Blu-ray Disc Format - DISC Archiving Systems

Blu-ray Disc Format - DISC Archiving Systems
Part3e040701rev-Final-040711.doc
White paper
Blu-ray Disc Format
2.A Logical and
Audio Visual Application
Format Specifications
for BD-RE
August 2004
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INDEX
3. The Logical and Application for Blu-ray Disc Rewritable Specifications
3.1 Blu-ray Disc Rewritable Application Format
3.1.1 Overview
3.1.2 Recording of Digital Broadcasts
3.1.3 Support of Analog Broadcasts
3.1.3.1 Self-Encoded Stream Format (SESF)
3.1.3.2 Compatibility with MPEG-2 PS
3.1.4 Direct Recording of DV Input
3.1.4.1 Overview
3.1.4.2 DV Stream Recording Format
3.1.4.3 Random Access Method
3.1.4.4 Minimum Extent Size
3.1.5 User Interface
3.1.6 Editing
3.1.6.1 Seamless Connection Editing
3.1.6.2 Audio Dubbing
3.1.7 Blu-ray Disc File System (BDFS)
3.1.7.1 A File System Suited to Video/Audio Stream Recording
3.1.7.2 Continuous Data Supply by Extents
3.1.8 Copy Protection System (CPS)
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3.1 Blu-ray Disc Rewritable Application Format
3.1.1 Overview
The Blu-ray Disc Rewritable (BD-RE) Application Format consists of: part2:File System Standard which
defines the format for recording data to disc and the file management system; part3:Application Standard
which defines the data structure of the file and the mechanism for stream management and user
presentation; and part4:Content Protection System which defines copyright protection functions.
BD-RE
BD-ROM
BD-R
(Rewritable)
(Prerecorded)
(Write once)
BD-RE
BD-RE
BD-ROM
BD-ROM
BD-RE
BD-RE
BD-ROM
BD-ROM
BD-RE
BD-RE
BD-ROM
BD-ROM
Application
Standard
(Part-3)
(Part-3)
File System
Standard
(Part-2)
(Part-2)
Physical
Standard
(Part-1)
(Part-1)
(Part-3)
(Part-3)
(Part-2)
(Part-2)
(Part-1)
(Part-1)
BD-R
BD-R
(Part-1)
(Part-1)
Figure 3.1.1.1: Structure of the BD Standard
The BD standard consists of three physical standards: 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. BD-RE consists of a file system
standard and application standard. BD-RE standard ver. 1.0 is complete, while
BD-ROM standard is under deliberation.
Since the commencement of BS digital broadcasting, digital Hi-Vision programs can be enjoyed on
several channels in Japan. And when terrestrial broadcasting is digitalized in the near future, digital
Hi-Vision broadcasting should spread to even more homes. The BD-RE Application Format takes advantage
of characteristic disc features such as ease-of-use and ease-of-editing and enables BS digital and digital
terrestrial broadcasts to be recorded and stored while maintaining the original picture quality. Making full
use of the large capacity and high transfer rate of the BD-RE disc, the BD-RE Application Format has been
designed to achieve the following:
• Recording of digital broadcasts including high-vision programmimg while maintaining the original
picture quality—up to 2 hours on a single-layer disc and 4 hours on a dual-layer disc
• Long time recording of analog broadcasts such as standard definition (SD) programs (With a picture
quality that is equivalent to that of VHS standard mode, approximately 12 hours can be recorded on a
single-layer disc or approximately 24 hours on a dual-layer disc.)
• Seamless, non-destructive editing which takes advantage of disc features
• Direct recording of DV contents from the DV terminal of the camcorder with no picture deterioration
(option)
• User interface that supports recorded content management in a visual manner
• Data allocation management which achieves seamless recording and playback of contents
• Content copyright protection and management by using copy protection technology
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Capacity and Recording time
Dual layer: 50GB
30
Single layer: 25GB
Multiplexing rate (Mbps)
DV: 28.8Mbps
25
BS digital HDTV: 24Mbps
20
15
SD(High quality): 15Mbps
10
SD(equivalent to VHS
SP mode): 4Mbps
5
0
0
10
20
30
40
50
Recording Time (Hour)
Figure 3.1.1.2: Relation between Capacity and Recording time
3.1.2 Recording of Digital Broadcasts
The characteristic of the recording format under the BD-RE Application Format is its adoption of MPEG-2
video for video codec and MPEG-2 TS (Transport Stream) for stream multiplexing.
DVD Video, on the other hand, employs MPEG-2 PS (Program Stream) as its multiplexing format. 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 called a full transport
stream (Fig. 3.1.2.1). On the other hand, a partial transport stream is made from the full transport stream
by extracting the video/audio/data components of a particular program and reconfiguring the PSI/SI
(Program Specific Information/Service Information), information which describes the programs.
