4. Data Essence Overview Introduction Data Essence System Overview Major Data Essence Concepts.

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1 4. Data Essence 4.1. Overview Introduction This section provides requirements for the subtitle and closed caption data essence. The subtitle specification provides the format of a digital video subtitle track file. The closed caption specification provides the format of timed text data contained within a digital video file/signal. A subtitle file contains a set of instructions for placing rendered text or graphical overlays at precise locations on distinct image frames. A caption file may provide graphical overlays or provide graphical information to a secondary system for display of text. Outside of providing to a secondary system most other parameters are the same as subtitle data essence Data Essence System Overview The general concept of Data Essence within the IMF is to enable the repurposing of the maximum amount of text data and to offer the flexibility to create whatever output file is specified in the OPL. There are two parallel objectives to achieve the flexibility required. The first would be manipulation of XML data from original domestic and international Digital Cinema projects. Pursuit of this approach will provide subtitle source material in a multitude of languages. A secondary, but equally important, objective is to allow the repurposing of any available closed caption data. Allowing for the reuse of this closed caption data is important for the output of any broadcast format files. This objective is also important in order to allow for the reuse of text data for previously released titles, such as library/archive content, for which a Digital Cinema project would not have been created. By pursuing these tandem approaches, it is intended that new release and library titles will receive the maximum amount of texting support. IMF text capabilities are to include subtitle and closed caption output options for all file formats listed in the image essence section 3.1 through as well as the manipulation of that data to provide subtitle and closed caption support for any and all output formats listed in section 8 which details the Output Profile List(OPL). The specific parameters involved in subtitle and caption appearance, synchronization and manipulation will be described in Output Profile List section Major Data Essence Concepts For the purpose of documenting the requirements and specifications for Data Essence, it is helpful to divide the system into a set of components. The specifications and requirements for each of these components will be described in the following sections: Subtitles o A subtitle track file contains a set of metadata and a set of subtitle structures which encode the content and temporal/spatial locations of subtitles to be displayed over a primary image. It is understood that this data will be output as a file and that the data in that file will remain related to associated video but that the information is not included as part of a video image file.

2 Captions o Generated data associated with video and intended for optional decode by consumer display devices which are equipped with caption decoders. The resulting text information, generated by the decoding unit, is displayed at specified times during the playback of an image file. For the purpose of the IMF we are specifically referencing timed text formats conforming to the CEA-608 and CEA-708 specifications which will identified further below Data Essence Fundamental Requirements Common File Formats The Essence and Data Essence is required to use a common standardized file format for each element (image, audio, subtitles, etc.). The image essence file format is required to be an SMPTE-conformant file based on existing SMPTE standards. The audio essence file format is required to be based on Broadcast Wave. The Subtitle essence should be based on PNG and XML file formats Frame Rates The image structure is required to support all the frame rates listed in both section 3 which details the Image Essence and section 8 which details the Output Profile List. The frame rate of any individual IMF source master is required to remain constant. Metadata is carried in the image data file format to indicate the frame rate Synchronization Files within the image and/or audio essence are required to carry information to provide for frame-based synchronization between each file. Both the timed text and subtitle functions are required to synchronize with the image file at any point. It is required that an IMF device establish correct location and synchronous playback while taking into account frame rate and editing decisions listed in the OPL Subtitle/Caption Concepts and Requirements Sub picture (Pre-rendered open text and/or graphics) Description A sub picture data stream is a multiple-image data stream intended for the transport of supplemental visual data to a pre-existing digital image. The data is designed for graphic overlay of the main image and for output to a file format specified by the OPL.(See Section 8) It can be designated as open display and/or closed display depending on the output format specified. The sub picture data stream, when employed, will typically be used for the transport of subtitle data. File Format Sub picture data is required to be encoded as a standardized, XML-based document. Such a standard is required to define both timed text and sub picture encoding methods allowing mixed-media rendering. Sub picture frames are required to be encoded as [ISO/IEC 15948:2004] PNG files. Rendering Intent PNG files are required to be pre-rendered at multiple resolutions. The subtitle resolutions rendered and associated with a given title will determine the options available in the OPL. The system must be able to match the color space and pixel

