Peak-ahead fifo for dvd system stream parsing

Abstract

A memory buffer allowing preliminary access to an upstream data portion in a data stream and a method for allowing the access. This memory buffer is a “peek-ahead” FIFO comprising a data input that receives a data stream, a data output, a circular FIFO buffer that stores data from the input at a circulating read location and provided data from a circulating write location to the data output. The memory buffer also has read and write pointers that indicate the read and write locations in the FIFO buffer. If the upstream data portion is stored in the memory buffer, the read pointer can temporarily advance by an offset number of memory locations to allow reading of the upstream data portion. In one embodiment, this memory buffer is included in a DVD decoder and is used to identify the type of an incoming packet before the entire header of the packet is processed. Also described is a method and system for parsing data words from an interleaved byte stream. The method has steps of: (a) reading a byte from the byte stream, (b) determining a type of the byte, that is—what type of data is carried in the packet that it comes from, (c) storing the byte in a word-length buffer for its type, (d) transferring the buffer to a word-write memory if the buffer is full, and (e) repeating steps (a)-(d) for subsequent bytes in the data stream.