  Age estimation is a classic learning problem in computer vision. Many larger
and deeper CNNs have been proposed with promising performance, such as AlexNet,
VggNet, GoogLeNet and ResNet. However, these models are not practical for the
embedded/mobile devices. Recently, MobileNets and ShuffleNets have been
proposed to reduce the number of parameters, yielding lightweight models.
However, their representation has been weakened because of the adoption of
depth-wise separable convolution. In this work, we investigate the limits of
compact model for small-scale image and propose an extremely Compact yet
efficient Cascade Context-based Age Estimation model(C3AE). This model
possesses only 1/9 and 1/2000 parameters compared with MobileNets/ShuffleNets
and VggNet, while achieves competitive performance. In particular, we re-define
age estimation problem by two-points representation, which is implemented by a
cascade model. Moreover, to fully utilize the facial context information,
multi-branch CNN network is proposed to aggregate multi-scale context.
Experiments are carried out on three age estimation datasets. The
state-of-the-art performance on compact model has been achieved with a
relatively large margin.