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(A) ES (Elementary stream) outputed from Encoder
Video ES V1
Audio ES A1
(B) PES (Packetized elementary stream)
PES packet header
Channel 1
PES packet
Video PES V1
Audio PES A1
Channel 2
Video PES V2
Audio PES A2
PAT
PMT
TS packet
188bytes
V1
V2
A1
V2
V1
V1
A2
TS packet header
(C) Example of MPEG-2 TS into which Channel 1 and Channel 2 are multiplexed
Figure 3.1.2.1: MPEG-2 Transport Stream that multiple channels are multiplexed
If a digital broadcast recorder were to record a full transport stream in its original form, the
video/audio/data components of unwanted channels would also be recorded and use up the recording
area. The conversion from full to partial transport stream is an important process for the recorder, as this
process lowers the recording rate and allows the recording area to be used efficiently (Fig. 3.1.2.2).
MPEG-2 Full TS
MPEG-2 Partial TS
PSI/SI
PSI/SI
PAT
EIT
PAT
PMT
PMT
PMT
PMT
SIT
Full – Partial
Conversion
Program 1
Program 1
Video 1
Audio 1
Program 2
Video 2
Audio 2
Program 3
Video 3
Audio 3
Video 1
Audio 1
Figure 3.1.2.2: Conversion from Full TS to Partial TS
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As shown in Fig. 3.1.2.3, in a partial transport stream which is reconstructed from the necessary
packets extracted from the full transport stream, the time intervals between packets are not always the
same. These packet intervals are determined by the buffer model and they 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. For this reason, a header is added to each TS packet during recording to indicate
the time that the TS packet arrived at the T-STD (Transport stream-System Target Decoder). Under the
BD-RE Application Format, a TS packet attached with its packet arrival time is called a source packet.
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 (Fig. 3.1.2.4 and Fig. 3.1.2.5).
Input from BS digital tuner
Inputted Full TS1
TS packets lined up contiguously with fixed rate
Time
Full-Partial Conversion
Partial TS with one program
TS packets are discretely located in a line on a time-axis
Time
Buffer Memory
Wait
Recording
Adding
Time stamp
Recording
until enough data is
accumulated in the buffer.
PSI/SI
Intermittent
recording
TS packet for Program1
To maintain the input time of TS to
decoder system, time stamp is added
to every TS packet. These TS
packets are stored into Buffer
Memory and the packet interval is
narrowed and they are recorded
intermittently.
TS packet for Program2
Disc
TS packet for Program2
Time stamp indicating input timing of its
TS packet to decoder system
Figure 3.1.2.3: Data flow until the inputted Transport Stream is recorded to the disc
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Transport Stream
packet
(MPEG-2 TS)
Input from
external digital
STB, or
Output of
internal encoder
27MHz
PLL
t(i)
Transport Stream
System Target
Decoder
27MHz
CLK
Display
device
Counter for
arrival time
clock
arrival_time_clock(i)
PCR
t(i)
Source
packetizer
RMAX
Source
packet
Write
Buffer
RUD
BD
Drive
t(i): time when i-th byte of the Transport stream is entered
arrival_time_clock(i): value of the Counter for arrival time clock at the time, t(i)
RMAX: transfer rate of Source packet from Source packetizer
RUD: data recording rate to BD drive
Figure 3.1.2.4: Recorder model for MPEG-2 TS
27MHz
CLK
27MHz
Clock
generator
Counter for
arrival time
clock
Load
initial counter value
BD
drive
R UD
Read
Buffer
R MAX
Source
packet
arrival_time_clock(i)
Source
de-packetizer
R TS
Transport Stream packet
(MPEG2 TS)
Output (to external device)
Transport Stream
System
Target Decoder
Display
device
arrival_time_clock(i ):
value of the Counter for arrival time clock at the time when
i -th byte
in the Transport Stream is outputted from Source de -packetizer
R
R
: read data rate from BD drive
UD
: read rate of Source packet from Read Buffer
MAX
R : mux_rate of the Transport Stream
TS
Figure 3.1.2.5: Player model for MPEG-2 TS
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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 as shown in Fig. 3.1.2.6, and multi-channel audio while keeping the original broadcast
quality.
Video
Profile and
Effective
Level
number of
pixel number
scanning lines
[email protected]
1080i
[email protected]
Horizontal
aspect ratio
bitrate
1920,
1440
16:9
24Mbps max
720p
1280
16:9
24Mbps max
[email protected]
480p
720
16:9
24Mbps max
[email protected]
480i
720, 544,
16:9 or 4:3
15Mbps max
480
Coding
MPEG-2 AAC LC profile
Channel
5.1channel max
bitrate
Stereo
144kbps max
HiFi stereo
(Compression mode B)
192kbps∼256kbps
Multi-channel
384kbps max
Audio
fs
48kHz, (32kHz is possible for Digital Radio service)
Figure 3.1.2.6: Video/Audio format of Japanese BS Digital Broadcast
The BD-RE Application Format also supports the recording of BS digital data broadcasts written in BML,
a language that is 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, and 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. Because the timing
of data multiplexing at the time of broadcast is retained under the BD-RE Application Format, the data
broadcast is recorded in MPEG-2 TS format without being separated into files.
