Patent Application
20090303241
The present invention generally relates to multimedia files with audio, video and textual data and in particular relates to optimizing font files for multimedia files.
Presentation of textual information can be an important part of the video viewing experience. Text information may be used to represent the movie title, chapter names, specific track data, as well as subtitles. Subtitles may be used for conveying the dialogue of a video presentation in different languages, to aid those with hearing impairments, poor listening comprehension, or to suit the viewer's current listening preferences and at times to present the director or even user commentary in environments where such information is available.
Typically, embedding textual information such as subtitles with audio and video data into multimedia files involves run-length-encoding bitmap images of the subtitle text information. The run-length encoding of bitmaps provides an efficient way of storing the information, and since bitmaps are a pictorial representation of the text rather than a textual representation, there are no additional requirements to render the subtitles, such as utilizing embedded or resident font files. However, despite its advantages, because the text information is stored as bitmaps, it adapts poorly to changes in image frame size and as a result cannot be scaled with acceptable visual results to multiple sizes. In addition to the problem with scalability, bitmap representations are not easily searchable as text, which is an attractive feature from the perspective of categorization, metadata and archival activities.
The use of the actual text with respect to a known alphabet of a particular language to represent the textual information, e.g., a title, chapter names, and/or a dialogue in a movie, is one alternative to using bitmaps to represent the information. Using text in a movie typically requires the encoding of the text in a commonly acceptable representation. ASCII and Unicode are two such representations, where ASCII is typically used for encoding European languages and allows a maximum of 256 symbols, and Unicode is used for representing over 100,000 characters and other symbols from a very comprehensive list of world languages.
The displaying of such text can be done through the use of a mixture of bitmap and non-bitmap image representations such as those stored in True Type Font files. However, the size of these representations may pose a problem especially when dynamically displayed or utilized with languages that utilize unique symbols to represent each individual word in their corresponding vocabularies.
Accordingly, there is a need to provide an optimized text generation and display system that overcomes the above-noted issues and/or additional problems in the art.
Generally, textual information creation and playback systems and methods for multimedia files are provided in which one or more optimized font files are utilized. In one embodiment, a method of generating textual information for a multimedia file comprises receiving text data, an original font file and a multimedia file having audio and video data by a processor; and generating an optimized font file from the text data and the original font file by the processor. The generated font file is specifically matched to the text data and different from the original font file.
In another embodiment, a method of generating textual information for a multimedia file comprises identifying a plurality of time segments of a multimedia file having audio and video data by a processor; and generating a plurality of font files by the processor from text data and an original font file Each generated font file is specifically matched to the text data for each identified time segment.
In yet another embodiment, a textual information rendering system for generating textual information for a multimedia file is provided. The system includes a general purpose processor and a demultiplexer that is configured to extract text data from a multimedia file having audio data and video data. The processor is configured to create a font file by processing the text data together with an original font file, with the generated font file being specifically matched to the extracted text data and at least one predetermined character. Memory is coupled to the processor and stores the generated font file.
In various embodiments, the text data may be provided as either separate file(s), to be incorporated into the multimedia file
The above-mentioned and other features of this invention and the manner of obtaining and using them will become more apparent, and will be best understood, by reference to the following description, taken in conjunction with the accompanying drawings. The drawings depict only typical embodiments of the invention and do not therefore limit its scope.
Generally, a multimedia textual information generation and playback system is provided that includes optimized font files for textual information. The font files are substantially reduced in file size relative to an original font file. The font files are specifically tailored to supply only the characters or words needed for a specific title of the multimedia file. In one embodiment, the font files are designed to accommodate a particular size and/or time frame relative to the multimedia file. In various embodiments, the font files are provided or are configured to be provided dynamically during the playback of the multimedia file. In various embodiments, multimedia textual information generation and/or playback systems and methods are provided to generate/display textual information that is searchable, scalable and/or reduces space requirements.
There are many methods for embedding textual information such as subtitles alongside the audio and video tracks of a video presentation. These methods include but are not limited to: still-frame images such as JPEG files, run-length-encoded bitmap images, and the direct embedding of the text along with the optional attachment of a font file suitable for displaying the subtitle characters. It should be noted that although subtitle data or information is used as an example throughout the application, this is merely an example of textual information to ease the description of the invention and should not be construed as limiting such information or the applicability thereof only to subtitles.
