Patent ID: 7970056
Filing Date: 2011-06-28
Classification: H04N

Abstract:
1. A method for decoding a bitstream comprising the steps of: (A) receiving a first encoded bitstream at an input of a pre-decoder, wherein said first encoded bitstream is an intra-only frame picture encoded bitstream comprising a frame header and alternating macroblock rows, with each macroblock row containing encoded data for a plurality of vertical lines from a single respective field of a frame picture encoded in said first encoded bitstream; (B) generating in said pre-decoder a first field header and a second field header using said frame header of said first encoded bitstream, wherein said first field header comprises a copy of said frame header modified to signal a first field picture and said second field header comprises a copy of said frame header modified to signal a second field picture; (C) storing said first field header and macroblock rows containing the encoded data for the plurality of vertical lines from a first field of the frame picture in a first buffer in said pre-decoder and storing said second field header and macroblock rows containing the encoded data for the plurality of vertical lines from a second field of the frame picture in a second buffer in said pre-decoder, wherein the encoded data for the plurality of vertical lines contained in each macroblock row in said first buffer and said second buffer is a copy of the encoded data for the plurality of vertical lines contained in a corresponding macroblock row in the first encoded bitstream; and (D) generating a second encoded bitstream using said pre-decoder, said second encoded bitstream comprising (i) said first field header, (ii) said macroblock rows containing the encoded data for the plurality of vertical lines from said first field of the frame picture, (iii) said second field header and (iv) said macroblock rows containing the encoded data for the plurality of vertical lines from said second field of the frame picture, wherein said second encoded bitstream is an intra-only field picture encoded bitstream; and (E) presenting said second encoded bitstream to an input of a standard, MPEG-2 compliant decoder, wherein said second encoded bitstream is decoded as two interlaced field pictures and the encoded data for the plurality of vertical lines contained in each macroblock row remains encoded from reception of said first encoded bitstream at said input of said pre-decoder through presentation of said second encoded bitstream to said input of said standard, MPEG-2 compliant decoder.