A convenient feature of digital broadcasting is EPG. 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.
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3.1.3 Support of Analog Broadcasts
3.1.3.1 Self-Encoded Stream Format (SESF)
Although the BD-RE Application Format was designed for recording and playing back high-definition (HD)
digital broadcasts, the format must also be capable of recording/playing analog broadcasts until all
broadcasts make the transition to digital. Also, in response to demands for a format that enables users to
dub video recorded on VTR and reuse streams that are encoded for DVD, a format for encoding analog
input signals called SESF has been established.
SESF makes it possible to record/play current analog broadcasts efficiently in addition to HD digital
broadcasts, and also guarantees compatibility between BD devices.
SESF conforms to the MPEG-2 TS systems standard (ISO/IEC 13818-1) and is limited to the streams
that are required for encoding NTSC (or PAL) video input signals. Thus, the video stream of SESF can be
decoded by standard MPEG decoders such as BS digital receivers.
As shown in Fig. 3.1.3.1.1, SESF recorded streams are defined as video, audio and teletext streams.
Video
Audio
Teletext
Tip data
MEPG-2 video
MPEG-1 audio
Dolby AC-3 audio
Linear PCM audio
supported for PAL
Tip TS
Figure 3.1.3.1.1: Elementary data of SESF
Video streams are encoded in MPEG-2 [email protected] format and recorded on a BD disc.
Video signals with the resolutions shown in Fig. 3.1.3.1.2 and Fig. 3.1.3.1.3 can be used and NTSC and
PAL video signals are guaranteed to be recorded at sufficient resolutions. NTSC signals can be recorded at
a maximum resolution of 720x480 pixels, which is equivalent to that of DVD packaged media.
720 x 480
704 x 480
544 x 480
480 x 480
352 x 480
352 x 240
720 x 576
704 x 576
544 x 576
480 x 576
352 x 576
352 x 288
Figure 3.1.3.1.2: Resolution under 525/60
Figure 3.1.3.1.3: Resolution under 625/50
SESF provides three types of recording formats for audio streams ranging from a low bit rate to high
audio quality, as shown in Fig. 3.1.3.1.4.
CODEC
MPEG-1 Layer 2
Dolby Digital
LPCM
fs
48 kHz
48 kHz
48 kHz
bits per sample
16, 20, 24 bits
channel
2 ch
5.1 ch max
2 ch
bitrate
32 kbps – 384 kbps
64 kbps – 448 kbps
1.536 Mbps – 2.304 Mbps
Figure 3.1.3.1.4: Audio CODEC for SESF
The first audio format is MPEG-1 Layer-2, which is widely used in general consumer equipment (e.g. DTV
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STB) and is suited to recording at comparatively low bit rates. The Dolby Digital (AC-3) format is the
standard used in US satellite broadcasts and DVDs and allows relatively high-quality audio recording. In
addition to these two formats, SESF provides a linear PCM format (optional) that supports 2-channel linear
PCM recording of up to 48kHz, 24 bits for audio recording of even higher quality than that of existing CD
and DVD recorders.
3.1.3.2 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. However, some 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, shown in Fig.
3.1.3.2.1 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.
Figure 3.1.3.2.1: Stream of Constrained SESF
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 described above, not only does the BD-RE Application Format enable recording of high-resolution HD
digital broadcasts but the format has been designed to support analog broadcast recording and the
utilization of existing video sources. 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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3.1.4 Direct Recording of DV Input
3.1.4.1 Overview
Taking advantage of the BD-RE drive’s high user transfer rate (36Mbps), the BD-RE Application Format
provides an optional functionality of recording DV streams (28.8Mbps) to BD-RE disc via the i.LINK.
BD recorders that support this functionality enable users to record video material taken with a DV
camcorder on BD-RE disc and take advantage of non-linear editing and other functions characteristic of
disc media.
3.1.4.2 DV Stream Recording Format
The recording format for the DV stream conforms to the DVCR digital interface standard (IEC 61883-2)
(Fig. 3.1.4.2.1). The DV stream received through i.LINK is not re-encoded but recorded directly to disc, with
aligning the beginning of the DV stream with the logical sector boundary, as shown in Fig. 3.1.4.2.2(a).
