Programmable filter for removing selected user data from an MPEG-2 bit stream

摘要

An MPEG-2 video decoder which identifies and removes selected User Data fields from an MPEG-2 bit-stream before storing the bit-stream into the VBV buffer of the decoder. The decoder monitors the MPEG-2 bit-stream with a state machine to determine the level of the record (Sequence, Group of Pictures or Picture) that is currently being decoded. The decoder also monitors the bit-stream for User Data Start Codes. When a User Data Start Code is encountered, the state of the state machine is compared to preprogrammed commands provided by a microprocessor. Only if these commands require the decoding of User Data at a particular level will the User Data following the User Data Start Code be passed to the VBV buffer. The commands provided by the microprocessor may be changed to selectively inhibit the storage of more or less User Data depending on the identified need for the User Data and the relative burden that processing the User Data through the VBV buffer places on the decoder.