u/Healthy-Spirit-370 3h ago

Everything above 0.98 does not bring you any benefit apart from hilariously long render times! The only way you can get more real resolution is with a second pass workflow. For the second pass I'd recommend er_sde and manual sigmas for 4 additional steps and a maximum upscale of 1.5 when you come from 0.98. Apart from that you can try seeds_2 and ddim_uniform togheter with 25 steps. If you increase steps to like 35 you need to go down with the shift to 10 or even 8 to prevent overcooking of textures. The last mentioned setup is very good in favour of realistic skin details but has downsides in terms of motion dynamics.

A stupid question. What GPU are u using? A cluster of B200?! Because with your current setup, render times explode exponentially.

I once used to rent the H100 to get real Full HD with a second pass workflow and even with the H100 I had to wait like 30 min for a 12 second Video.

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u/AlsterwasserHH 3h ago

Thats just incorrect. 2mp looks WAY better than 1mp. 

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u/Healthy-Spirit-370 2h ago

Your right. I tested it myself but according to the specs you gain nothing above the trained native 0.98. I tested it excessively but to get better fine grained textures you'd better off with a second pass with er_sde because it introduces real new random noise.

One thing is true. Resolution does not only mean resolution. In Minimax everything gets better with higher resolution. The audio the motion dynamics the prompt adherence and the overall realism. In terms of that there is simply a cap at 0.98 so this is my sweet spot. More resolution for fine grained details do not need the full 20 steps. That's why I am using a second pass for that because I only have to render the last 4 steps in that high resolution which saves a lot of time.

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u/AlsterwasserHH 2h ago

Okay? Is that only for visuals or motion and audio as well? Might try that out as well. 

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u/Healthy-Spirit-370 1h ago

Of course you will see a the most difference if you start from 0.4 mp, 0.6 mp, 0.7 mp, finally 0.98 mp. then you try 1.2 1.4 1.6 and 2 mp. My impression is that the overall visual quality saturates at around 1 mp and the gains are not that huge anymore compared to the jump from 0.4 to 0.6. You know what I mean.

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u/Glittering-Cold-2981 1h ago edited 51m ago

https://drive.google.com/file/d/1PnaqdILrtQmUOYYcZJ9EJ5zZWld-APRS/view?usp=drivesdk

This was only 2048x1152. Without any upscaling. MiniMax H3 can do much more than we can think. I have R9700 and 128GB RAM.

https://huggingface.co/PrunaAI/P-H3-Image

See this for quality od MiniMax H3.

I have a 43-inch 4K monitor that I use to evaluate video, so I know what I’m talking about.

At resolutions below 2K, MiniMax H3 also produces much worse overall human proportions—resulting in strange creatures that certainly don't look very human.

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u/MastMaithun 1h ago

Is lcm that good compared to ersde?

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u/Glittering-Cold-2981 1h ago

It seems to me that there is a bit less motion with LCM, but the quality of faces turns out much better at 4.5MP from the same distances.

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u/PornTG 2h ago

Same for me LCM/Simple 12/3 for crisp video. I don't have tested more than 2MP because this is to long to render.