Data in one frame
DIF sequence
DIF seq. 0
Structure of
DIF sequence
Header
DIF Block
DIF seq. 1
Subcode
DIF seq. n-1
VAUX
DIF Block 0 DIF Block 1 DIF Block 2
Structure of
DIF Block
ID
3 bytes
120,000 bytes (525 / 60)
144,000 bytes (626 / 50)
n=10 (525 / 60)
n=12 (626 / 50)
Audio and Video
DIF Block 148 DIF Block 149
Data
77 bytes
DIF: Digital Interface
Figure 3.1.4.2.1: Data structure of DV stream
(compliant with digital interface standard for DVCR)
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Portion
to be deleted
(a) First recording
120,000 bytes (525 / 60)
144,000 bytes (626 / 50)
#N-1
#N
#N+1
DV stream file
Data allocation
on a disc
Frame No.
Frame No.
#0
DV stream
#N
#0
Sector boundary
Relative address
from the top of file
(unit in bytes)
Logical sector
(b) After delete-operation
DV stream
削除
フレーム
#N
#N+1
DV stream after delete-operation
Data allocation
on a disc
S
Figure 3.1.4.2.2: DV stream on Disc
Also, as well as MPEG-2 TS recording, a Clip information file in which DV stream property information is
stored is created for each stream file. Since the DV stream and MPEG-2 transport stream have different
structures, a Clip information file that provides basic information for random access is defined for DV
stream. In this way, differences in stream structure are absorbed by the Clip information file so that the
PlayList as a top-layer of DV and MPEG-2 TS uses the same data structure.
Fig. 3.1.4.2.3 shows the directory and file structures. DV stream files are stored in the /BDAV/STREAM
directory as are TS files. DV stream files have the extension “dvsd” and are accordingly distinguished from
TS files. Clip information files and PlayLists are stored in the same directories as for TS files,
BDAV/CLIPINF and /BDAV/PLAYLIST respectively.
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root
BDAV
info.bdav
PLAYLIST
01001.rpls
02002.rpls
99999.vpls
CLIPINF
01000.clpi
02000.clpi
Clip Information file
corresponding to the DV stream file,
02000.dvsd
03000.clpi
STREAM
01000.m2ts
02000.dvsd
DV stream file
03000.m2ts
Figure 3.1.4.2.3: Stream file and Clip Information file for DV in BDAV
directory
3.1.4.3 Random Access Method
Since the video compression method adopted by the DV format is intraframe coding, each frame in the
DV stream has a fixed number of bytes (525/60:120,000byte, 625/50:144,000byte). Therefore, the
addresses of the frame data corresponding to the playback start and end times specified in the PlayList
can be obtained using a simple calculation.
As shown in Fig. 3.1.4.2.2(a), the frame numbers counted from the beginning of the file and their
relative addresses are proportional to each other and this relationship can be used to easily obtain the
relative address of a random access point.
This is why with the Clip information file for a DV stream there is no need to create a table (CPI) for
random access such as EP_map or TU_map (see 3.1.5), which are required for MPEG-2 TS recording.
With linear editing, there may be cases where part of the DV stream file is removed (for instance, frames
#0 to #N-1 in Fig. 3.1.4.2.2(a)). Because files are managed in logical sector units by the file system, after
part of the file is removed, the beginning of the first frame will be offset from the beginning of new file, as
indicated by the dark shade in Fig. 3.1.4.2.2(b). In this case, offset information S and the new top frame
number #N are recorded in the Clip information file so that there is no need to shift stream data or add
changes to the PlayList.
3.1.4.4 Minimum Extent Size
In general, the minimum extent size for recording needs to be defined in order to achieve seamless
recording and playback. Because the DV stream has a comparatively high transfer rate of 28.8Mbps, the
minimum extent size must be sufficiently large. The BD-RE Application Format provides for two minimum
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extent sizes according to stream rate so that streams with a lower transfer rate than the DV stream can be
recorded in an efficient manner. Defining the minimum extent size in this way makes seamless playback
possible.
If part of a stream is removed, as described above, the stream may end up with sections that do not
meet the conditions for contiguous recording required for seamless playback. However, even in this case,
seamless playback can be achieved after part of the DV stream is removed by using the bridge sequence
described later.
3.1.5 User Interface
Fig. 3.1.5.1 shows a conceptual diagram of stream management under the BD-RE Application Format.
Stream management consists of two main layers, the PlayList layer and the Clip layer. The PlayList is a
unit that represents a grouping of video/audio data to the user. For instance, a sequence of video/audio
data from recording start to end constitutes a single PlayList and PlayList construction information is
recorded as a single PlayList file. Only the PlayList layer can be seen from the user.
Management structure for
Blu-ray Disc Rewritable Application
Real PlayList
Real PlayList
Virtual PlayList
PlayItem
PlayItem
PlayList layer
Time
Clip Layer
Time to
Byte address
conversion
Stream data
for seamless
connection
Clip Information file
Clip Information
file
Clip Information
file
Clip AV stream
Clip AV stream
Clip AV stream
Clip
Bridge Clip
Byte
Clip
Figure 3.1.5.1: Management structure of stream in BD-RE Application format
The layer below the PlayList layer is the Clip layer which manages AV stream files. The Clip layer consists
of AV stream files which store actual video/audio stream data and Clip information files that correspond
one to one with Clip AV streams.
