mvit.py

import math
from dataclasses import dataclass
from functools import partial
from typing import Any, Callable, Dict, List, Optional, Sequence, Tuple

import torch
import torch.fx
import torch.nn as nn

from ...ops import MLP, StochasticDepth
from ...transforms._presets import VideoClassification
from ...utils import _log_api_usage_once
from .._api import register_model, Weights, WeightsEnum
from .._meta import _KINETICS400_CATEGORIES
from .._utils import _ovewrite_named_param, handle_legacy_interface


__all__ = [
    "MViT",
    "MViT_V1_B_Weights",
    "mvit_v1_b",
    "MViT_V2_S_Weights",
    "mvit_v2_s",
]


@dataclass
class MSBlockConfig:
    num_heads: int
    input_channels: int
    output_channels: int
    kernel_q: List[int]
    kernel_kv: List[int]
    stride_q: List[int]
    stride_kv: List[int]


def _prod(s: Sequence[int]) -> int:
    product = 1
    for v in s:
        product *= v
    return product


def _unsqueeze(x: torch.Tensor, target_dim: int, expand_dim: int) -> Tuple[torch.Tensor, int]:
    tensor_dim = x.dim()
    if tensor_dim == target_dim - 1:
        x = x.unsqueeze(expand_dim)
    elif tensor_dim != target_dim:
        raise ValueError(f"Unsupported input dimension {x.shape}")
    return x, tensor_dim


def _squeeze(x: torch.Tensor, target_dim: int, expand_dim: int, tensor_dim: int) -> torch.Tensor:
    if tensor_dim == target_dim - 1:
        x = x.squeeze(expand_dim)
    return x


torch.fx.wrap("_unsqueeze")
torch.fx.wrap("_squeeze")


class Pool(nn.Module):
    def __init__(
        self,
        pool: nn.Module,
        norm: Optional[nn.Module],
        activation: Optional[nn.Module] = None,
        norm_before_pool: bool = False,
    ) -> None:
        super().__init__()
        self.pool = pool
        layers = []
        if norm is not None:
            layers.append(norm)
        if activation is not None:
            layers.append(activation)
        self.norm_act = nn.Sequential(*layers) if layers else None
        self.norm_before_pool = norm_before_pool

    def forward(self, x: torch.Tensor, thw: Tuple[int, int, int]) -> Tuple[torch.Tensor, Tuple[int, int, int]]:
        x, tensor_dim = _unsqueeze(x, 4, 1)

        # Separate the class token and reshape the input
        class_token, x = torch.tensor_split(x, indices=(1,), dim=2)
        x = x.transpose(2, 3)
        B, N, C = x.shape[:3]
        x = x.reshape((B * N, C) + thw).contiguous()

        # normalizing prior pooling is useful when we use BN which can be absorbed to speed up inference
        if self.norm_before_pool and self.norm_act is not None:
            x = self.norm_act(x)

        # apply the pool on the input and add back the token
        x = self.pool(x)
        T, H, W = x.shape[2:]
        x = x.reshape(B, N, C, -1).transpose(2, 3)
        x = torch.cat((class_token, x), dim=2)

        if not self.norm_before_pool and self.norm_act is not None:
            x = self.norm_act(x)

        x = _squeeze(x, 4, 1, tensor_dim)
        return x, (T, H, W)


def _interpolate(embedding: torch.Tensor, d: int) -> torch.Tensor:
    if embedding.shape[0] == d:
        return embedding

    return (
        nn.functional.interpolate(
            embedding.permute(1, 0).unsqueeze(0),
            size=d,
            mode="linear",
        )
        .squeeze(0)
        .permute(1, 0)
    )


def _add_rel_pos(
    attn: torch.Tensor,
    q: torch.Tensor,
    q_thw: Tuple[int, int, int],
    k_thw: Tuple[int, int, int],
    rel_pos_h: torch.Tensor,
    rel_pos_w: torch.Tensor,
    rel_pos_t: torch.Tensor,
) -> torch.Tensor:
    # Modified code from: https://github.com/facebookresearch/SlowFast/commit/1aebd71a2efad823d52b827a3deaf15a56cf4932
    q_t, q_h, q_w = q_thw
    k_t, k_h, k_w = k_thw
    dh = int(2 * max(q_h, k_h) - 1)
    dw = int(2 * max(q_w, k_w) - 1)
    dt = int(2 * max(q_t, k_t) - 1)

