› labaspl › edu › mpeg2_ts(nctu2)a.pdf · dvb-t transport streamtable pointer to pmt 4 … ts...

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DVB-T Transport Stream陳偉凱

尤信程

國立台北科技大學

資工系

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致謝感謝台北科技大學資工系

林彥龍同學

協助製作本投影片

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Outline

• Introduction to MPEG-2 part 1• Overview of MPEG-2 Transport Stream (TS)• TS defined (used) in DVB-T• Synchronization technique• Examples from “real” TS files• Conclusions

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Introduction (1)

DVB-T Channel coder & modulator

Transport Stream (TS)

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Introduction (2)

MPEG-2 Encoder

MPEG-1 Encoder

Packetizer

Packetizer

MUXMPEG-2 part 1

VideoSource

AudioSource

MPEG encoded stream

DataSource Packetizer

Uncompressed stream PES TS

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Introduction (3)

• MPEG-2 part 1(ISO 13818-1) defines multiplexing scheme for streams of video, audio, and data

• Used by – DVB– DVD– ATSC

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Introduction (4)

• MPEG-2 part 1 defines two schemes for the multiplexing process– Program Stream– Transport Stream

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Introduction (5)

• Program Stream– Mainly for storage media, eg. Disc or Hard Disk– Grouping of video, audio, and data elementary streams that have

a common time base– Each program stream consists of only one program– Useful in error free environments

• Large packet size • Packet size may be variable (hard for decoder to predict start

and end of packets)– DVD standard uses the MPEG-2 Program Stream

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MPEG-2 Transport Stream (1)

• Transport Stream– Combines multiple programs into a single stream– The programs may or may not have common time base– Fixed length packet size

• Intended for non-error-free environments• Easier to detect start and end of frames• Easy to recover from packet loss/corruption• More difficult to produce and de-multiplex than program

stream

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EncoderVideo

Audio

EncoderVideo

Audio

EncoderVideo

Audio

Program1

Program2

Program3

MPEG

TS MU

LTIPLEXER

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• ES: Elementary Stream• PES: Packetized Elementary Stream• PES packet: variable length, up to 64 kbytes

payload• Transport stream packet: 188 bytes• Video, audio, and data (including Program

Specific Information, PSI) are MUX’ed

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Packetized Elementary Stream (1)

PES PAYLOAD

3byte star code prefix 00 00 01

PES Header

1byte stream type

2byte length indicator

Optional PES Header (including DTS/PTS)

Up to 64 kbytes

Var length

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• A PES packet is not equal to one frame of video or audio stream

• The size of a specific PES is solely determined by the multiplexer without parsing the elementary streams

• Buffer status is the main concern to determine the PES size

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PES packet payload

Header Payload Adaptation Field(used for stuffing here)

PES packet Header

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Transport Stream Packet (1)

188 bytes

4 bytes

- sync_byte(sync the decoder: 0x47)- tansport_error_indicator- payload_unit_start_indicator (PSI or PES packet)- transport priority (usefule in scalable MPEG2)- PID (13 bit id for each stream)- transport_scrambling control- adaptation_field _control- continuity_counter(counts packets of PES)- PES packet length

Adaptation field(may not be present)Header

- discontinuity_indicator- random_access_indicator- ES_priority_indicator- various flags (PCR_flag...)- PCR (if PCR_flag is set) (system time clock,

every 0.1sec, sync decoder and encoder time)- other fields depending of which flags are set

Payload(may not be present)

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Transport Stream Packet (2)

• Packet header: 0x47. Detecting of five consecutive 0x47 every 188 bytes confirms the correct lock of packet header

• PID: Program ID, the unique number assigned to each type of elementary streams

• PCR: Program Counter Reference, used for audio & video synchronization

• Recall that one PES packet may across many TS packets

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Program Specific Information (1)

• Having so many packets, where to start de-multiplexing? Answer: PSI

• PSI transport packets - used by decoder to learn about the transport stream

• Must decode PSI to know the information related to the “program”

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PAT Program Association Table PMT Program Map TableCAT Condition Access TableNIT Network Information Table

NIT Network Information TableSDT Service Description Table

BAT Bouquet Association TableEIT Event Information TableRST Running Status TableTDT Time and Date TableTOT Time Offset Table

