数字电视基础知识.ppt

数字电视基础知识,内容提要,数据压缩技术MPEG-2DVB,压缩分类,数据压缩技术,无失真压缩用于文本压缩、要求无失真的静止图象压缩对一般图象的压缩比不大于2高保真压缩用于要求较高的医学、军事、航天等领域，一般压缩比不大于10大压缩比压缩用于运动图象、数据库数据存储等领域，一般压缩比在20倍以上,数据压缩技术简介,压缩的可行性统计的冗余(数学意义上的冗余)感知能力的局限(心理学意义上的冗余)运动图象中的冗余空间上的冗余时间上的冗余压缩的极限数学上：信息熵差别的感受性：韦伯定律、心理学模型,数据压缩技术,真彩色图象,256色图象,感知能力限制(1),数据压缩技术,真彩色图象,256色1/4采样率图象,感知能力限制（2）,数据压缩技术,主流压缩方法,预测一维：DPCM二维：块预测、模型匹配变换编码(FFT、DCT、Wavelet等)量化(标量、矢量、LZW)统计编码Huffman、算术编码分形,数据压缩技术,预测技术,缩小了值的范围压缩效果依赖于预测模型和量化技术一维信号预测：f(t)=g(t)+e(t)f(t)输入信号g(t)预测信号e(t)误差值对输入信号的编码转化为对误差的编码,数据压缩技术,预测技术(2),二维信号预测：,A,B,C,D,X,前一行,当前行,三维信号预测：,运动向量,数据压缩技术,变换编码,选择正交变换，频率分辨率换取空间分辨率常用的变换编码FFT,DCT,Wavelet,哈德码易于快速计算,数据压缩技术,量化(1),0,m,7654321,标量量化,数据压缩技术,量化(2),720X576图象有414720个象素24bits真彩色可以表达16777216个不同颜色,数据压缩技术,统计编码,5个不同事件W1,W2,W5,需要3bits,平均码长=0.6*1+0.2*2+0.1*3+0.05*4+0.05*4=1.7bits,数据压缩技术,内容提要,数据压缩技术 MPEG-2DVB,MPEG的沿革,从JPEG到MPEG1993年通过MPEG-1标准(ISO-11172)，目标是支持VHS分辨率水平的数字节目传输、存储和播放1994年通过MPEG-2标准(ISO-13818)，目标是支持从VHS分辨率水平直至高清晰度电视水平的传输、存储和播放1999年通过MPEG-4标准正在制定MPEG-7、MPEG21标准,MPEG-2,MPEG-2标准的组成,系统(ISO 13818-1)视频(ISO 13818-2)音频(ISO 13818-3),MPEG-2,MPEG-2系统,通用的码流传输和存储机制允许定义私有数据、支持扩展系统流分类节目流考虑很好的信道条件，误码损失较大传输流考虑较差的信道条件，误码损失较小,MPEG-2,MPEG-2视频,算法的易实现与效果的折衷考虑了与MPEG-1的兼容性针对不同应用分成不同的类(Profile)和级(Level),MPEG-2,MPEG-2音频,支持5.1路声道支持多语种压缩方法采用心理学模型利用子带编码利用差帧非均匀量化,MPEG-2,MPEG-2适用范围,作用框架压缩方法传输广播（音、视频）交互(电视会议、点播服务)存储存储媒体、图象数据库,MPEG-2,MPEG-2批判,商业利益的折衷技术手段的迁就图象只是二进制串缺乏理解、难以交互压缩比远未到达理论、技术的极限8X8 DCT、有限范围ME,MPEG-2,内容提要,数据压缩技术MPEG-2 DVB,DVB标准概况,DVB,DVB,我国目前数字卫星压缩电视节目现状,DVB,DVB标准的组成,DVB,DVB标准的组成(续1),DVB,DVB标准的组成(续2),DVB,DVB标准的组成(续3),ETS 300 748 Digital broadcasting systems for television,sound and data services;Framing structure,channel coding and modulation for Multipoint Video Distribution Systems at 10 GHz and aboveETS 300 749 Digital broadcasting systems for television,sound and data services;Framing structure,channel coding and modulation for Multipoint Video Distribution Systems below 10 GHz,DVB,DVB标准的组成(续4),ETR 154 Digital broadcasting systems for television;Implementation guidelines for the use of MPEG-2 systems;Video and audio in satellite and cable broadcasting applicationsETR 290 Measurement guidelines for DVB systemsprEN 50201 Interface for DVB-IRDs,DVB,DVB标准的组成(续5),ETR 289 Digital Video Broadcasting(DVB);The Common Scrambling system descriptionTS 101 197 Digital Video Broadcasting(DVB);Technical specification of SimulCrypt in DVB systemsprEN 50221 Common Interface Specification for Conditional Access and other Digital Video Broadcasting Decoder Applications,DVB,DVB标准的组成(续6),prTS 101 192 Digital Video Broadcasting(DVB);Specification for the transmission of data services in DVB bitstreamsprEN 50083-9 Interfaces for CATV/SMATV Headends and similar Professional EquipmentprETS 300 743 Digital broadcasting