    # Scale up rel pos if shapes for q and k are different.
    q_h_ratio = max(k_h / q_h, 1.0)
    k_h_ratio = max(q_h / k_h, 1.0)
    dist_h = torch.arange(q_h)[:, None] * q_h_ratio - (torch.arange(k_h)[None, :] + (1.0 - k_h)) * k_h_ratio
    q_w_ratio = max(k_w / q_w, 1.0)
    k_w_ratio = max(q_w / k_w, 1.0)
    dist_w = torch.arange(q_w)[:, None] * q_w_ratio - (torch.arange(k_w)[None, :] + (1.0 - k_w)) * k_w_ratio
    q_t_ratio = max(k_t / q_t, 1.0)
    k_t_ratio = max(q_t / k_t, 1.0)
    dist_t = torch.arange(q_t)[:, None] * q_t_ratio - (torch.arange(k_t)[None, :] + (1.0 - k_t)) * k_t_ratio

    # Interpolate rel pos if needed.
    rel_pos_h = _interpolate(rel_pos_h, dh)
    rel_pos_w = _interpolate(rel_pos_w, dw)
    rel_pos_t = _interpolate(rel_pos_t, dt)
    Rh = rel_pos_h[dist_h.long()]
    Rw = rel_pos_w[dist_w.long()]
    Rt = rel_pos_t[dist_t.long()]

    B, n_head, _, dim = q.shape

    r_q = q[:, :, 1:].reshape(B, n_head, q_t, q_h, q_w, dim)
    rel_h_q = torch.einsum("bythwc,hkc->bythwk", r_q, Rh)  # [B, H, q_t, qh, qw, k_h]
    rel_w_q = torch.einsum("bythwc,wkc->bythwk", r_q, Rw)  # [B, H, q_t, qh, qw, k_w]
    # [B, H, q_t, q_h, q_w, dim] -> [q_t, B, H, q_h, q_w, dim] -> [q_t, B*H*q_h*q_w, dim]
    r_q = r_q.permute(2, 0, 1, 3, 4, 5).reshape(q_t, B * n_head * q_h * q_w, dim)
    # [q_t, B*H*q_h*q_w, dim] * [q_t, dim, k_t] = [q_t, B*H*q_h*q_w, k_t] -> [B*H*q_h*q_w, q_t, k_t]
    rel_q_t = torch.matmul(r_q, Rt.transpose(1, 2)).transpose(0, 1)
    # [B*H*q_h*q_w, q_t, k_t] -> [B, H, q_t, q_h, q_w, k_t]
    rel_q_t = rel_q_t.view(B, n_head, q_h, q_w, q_t, k_t).permute(0, 1, 4, 2, 3, 5)

    # Combine rel pos.
    rel_pos = (
        rel_h_q[:, :, :, :, :, None, :, None]
        + rel_w_q[:, :, :, :, :, None, None, :]
        + rel_q_t[:, :, :, :, :, :, None, None]
    ).reshape(B, n_head, q_t * q_h * q_w, k_t * k_h * k_w)

    # Add it to attention
    attn[:, :, 1:, 1:] += rel_pos

    return attn


def _add_shortcut(x: torch.Tensor, shortcut: torch.Tensor, residual_with_cls_embed: bool):
    if residual_with_cls_embed:
        x.add_(shortcut)
    else:
        x[:, :, 1:, :] += shortcut[:, :, 1:, :]
    return x


torch.fx.wrap("_add_rel_pos")
torch.fx.wrap("_add_shortcut")


class MultiscaleAttention(nn.Module):
    def __init__(
        self,
        input_size: List[int],
        embed_dim: int,
        output_dim: int,
        num_heads: int,
        kernel_q: List[int],
        kernel_kv: List[int],
        stride_q: List[int],
        stride_kv: List[int],
        residual_pool: bool,
        residual_with_cls_embed: bool,
        rel_pos_embed: bool,
        dropout: float = 0.0,
        norm_layer: Callable[..., nn.Module] = nn.LayerNorm,
    ) -> None:
        super().__init__()
        self.embed_dim = embed_dim
        self.output_dim = output_dim
        self.num_heads = num_heads
        self.head_dim = output_dim // num_heads
        self.scaler = 1.0 / math.sqrt(self.head_dim)
        self.residual_pool = residual_pool
        self.residual_with_cls_embed = residual_with_cls_embed

