the quantization parameter qp is well - known in digital video compression as an indication of picture quality . digital symbols representing a moving image are quantized with a quantizing step that is a function qsn of the quantization parameter qp , which function qsn has been normalized to the most significant bit of the bit depth of the digital symbols . as a result , the effect of a given qp is essentially independent of bit depth a particular qp value has a standard effect on image quality , regardless of bit depth . the invention is useful , for example , in encoding and decoding at different bit depths , to generate compatible , bitstreams having different bit depths , and to allow different bit depths for different components of a video signal by compressing each with the same fidelity .