ST Stuffing Table

MPEG2Program Specific Information

DVB Service Information

Private Table

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• Program Association Table (PAT)– Contains complete list of all programs in the transport stream

along with the PID for the PMT for each program– Transmitted in transport packets with PID 0– Program number 0 point to the NIT

• Program Map Table (PMT)– contains the PID for each of the channels associated with a

particular program– Transmitted in transport packets with PID provided by PAT

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…

TSheader

Payload ofTS packet

PID = 0x00 pointer toPMT 1

pointer toPMT 2

pointer toPMT 3

PAT = Program Association

Table

pointer toPMT 4

…

TSheader

Payload ofTS packet

PID fromPAT

pointer tovideo ES

pointer toaudio ES

PMT = Program Map

Table

1 PID entry per program

1 PID entry per elementary stream

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• Conditional Access Table (CAT)– must be sent when the elementary stream is scrambled– Not currently in use in Taiwan– Many different methods available – Some approaches uses smart card

• Some additional information are defined in the DVB-T standard (ETSI EN 300 468), but not in MPEG-2 system part

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DVB Service Information (1)

• Network Information Table (NIT)– Optional and contents are private (not part of MPEG standard)– Actual / other transport stream– service id (program number)– service type– transmission mode– radio frequency– order of QAM– network provider name– bandwidth

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• Service Description Table (SDT)– List the names and other parameter of the service with TS– Actual / other transport stream– service name– service provider name– EIT present/following and schedule exit actual TS?– service running status– service scrambling

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• Event Information Table (EIT)– Transmission information about present, following, and future

events– Actual / other transport stream– EIT present/following – EIT schedule– event id– event name– additional event information

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• Time and Date Table (TDT)– Transmission actual UCT-time coded as Modified Julian Date

(MJD) – It may be used to synchronize the internal clock of an Integrated

Receiver Decoder (IRD)

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Decoding Flow (1)

Transport stream synchronization Sync byte 0x47

Read out of TS content Program specificationInformation PAT PMT

Accessing programs Packet identification PID

Descrambling if require Condition access tableCAT

Program Synchronization PCR DTS PTS

Decoding additional data Service information

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Decoding Flow (2)Start

Parse PMT

Parse NIT

No header error

No

YesNo

Is PID=0x10 Yes

No

Parse SDTIs PID=0x11 Yes

No

Parse EITIs PID=0x12Yes

Parse PATIs PID=0

Yes

No

Is PID in PM_PID

Yes

Parse TS header

Find sync_byte and Read a ts packet

Define PN and PM_PID

More ts packets?

EndNo

No

Parse PESIS PID in ES_PIDYes

No

Define PN ES_PID

2 1 2

1

No

Yes

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PSI Association (1)PAT

(PID=0x00)NIT

(PID=0x10)定義

PMT(PID 由 PAT

定義)

SDT(PID=0x11)

EIT(PID=0x12)

TDT(PID=0x14)

讀取讀取讀取

定義

定義提供提供

提供

提供

Service(每個service對應一個

service_id即program_number)

提供UTC-time,可用來同步IRD的

internal clock

每個program 對應之video 與audio之

PID

每個service對應的 name與其他

service info

每個service目前/未來所播放之節目資訊,如：播放時間,節目摘要

每個service的詳細節目單如：播放時間,節目摘要等

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PSI Association (2)

傳送UTC-time，可用來與IDR的internal clock作同步TDT

提供每一個service的event information。分為 present/following EIT 與schedule EIT。present/following EIT提供目前與下一個播放節目的資訊如:開始播放時間、節目時間長度、節目摘要等)；schedule EIT提供較詳細(不限於目前與下一個節目)的節目單

EIT

定義每一個service的service info，如service name、service provider name等，以及一個service是否具有EIT present/following或schedule

SDT

定義每一個program 所對應之service、service_id(program_number)及此service之type(如DBS、DTS)，並提供此transport stream 之transmission parameter，如:QAM order, bandwidth等

NIT

定義一個program所對應之 video、audio及 other data之PIDPMT

定義此transport stream 所包含之program number(可能有好幾個)，並提供每個program所對應的PMT的PID(簡寫為PM_PID)

PAT說明PSI名稱

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A/V Synchronization (1)

• Audio & Video synchronization is necessary• Why? To have lip sync• The A/V sync has nothing to do with the OFDM

sync (including sampling rate 48/7 MHz)• Therefore, there are two independent timing

systems inside the DVB-T receiver

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• A/V sync is achieved via STC, PCR, PTS, & DTS• STC: System Time Clock• PCR: Program Counter Reference• PTS : Presentation time stamp • DTS : Decoding time stamp

