vos_inference.py

# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.

# This source code is licensed under the license found in the
# LICENSE file in the root directory of this source tree.

import argparse
import os

import numpy as np
import torch
from PIL import Image
from sam2.build_sam import build_sam2_video_predictor


# the PNG palette for DAVIS 2017 dataset
DAVIS_PALETTE = b"\x00\x00\x00\x80\x00\x00\x00\x80\x00\x80\x80\x00\x00\x00\x80\x80\x00\x80\x00\x80\x80\x80\x80\x80@\x00\x00\xc0\x00\x00@\x80\x00\xc0\x80\x00@\x00\x80\xc0\x00\x80@\x80\x80\xc0\x80\x80\x00@\x00\x80@\x00\x00\xc0\x00\x80\xc0\x00\x00@\x80\x80@\x80\x00\xc0\x80\x80\xc0\x80@@\x00\xc0@\x00@\xc0\x00\xc0\xc0\x00@@\x80\xc0@\x80@\xc0\x80\xc0\xc0\x80\x00\x00@\x80\x00@\x00\x80@\x80\x80@\x00\x00\xc0\x80\x00\xc0\x00\x80\xc0\x80\x80\xc0@\x00@\xc0\x00@@\x80@\xc0\x80@@\x00\xc0\xc0\x00\xc0@\x80\xc0\xc0\x80\xc0\x00@@\x80@@\x00\xc0@\x80\xc0@\x00@\xc0\x80@\xc0\x00\xc0\xc0\x80\xc0\xc0@@@\xc0@@@\xc0@\xc0\xc0@@@\xc0\xc0@\xc0@\xc0\xc0\xc0\xc0\xc0 \x00\x00\xa0\x00\x00 \x80\x00\xa0\x80\x00 \x00\x80\xa0\x00\x80 \x80\x80\xa0\x80\x80`\x00\x00\xe0\x00\x00`\x80\x00\xe0\x80\x00`\x00\x80\xe0\x00\x80`\x80\x80\xe0\x80\x80 @\x00\xa0@\x00 \xc0\x00\xa0\xc0\x00 @\x80\xa0@\x80 \xc0\x80\xa0\xc0\x80`@\x00\xe0@\x00`\xc0\x00\xe0\xc0\x00`@\x80\xe0@\x80`\xc0\x80\xe0\xc0\x80 \x00@\xa0\x00@ \x80@\xa0\x80@ \x00\xc0\xa0\x00\xc0 \x80\xc0\xa0\x80\xc0`\x00@\xe0\x00@`\x80@\xe0\x80@`\x00\xc0\xe0\x00\xc0`\x80\xc0\xe0\x80\xc0 @@\xa0@@ \xc0@\xa0\xc0@ @\xc0\xa0@\xc0 \xc0\xc0\xa0\xc0\xc0`@@\xe0@@`\xc0@\xe0\xc0@`@\xc0\xe0@\xc0`\xc0\xc0\xe0\xc0\xc0\x00 \x00\x80 \x00\x00\xa0\x00\x80\xa0\x00\x00 \x80\x80 \x80\x00\xa0\x80\x80\xa0\x80@ \x00\xc0 \x00@\xa0\x00\xc0\xa0\x00@ \x80\xc0 \x80@\xa0\x80\xc0\xa0\x80\x00`\x00\x80`\x00\x00\xe0\x00\x80\xe0\x00\x00`\x80\x80`\x80\x00\xe0\x80\x80\xe0\x80@`\x00\xc0`\x00@\xe0\x00\xc0\xe0\x00@`\x80\xc0`\x80@\xe0\x80\xc0\xe0\x80\x00 @\x80 @\x00\xa0@\x80\xa0@\x00 \xc0\x80 \xc0\x00\xa0\xc0\x80\xa0\xc0@ @\xc0 @@\xa0@\xc0\xa0@@ \xc0\xc0 \xc0@\xa0\xc0\xc0\xa0\xc0\x00`@\x80`@\x00\xe0@\x80\xe0@\x00`\xc0\x80`\xc0\x00\xe0\xc0\x80\xe0\xc0@`@\xc0`@@\xe0@\xc0\xe0@@`\xc0\xc0`\xc0@\xe0\xc0\xc0\xe0\xc0  \x00\xa0 \x00 \xa0\x00\xa0\xa0\x00  \x80\xa0 \x80 \xa0\x80\xa0\xa0\x80` \x00\xe0 \x00`\xa0\x00\xe0\xa0\x00` \x80\xe0 \x80`\xa0\x80\xe0\xa0\x80 `\x00\xa0`\x00 \xe0\x00\xa0\xe0\x00 `\x80\xa0`\x80 \xe0\x80\xa0\xe0\x80``\x00\xe0`\x00`\xe0\x00\xe0\xe0\x00``\x80\xe0`\x80`\xe0\x80\xe0\xe0\x80  @\xa0 @ \xa0@\xa0\xa0@  \xc0\xa0 \xc0 \xa0\xc0\xa0\xa0\xc0` @\xe0 @`\xa0@\xe0\xa0@` \xc0\xe0 \xc0`\xa0\xc0\xe0\xa0\xc0 `@\xa0`@ \xe0@\xa0\xe0@ `\xc0\xa0`\xc0 \xe0\xc0\xa0\xe0\xc0``@\xe0`@`\xe0@\xe0\xe0@``\xc0\xe0`\xc0`\xe0\xc0\xe0\xe0\xc0"


