The CDTWP: A programmable processor for connected word recognition

The architecture of a single board processor for executing a variety of frame-by-frame connected pattern matching techniques which use dynamic time warping is described. The connected dynamic time warp processor (CDTWP) will operate with existing hardware presently used for isolated word recognition. The CDTWP receives input in the form of a sequence of LPC-based feature vectors calculated from a spoken string of connected words. Each input vector, presented at a period of 15 msec, is compared with each frame of every reference template and the results are used to continuously update a hypothesized concatenation of reference templates that best matches the input. This comparison and update operation is completed for a given test frame before the next test frame arrives 15 msec later, and as a result, the CDTWP may be used to recognize the earlier portions of a connected string before the later portions have been spoken. The CDTWP is an experimental tool to examine a class of connected word recognition algorithms and architectures in real time. As a result, it is designed to be programmable and to fit within an existing word recognition system. The programmability and single board constraints limit the total number of reference frames to 455 (about 11 word templates). Current design work on a processor for isolated word dynamic time warping, the DTWP, suggests that a second generation CDTWP may handle 6000 reference frames (150 templates) by the use of existing nonprogrammable processing elements and addition of more template memory.