The Clip information file is composed of database which contains the information of non-contiguous
STC points and program information regarding MPEG-2 TS, and stream’s characteristic point information
(CPI), and so on. The CPI is entry point information and is used to achieve high-speed random access and
variable-speed playback.
First, the BD-RE Application Format assumed streams to be variable bit-rate MPEG video and defined an
EP_map (Fig. 3.1.5.2) to store the byte positions in the file from which decoding can be started, such as
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the beginning of a GOP. From this table, which defines the relationship between pts and the source packet
numbers representing byte positions in the file, the address within the file for a specific time can be known
immediately even for VBR (Variable Bit Rate) encoded streams. The BD-RE Application Format also defined
a TU_map (Fig. 3.1.5.3) for recording transport streams other than MPEG video.
pts(x1)
pts(y1)
pts(z1)
pts(y2)
pts(x2)
pts(z2)
Clip
AV stream
pts(yn)
pts(zm)
pts(xk)
...
X1
X2
Y1
SPN
(Source packet No.)
Xk
Y2
Yn
Z1
Z2
Zm
Source packet which contains the first byte of the Sequence header
video_PID=x
Source packet which contains the first byte of the Sequence header
video_PID=y
Source packet which contains the first byte of the Sequence header
video_PID=z
EP_map
EP_map1
EP_map2
PID of the stream = x
Number of Entry points = k
PID of the stream = y
Number of Entry points = n
PID of the stream = z
Number of Entry points = m
pts of the SPN of the
Entry point Entry point
pts of the SPN of the
Entry point Entry point
pts of the SPN of the
Entry point Entry point
pts(x1)
pts(x2)
...
pts(xk)
X1
X2
...
Xk
pts(y1)
pts(y2)
...
pts(yn)
Y1
Y2
...
Yn
EP_map3
pts(z1)
pts(z2)
...
pts(zm)
Z1
Z2
...
Zm
Figure 3.1.5.2: Example of EP_map
This example shows that three Video elementary streams are contained in one TS
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TU_time_base
arrival_end_time
:
arrival_start_time
...
time_unit_size
Arrival
time clock
TU_map
Time of 1 time_unit
offset_arrival_time(Time at starting point)
offset_ arrival_time
=TU_start_time #0
TU_start_
time #1
time_unit #0
TU_start_
time #2
...
time_unit #1
input
transport
packets
SPN_time_unit_start #0
SPN_time_unit_start #1
SPN_time_unit_start #2
TU_start_
time #N
time_unit #N
transport
packet
SPN_time_unit_start #3
:
:
:
...
Arrival
time clock
ATC-sequence
...
source packet
SPN (Source packet number)
SPN_
time_unit
start #0
SPN_
SPN_
time_unit time_unit
start #1
start #N
Figure 3.1.5.3: Example of TU-map
In case a stream is recorded, the source packet number of which the packet
arrives first within a certain time interval defined as a time_unit is stored.
SPN_time_unit is the relative byte position in a file.
When the TU_map is used, time access is performed in units of time_unit and becomes less precise;
however, random access operation of arbitrary transport streams becomes possible. The EP_map together
with the TU_map are called CPI. These databases are created by the recorder when it records the stream.
The PlayList is a sequence of play-items. A play-item is a set of IN, OUT points that represent the
playback time range within a Clip. PlayLists are created automatically whenever a new recording is made;
these PlayLists are called real PlayLists. “Real” indicates that the PlayList is created one to one with a Clip
at the same time as the Clip is recorded.
PlayLists can be generated by editing operations in addition to when new recordings are made. One
method of editing is to add a change such as divide, combine, or delete (Fig. 3.1.5.4 to an existing PlayList.
Editing may result in many-to-many relations between real PlayLists and Clips but the valid part of the clip
is always referenced by a real PlayList. Deleting a real PlayList means the Clips which the PlayList refers to
are also erased from the disc.
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(1) PlayList and Clip before editing
(2) Divide-operation
Real PlayList
Real PlayList
Clip
Clip
Divide point
Real
PlayList
Real PlayList
No change in Clip layer
Clip
Clip
(3) Combine-operation
Real
PlayList
Combine
Real
PlayList 1
Real
PlayList 2
Clip 1
Clip 2
Real PlayList1
Clip 1
No change in Clip layer
Clip 2
(4) Partial deletion
Delete a portion of Real PlayList
A portion of Clip
corresponding to
partial deletion is
deleted
Real PlayList
Real PlayList
Clip
Clip
Figure 3.1.5.4: Example of editing
There is also the option of creating a new PlayList without altering an existing PlayList. Under the BD-RE
Application Format, this is referred to as creating a virtual PlayList (Fig. 3.1.5.5).