        self.qkv = nn.Linear(embed_dim, 3 * output_dim)
        layers: List[nn.Module] = [nn.Linear(output_dim, output_dim)]
        if dropout > 0.0:
            layers.append(nn.Dropout(dropout, inplace=True))
        self.project = nn.Sequential(*layers)

        self.pool_q: Optional[nn.Module] = None
        if _prod(kernel_q) > 1 or _prod(stride_q) > 1:
            padding_q = [int(q // 2) for q in kernel_q]
            self.pool_q = Pool(
                nn.Conv3d(
                    self.head_dim,
                    self.head_dim,
                    kernel_q,  # type: ignore[arg-type]
                    stride=stride_q,  # type: ignore[arg-type]
                    padding=padding_q,  # type: ignore[arg-type]
                    groups=self.head_dim,
                    bias=False,
                ),
                norm_layer(self.head_dim),
            )

        self.pool_k: Optional[nn.Module] = None
        self.pool_v: Optional[nn.Module] = None
        if _prod(kernel_kv) > 1 or _prod(stride_kv) > 1:
            padding_kv = [int(kv // 2) for kv in kernel_kv]
            self.pool_k = Pool(
                nn.Conv3d(
                    self.head_dim,
                    self.head_dim,
                    kernel_kv,  # type: ignore[arg-type]
                    stride=stride_kv,  # type: ignore[arg-type]
                    padding=padding_kv,  # type: ignore[arg-type]
                    groups=self.head_dim,
                    bias=False,
                ),
                norm_layer(self.head_dim),
            )
            self.pool_v = Pool(
                nn.Conv3d(
                    self.head_dim,
                    self.head_dim,
                    kernel_kv,  # type: ignore[arg-type]
                    stride=stride_kv,  # type: ignore[arg-type]
                    padding=padding_kv,  # type: ignore[arg-type]
                    groups=self.head_dim,
                    bias=False,
                ),
                norm_layer(self.head_dim),
            )

        self.rel_pos_h: Optional[nn.Parameter] = None
        self.rel_pos_w: Optional[nn.Parameter] = None
        self.rel_pos_t: Optional[nn.Parameter] = None
        if rel_pos_embed:
            size = max(input_size[1:])
            q_size = size // stride_q[1] if len(stride_q) > 0 else size
            kv_size = size // stride_kv[1] if len(stride_kv) > 0 else size
            spatial_dim = 2 * max(q_size, kv_size) - 1
            temporal_dim = 2 * input_size[0] - 1
            self.rel_pos_h = nn.Parameter(torch.zeros(spatial_dim, self.head_dim))
            self.rel_pos_w = nn.Parameter(torch.zeros(spatial_dim, self.head_dim))
            self.rel_pos_t = nn.Parameter(torch.zeros(temporal_dim, self.head_dim))
            nn.init.trunc_normal_(self.rel_pos_h, std=0.02)
            nn.init.trunc_normal_(self.rel_pos_w, std=0.02)
            nn.init.trunc_normal_(self.rel_pos_t, std=0.02)

    def forward(self, x: torch.Tensor, thw: Tuple[int, int, int]) -> Tuple[torch.Tensor, Tuple[int, int, int]]:
        B, N, C = x.shape
        q, k, v = self.qkv(x).reshape(B, N, 3, self.num_heads, self.head_dim).transpose(1, 3).unbind(dim=2)

        if self.pool_k is not None:
            k, k_thw = self.pool_k(k, thw)
        else:
            k_thw = thw
        if self.pool_v is not None:
            v = self.pool_v(v, thw)[0]
        if self.pool_q is not None:
            q, thw = self.pool_q(q, thw)

