MiniMax-H3-FL2VA-MLX-Serve-2bit-text-encoder

MiniMax-H3 FL2VA — MLX-Serve, 2-bit text encoder / 4-bit DiT

Variant of the 4-bit MLX-Serve conversion of MiniMax-H3's FL2VA checkpoint: only the Qwen3-VL text encoder is quantized to MLX affine 2-bit (group size 64); the DiT stays affine 4-bit and the VAEs, tokenizer and config are byte-for-byte identical to the 4-bit release. Runs natively on Apple Silicon via mlx-serve. Text-to-audio-video: the DiT denoises video and stereo audio jointly in one packed sequence.

How it loads: mlx-serve's MfLinear (shared by the H3 and MageFlow backends) derives (bits, group_size) per tensor from the packed geometry — bits = 32·w_cols/in_features, group_size = in_features/scales_cols — so each file is self-describing and no config change is needed. Every quantized tensor in text_encoder.safetensors solves to (2, 64); the DiT solves to (4, 64). The quantization block in config.json is advisory for this backend (reporting only) and still describes the DiT.

Same staged residency as the 4-bit release: the text encoder is loaded, run and freed before the DiT loads. The 2-bit encoder packs ~9.6 GB on disk vs ~15.8 GB at 4-bit.

Quality note: 2-bit affine is lossier than 4-bit by design. The text conditioning (prompt adherence) is where you may notice it; the DiT, VAEs and tokenizer are untouched, so frame/audio quality is otherwise the 4-bit release's.

Usage

Serve it with mlx-serve (a 32 GB Mac needs --skip-mem-preflight):

/Applications/MLX Core.app/Contents/MacOS/mlx-serve \
  --model /path/to/MiniMax-H3-FL2VA-MLX-Serve-2bit-text-encoder \
  --serve --host 127.0.0.1 --port 11235 --skip-mem-preflight

Then POST /v1/video/generations with {"prompt", "width", "height", "num_frames", "steps", "seed"} — the response is base64 rgb8 frames plus pcm_s16le audio on the standard native wire format. A ready-to-run wrapper script is provided in the source directory of this conversion (h3gen.sh), with --te=2bit|4bit to switch between this variant and the original 4-bit release.

Modifications

These are MODIFIED files. The text encoder is quantized to 2-bit and the DiT to 4-bit; see MODIFICATIONS.md for the full list. The VAEs and tokenizer are unmodified copies.

License

Powered by MiniMax H3. Licensed under the MiniMax H3 Community License Agreement -- see LICENSE and NOTICE, both included here.

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