def load_ann_png(path):
    """Load a PNG file as a mask and its palette."""
    mask = Image.open(path)
    palette = mask.getpalette()
    mask = np.array(mask).astype(np.uint8)
    return mask, palette


def save_ann_png(path, mask, palette):
    """Save a mask as a PNG file with the given palette."""
    assert mask.dtype == np.uint8
    assert mask.ndim == 2
    output_mask = Image.fromarray(mask)
    output_mask.putpalette(palette)
    output_mask.save(path)


def get_per_obj_mask(mask):
    """Split a mask into per-object masks."""
    object_ids = np.unique(mask)
    object_ids = object_ids[object_ids > 0].tolist()
    per_obj_mask = {object_id: (mask == object_id) for object_id in object_ids}
    return per_obj_mask


def put_per_obj_mask(per_obj_mask, height, width):
    """Combine per-object masks into a single mask."""
    mask = np.zeros((height, width), dtype=np.uint8)
    object_ids = sorted(per_obj_mask)[::-1]
    for object_id in object_ids:
        object_mask = per_obj_mask[object_id]
        object_mask = object_mask.reshape(height, width)
        mask[object_mask] = object_id
    return mask


def load_masks_from_dir(input_mask_dir, video_name, frame_name, per_obj_png_file):
    """Load masks from a directory as a dict of per-object masks."""
    if not per_obj_png_file:
        input_mask_path = os.path.join(input_mask_dir, video_name, f"{frame_name}.png")
        input_mask, input_palette = load_ann_png(input_mask_path)
        per_obj_input_mask = get_per_obj_mask(input_mask)
    else:
        per_obj_input_mask = {}
        # each object is a directory in "{object_id:%03d}" format
        for object_name in os.listdir(os.path.join(input_mask_dir, video_name)):
            object_id = int(object_name)
            input_mask_path = os.path.join(
                input_mask_dir, video_name, object_name, f"{frame_name}.png"
            )
            input_mask, input_palette = load_ann_png(input_mask_path)
            per_obj_input_mask[object_id] = input_mask > 0