        attn = torch.matmul(self.scaler * q, k.transpose(2, 3))
        if self.rel_pos_h is not None and self.rel_pos_w is not None and self.rel_pos_t is not None:
            attn = _add_rel_pos(
                attn,
                q,
                thw,
                k_thw,
                self.rel_pos_h,
                self.rel_pos_w,
                self.rel_pos_t,
            )
        attn = attn.softmax(dim=-1)

        x = torch.matmul(attn, v)
        if self.residual_pool:
            _add_shortcut(x, q, self.residual_with_cls_embed)
        x = x.transpose(1, 2).reshape(B, -1, self.output_dim)
        x = self.project(x)

        return x, thw


class MultiscaleBlock(nn.Module):
    def __init__(
        self,
        input_size: List[int],
        cnf: MSBlockConfig,
        residual_pool: bool,
        residual_with_cls_embed: bool,
        rel_pos_embed: bool,
        proj_after_attn: bool,
        dropout: float = 0.0,
        stochastic_depth_prob: float = 0.0,
        norm_layer: Callable[..., nn.Module] = nn.LayerNorm,
    ) -> None:
        super().__init__()
        self.proj_after_attn = proj_after_attn

        self.pool_skip: Optional[nn.Module] = None
        if _prod(cnf.stride_q) > 1:
            kernel_skip = [s + 1 if s > 1 else s for s in cnf.stride_q]
            padding_skip = [int(k // 2) for k in kernel_skip]
            self.pool_skip = Pool(
                nn.MaxPool3d(kernel_skip, stride=cnf.stride_q, padding=padding_skip), None  # type: ignore[arg-type]
            )

        attn_dim = cnf.output_channels if proj_after_attn else cnf.input_channels

        self.norm1 = norm_layer(cnf.input_channels)
        self.norm2 = norm_layer(attn_dim)
        self.needs_transposal = isinstance(self.norm1, nn.BatchNorm1d)

        self.attn = MultiscaleAttention(
            input_size,
            cnf.input_channels,
            attn_dim,
            cnf.num_heads,
            kernel_q=cnf.kernel_q,
            kernel_kv=cnf.kernel_kv,
            stride_q=cnf.stride_q,
            stride_kv=cnf.stride_kv,
            rel_pos_embed=rel_pos_embed,
            residual_pool=residual_pool,
            residual_with_cls_embed=residual_with_cls_embed,
            dropout=dropout,
            norm_layer=norm_layer,
        )
        self.mlp = MLP(
            attn_dim,
            [4 * attn_dim, cnf.output_channels],
            activation_layer=nn.GELU,
            dropout=dropout,
            inplace=None,
        )

        self.stochastic_depth = StochasticDepth(stochastic_depth_prob, "row")

        self.project: Optional[nn.Module] = None
        if cnf.input_channels != cnf.output_channels:
            self.project = nn.Linear(cnf.input_channels, cnf.output_channels)

    def forward(self, x: torch.Tensor, thw: Tuple[int, int, int]) -> Tuple[torch.Tensor, Tuple[int, int, int]]:
        x_norm1 = self.norm1(x.transpose(1, 2)).transpose(1, 2) if self.needs_transposal else self.norm1(x)
        x_attn, thw_new = self.attn(x_norm1, thw)
        x = x if self.project is None or not self.proj_after_attn else self.project(x_norm1)
        x_skip = x if self.pool_skip is None else self.pool_skip(x, thw)[0]
        x = x_skip + self.stochastic_depth(x_attn)

        x_norm2 = self.norm2(x.transpose(1, 2)).transpose(1, 2) if self.needs_transposal else self.norm2(x)
        x_proj = x if self.project is None or self.proj_after_attn else self.project(x_norm2)

        return x_proj + self.stochastic_depth(self.mlp(x_norm2)), thw_new


class PositionalEncoding(nn.Module):
    def __init__(self, embed_size: int, spatial_size: Tuple[int, int], temporal_size: int, rel_pos_embed: bool) -> None:
        super().__init__()
        self.spatial_size = spatial_size
        self.temporal_size = temporal_size

        self.class_token = nn.Parameter(torch.zeros(embed_size))
        self.spatial_pos: Optional[nn.Parameter] = None
        self.temporal_pos: Optional[nn.Parameter] = None
        self.class_pos: Optional[nn.Parameter] = None
        if not rel_pos_embed:
            self.spatial_pos = nn.Parameter(torch.zeros(self.spatial_size[0] * self.spatial_size[1], embed_size))
            self.temporal_pos = nn.Parameter(torch.zeros(self.temporal_size, embed_size))
            self.class_pos = nn.Parameter(torch.zeros(embed_size))

