Embodiments of the invention provide a run length coding instruction for determining output context and decision values. Pixel coefficient bit values are used after wavelet transformation to determine output context (CX) and decision (D) values. The input is comprised of coefficient bit values (bit1, bit2, bit3, bit 4) in accordance with the scan order and the output are CX and D values. The CX and D pairs are processed together by arithmetic encoder to produce compressed data output (CD). CX selects the probability estimate to use during the coding of D.