COMPRESSED IMAGE DATA DECODING DEVICE HAVING OSD FUNCTION AND OSD DATA COMPRESSION METHOD USED FOR THE DECODING DEVICE

摘要

PROBLEM TO BE SOLVED: To attain an OSD function via a general-purpose memory by reducing the capacity of a frame memory against a B picture, storing the compressed on-screen display data in a memory, and expanding the display data in response to their display. SOLUTION: The compressed bit map-shaped OSD data are directly written into a position of a memory 13 by an OSD writing circuit 6 and with the timing that is shown by a timing/operation setting circuit 1. Then the OSD data are read out by an OSD data reading circuit 12 with the timing shown by the circuit 1 and supplied to an OSD data expanding circuit 14. Thus the compressed OSD data are expanded by the circuit 14 and restored into the OSD data corresponding to the original bit map. Then the restored OSD data are supplied to a display circuit 5 synchronously with a display synchronizing signal and overlaid the decoded image data for display.