Is it necessary to use a vid2hid layer before the rnn cell?

[Nash2325138]

video-caption.pytorch/models/EncoderRNN.py

Line 25 in 9e4759d

self.vid2hid = nn.Linear(dim_vid, dim_hidden)

As the title, why do we need another linear transform layer for video features when the rnn will do it inside the cell?

If it is to save the number of parameters, will it be better if we specify the rnn input dimension using another variable?
For instance:

self.vid2hid = nn.Linear(dim_vid, dim_rnn_input)
...
self.rnn = self.rnn_cell(dim_rnn_input, dim_hidden, n_layers, batch_first=True,
                         bidirectional=bidirectional, dropout=self.rnn_dropout_p)