一、背景

        0、Hybrid Transformer 论文解读

        1、代码复现|Demucs Music Source Separation_demucs架构原理-CSDN博客

        2、Hybrid Transformer 各个模块对应的代码具体在工程的哪个地方

        3、Hybrid Transformer 各个模块的底层到底是个啥（初步感受）？

        4、Hybrid Transformer 各个模块处理后，数据的维度大小是咋变换的？

        5、Hybrid Transformer 拆解STFT模块

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        从模块上划分，Hybrid Transformer Demucs 共包含 （STFT模块、时域编码模块、频域编码模块、Cross-Domain Transformer Encoder模块、时域解码模块、频域解码模块、ISTFT模块）7个模块。

        本篇目标：拆解频域编码模块的底层。

        时域编码和频域编码原理类似（后续不再拆解时域编码模块）。

二、频域编码模块

class HEncLayer(nn.Module):def __init__(self, chin, chout, kernel_size=8, stride=4, norm_groups=1, empty=False,freq=True, dconv=True, norm=True, context=0, dconv_kw={}, pad=True,rewrite=True):"""Encoder layer. This used both by the time and the frequency branch.Args:chin: number of input channels.chout: number of output channels.norm_groups: number of groups for group norm.empty: used to make a layer with just the first conv. this is usedbefore merging the time and freq. branches.freq: this is acting on frequencies.dconv: insert DConv residual branches.norm: use GroupNorm.context: context size for the 1x1 conv.dconv_kw: list of kwargs for the DConv class.pad: pad the input. Padding is done so that the output size isalways the input size / stride.rewrite: add 1x1 conv at the end of the layer."""super().__init__()norm_fn = lambda d: nn.Identity()  # noqaif norm:norm_fn = lambda d: nn.GroupNorm(norm_groups, d)  # noqaif pad:pad = kernel_size // 4else:pad = 0klass = nn.Conv1dself.freq = freqself.kernel_size = kernel_sizeself.stride = strideself.empty = emptyself.norm = normself.pad = padif freq:kernel_size = [kernel_size, 1]stride = [stride, 1]pad = [pad, 0]klass = nn.Conv2dself.conv = klass(chin, chout, kernel_size, stride, pad)if self.empty:returnself.norm1 = norm_fn(chout)self.rewrite = Noneif rewrite:self.rewrite = klass(chout, 2 * chout, 1 + 2 * context, 1, context)self.norm2 = norm_fn(2 * chout)self.dconv = Noneif dconv:self.dconv = DConv(chout, **dconv_kw)def forward(self, x, inject=None):"""`inject` is used to inject the result from the time branch into the frequency branch,when both have the same stride."""if not self.freq and x.dim() == 4:B, C, Fr, T = x.shapex = x.view(B, -1, T)if not self.freq:le = x.shape[-1]if not le % self.stride == 0:x = F.pad(x, (0, self.stride - (le % self.stride)))y = self.conv(x)if self.empty:return yif inject is not None:assert inject.shape[-1] == y.shape[-1], (inject.shape, y.shape)if inject.dim() == 3 and y.dim() == 4:inject = inject[:, :, None]y = y + injecty = F.gelu(self.norm1(y))if self.dconv:if self.freq:B, C, Fr, T = y.shapey = y.permute(0, 2, 1, 3).reshape(-1, C, T)y = self.dconv(y)if self.freq:y = y.view(B, Fr, C, T).permute(0, 2, 1, 3)if self.rewrite:z = self.norm2(self.rewrite(y))z = F.glu(z, dim=1)else:z = yreturn z

        核心代码如上所示。

        使用print函数打印出各个关键节点的信息，可以得到频域编解码模块的全景图。

        编码层:Conv2d+Norm1+GELU,  Norm1：Identity()

        残差连接：（Conv1d+GroupNorm+GELU +Conv1d+GroupNorm+GLU+LayerScale()）

        +（Conv2d+Norm2+GLU），Norm2：Identity() ，备注：Identity可以理解成直通

#上图均是自己读完代码绘制的。相信自己也可以。
#具体的，编码层1-4的Conv2d分别是：
Conv2d(4, 48, kernel_size=(8, 1), stride=(4, 1), padding=(2, 0))
Conv2d(48, 96, kernel_size=(8, 1), stride=(4, 1), padding=(2, 0))
Conv2d(96, 192, kernel_size=(8, 1), stride=(4, 1), padding=(2, 0))
Conv2d(192, 384, kernel_size=(8, 1), stride=(4, 1), padding=(2, 0))

