End To End Compression

Our team’s work on USTC iVC Seminar programming playground.

Baseline

We use the framework proposed in the following paper as our work’s baseline.

Ballé J, Laparra V, Simoncelli E P. End-to-end optimized image compression[J]. arXiv preprint arXiv:1611.01704, 2016.

The paper is available here.

Framework

GDN

class GDN(nn.Module):
    def __init__(self, num_output_channel, beta_min=1e-6, beta_init=0.1, gamma_min=1e-6, gamma_init=0.1,
                 min_boundary=2e-5, inverse=False):
        """
        :param beta_min: a small positive value to ensure beta' in range(2e-5,...)
        :param gamma_init: gamma initiated value
        :param num_output_channel: It is same for in/out because it is only a 'nomalization'
        :param min_boundary: the lower boundary for 'gamma' and 'beta''
        :param inverse: Identify GDN or IGDN
        """
        super(GDN, self).__init__()
        self.min_boundary = min_boundary
        self.inverse = inverse
        self.num_output_channel = num_output_channel
        self.reparam_offset = min_boundary ** 2
        self.beta_bound = (beta_min + self.reparam_offset) ** 0.5
        self.gamma_bound = (gamma_min + self.reparam_offset) ** 0.5

        # beta, gamma
        self.beta = nn.Parameter(torch.sqrt(torch.ones(num_output_channel) * beta_init + self.reparam_offset))
        self.gamma = nn.Parameter(torch.sqrt(torch.eye(num_output_channel) * gamma_init + self.reparam_offset))

    def forward(self, inputs):
        # transpose average
        gamma_T = self.gamma.transpose(0, 1)
        gamma_p = (self.gamma + gamma_T) / 2

        # lower boundary
        beta_p = SetMinBoundary.apply(self.beta, self.beta_bound)
        beta = beta_p ** 2 - self.reparam_offset

        gamma_p = SetMinBoundary.apply(gamma_p, self.gamma_bound)
        gamma = gamma_p ** 2 - self.reparam_offset
        # tensor转化为一维
        gamma = gamma.view(self.num_output_channel, self.num_output_channel, 1, 1)

        # normalization, resemble to 2d conv with kernel size set to 1
        norm = F.conv2d(inputs ** 2, gamma,
                        beta)  # 采用二维卷积来实现[batch_size, channel_size, H, W]*[channel_size, channel_size, 1 ,1 ]
        if self.inverse:
            outputs = inputs * norm
        else:
            outputs = inputs / norm
        return outputs

Support or Contact

You may contact us via our website on https://ustc-ivcseminar-team2.github.io/end-to-end_compression/.