    return per_obj_input_mask, input_palette


def save_masks_to_dir(
    output_mask_dir,
    video_name,
    frame_name,
    per_obj_output_mask,
    height,
    width,
    per_obj_png_file,
    output_palette,
):
    """Save masks to a directory as PNG files."""
    os.makedirs(os.path.join(output_mask_dir, video_name), exist_ok=True)
    if not per_obj_png_file:
        output_mask = put_per_obj_mask(per_obj_output_mask, height, width)
        output_mask_path = os.path.join(
            output_mask_dir, video_name, f"{frame_name}.png"
        )
        save_ann_png(output_mask_path, output_mask, output_palette)
    else:
        for object_id, object_mask in per_obj_output_mask.items():
            object_name = f"{object_id:03d}"
            os.makedirs(
                os.path.join(output_mask_dir, video_name, object_name),
                exist_ok=True,
            )
            output_mask = object_mask.reshape(height, width).astype(np.uint8)
            output_mask_path = os.path.join(
                output_mask_dir, video_name, object_name, f"{frame_name}.png"
            )
            save_ann_png(output_mask_path, output_mask, output_palette)


@torch.inference_mode()
@torch.autocast(device_type="cuda", dtype=torch.bfloat16)
def vos_inference(
    predictor,
    base_video_dir,
    input_mask_dir,
    output_mask_dir,
    video_name,
    score_thresh=0.0,
    use_all_masks=False,
    per_obj_png_file=False,
):
    """Run VOS inference on a single video with the given predictor."""
    # load the video frames and initialize the inference state on this video
    video_dir = os.path.join(base_video_dir, video_name)
    frame_names = [
        os.path.splitext(p)[0]
        for p in os.listdir(video_dir)
        if os.path.splitext(p)[-1] in [".jpg", ".jpeg", ".JPG", ".JPEG"]
    ]
    frame_names.sort(key=lambda p: int(os.path.splitext(p)[0]))
    inference_state = predictor.init_state(
        video_path=video_dir, async_loading_frames=False
    )
    height = inference_state["video_height"]
    width = inference_state["video_width"]
    input_palette = None

    # fetch mask inputs from input_mask_dir (either only mask for the first frame, or all available masks)
    if not use_all_masks:
        # use only the first video's ground-truth mask as the input mask
        input_frame_inds = [0]
    else:
        # use all mask files available in the input_mask_dir as the input masks
        if not per_obj_png_file:
            input_frame_inds = [
                idx
                for idx, name in enumerate(frame_names)
                if os.path.exists(
                    os.path.join(input_mask_dir, video_name, f"{name}.png")
                )
            ]
        else:
            input_frame_inds = [
                idx
                for object_name in os.listdir(os.path.join(input_mask_dir, video_name))
                for idx, name in enumerate(frame_names)
                if os.path.exists(
                    os.path.join(input_mask_dir, video_name, object_name, f"{name}.png")
                )
            ]
        input_frame_inds = sorted(set(input_frame_inds))

    # add those input masks to SAM 2 inference state before propagation
    for input_frame_idx in input_frame_inds:
        per_obj_input_mask, input_palette = load_masks_from_dir(
            input_mask_dir=input_mask_dir,
            video_name=video_name,
            frame_name=frame_names[input_frame_idx],
            per_obj_png_file=per_obj_png_file,
        )
        for object_id, object_mask in per_obj_input_mask.items():
            predictor.add_new_mask(
                inference_state=inference_state,
                frame_idx=input_frame_idx,
                obj_id=object_id,
                mask=object_mask,
            )

    # run propagation throughout the video and collect the results in a dict
    os.makedirs(os.path.join(output_mask_dir, video_name), exist_ok=True)
    output_palette = input_palette or DAVIS_PALETTE
    video_segments = {}  # video_segments contains the per-frame segmentation results
    for out_frame_idx, out_obj_ids, out_mask_logits in predictor.propagate_in_video(
        inference_state
    ):
        per_obj_output_mask = {
            out_obj_id: (out_mask_logits[i] > score_thresh).cpu().numpy()
            for i, out_obj_id in enumerate(out_obj_ids)
        }
        video_segments[out_frame_idx] = per_obj_output_mask

    # write the output masks as palette PNG files to output_mask_dir
    for out_frame_idx, per_obj_output_mask in video_segments.items():
        save_masks_to_dir(
            output_mask_dir=output_mask_dir,
            video_name=video_name,
            frame_name=frame_names[out_frame_idx],
            per_obj_output_mask=per_obj_output_mask,
            height=height,
            width=width,
            per_obj_png_file=per_obj_png_file,
            output_palette=output_palette,
        )