IN1
OUT1
IN2
OUT2
Real PlayList 1
Real PlayList 2
Clip 1
Clip 2
Making a Virtual PlayList which consists of
IN1-OUT1 portion of Real PlayList1 and
IN2-OUT2 portion of Real PlayList2
Virtual PlayList
IN1
PlayItem
OUT1
IN2
OUT2
PlayItem
Real PlayList 1
Real PlayList 2
Clip 1
Clip 2
Figure 3.1.5.5: Creation of Virtual PlayList
New PlayList can be made without any change in existing PlayLists
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The virtual PlayList is a sequence of play-items that reference parts of other PlayLists; bridge sequences,
described later, are used to achieve seamless playback even with non-destructive editing.
The BD-RE Application Format provides many other functions to improve ease-of-operation, such as
thumbnails, marks, write protection, and playback-lock of individual discs using passwords.
Thumbnails are small still images and represent directory and PlayList contents in a visual manner.
Under the BD-RE Application Format, thumbnails can be set to represent the entire recorded contents
under the BDAV directory and also individual PlayLists.
A mark is the generic term for an index point that the user sets on the playback timeline to enhance
ease-of-operation. Standard marks provided are bookmarks used for locating specific scenes, skip marks
for skipping certain intervals during playback and resume marks for resuming playback from the scene
where playback was previously stopped. Manufacturers can also add their own mark functions.
Fig. 3.1.5.6 shows the directory/file structure of the BD-RE Application Format where AV streams and
databases are stored.
root
BDAV
Basic BDAV directory
info.bdav
Management information for the parent BDAV directory
menu.tidx
Representative pictures for the parent BDAV directory
menu.tdt1
and/or each PlayList in this BDAV directory are stored as a
menu.tdt2
Thumbnail
mark.tidx
The index information which manages the thumbnail
mark.tdt1
picture of a mark position, and its thumbnail image data
are stored.
mark.tdt2
PLAYLIST
01001.rpls
PlayList file
02002.rpls
PlayList describes construction
information of the PlayList.
10000.vpls
CLIPINF
File extension of “.rpls” shows Real
PlayList and “.vpls” shows Virtual PlayList
:
01000.clpi
Clip Information file。
02000.clpi
One Clip Information file is created for
corresponding Clip AV stream file.
:
Attribute and Characteristic point
Information are stored.
STREAM
01000.m2ts
02000.m2ts
Clip AV stream file
MPEG-2 TS with arrival time stamp is
stored in this file.
:
BDAV1
BDAV2
..
.
Aux BDAV directory
BDAVn
Figure 3.1.5.6: Example of directory and file structure for BD-RE Application format
3.1.6 Editing
3.1.6.1 Seamless Connection Editing
It is very important for a recording system to have easy-to-use editing functions that enable users to
save wanted sections and cut out unwanted scenes from recorded contents (titles). The BD-RE Application
Format realizes such editing functions through the virtual PlayList. For instance, by using the virtual
PlayList, the user can select highlight scenes from different titles recorded on disc to create (edit) a new
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title of highlight scenes and organize/save the new title on disc (Fig. 3.1.5.1, Fig. 3.1.5.5).
As previously described, the BD-RE Application Format adopts MPEG2 and DV formats as its video
recording format (recording codec). When MPEG2 is used for recording, each frame image of the content
is coded into either of three types—I-picture, P-picture, or B-picture—and compressed and recorded. To give
a brief description of the characteristics of the three compressed image types: I-picture is an image that is
coded using only its own data information (intraframe coded picture), P-picture is an image that is coded
based on a prediction of the preceding I-picture or P-picture (interframe forward-direction predictive coded
picture) and B-picture is an image that is coded by processing the I-picture and P-picture first and then
being inserted in between (bi-directional predictive coded picture). If, as shown in the figure, two scenes
are selected from different titles (that is, separate contents that were recorded at different times) and
connected or two scenes separated in time are selected from the same single recording and connected to
create a new title, simply gathering the Clip AV streams and decoding the streams in succession will cause
a break in the MPEG2 compression pattern at the connection point (editing point) and, as a result, image
frames will not be displayed contiguously. In other words, to display images contiguously even across the
point where edited scenes are connected, the data needs to restructured. The BD-RE Application Format
specifies a structure (mechanism) called a bridge sequence to secure physical contiguousness and ensure
contiguous playback across the editing point. Bridge sequences are managed by the virtual PlayList which
is a logical mechanism. A brief description is provided below of the concept of the bridge sequence based
on Fig. 3.1.6.1.1.