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• STC is a clock source with a frequency of 27 MHz• PCR is at the adaptation field of the TS packet• PCR is transmitted every 40 ms• For encoder, PCR is a 42-bit counter whose input

clock is from STC

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• PTS & DTS are at the optional PES headers• PTS & DTS are 33 bits in length• PTS & DTS are transmitted less frequently than

the PCR case

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• Synchronization approach– Hardware-based approach– Software-based approach

• Hardware approach requires the actual implementation of the STC at the receiver side. It is suitable for set-top box

• Software approach requires no additional hardware, and is for PC-based solution

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counter

27MHz STC

MPEG-2Encoder

42bit

Video

Audio

copy

MPEG-2Decoder

counter

27MHz STC

load

PCRPCR

MPEG2-ts

Every 40ms

+

42bit

Video

Audio

LPF

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Decoded Example (1)PAT

0x0149program map PID0x00B4 program number

0x05DCprogram map PID0x0096 program number

0x03FCprogram map PID0x0066 program number

0x03F2program map PID0x0065 program number

0x03E8program map PID0x0064 program number

0x0010Network PID0x0000program number

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Decoded Example (2)

program number 0x65 之 PMT0x3F2program number 0x64 之 audio elementary stream PID0x3EBprogram number 0x64 之 audio elementary stream PID0x3EAprogram number 0x64 之 video elementary stream PID0x3E9program number 0x64 之 PMT0x3E8TDT0x14EIT0x12SDT0x11NIT0x10

PAT(定義program_number 0x64、0x65、0x66、0x96、0xB4及其對應之PM_PID 0x3E8、0x3F2、0x3FC、0x5DC、0x149)

0x0說明PID

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Decoded Example (3)

null packet0x1FFF

program number 0xB4之MPEG2 private section packet PID0x150

program number 0xB4之PMT0x149

program number 0x96之 MPEG2 part 6 type D packet PID0x5DE

program number 0x96之 MPEG2 part 6 type D packet PID0x5DD

program number 0x96之 PMT0x5DC

program number 0x66之 audio elementary stream PID0x3FE

program number 0x66之 video elementary stream PID0x3FD

program number 0x66之 PMT0x3FC

program number 0x65之 audio elementary stream PID0x3F4

program number 0x65之 video elementary stream PID0x3F3

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Decoded Example (4)

program_number:0x0066 PMT

0x03FEelementary PIDMPEG2 audiostream type0x03FDelementary PIDMPEG2 video stream type0x3FDPCR_PID


0x03F4elementary PIDMPEG2 audiostream type0x03F3elementary PIDMPEG2 video stream type0x3F3PCR_PID


0x03EAelementary PID

0x03E9elementary PID

MPEG2 audiostream type

MPEG2 audiostream type0x03E8elementary PIDMPEG2 video stream type0x3E8PCR_PID

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Decoded Example (5)


0x05DEelementary PIDMPEG2 part 6 type Dstream type005DDelementary PIDMPEG2 part 6 type Dstream typeNULLPCR_PID

program_number:0x00B4 PMT

0x0150elementary PIDMPEG2 private sectionstream typeNULLPCR_PID

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Decoded Example (6)

DBSservice_type

0x96service_id

DTSservice_type

0x66service_id

DTSservice_type

0x65service_id

DTSservice_type

0x64service_id

CTVchar

network name descriptor

no other frequencyother_frequency_flag

8k modetransmission_mode

guard interval value 1/4guard_interval

2/3 modulation levelcode_rate_LP_stream

2/3 modulation levelcode_rate_HP_stream

no hierarchyhierarchy_information

16-QAMconstellation

MPE_FEC not usedMPE_FEC_indicator

Time Slicing not usedTime_Slicing_indicator

high priorityPriority

6 MHzbandwhidth

6.8228MHzcentre_frequency

terrestrial delivery descriptor

NIT

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Decoded Example (7)

中視數位台char

CTVchar

DTSservice_type

0x64service_id

service descriptor

中視新聞台char

CTVchar

DTSservice_type

0x65service_id

service descriptor

生活頻道Char

CTVchar

DTSservice_type

0x66service_id

service descriptor

SDT

GEMSTARchar

CTVchar

DBSservice_type

0x96service_id

service descriptor

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Decoded Example (8)