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "--sam2_cfg",
        type=str,
        default="sam2_hiera_b+.yaml",
        help="SAM 2 model configuration file",
    )
    parser.add_argument(
        "--sam2_checkpoint",
        type=str,
        default="./checkpoints/sam2_hiera_b+.pt",
        help="path to the SAM 2 model checkpoint",
    )
    parser.add_argument(
        "--base_video_dir",
        type=str,
        required=True,
        help="directory containing videos (as JPEG files) to run VOS prediction on",
    )
    parser.add_argument(
        "--input_mask_dir",
        type=str,
        required=True,
        help="directory containing input masks (as PNG files) of each video",
    )
    parser.add_argument(
        "--video_list_file",
        type=str,
        default=None,
        help="text file containing the list of video names to run VOS prediction on",
    )
    parser.add_argument(
        "--output_mask_dir",
        type=str,
        required=True,
        help="directory to save the output masks (as PNG files)",
    )
    parser.add_argument(
        "--score_thresh",
        type=float,
        default=0.0,
        help="threshold for the output mask logits (default: 0.0)",
    )
    parser.add_argument(
        "--use_all_masks",
        action="store_true",
        help="whether to use all available PNG files in input_mask_dir "
        "(default without this flag: just the first PNG file as input to the SAM 2 model; "
        "usually we don't need this flag, since semi-supervised VOS evaluation usually takes input from the first frame only)",
    )
    parser.add_argument(
        "--per_obj_png_file",
        action="store_true",
        help="whether use separate per-object PNG files for input and output masks "
        "(default without this flag: all object masks are packed into a single PNG file on each frame following DAVIS format; "
        "note that the SA-V dataset stores each object mask as an individual PNG file and requires this flag)",
    )
    parser.add_argument(
        "--apply_postprocessing",
        action="store_true",
        help="whether to apply postprocessing (e.g. hole-filling) to the output masks "
        "(we don't apply such post-processing in the SAM 2 model evaluation)",
    )
    args = parser.parse_args()

    # if we use per-object PNG files, they could possibly overlap in inputs and outputs
    hydra_overrides_extra = [
        "++model.non_overlap_masks=" + ("false" if args.per_obj_png_file else "true")
    ]
    predictor = build_sam2_video_predictor(
        config_file=args.sam2_cfg,
        ckpt_path=args.sam2_checkpoint,
        apply_postprocessing=args.apply_postprocessing,
        hydra_overrides_extra=hydra_overrides_extra,
    )

    if args.use_all_masks:
        print("using all available masks in input_mask_dir as input to the SAM 2 model")
    else:
        print(
            "using only the first frame's mask in input_mask_dir as input to the SAM 2 model"
        )
    # if a video list file is provided, read the video names from the file
    # (otherwise, we use all subdirectories in base_video_dir)
    if args.video_list_file is not None:
        with open(args.video_list_file, "r") as f:
            video_names = [v.strip() for v in f.readlines()]
    else:
        video_names = [
            p
            for p in os.listdir(args.base_video_dir)
            if os.path.isdir(os.path.join(args.base_video_dir, p))
        ]
    print(f"running VOS prediction on {len(video_names)} videos:\n{video_names}")

    for n_video, video_name in enumerate(video_names):
        print(f"\n{n_video + 1}/{len(video_names)} - running on {video_name}")
        vos_inference(
            predictor=predictor,
            base_video_dir=args.base_video_dir,
            input_mask_dir=args.input_mask_dir,
            output_mask_dir=args.output_mask_dir,
            video_name=video_name,
            score_thresh=args.score_thresh,
            use_all_masks=args.use_all_masks,
            per_obj_png_file=args.per_obj_png_file,
        )

    print(
        f"completed VOS prediction on {len(video_names)} videos -- "
        f"output masks saved to {args.output_mask_dir}"
    )


if __name__ == "__main__":
    main()