3 matrix of the pre-rendered PNG files with the corresponding output parameters designated by in the OPL in order to create a given output file. Down sampling is not desired as the loss of resolution will negatively impact the quality of the PNG image. Frame Rate and Timing The XML navigation file specifies the temporal resolution of the sub picture file. A Frame count, Time In, Time Out, Fade Up Time and Fade Down Time, which correspond to the image, shall be included. The sub picture frame rate shall be equal to the frame rate of the associated image Essence and will be modified by the system to match whatever output is specified by the OPL. Synchronization The equipment or system that encodes or decodes the sub picture file is required to ensure that temporal transitions within the sub picture file are correctly synchronized with associated output files Timed Text (Presentation of text in sync with audio and video) Description Timed Text is text information that is displayed at specified times during the playback of an image file. File Format For the IMF, Timed Text data would, ideally, be encoded as a standardized, XMLbased document which could then be input into an IMF system in an identical manner to Digital Cinema subtitle data. It is understood, however, that previously released content, as well as broadcast content, may have timed text available in a multitude of formats and at lower resolutions. Therefore, in addition to an XML-based document, it is the intent of the IMF to accept timed text data into the system in formats conforming to the CEA-608 and CEA-708 specifications. This would include many of the pre-existing closed caption file formats, the inclusion of caption data in an existing video signal from tape and/or capture of the caption data from an existing video signal. It is understood that this will limit the available resolution of text ingested in this manner but will provide flexibility for all down stream resolutions and output formats. Default Fonts Font files are required to be used to render Timed Text for subtitle applications. Font files can be used to render Timed Text for subtitle and/or caption applications. When used, font files are required to conform to [ISO/IEC OpenType6]. Timed Text files are required to be accompanied by all font files required for reproduction of the Timed Text. The Timed Text file format is required to support a default character set. It is required that there be a default Unicode character set and a default font for that character set. In the event that an external font file is missing or damaged, the subtitle rendering device is required to use a default font supplied by the manufacturer. The default character set is required to be a Unicode ISO Latin-1 character set. The default font is required to conform to [ISO/IEC OpenType] and support the ISO Latin-1 character set. Identification The Timed Text format requires the cardinal language of the text to be identified.

4 Searchability A pure text stream is encouraged to isolate content from rendering markup for searchability. Multiple Captions The Timed Text format shall allow the display of multiple captions simultaneously. There shall be a maximum number of 3 lines of text allowed for simultaneous display. Note: This allows for spatial representation for captions when two people are talking simultaneously. Synchronization The equipment or system that encodes or decodes the Timed Text file is required to ensure that temporal transitions within the data stream are correctly synchronized with associated data streams. The timed text function is required to synchronize with the image at any point. It is required to establish correct location and synchronous playback while taking into account frame rate and editing decisions listed in the OPL Subtitle Specification Textual representation of the audio track, usually just the dialog and usually in a language other than the audio track dialog, intended for foreign language audiences. Assumes the viewer can hear but may not understand the audio language. For the purposes of the IMF, subtitles can be one of the following: Rendered in a specified font (Timed Text) and overlaid by the system Pre-rendered PNG bitmaps (sub picture) Pre-composited into the source image files (burned-in to the source video) (Only acceptable if no other source exists) 4.3. Caption Specification Caption Types: Closed Captions Indicates that not all viewers can see the text. The playback device must be activated in order for the text to be visible. Assumes the viewer cannot hear the program audio and therefore all pertinent audio information is described. Delivered to consumers as part of the video signal and decoded by the display device. Open Captioning Text is visible to all viewers and cannot be removed or turned off. This would mean that the text is burned in to the video. Delivered as part of the video Specific Compliance Requirements Adherence to and compatibility with: o CEA-608-E ANSI CEA Line 21 Data Services Specification and

5 o CEA-708-D DTV Closed Captioning Specification Website: type=committee&committeeid= &name=r4.3%20television %20Data%20Systems%20Subcommittee