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Blu-ray Disc Rewritable Application Format
Shawn Dave
Tape4Backup
The Blu-ray Disc Rewritable (BD-RE) Application Format consists of File System Standard, Application Standard and Content Protection System. The file system standard defines the format for recording data to disc and the file management system. Application standard defines the data structure of the file and the mechanism for stream management and user presentation. The content protection system defines copyright protection functions.
There are three physical standards of BD standard: BD-Recordable (BD-RE), BD-Pre-recorded (BD-ROM) and BD-Write Once (BD-R). The "BD-RE" consists of a file system standard and an application standard. The BD-RE Application Format has advantage over other disc formats because of disc features like ease-of-use and ease-of-editing. It also enables digital terrestrial broadcasts and BS digital to be recorded and stored while the original picture quality is maintained.
The BD-RE application format provides the facility to record digital broadcasts including high-vision programmimg while maintaining the original picture quality. This recording can be up to 2 hours on a single layer disc and up to 4 hours on a dual layer disc. Long time recording of analog broadcast can also be done, like SD standard definition programs. In SD programs approximately 12 hours can be recorded on a single-layer disc or approximately 24 hours on a dual-layer disc with picture quality that is equivalent to that of VHS standard mode.
The BD-R application format provides direct recording of DV contents from the DV terminal of the camcorder with no picture deterioration and has user interface that supports recorded content management in a visual manner. In this format data allocation management achieves seamless recording and playback of contents. This format also provides content copyright protection and management by using copy protection technology.
The recording of digital broadcasts in BD-RE Format
The BD-RE Application's recording format adopts MPEG-2 TS (Transport Stream) for stream multiplexing and MPEG-2 video for video codec. For multiplexing in DVD Video, it employs MPEG-2 PS (Program Stream). In comparison with MPEG-2 PS, MPEG-2 TS has a small packet size fixed at 188 bytes; it can multiplex multiple channels and EPG (Electronic Program Guide) information and is altogether more suited to broadcasting. The BD-RE Application Format enables transport streams of digital broadcasts to be recorded as they are without altering the format.
In current BS digital broadcasting systems, a single transponder is occupied by two or four transport streams and multiple programs (that is channels) are multiplexed in a single transport stream. A transport stream like this that is used for broadcasting and contains multiple programs is known as a full transport stream . The partial transport stream is made from the full transport stream which is done by extracting the audio/data/video components of a particular program and reconfiguring the Program Specific Information/Service Information (PSI/SI), information which describes the programs. The audio/data/video components of unwanted channels would also be recorded and use up the recording area, if a digital broadcast recorder were to record a full transport stream in its original form. The conversion from full to partial transport stream is an important process for the recorder. This conversion process allows the recording area to be used efficiently by lowering the recording rate.
The time intervals between packets are not always the same in a partial transport stream which is reconstructed from the necessary packets extracted from the full transport stream. These packet intervals are determined by the buffer model. The packets must be observed when the packets are input to the demultiplexer /decoder or else the buffer will overflow or underflow and data will not be decoded correctly. In order to overcome this problem, a header is added to each TS packet during recording to indicate the time that the TS packet arrived at the Transport stream-System Target Decoder (T-STD). TS packet attached with its packet arrival time is called a source packet under the BD-RE Application Format. During playback, the packet intervals before recording are reproduced accurately based on the packet arrival times recorded in the source packet headers and the packets are then output to the T-STD or to outside the device.
When recording a transport stream to disc, the information of other programs and other unwanted information are deleted from the PSI/SI and the information reconfigured and the recording is processed in accordance with copy control information; however, no changes are necessary at the coded data level (elementary stream) such as down-converting or re-encoding which affect picture and sound quality. This is how the BD-RE Application Format enables recording of Hi-Vision video, which can have a maximum bit rate of 24Mbps, and multi-channel audio while keeping the original broadcast quality.