晚間新聞搶先報event_name_char

MPEG2 video aspect ratio 30Hzcomponent_type

MPEG1 layer 2 audio dual mono channelcomponent_type

1小時Duration

2006-6-28-10:00:00start_time

0x0Bevent_id

presentpresent/following

0x0066service_id

EIT present/following

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Decoded Example (9)

中視新聞全球報導LIVEevent_name_char



1小時Duration

2006-6-28-11:00:00start_time

0x0Bevent_id

followingpresent/following

0x0066service_id

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Decoded Example (10)

非常男女event_name_char



1小時Duration

2006-6-28-10:00:00start_time

0x0Bevent_id

presentpresent/following

0x0065service_id

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晚間新聞(聯播母台)event_name_charMPEG2 video aspect ratio 30Hzcomponent_type


1小時Duration

2006-6-28-11:00:00start_time

0x0Bevent_id


0x0065service_id

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大家來說笑event_name_charMPEG2 video aspect ratio 30Hzcomponent_typeMPEG1 layer 2 audio dual mono channelcomponent_type 1小時Duration2006-6-28-10:00:00start_time0x0Bevent_idpresentpresent/following0x0064service_id

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大家來說笑集數： 669 1、康丁說笑話、吐槽素珠、石松2 、康丁演唱 “ 可憐的戀花再會吧 “3、素珠說笑話、吐槽康丁、石松4 、素珠演唱 “ 四季紅 “5 、石松說笑話、吐槽康丁、素珠6 、石松演唱 “ 阿公店 “

text_char

康康郁方康丁素珠石松text_char

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中視新聞全球報導event_name_char



1小時Duration

2006-6-28-11:00:00start_time

0x0Bevent_id


0x0064service_id

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EIT schedule (以0x64部份schedule為例)

大家來說笑event_name_charMPEG2 video aspect ratio 30Hzcomponent_typeMPEG1 layer 2 audio dual mono channelcomponent_type 1小時Duration

2006-6-28-10:00:00start_time

0x15event_id

0x0064service_id

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大家來說笑集數： 669 1、康丁說笑話、吐槽素珠、石松2 、康丁演唱 “ 可憐的戀花再會吧 “3、素珠說笑話、吐槽康丁、石松4 、素珠演唱 “ 四季紅 “5 、石松說笑話、吐槽康丁、素珠6 、石松演唱 “ 阿公店 “

text_char

康康郁方康丁素珠石松text_char

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中視新聞全球報導event_name_char



1小時Duration

2006-6-28-11:00:00start_time

0x16event_id


0x0064service_id

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紅拂女第 8 集李密卻趁機設計翟讓被殺是虯髯客所為，將花夫人囚禁在石牢中，準備等虯髯客來救妻子時，將他一舉成擒。逃跑的程咬金無意間發現李密勾結宇文化及，陰謀讓瓦崗軍和李淵的軍隊相鬥，漁翁得利。虯髯客大急，但苦於重傷，只得忍耐等待時機。 …

text_char

data占207bytetext_length

舒淇霍建華於榮光鄭則仕text_char

風塵三俠之紅拂女event_name_char



1小時 30 分鐘duration

2006-6-28-12:00:00start_time

0x17event_id

0x0064service_id

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愛上九點半event_name_charMPEG2 video aspect ratio 30Hzcomponent_typeMPEG1 layer 2 audio dual mono channelcomponent_type 1小時duration2006-6-28-13:30:00start_time0x18event_idfollowingpresent/following0x0064service_id

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文茜小妹大event_name_charMPEG2 video aspect ratio 30Hzcomponent_typeMPEG1 layer 2 audio dual mono channelcomponent_type 1小時duration2006-6-28-14:30:00start_time0x19event_idfollowingpresent/following0x0064service_id

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孝莊秘史event_name_charMPEG2 video aspect ratio 30Hzcomponent_typeMPEG1 layer 2 audio dual mono channelcomponent_type 1小時duration2006-6-28-15:30:00start_time0x1Aevent_idfollowingpresent/following0x0064service_id

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Conclusions

• MPEG-2 system overview• Terminologies explained: ES, PES, TS, TS packet,

etc• MPEG-2 defined: PAT, PMT, and CAT• DVB SI: NIT, SDT, EIT, and TDT• Synchronization concepts• Decoded examples

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