1. A method of coding data of a video sequence, the method comprising: defining one or more vectors of transform coefficients for vectorized entropy coding of enhancement layer video blocks of a coded unit in the video sequence, wherein each vector of the defined one or more vectors comprises a set of one or more of the transform coefficients in a scan order having an end position indicated by a vector control signal; determining whether the defined one or more vectors include only one vector per enhancement layer video block of the enhancement layer video blocks or the defined one or more vectors include two or more vectors per enhancement layer video block of the enhancement layer video blocks; selecting a prediction mode for the enhancement layer video blocks of the coded unit by performing one of: selecting weighted prediction as the selected prediction mode in response to determining that the defined one or more vectors are determined to include two or more vectors per enhancement layer video block of the enhancement layer video blocks, the selected prediction mode of weighted prediction comprising prediction based on predictive blocks formed as weighted combinations of predictive enhancement layer video blocks and predictive base layer video blocks in the video sequence, or selecting non-weighted prediction as the selected prediction mode in response to determining that the defined one or more vectors are determined to include a single vector per enhancement layer video block of the enhancement layer video blocks, the selected prediction mode of non-weighted prediction comprising sequential prediction; coding the enhancement layer video blocks according to the selected prediction mode to form two-dimensional blocks of transform coefficients; vectorized entropy coding the two-dimensional blocks of transform coefficients by: scanning the two-dimensional blocks of transform coefficients into the defined one or more vectors; and separately entropy coding each vector of the defined one or more vectors, wherein the transform coefficients of the one or more vectors comprise one-dimensional sets of the two-dimensional blocks of transform coefficients, wherein coding the enhancement layer video blocks comprises separately entropy coding each one-dimensional set of the one-dimensional sets of the defined one or more vectors of transform coefficients; and coding one or more control signals that signify which coefficients of the two-dimensional blocks of coefficients are included in each defined vector of the defined one or more vectors of transform coefficients.