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        class_token = self.class_token.expand(x.size(0), -1).unsqueeze(1)
        x = torch.cat((class_token, x), dim=1)

        if self.spatial_pos is not None and self.temporal_pos is not None and self.class_pos is not None:
            hw_size, embed_size = self.spatial_pos.shape
            pos_embedding = torch.repeat_interleave(self.temporal_pos, hw_size, dim=0)
            pos_embedding.add_(self.spatial_pos.unsqueeze(0).expand(self.temporal_size, -1, -1).reshape(-1, embed_size))
            pos_embedding = torch.cat((self.class_pos.unsqueeze(0), pos_embedding), dim=0).unsqueeze(0)
            x.add_(pos_embedding)

        return x


class MViT(nn.Module):
    def __init__(
        self,
        spatial_size: Tuple[int, int],
        temporal_size: int,
        block_setting: Sequence[MSBlockConfig],
        residual_pool: bool,
        residual_with_cls_embed: bool,
        rel_pos_embed: bool,
        proj_after_attn: bool,
        dropout: float = 0.5,
        attention_dropout: float = 0.0,
        stochastic_depth_prob: float = 0.0,
        num_classes: int = 400,
        block: Optional[Callable[..., nn.Module]] = None,
        norm_layer: Optional[Callable[..., nn.Module]] = None,
        patch_embed_kernel: Tuple[int, int, int] = (3, 7, 7),
        patch_embed_stride: Tuple[int, int, int] = (2, 4, 4),
        patch_embed_padding: Tuple[int, int, int] = (1, 3, 3),
    ) -> None:
        """
        MViT main class.

        Args:
            spatial_size (tuple of ints): The spacial size of the input as ``(H, W)``.
            temporal_size (int): The temporal size ``T`` of the input.
            block_setting (sequence of MSBlockConfig): The Network structure.
            residual_pool (bool): If True, use MViTv2 pooling residual connection.
            residual_with_cls_embed (bool): If True, the addition on the residual connection will include
                the class embedding.
            rel_pos_embed (bool): If True, use MViTv2's relative positional embeddings.
            proj_after_attn (bool): If True, apply the projection after the attention.
            dropout (float): Dropout rate. Default: 0.0.
            attention_dropout (float): Attention dropout rate. Default: 0.0.
            stochastic_depth_prob: (float): Stochastic depth rate. Default: 0.0.
            num_classes (int): The number of classes.
            block (callable, optional): Module specifying the layer which consists of the attention and mlp.
            norm_layer (callable, optional): Module specifying the normalization layer to use.
            patch_embed_kernel (tuple of ints): The kernel of the convolution that patchifies the input.
            patch_embed_stride (tuple of ints): The stride of the convolution that patchifies the input.
            patch_embed_padding (tuple of ints): The padding of the convolution that patchifies the input.
        """
        super().__init__()
        # This implementation employs a different parameterization scheme than the one used at PyTorch Video:
        # https://github.com/facebookresearch/pytorchvideo/blob/718d0a4/pytorchvideo/models/vision_transformers.py
        # We remove any experimental configuration that didn't make it to the final variants of the models. To represent
        # the configuration of the architecture we use the simplified form suggested at Table 1 of the paper.
        _log_api_usage_once(self)
        total_stage_blocks = len(block_setting)
        if total_stage_blocks == 0:
            raise ValueError("The configuration parameter can't be empty.")

        if block is None:
            block = MultiscaleBlock

        if norm_layer is None:
            norm_layer = partial(nn.LayerNorm, eps=1e-6)

        # Patch Embedding module
        self.conv_proj = nn.Conv3d(
            in_channels=3,
            out_channels=block_setting[0].input_channels,
            kernel_size=patch_embed_kernel,
            stride=patch_embed_stride,
            padding=patch_embed_padding,
        )

        input_size = [size // stride for size, stride in zip((temporal_size,) + spatial_size, self.conv_proj.stride)]