The BD-RE Application Format also supports the recording of BS digital data broadcasts written in BML (Broadcast Markup Language ). BML is a language based on XML. A data broadcast is made up of several files and consists of video/audio elements and a program that controls these elements. The files are segmented into sections, a format defined by MPEG-2 TS. These sections are transmitted repeatedly by the broadcast station in predetermined cycles (data carousel transmission). The receiver obtains one cycle of data beginning from a certain time and extracts the data in its internal memory to restore the files and execute the program. The data broadcast is recorded in MPEG-2 TS format without being separated into files because the timing of data multiplexing at the time of broadcast is retained under the BD-RE Application Format.
EPG is a convenient feature of digital broadcasting . The EPG is reconstructed from the PSI/SI multiplexed in the full transport stream. When recording to disc, the necessary information of recorded program is extracted from the PSI/SI and program information is reconstructed in a table called SIT and recorded. This makes it possible to view detailed program information even during playback. The partial transport stream is also used as the multiplexing format for MPEG-2 streams that pass through i.LINK. Transport streams that are input to the BD-RE recorder from an external digital broadcast receiver via i.LINK can also be recorded without picture/audio deterioration. In addition to digital broadcasting in Japan , there is DTV in America and DVB in Europe ; partial transport stream recording is a highly adaptable recording format which can also be applied to these broadcasting systems.
The SESF (Self-Encoded Stream Format) of BD-RE Format
A format for encoding analog input signals called SESF has been established in response to demands for a format that enables users to dub video recorded on VTR and reuse streams that are encoded for DVD. In addition to HD digital broadcasts, SESF makes it possible to play/record current analog broadcasts efficiently. It also provides compatibility between BD devices. SESF conforms to the MPEG-2 TS systems standard (ISO/IEC 13818-1). SESF is limited to the streams that are required for encoding NTSC (or PAL) video input signals. The standard MPEG decoders such as BS digital receivers can be used to decode the video stream of SESF.
SESF recorded streams are defined as audio, video and teletext streams. The elementary data of SESF are audio (MPEG-1 audio), video (MEPG-2 video), dolby (AC-3 audio) , linear (PCM audio), teletext (supported for PAL), tip data (Tip TS).
Video signals with the resolutions given below can be used and NTSC and PAL video signals are guaranteed to be recorded at sufficient resolutions
720 x 480 ,704 x 480, 544 x 480, 480 x 480, 352 x 480, 352 x 240 (Resolution under 525/60)
720 x 576 ,704 x 576, 544 x 576, 480 x 576, 352 x 576, 352 x 288 (Resolution under 625/50)
The NTSC signals can be recorded at a maximum resolution of 720x480 pixels, which is equivalent to that of DVD packaged media.
The BD-RE format's compatibility with MPEG-2 PS
The stream recording format adopted by the BD-RE Application Format is based on MPEG-2 TS, the format used in digital broadcasts. Digital video recording devices such as DVD recorders use the MPEG-2 PS format, which is not directly compatible with the MPEG-2 TS format. In order to achieve a higher level of compatibility with existing digital video recording devices and to utilize existing video sources, the BD-RE Application Format defines a method for transcoding from a program stream to a transport stream and vice versa. The stream used for this conversion is called the constrained SESF. The Constrained SESF handles 11 TS packets as a single unit called a multiplexing unit. A multiplexing unit holds up to 2048 bytes of valid data and can be converted to a program stream and recorded in a 2048-byte sector.
An SESF capsule is a grouping of video and audio data that consist of one or more GOPs (Group of Pictures) and has been designed to enable playback and editing in units of SESF capsules. A Tip packet and PAT, PMT are inserted at the beginning of the SESF capsule. The Tip packet contains display information such as the aspect ratio of the video data in the stream, CGMS such as the copy control information, and coding information such as the video resolution, and so on. All of this information makes it possible to quickly identify the decoding method before decoding the data. During skip or high-speed playback, video data can be easily decoded by starting playback from the beginning of the SESF capsule. As a medium that records and plays all broadcasts, the BD-RE disc will enable a smooth transition from DVD and other existing recording media.
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ShawnPaul
Tape4backup.com,
34972 Newark Blvd, # 501 , Newark CA 94560
Tel : 888-491-4949
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Article submitted Friday, May 23, 2008
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