Recording method and recording medium playback system

1. A recording method for recording, on an optical disc, a multiplexed stream and an audio stream constituting a browsing slideshow, the recording method comprising:

creating the multiplexed stream by multiplexing a video stream and a graphics stream;

creating the audio stream;

creating playlist information and stream information; and

recording the multiplexed stream and the audio stream respectively in a multiplexed stream recording area and an audio stream recording area of the optical disc without multiplexing the multiplexed stream and the audio stream, and recording the playlist information and the stream information on the optical disc, wherein

the multiplexed stream is a transport stream in which the video stream and the graphics stream are multiplexed, the video stream including a plurality of pieces of picture data, the graphics stream including a plurality of function segments, the plurality of pieces of picture data and the plurality of function segments having being multiplexed after being converted into TS packets, a TS packet constituting one or more of the plurality of pieces of picture data and a TS packet constituting a group of function segments from among the plurality of function segments constituting a browsing unit in the multiplexed stream,

the group of function segments constitutes a subtitle to be displayed by being combined with the plurality of pieces of picture data, and includes (i) an object definition segment for defining a graphics object representing the subtitle, (ii) a presentation control segment for defining screen configuration using the graphics object and (iii) an end segment indicating an end of each of the function segments, the presentation control segment including state information in accordance with which a graphics decoder starts memory management by clearing content of an object buffer of the graphics decoder, the object buffer being for storing therein the graphics object obtained by decoding the function segments,

the stream information includes transfer rate information indicating a transfer rate of the TS packets constituting the multiplexed stream from a PID filter included in a playback apparatus to a transport buffer included in a decoder, and

the playlist information includes two or more pieces of playitem information each including period information indicating a time required to read, when the playitem information is current playitem information, a next browsing unit specified by playitem information subsequent to the current playitem information to the transport buffer included in the decoder, the time being based on a value obtained by dividing a data size of the next browsing unit by the transfer rate of the TS packets indicated by the transfer rate information.

2. A recording medium playback system including a playback apparatus and the optical disc on which the playlist information, the multiplexed stream, the audio stream and the stream information have been recorded by the recording method of claim 1 , wherein

the playback apparatus includes:

a read unit operable to read the multiplexed stream and the audio stream from the optical disc;

a first read buffer;

a second read buffer;

a video decoder operable to decode the plurality of pieces of picture data;

the graphics decoder operable to decode the plurality of function segments after storing the function segments in a coded data buffer;

an audio decoder operable to decode the audio stream; and

a control unit operable to perform playback control based on the playlist information,

the plurality of pieces of picture data included in the video stream are read from the optical disc and stored in a buffer for video via the first read buffer,

the plurality of function segments included in the graphics stream are read from the optical disc and stored in the coded data buffer via the first read buffer,

the audio stream is read from the optical disc and stored in a buffer for audio via the second read buffer,

the graphics decoder includes:

a processor operable to decode the function segments to obtain the graphics object; and

the object buffer for storing therein the obtained graphics object, and

when the browsing unit is read from the optical disc, starts the memory management by clearing the content of the object buffer in accordance with the state information included in the presentation control segment included in the group of function segments constituting the browsing unit together with the one or more of the plurality of pieces of picture data.

3. The recording medium playback system of claim 2 , wherein

a size of the first read buffer RB 1 is 1.5 MB, and

the size of the first read buffer RB 1 and a size of the second read buffer RB 2 satisfy the following relationship:

RB1≧ R max1×{2× T jump+RB2/( Rud−R max2)}; and

RB2 ≧R max2×{2× T jump+RB1/( Rud−R max1)}, where

Rud represents a transfer rate between the optical disc and each of the first and second read buffers, Rmax 1 represents a transfer rate between the first read buffer and the buffer for video, Rmax 2 represents a transfer rate between the second read buffer and the buffer for audio, and Tjump represents a time required for an optical pickup to jump between the multiplexed stream recording area and the audio stream recording area of the optical disc.