1. A method for assessing video encoding quality, comprising: acquiring a quantization parameter of a slice of a video frame of a video stream and a quantity of bytes per pixel of the slice of the video frame of the video stream; determining a quantization parameter of a video according to the quantization parameter of the slice of the video frame of the video stream; determining a complexity of content of the video according to the quantity of bytes per pixel of the slice of the video frame of the video stream; and predicting the video encoding quality according to the complexity of the content of the video and the quantization parameter of the video, wherein determining the complexity of the content of the video according to the quantity of bytes per pixel of the slice of the video frame of the video stream comprises: determining a quantity of bytes per pixel of the k th slice among Num slices of the video frame using the following formula: f_slice ⁢ _byte ⁢ _per ⁢ _ ⁢ pixel k = i_slice ⁢ _ ⁢ size k i_slice ⁢ _ ⁢ pixel k , wherein i_slice 13 size k is a quantity of byes of the k th slice among the Num slices of the video frame, wherein i_slice_pixel k is a quantity of pixels of the k th slice among the Num slices of the video frame, wherein k is a positive integer, wherein in the video frame, k ranges from 1 to Num, and wherein Num is a positive integer: determining complexity of content of the k th slice among the Num slices of the video frame using the following formula: 
 f _slice_content_complexity k = a[i _slice_qp k ]·f _slice_byte_per_pixel k +b[i _slice_qp k ], wherein both a[i_slice_qp k ] and b[i_slice_qp k ] are values corresponding to a quantization parameter of the k th slice among the Num slices of the video frame; determining complexity of content of the video frame using the following formula: f_frame ⁢ _content ⁢ _complexity = ∑ k = 1 Num ⁢ ⁢ f_slice ⁢ _content ⁢ _ ⁢ complexity k Num ; and determining the complexity of the content of the video according to the complexity of the content of the video frame.