IN_time1
OUT_time1
Preceding PlayItem
SPN which indicates the
address of out-point from
this Clip to Bridge Clip
IN_time2
OUT_time2
Succeeding PlayItem
SPN which indicates the
address of in-point from
Bridge Clip to this Clip
Clip 2
Clip 1
Bridge Clip
Seamless connection point of
the preceding PlayItem and the
succeeding PlayItem
Figure 3.1.6.1.1: Bridge sequence
The bridge sequence reconstructs only the required parts as shown in Fig. 3.1.6.1.2 and is designed to
keep data processing of editing points by the recorder to a minimum.
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・・・
Clip 1
I2
B0
B1
Data copied
from Clip 1
B3
Bridge Clip
P5
B3
B4
P8
B6
(order decoded)
Data copied
from Clip 2
Data reencoded
Data reencoded
B4
・・・
B7
P7
B6
i0
p1
p4
b2
b3
B6
B7
b3
b4
p8
b6
b7
Encode type of
original Clip
Seamless
connection point
Clip 2
・・・
b1
p5
b3
b4
p8
b6
b7
i11
b9
b10
p14
b12
b13
・・・
Figure 3.1.6.1.2: Structure of Bridge Clip
During playback, data is decoded in order of Clip 1ÆBridge ClipÆClip 2 as shown in Fig. 3.1.6.1.3 to
ensure contiguous playback across the editing point.
Title 3
(e.g. Highlight)
Title 1
Title 2
Real PlayList 1
Clip 1
Virtual PlayList
Real PlayList 2
Clip 2
Used for
seamless
connection
Bridge Clip
Figure 3.1.6.1.3: Playback of Bridge sequence
Playback(decode) order is, Clip 1 Î Bridge Clip Î Clip 2.
Seamless playback can be done even on the editing point
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3.1.6.2 Audio Dubbing
In general, when recording contents under the BD-RE Application Format, a set of video and audio data
is multiplexed in the transport stream and is recorded as a single Clip. (This transport stream is called the
main-path.) For instance, this mechanism is used for time-shift recording of broadcast programs.
An important editing function that enhances the recording system is audio dubbing, which allows the
user to easily add other audio data to content after it is recorded. The BD-RE Application Format realizes
an audio dubbing function by providing a mechanism called the sub-path. The sub-path is a structure that
enables the user to select a separate stream during playback of a Clip on the main-path and play back the
stream simultaneously with data on the main-path or by itself. For instance, this functionality can be used
with content on which audio dubbing was performed to play back the audio data on the main-path and the
audio data of a separate Clip on the sub-path at the same time or singly. Fig. 3.1.6.2.1 shows the relation
between the main-path and the sub-path.
Virtual PlayList
PlayItem (main-path)
Sub-PlayItem
(sub-path)
IN1
OUT1
IN2
OUT2
Real PlayList 1
Peal PlayList 2
Clip 1
Clip 2
Figure 3.1.6.2.1: main-path/sub-path
Stream which is decoded synchronously with main video
and audio can be referred by Sub-PlayItem
As shown in the figure, a sub-play-item is logically added to the play-item in the virtual PlayList to
associate a separate Clip (sub-path) to the play-item on the main-path. The playback start time of the
sub–play-item can be associated with the playback time (pts) of the play-item on the main-path. The
recorder determines differences (such as the PCR value) in the timelines of the Clips on the main-path and
the sub-path during playback and commences decoding.
3.1.7 Blu-ray Disc File System (BDFS)
3.1.7.1 A File System Suited to Video/Audio Stream Recording
The purpose of the file system is to manage/execute the data allocation on disc of video/audio streams
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and the databases that manage those streams. The file system manages the recording area on the disc in
units of logical sectors and provides read/write functions from/to disc for applications. Streams and
databases are recorded as files to disc by the file system. There are huge differences in file sizes, with
stream files exceeding one gigabyte in size while database files that manage the streams ranging from
only a few kilobytes to a few megabytes. Also, the stream file is used only during actual video/audio
playback when a certain amount of data must be read reliably from the file within a certain length of time,
while the database file is used often such as during menu display when multiple files need to be
read/written rapidly and frequently.
Stream file
Database file
File size
Large ( MB to GB )
Small ( KB to MB )
Frequency of Read/Write
little
many
Timing of Read/Write
Real-time Read/Write is necessary
Real-time Read/Write is not mandated
Action to error
The influence of an error is local.
Real-time is more important than error
retry procedure even when error occurs
Error retry procedure and duplex writing
are important because occurrence of
error may cause a serious obstacle
Management in BDFS
File is stored into real-time data area
Reference player mode
File is stored into Gathered file area
Duplex writing by the robust attribute
Table 3.1.7.1.1: Difference between stream file and database file
The BDFS separates the recording area on disc into the gathered file area and the real-time data area as
shown in Fig. 3.1.7.1.1 and records the file system’s management information and the application layer’s
database files together in the gathered file area and other video/audio stream files in the real-time data
area. This means that the files recorded in the gathered file area can be read with a fewer number of
seeks and the response time during PlayList editing and menu display is shortened and, as a result, the
response of the system is greatly improved.
