Text subtitle decoder and method for decoding text subtitle streams

This application is a continuation of and claims the benefit under 35 U.S.C. § 120 to U.S. application Ser. No. 11/013,379, filed on Dec. 17, 2004, which claims the benefit under 35 U.S.C. § 119 to Korean Patent Application No. 10-2004-0016564, filed on Mar. 11, 2004, and Provisional Applications 60/543,328 filed Feb. 11, 2004; 60/548,852 filed Feb. 10, 2004; and 60/548,850 filed Feb. 10, 2004; all of which are hereby incorporated by reference.

1. Field

The present invention relates to a text subtitle decoder and a method for decoding text subtitle streams recorded on a recording medium, an example of which is a Blu-ray disc (BD).

2. Discussion of the Related Art

Optical discs are widely used as an optical recording medium for recording mass data. Presently, among a wide range of optical discs, a new high-density digital video disc (hereinafter referred to as “HD-DVD”), such as a Blu-ray Disc (hereafter referred to as “BD”), is under development for writing and storing high definition video and audio data. Currently, global standard technical specifications of the Blu-ray Disc (BD), which is known to be the next generation HD-DVD technology, are under establishment as a next generation optical recording solution that is able to have a data significantly surpassing the conventional DVD, along with many other digital apparatuses.

Accordingly, optical reproducing apparatuses having the Blu-ray Disc (BD) standards applied thereto are also being developed. However, since the Blu-ray Disc (BD) standards are yet to be completed, there have been many difficulties in developing a complete optical reproducing apparatus. Particularly, in order to effectively reproduce the data from the Blu-ray Disc (BD), not only should the main AV data as well as various data required for a user\'s convenience, such as subtitle information as the supplementary data related to the main AV data, be provided, but also managing information for reproducing the main data and the subtitle data recorded in the optical disc should be systemized and provided.

However, in the present Blu-ray Disc (BD) standards, since the standards of the supplementary data, particularly the subtitle information, are not completely consolidated, there are many restrictions in the full-scale development of a Blu-ray Disc (BD) basis optical reproducing apparatus. And, such restrictions cause problems in providing the supplementary data such as subtitles to the user.

Accordingly, the present invention is directed to a text subtitle decoder and a method for decoding text subtitle streams recorded on a recording medium that substantially obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a method and a text subtitle decoder for decoding a text subtitle stream recorded on a recording medium, which includes text strings for each dialog region and composition and rendering information required for decoding the text strings.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method for decoding a text subtitle stream recorded on a recording medium is provided. Initially, a text subtitle stream recorded on the recording medium is loaded into a subtitle loading buffer, where the text subtitle stream includes a dialog style segment and a dialog presentation segment. The dialog style segment defines a group of region styles, and the dialog presentation segment includes dialog presentation information and dialog text data for dialog having at least one region. Thereafter, the dialog presentation segment is parsed into composition information, rendering information, and the dialog text data for each region.

The parsed composition information and rendering information are then stored in a first buffer, and the parsed dialog text data are stored in a second buffer, where the dialog text data stored in the second buffer includes one or more text strings for each region. The text strings stored in the second buffer are rendered into a bitmap object for each region according to the rendering information, and the rendered bitmap object is stored into a third buffer. Finally, the stored bitmap object is composed in a graphics plane for each region according to the composition information.

In another aspect of the present invention, a text subtitle decoder for decoding a text subtitle stream recorded on a recording medium includes a subtitle loading buffer, a text subtitle processor, a dialog composition buffer, a dialog buffer, a text renderer, a bitmap object buffer, and a graphics plane. The subtitle loading buffer initially loads the text subtitle stream, which includes a dialog style segment defining a group of region styles and a dialog presentation segment including dialog presentation information and dialog text data for a dialog having at least one region. The text subtitle processor parses the dialog presentation segment into composition information, rendering information, and the dialog text data for each region. Next, the dialog composition buffer stores the composition and rendering information parsed from the text subtitle processor, and the dialog buffer stores the dialog text data, which includes one or more text strings for each region.

Thereafter, the text renderer included in the text subtitle decoder renders the text strings stored in the dialog buffer into a bitmap object for each region according to the rendering information, and the bitmap object buffer stores the rendered bitmap object. Finally, each bitmap object stored in the bitmap object buffer is composed in the graphics plane according to the composition information.

In further aspect of the present invention, an optical disc player for reproducing text subtitle streams recorded on an optical disc includes an audio decoder configured to decode audio streams recorded on the optical disc into audio data, a video decoder configured to decode video streams recorded on the optical disc into video image data, a text subtitle decoder configured to decode a text subtitle stream recorded on the optical disc into text subtitle image data, and an image superimposition unit configured to superimpose the decoded text subtitle image data with the decoded video image data. The text subtitle decoder includes a text subtitle processor, a text renderer, and a graphics plane. The text subtitle processor initially parses the text subtitle stream into composition information, rendering information, and dialog text data for a dialog having at least one region, where the dialog text data include one or more text strings for each region. The text renderer renders the text strings into graphic data for each region according to the rendering information, and the graphics plane composes the rendered graphic data according to the composition information.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.