        # Spatio-Temporal Class Positional Encoding
        self.pos_encoding = PositionalEncoding(
            embed_size=block_setting[0].input_channels,
            spatial_size=(input_size[1], input_size[2]),
            temporal_size=input_size[0],
            rel_pos_embed=rel_pos_embed,
        )

        # Encoder module
        self.blocks = nn.ModuleList()
        for stage_block_id, cnf in enumerate(block_setting):
            # adjust stochastic depth probability based on the depth of the stage block
            sd_prob = stochastic_depth_prob * stage_block_id / (total_stage_blocks - 1.0)

            self.blocks.append(
                block(
                    input_size=input_size,
                    cnf=cnf,
                    residual_pool=residual_pool,
                    residual_with_cls_embed=residual_with_cls_embed,
                    rel_pos_embed=rel_pos_embed,
                    proj_after_attn=proj_after_attn,
                    dropout=attention_dropout,
                    stochastic_depth_prob=sd_prob,
                    norm_layer=norm_layer,
                )
            )

            if len(cnf.stride_q) > 0:
                input_size = [size // stride for size, stride in zip(input_size, cnf.stride_q)]
        self.norm = norm_layer(block_setting[-1].output_channels)

        # Classifier module
        self.head = nn.Sequential(
            nn.Dropout(dropout, inplace=True),
            nn.Linear(block_setting[-1].output_channels, num_classes),
        )

        for m in self.modules():
            if isinstance(m, nn.Linear):
                nn.init.trunc_normal_(m.weight, std=0.02)
                if isinstance(m, nn.Linear) and m.bias is not None:
                    nn.init.constant_(m.bias, 0.0)
            elif isinstance(m, nn.LayerNorm):
                if m.weight is not None:
                    nn.init.constant_(m.weight, 1.0)
                if m.bias is not None:
                    nn.init.constant_(m.bias, 0.0)
            elif isinstance(m, PositionalEncoding):
                for weights in m.parameters():
                    nn.init.trunc_normal_(weights, std=0.02)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        # Convert if necessary (B, C, H, W) -> (B, C, 1, H, W)
        x = _unsqueeze(x, 5, 2)[0]
        # patchify and reshape: (B, C, T, H, W) -> (B, embed_channels[0], T', H', W') -> (B, THW', embed_channels[0])
        x = self.conv_proj(x)
        x = x.flatten(2).transpose(1, 2)

        # add positional encoding
        x = self.pos_encoding(x)

        # pass patches through the encoder
        thw = (self.pos_encoding.temporal_size,) + self.pos_encoding.spatial_size
        for block in self.blocks:
            x, thw = block(x, thw)
        x = self.norm(x)

        # classifier "token" as used by standard language architectures
        x = x[:, 0]
        x = self.head(x)

        return x


def _mvit(
    block_setting: List[MSBlockConfig],
    stochastic_depth_prob: float,
    weights: Optional[WeightsEnum],
    progress: bool,
    **kwargs: Any,
) -> MViT:
    if weights is not None:
        _ovewrite_named_param(kwargs, "num_classes", len(weights.meta["categories"]))
        assert weights.meta["min_size"][0] == weights.meta["min_size"][1]
        _ovewrite_named_param(kwargs, "spatial_size", weights.meta["min_size"])
        _ovewrite_named_param(kwargs, "temporal_size", weights.meta["min_temporal_size"])
    spatial_size = kwargs.pop("spatial_size", (224, 224))
    temporal_size = kwargs.pop("temporal_size", 16)

    model = MViT(
        spatial_size=spatial_size,
        temporal_size=temporal_size,
        block_setting=block_setting,
        residual_pool=kwargs.pop("residual_pool", False),
        residual_with_cls_embed=kwargs.pop("residual_with_cls_embed", True),
        rel_pos_embed=kwargs.pop("rel_pos_embed", False),
        proj_after_attn=kwargs.pop("proj_after_attn", False),
        stochastic_depth_prob=stochastic_depth_prob,
        **kwargs,
    )

    if weights is not None:
        model.load_state_dict(weights.get_state_dict(progress=progress))

