US Patent 7558815 Processing of performance sensitive transforms

The present invention provides a method, apparatus, and article of manufacture for controlling truncation error which is introduced when performing a transform equation as a result of lowering the precision of elements of the equation using shift right operations. This is achieved by associating a predetermined truncation amount with a plurality of operations of the transform equation and defining an ordered set of the operations to perform the transform which control the truncation error in the result if each operation introduced the predetermined truncation amount associated with it. Accordingly the transform is performed using the defined ordered set. For example the pre-determined truncation error could be an average truncation error.