As will be discussed in greater detail below, for a personal computer or a consumer electronic device, font files are used to render the text or characters to be displayed. Font files are electronic data files containing a set of representations for displaying characters or symbols. These representations or glyphs may be made in the form of individual bitmaps, drawing instructions for mathematical formulas for specifying the outline of a character, or instructions on drawing a series of lines with specific sizes and shapes. The advantage of specifying the glyph shape using drawing instructions and mathematical formulas is that the size of the character representation may be scaled to different sizes while generally maintaining their intended shape of the character. A font may also be composed of a mixture of bitmap and non-bitmap glyphs, where bitmap specifications could be used for only depicting certain character sizes.
Additionally, some languages, such as Chinese, Japanese, and Korean, utilize a unique symbol for representing each individual word in their corresponding vocabularies. The large number of words making up these different languages leads to very large font files as compared to languages which utilize combination of letters in a unique alphabet to form words. Font files for these languages may be in the 1 to 10 Mbytes range, and can sometimes be as large as 30 Mbytes. While the size of these fonts may not be an issue for processing on a personal computer, in an embedded or a consumer electronic device, such large font sizes may pose a problem especially if the fonts are expected to be dynamically available in memory for the device's rendering engine. When the size of the required representation file exceeds the resource handling capability of an embedded device, the behavior exhibited by these devices and the resulting user-experience may be non-uniform.
As will be described in greater detail below, efficient methods and systems are provided in which a standard font file for any language is customized to a specific multimedia file, e.g., a movie, such that only those characters that are present in the actual textual elements used by that movie are included in one or more font files. This optimization is expected to reduce the amount of data necessary for each font file as compared to the original font file. While these reductions in absolute terms may appear small relative to the overall high-resolution video file sizes, the impact of the reduction is significant because an entire font file can be available during playback in the local memory of the playback device. This optimization is then further extended for even more limited memory conditions, where smaller font files can be optionally generated for a single movie subtitle, where the fonts files may be dynamically loaded based on the progression of the video and/or audio timeline.
Referring now to the drawings, in
The font file in one embodiment is stored in memory 17 for access by a text-rendering module 19. It should be appreciated that for a successful presentation of the text data, a complete representation of all the characters of the text is provided by the font file. For example, when considering subtitles for specific languages, the font files can be very large as such languages can require a representation in the font file for each individual word. Also, since in many environments it cannot be assumed that the playback system has an existing and efficient way of representing such specific fonts, a large amount of memory may be required to host these fonts during the movie playback.
The rendering module utilizes the decoded text data and the retrieved or accessed font file from memory to provide selected text data along with the decoded video to be combined by a video mixer 20. The combined video is supplied to a display device, stored, transmitted or otherwise provided to be displayed at a later time. In the illustrated embodiment, the font file supplied with the multimedia file is an optimized font file. In other various embodiments, an optimized font file is generated from a font file supplied with the multimedia file and the decoded text data.
The optimized font file contains only the representations that are required for rendering the particular characters used by the different textual elements of an individual multimedia file, e.g., the subtitle information of an individual movie. The representations used in the font may be in form of bitmaps, instructions, mathematical formulas, or other similar techniques utilizing the font file to render the characters in the textual elements of the multimedia presentation. A single textual element may have many unique optimized font files associated with it as required to support the different languages of a multimedia title. In addition to support for different languages, customized and optimized font files may also be created for different stylistic variations (e.g. bold, italics) of a single font. In one embodiment, some implementations include a set of predetermined characters, in addition to the unique characters used by the textual elements of a movie, to be represented by the optimized font file.
However, by limiting the total number of characters to those only used by the multimedia file, e.g., a movie's subtitles, a font file is created that is specifically designed for use by that individual movie, where this font file would not be expected to correctly render the text of another movie. Such tailoring thus reduces the size of the one or more font files, especially in the case of languages that textual characters represent individual words used by the different elements in the multimedia presentation, e.g., the dialogue of the movie. The one or more optimized font file in various embodiments can then be included with the movie, together with the text information, and multiplexed in a way that makes them extractable by a de-multiplexer hardware and/or software module in a decoding system.
