Method and apparatus for normal reverse playback

An apparatus for performing normal reverse playback from an Xth Group Of Pictures (GOP) of GOPs of a generated bitstream stored in a storage medium, the apparatus comprising:

• an MPEG decoder which reads a first bitstream corresponding to an Xth GOP and an (X−1)th GOP from the storage medium and which decodes pictures of the Xth GOP and reference pictures of the (X−1)th GOP using the read first bitstream;
• a frame buffer which stores the pictures decoded by the MPEG decoder;
• and
• a display block which displays the decoded pictures stored in the frame buffer,
• wherein during the normal reverse playback, the apparatus displays all the decoded pictures only once, and each display time of the decoded pictures displayed only once is the same,
• wherein the MPEG decoder decodes all reference pictures in the Xth GOP;
• decodes a first reference picture in a stream order in the (X−1)th GOP;
• and sequentially designates each picture from a first picture in a reverse display order in the Xth GOP as an nth picture having a reverse display order number n and when the nth picture having the reverse display order number n is designated as a display picture, performs the following:
• if the nth picture having the reverse display order number n is a reference picture or a B picture and an (n+1)th picture having a reverse display order number (n+1) is a B picture, decoding the (n+1)th picture having the reverse display order number (n+1) in the Xth GOP:
• if the nth picture having the reverse display order number n is the B picture and the (n+1)th picture having the reverse display order number (n+1) is a reference picture, decoding a next reference picture in the stream order among undecoded reference pictures in the (X−1)th GOP;
• and
• if the nth picture having the reverse display order number n is a first picture in a forward display order in the Xth GOP, decoding another first reference picture in a stream order in an (X−2)th GOP.

A non-transitory computer readable recording medium storing a computer readable program for implementing functions of normal reverse playback from an Xth Group of Pictures (GOP) of GOPs of a bitstream, said functions comprising:

• decoding all reference pictures in the Xth GOP;
• decoding a first reference picture in a stream order in an (X−1)th GOP;
• and
• sequentially designating each picture from a first picture in a reverse display order in the Xth GOP as an nth picture having a reverse display order number n and when the nth picture having the reverse display order number n is designated as a display picture, performing:
• if the nth picture is a reference picture or a B picture and an (n+1)th picture having a reverse display order number (n+1) is a B picture, decoding the (n+1)th picture in the Xth GOP;
• if the nth picture is the B picture and the (n+1)th picture is a reference picture, decoding a next reference picture in the stream order among undecoded reference pictures in the (X−1)th GOP;
• and
• if the nth picture is a first picture in a forward display order in the Xth GOP, decoding another first reference picture in a stream order in an (X−2)th GOP.