    return model


class MViT_V1_B_Weights(WeightsEnum):
    KINETICS400_V1 = Weights(
        url="https://download.pytorch.org/models/mvit_v1_b-dbeb1030.pth",
        transforms=partial(
            VideoClassification,
            crop_size=(224, 224),
            resize_size=(256,),
            mean=(0.45, 0.45, 0.45),
            std=(0.225, 0.225, 0.225),
        ),
        meta={
            "min_size": (224, 224),
            "min_temporal_size": 16,
            "categories": _KINETICS400_CATEGORIES,
            "recipe": "https://github.com/facebookresearch/pytorchvideo/blob/main/docs/source/model_zoo.md",
            "_docs": (
                "The weights were ported from the paper. The accuracies are estimated on video-level "
                "with parameters `frame_rate=7.5`, `clips_per_video=5`, and `clip_len=16`"
            ),
            "num_params": 36610672,
            "_metrics": {
                "Kinetics-400": {
                    "acc@1": 78.477,
                    "acc@5": 93.582,
                }
            },
        },
    )
    DEFAULT = KINETICS400_V1


class MViT_V2_S_Weights(WeightsEnum):
    KINETICS400_V1 = Weights(
        url="https://download.pytorch.org/models/mvit_v2_s-ae3be167.pth",
        transforms=partial(
            VideoClassification,
            crop_size=(224, 224),
            resize_size=(256,),
            mean=(0.45, 0.45, 0.45),
            std=(0.225, 0.225, 0.225),
        ),
        meta={
            "min_size": (224, 224),
            "min_temporal_size": 16,
            "categories": _KINETICS400_CATEGORIES,
            "recipe": "https://github.com/facebookresearch/SlowFast/blob/main/MODEL_ZOO.md",
            "_docs": (
                "The weights were ported from the paper. The accuracies are estimated on video-level "
                "with parameters `frame_rate=7.5`, `clips_per_video=5`, and `clip_len=16`"
            ),
            "num_params": 34537744,
            "_metrics": {
                "Kinetics-400": {
                    "acc@1": 80.757,
                    "acc@5": 94.665,
                }
            },
        },
    )
    DEFAULT = KINETICS400_V1


@register_model()
@handle_legacy_interface(weights=("pretrained", MViT_V1_B_Weights.KINETICS400_V1))
def mvit_v1_b(*, weights: Optional[MViT_V1_B_Weights] = None, progress: bool = True, **kwargs: Any) -> MViT:
    """
    Constructs a base MViTV1 architecture from
    `Multiscale Vision Transformers <https://arxiv.org/abs/2104.11227>`__.

    .. betastatus:: video module

    Args:
        weights (:class:`~torchvision.models.video.MViT_V1_B_Weights`, optional): The
            pretrained weights to use. See
            :class:`~torchvision.models.video.MViT_V1_B_Weights` below for
            more details, and possible values. By default, no pre-trained
            weights are used.
        progress (bool, optional): If True, displays a progress bar of the
            download to stderr. Default is True.
        **kwargs: parameters passed to the ``torchvision.models.video.MViT``
            base class. Please refer to the `source code
            <https://github.com/pytorch/vision/blob/main/torchvision/models/video/mvit.py>`_
            for more details about this class.

    .. autoclass:: torchvision.models.video.MViT_V1_B_Weights
        :members:
    """
    weights = MViT_V1_B_Weights.verify(weights)

    config: Dict[str, List] = {
        "num_heads": [1, 2, 2, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 8, 8],
        "input_channels": [96, 192, 192, 384, 384, 384, 384, 384, 384, 384, 384, 384, 384, 384, 768, 768],
        "output_channels": [192, 192, 384, 384, 384, 384, 384, 384, 384, 384, 384, 384, 384, 768, 768, 768],
        "kernel_q": [[], [3, 3, 3], [], [3, 3, 3], [], [], [], [], [], [], [], [], [], [], [3, 3, 3], []],
        "kernel_kv": [
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
        ],
        "stride_q": [[], [1, 2, 2], [], [1, 2, 2], [], [], [], [], [], [], [], [], [], [], [1, 2, 2], []],
        "stride_kv": [
            [1, 8, 8],
            [1, 4, 4],
            [1, 4, 4],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 1, 1],
            [1, 1, 1],
        ],
    }