#残差连接1
DConv((layers): ModuleList((0): Sequential((0): Conv1d(48, 6, kernel_size=(3,), stride=(1,), padding=(1,))(1): GroupNorm(1, 6, eps=1e-05, affine=True)(2): GELU(approximate=none)(3): Conv1d(6, 96, kernel_size=(1,), stride=(1,))(4): GroupNorm(1, 96, eps=1e-05, affine=True)(5): GLU(dim=1)(6): LayerScale())(1): Sequential((0): Conv1d(48, 6, kernel_size=(3,), stride=(1,), padding=(2,), dilation=(2,))(1): GroupNorm(1, 6, eps=1e-05, affine=True)(2): GELU(approximate=none)(3): Conv1d(6, 96, kernel_size=(1,), stride=(1,))(4): GroupNorm(1, 96, eps=1e-05, affine=True)(5): GLU(dim=1)(6): LayerScale()))
)
Conv2d(48, 96, kernel_size=(1, 1), stride=(1, 1))#残差连接2
DConv((layers): ModuleList((0): Sequential((0): Conv1d(96, 12, kernel_size=(3,), stride=(1,), padding=(1,))(1): GroupNorm(1, 12, eps=1e-05, affine=True)(2): GELU(approximate=none)(3): Conv1d(12, 192, kernel_size=(1,), stride=(1,))(4): GroupNorm(1, 192, eps=1e-05, affine=True)(5): GLU(dim=1)(6): LayerScale())(1): Sequential((0): Conv1d(96, 12, kernel_size=(3,), stride=(1,), padding=(2,), dilation=(2,))(1): GroupNorm(1, 12, eps=1e-05, affine=True)(2): GELU(approximate=none)(3): Conv1d(12, 192, kernel_size=(1,), stride=(1,))(4): GroupNorm(1, 192, eps=1e-05, affine=True)(5): GLU(dim=1)(6): LayerScale()))
)
Conv2d(96, 192, kernel_size=(1, 1), stride=(1, 1))#残差连接3
DConv((layers): ModuleList((0): Sequential((0): Conv1d(192, 24, kernel_size=(3,), stride=(1,), padding=(1,))(1): GroupNorm(1, 24, eps=1e-05, affine=True)(2): GELU(approximate=none)(3): Conv1d(24, 384, kernel_size=(1,), stride=(1,))(4): GroupNorm(1, 384, eps=1e-05, affine=True)(5): GLU(dim=1)(6): LayerScale())(1): Sequential((0): Conv1d(192, 24, kernel_size=(3,), stride=(1,), padding=(2,), dilation=(2,))(1): GroupNorm(1, 24, eps=1e-05, affine=True)(2): GELU(approximate=none)(3): Conv1d(24, 384, kernel_size=(1,), stride=(1,))(4): GroupNorm(1, 384, eps=1e-05, affine=True)(5): GLU(dim=1)(6): LayerScale()))
)
Conv2d(192, 384, kernel_size=(1, 1), stride=(1, 1))#残差连接4
DConv((layers): ModuleList((0): Sequential((0): Conv1d(384, 48, kernel_size=(3,), stride=(1,), padding=(1,))(1): GroupNorm(1, 48, eps=1e-05, affine=True)(2): GELU(approximate=none)(3): Conv1d(48, 768, kernel_size=(1,), stride=(1,))(4): GroupNorm(1, 768, eps=1e-05, affine=True)(5): GLU(dim=1)(6): LayerScale())(1): Sequential((0): Conv1d(384, 48, kernel_size=(3,), stride=(1,), padding=(2,), dilation=(2,))(1): GroupNorm(1, 48, eps=1e-05, affine=True)(2): GELU(approximate=none)(3): Conv1d(48, 768, kernel_size=(1,), stride=(1,))(4): GroupNorm(1, 768, eps=1e-05, affine=True)(5): GLU(dim=1)(6): LayerScale()))
)
Conv2d(384, 768, kernel_size=(1, 1), stride=(1, 1))

        关于，各个卷积模块输出数据的shape计算，可以读这篇文章。

        没有所谓天生的大佬，如果有那么我愿称他/她为圣人。我相信，能读到这儿的都会成为大佬~。Believe yourself，one day，you will be somebody.

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