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In various embodiments, an optimized font file can be used in cases where an existing font file(s) representing a desired character set is not present or where the accompanied font file has a better representation of the characters used by the movie. For example, some systems may host native fonts which aim at representing a majority of languages that are presented to them. However, the amount of memory required to make a sufficient and accurate representation of the character sets from different languages may be overly burdensome. As a result, certain character sets may be unified in the font file, leading to the undesirable effect of having character representations from one language displayed when the same character appears in a different language, for example, elements of the written Chinese characters which appear in both Japanese and Korean writing, but where each character should be represented with a glyph appropriate to the particular language. Therefore, by generating optimized font files tailored to a specific multimedia presentation that sufficiently and accurately represent the character sets from different languages the amount of memory occupied by such font files is significantly reduced as compared to the original host native font files. Accordingly, the use of unified font files and thereby their undesirable effects can be avoided. It should however be appreciated that unified font files can also be optimized and thus reduced in file size in cases where unified font files are acceptable or further reduction in file size is desired.
The font optimization system and process can also be extended to satisfy various memory and/or timing conditions for various systems. In such embodiments, the font optimization includes a limitation on the maximum size of the font file. As a result, the font file may only partially represent the textual information of the multimedia presentation. For example, in
If it is desirable that the font files all be of an approximate equal size, then the time covered by a font file may vary, e.g., one font file may cover a time period longer than another font file, depending on the amount of conversation occurring as well as the number of unique characters representing those conversations. It may also be desirable to create font files such that they all span an approximately equal amount of time in a movie. In this case, the font files may have different file sizes. A hybrid approach could also be used, where a maximum font file is selected over a fixed time period, and for other time periods the font files are smaller in size. It should be appreciated that there may be exceptions in the uniformity of the font file sizes and/or their time spans depending on their location in the movie and the alignment of the subtitles with respect to the overall video timeline.
The exact representation of fonts in any specific multimedia container standard may differ greatly. One such multimedia standard known as Matroska has provisions for attaching font files and allowing pre-defined elements to specify the association of those attachments with a particular multimedia track such as subtitles. Utilizing the description of this standard for associating a single font to a subtitle track, the same identification mechanism (AttachmentLink) in a Track element may be repeated multiple times to associate multiple fonts with the Track containing the subtitle data. Additionally, an AttachmentStartTime field and AttachmentEndTime field may be added to the description of each individual attachment (AttachedFile) to denote the start and end times for which a font shall be utilized for the rendering of textual elements of a particular subtitle track. Some embodiments may associate a single font file for use by the movie, where AttachmentStartTime may be set to zero and AttachmentEndTime may be set to the time reflecting the entire duration of the movie.
The same standard may not have a specific way of associating other textual elements of the file (such as the movie title or track names) that are not part of the multimedia track hierarchy with a specific font. In one embodiment, with respect to the Matroska specification or format, the association of textual information of the file with an attached font file can be specified in the following manner:
In the above description, the optimized font file is described by a hierarchy of a base Tag element associating an optimized font with a series of textual elements which use the existing Matroska Tag mechanism. In this scheme, the font file is described by the first SimpleTag element as shown above, and the actual binary data of the font may be encapsulated as a TagBinary field. The subsequent Tag elements following the first SimpleTag structure may be used to host all the textual elements related to this particular font description. A second Tag element appearing as the immediate child of the parent Tags may be used to host a second font file and associated textual elements, following the same hierarchical structure.
While the above description contains many specific embodiments of the invention, these should not be construed as limitations on the scope of the invention, but rather as an example of one embodiment thereof. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their equivalents.
This application claims the benefit of U.S. Provisional Patent Application Nos. 61/059,547, filed on Jun. 6, 2008, and 61/109,476, filed on Oct. 29, 2008, the entire disclosures of which are hereby incorporated by reference as if set in full herein.
| Number | Date | Country | |
|---|---|---|---|
| 61059547 | Jun 2008 | US | |
| 61109476 | Oct 2008 | US |
