[new-model] Re-add PAN2 text-to-video and image-to-video (reverts #2025)

This reverts commit 6743f4b4b, restoring #1961.

examples/inference/basic/basic_pan2.py

@@ -0,0 +1,40 @@
+import os
+
+from fastvideo import VideoGenerator
+
+# PAN2 is trained on the structured captions its prompt rewriter produces (serialized as one-line JSON). Plain
+# prompts like this one work, with weaker results.
+PROMPT = ("A red fox trots through fresh snow in a pine forest at dawn, its breath visible in the cold air. "
+          "The camera tracks it from the side at ground level as low golden light filters through the trees.")
+
+OUTPUT_PATH = "video_samples_pan2"
+MODEL_PATH = os.environ.get("PAN2_MODEL_PATH", "IFM/PAN2")
+
+# Set to a first frame (e.g. "assets/images/girl.png") for image-to-video; the same pipeline runs both modes.
+IMAGE_PATH = None
+
+
+def main():
+    # The 29B DiT runs in bf16; with more GPUs, num_gpus enables Ulysses sequence parallelism (the 32 attention
+    # heads must be divisible by it).
+    generator = VideoGenerator.from_pretrained(
+        MODEL_PATH,
+        num_gpus=int(os.environ.get("PAN2_NUM_GPUS", "1")),
+        use_fsdp_inference=False,
+        dit_cpu_offload=False,
+        dit_layerwise_offload=False,
+        vae_cpu_offload=False,
+        text_encoder_cpu_offload=True,
+        pin_cpu_memory=True,
+    )
+
+    generator.generate_video(
+        PROMPT,
+        image_path=IMAGE_PATH,
+        output_path=OUTPUT_PATH,
+        save_video=True,
+    )
+
+
+if __name__ == "__main__":
+    main()