Gathered file area
Management information for AV application
is stored into this area
Read-time data area
Stream data for video and audio is stored into this area
Figure 3.1.7.1.1: Recording area for each file
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The cyclability of the disc depends on the physical properties of the media and is a sufficiently large
value as long as the disc is used normally. However, with a recording system that frequently rewrites only a
particular area the disc may have a shorter life. For instance, with a recording system that constantly uses
empty areas beginning with the inner perimeter, the recording surfaces of the inner perimeter may have a
shorter life than the outer perimeter. BDFS solves this problem by using a system which uses the free
spaces on the disc with equal frequency.
3.1.7.2 Continuous Data Supply by Extents
When recording, delete or edit operations are performed repeatedly, small areas of empty space will
occur all over the disc. These small areas are used to record a new file and this results in a single file
composed of small groups of data that are scattered all over the disc. A group of data in such a file that is
recorded on contiguous logical sectors is called an extent under the BDFS (Fig. 3.1.7.2.1). When a single
file is made up of several extents, the file is read by jumping from one extent to the next and reading the
extents in succession. However, when jumping from one extent to another, the disc rotation speed needs to
be changed and the optical pickup needs to be moved. Data cannot be retrieved during this interval
although the decoding/playback of video/audio data will continue without interruption. So to prevent any
breaks occurring during playback, a mechanism is required to absorb the effects of the access intervals
that occur between extents.
Extent
Figure 3.1.7.2.1: Extent
To prevent the interruption in video/audio playback when reading data from disc, the buffer memory
must not be emptied of data before readout from the next extent becomes possible. This is the condition
for continuous supply that is met for seamless playback (Fig. 3.1.7.2.2, Fig. 3.1.7.2.3). The minimum
extent size is defined by the BDFS so that the buffer does not become empty when jumping from one
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extent to another on the disc. A restriction is placed on the minimum extent size to allow for a sufficient
amount of data to be accumulated in the buffer before the next extent is accessed.
Output TS packet
Timing management
Allocation
management
BD
Drive
RUD
Read
Buffer
Source depacketizer
RMAX
Transport
Stream System
Target Decoder
RTS
Display
device
TS packet
(MPEG2 TS)
Source packet
Figure 3.1.7.2.2: Buffer model for reading data from disc
The amount of data
accumulated in buffer
Transition of amount
of data in buffer
35Mbps
0Mbps
RMAX
Seamless playback condition
R UD =35Mbps
X
read
Tr
X>Y
Y
t X[Mbit] = 35[Mbps]×Tr[s]
Y[Mbps] = RMAX[Mbps]×(Tr+Tj)[s]
jump
Tj
Jump
Read
Extent
Figure 3.1.7.2.3: Transition of the amount of data accumulated in the
buffer and the seamless playback condition
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3.1.8 Copy Protection System (CPS)
Digital broadcasting transmits a content’s copy control information together with its video/audio data. In
general, contents that are broadcast as pay-TV have the restriction information “copy once.” Pay-per-view
(PPV) contents may have the restriction “copy never.” BD-RE recorders are required to operate
appropriately in accordance with the copy control information.
Specifically, the BD-RE recorder records only contents that are labeled “copy once” or “copy free.” When
a content labeled “copy once” is recorded, the copy control information is changed to “copy no more” to
prevent further copies being made and the copy control information is encrypted together with the content
and recorded to disc. Furthermore, this content can only be outputted to the interface that is equipped with
prescribed content protection technology so that copy control information is transmitted securely and
managed correctly in the destination device.
BD-RE copyright protection has the following features:
• Optimized for the BD-RE AV format, which is an MPEG TS recording format
• Allows revocation of the device key to revoke invalid devices (adopts a revocation system)
• Encrypts content and its copyright control information before recording to disc
• Pre-records a unique value in the disc and uses that value for encryption (blocks bit-by-bit copy)
Contents and copy control information are encrypted
and stored into the disc according to the copy control
information inputted
DTCP, etc
HDCP, etc
CGMS-A, MV, etc
Contents played back is outputted from the
interface which has predetermined copy
protection technologies according to the copy
control information of the contents
Figure 3.1.8.1: Outline of copy protection system of BD-RE
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Device Key
Device Key
Renewal
Key Block
Decryptor
Media Key
Mixture
Compressed
AV data
Decryptor
Media Key
Mixture
Disc ID
Content Key
Content Key
Encrypted
contents
Cipher
BD Recording module
Cipher
Compressed
AV Data
BD Playback module
Figure 3.1.8.2: Copy protection system of BD-RE
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