    block_setting = []
    for i in range(len(config["num_heads"])):
        block_setting.append(
            MSBlockConfig(
                num_heads=config["num_heads"][i],
                input_channels=config["input_channels"][i],
                output_channels=config["output_channels"][i],
                kernel_q=config["kernel_q"][i],
                kernel_kv=config["kernel_kv"][i],
                stride_q=config["stride_q"][i],
                stride_kv=config["stride_kv"][i],
            )
        )

    return _mvit(
        spatial_size=(224, 224),
        temporal_size=16,
        block_setting=block_setting,
        residual_pool=False,
        residual_with_cls_embed=False,
        stochastic_depth_prob=kwargs.pop("stochastic_depth_prob", 0.2),
        weights=weights,
        progress=progress,
        **kwargs,
    )


@register_model()
@handle_legacy_interface(weights=("pretrained", MViT_V2_S_Weights.KINETICS400_V1))
def mvit_v2_s(*, weights: Optional[MViT_V2_S_Weights] = None, progress: bool = True, **kwargs: Any) -> MViT:
    """
    Constructs a small MViTV2 architecture from
    `Multiscale Vision Transformers <https://arxiv.org/abs/2104.11227>`__.

    .. betastatus:: video module

    Args:
        weights (:class:`~torchvision.models.video.MViT_V2_S_Weights`, optional): The
            pretrained weights to use. See
            :class:`~torchvision.models.video.MViT_V2_S_Weights` below for
            more details, and possible values. By default, no pre-trained
            weights are used.
        progress (bool, optional): If True, displays a progress bar of the
            download to stderr. Default is True.
        **kwargs: parameters passed to the ``torchvision.models.video.MViT``
            base class. Please refer to the `source code
            <https://github.com/pytorch/vision/blob/main/torchvision/models/video/mvit.py>`_
            for more details about this class.

    .. autoclass:: torchvision.models.video.MViT_V2_S_Weights
        :members:
    """
    weights = MViT_V2_S_Weights.verify(weights)

    config: Dict[str, List] = {
        "num_heads": [1, 2, 2, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 8, 8],
        "input_channels": [96, 96, 192, 192, 384, 384, 384, 384, 384, 384, 384, 384, 384, 384, 384, 768],
        "output_channels": [96, 192, 192, 384, 384, 384, 384, 384, 384, 384, 384, 384, 384, 384, 768, 768],
        "kernel_q": [
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
        ],
        "kernel_kv": [
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
            [3, 3, 3],
        ],
        "stride_q": [
            [1, 1, 1],
            [1, 2, 2],
            [1, 1, 1],
            [1, 2, 2],
            [1, 1, 1],
            [1, 1, 1],
            [1, 1, 1],
            [1, 1, 1],
            [1, 1, 1],
            [1, 1, 1],
            [1, 1, 1],
            [1, 1, 1],
            [1, 1, 1],
            [1, 1, 1],
            [1, 2, 2],
            [1, 1, 1],
        ],
        "stride_kv": [
            [1, 8, 8],
            [1, 4, 4],
            [1, 4, 4],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 2, 2],
            [1, 1, 1],
            [1, 1, 1],
        ],
    }

    block_setting = []
    for i in range(len(config["num_heads"])):
        block_setting.append(
            MSBlockConfig(
                num_heads=config["num_heads"][i],
                input_channels=config["input_channels"][i],
                output_channels=config["output_channels"][i],
                kernel_q=config["kernel_q"][i],
                kernel_kv=config["kernel_kv"][i],
                stride_q=config["stride_q"][i],
                stride_kv=config["stride_kv"][i],
            )
        )

    return _mvit(
        spatial_size=(224, 224),
        temporal_size=16,
        block_setting=block_setting,
        residual_pool=True,
        residual_with_cls_embed=False,
        rel_pos_embed=True,
        proj_after_attn=True,
        stochastic_depth_prob=kwargs.pop("stochastic_depth_prob", 0.2),
        weights=weights,
        progress=progress,
        **kwargs,
    )