systems for television,sound and data services;Subtitling systems,DVB,DVB标准的组成(续7),ETS 300 800 Digital Video Broadcasting(DVB);DVB interaction channel for Cable TV distribution system(CATV)ETS 300 801 Digital Video Broadcasting(DVB);DVB interaction channel through the Public Switched Telecommunications System(PSTN)/Integrated Services Digital Network(ISDN),DVB,DVB标准的组成(续8),ETS 300 802 Digital Video Broadcasting(DVB);Network Independent Protocols for DVB Interactive ServicesETS 300 803 Digital Video Broadcasting(DVB);DVB interaction channel for Satellite Master Antenna TV distribution systems(SMATV),DVB,DVB标准的组成(续9),ETS 300 813 Interfacing to PDH networksETS 300 814 Interfacing to SDH networksETS 300 815 DVB interfaces to ATM networks,DVB,DVB标准的组成(续10),ETSI TS 101 812 Multimedia Home Platform Specification 1.0,DVB,DVB-SI,概述,SI-Service Information前端系统提供服务、事件信息的渠道接收端根据该信息进行自动配置兼容PSI，比PSI提供更多的信息调谐、信道解码等提供一种实现EPG的方式,Bouquet,Satellite,Transponder1,Transponder2,Transponder3,TransponderT,Cable,Channel1,Channel 2,ChannelC,Terrestrial,Channel1,Channel2,ChannelC,Service 1,Service2,Service3,ServiceS,Video,Audio 1,Audio 2,Data,Service1,Service 2,ServiceS,Service1,Service 2,ServiceS,Networks,Multiplexes,Service,Components,相关标准,1 ISO/IEC 13818-1:Information Technology-Generic Coding of Moving Pictures and Associated Audio Recommendation H.222.0(systems).2 ISO 3166:Codes for the representation of names of countries.3 ISO 639.2:Code for the representation of names of languages.4 EBU SPB 492(1992):Teletext specification(625 line Television Systems).,相关标准（续）,5 ISO 8859:Information processing-8-bit single-byte coded graphic character sets,Latin alphabets.6 ETR 162:Digital Video Broadcasting(DVB);Allocation of Service Information(SI)codes for DVB systems.7 ETR 211:Digital Video Broadcasting(DVB);Guidelines on implementation and usage of Service Information(SI).,相关标准（续）,8 ISO/IEC 10646-1:Information Technology-Universal Multiple-Octet Coded Character Set(UCS)-Part 1:Architecture and Basic Multilingual Plane.9 ISO/IEC 6937:Information Technology-Coded graphic character set for text communication Latin alphabet.10 ETR 289:Digital Video Broadcasting(DVB);Support for use of scrambling and Conditional Access(CA)within digital broadcasting systems.,相关标准（续）,11 IEC CD-100C/1883:Parts 1 and 4 Digital Interface for Consumer Electronic Audio/Video Equipment.12 ETR 154:Digital Video Broadcasting(DVB);Implementation guidelines for the use of MPEG-2 Systems,Video and Audio in satellite,cable and terrestrial broadcasting applications.13 IEEE 1394:High Performance Serial Bus.,服务信息描述-PSI,四种类型的表构成PSI信息，PSI信息是复用器必须的信息PAT 节目关联表节目入口点、索引CAT 条件接收表PMT 节目映射表节目、服务及PCR和PID的对应关系NIT 网络信息表,服务信息描述-SI,下面的9个表是DVB扩展的进一步对服务和事件进行描述BAT 服务花束（Bouquet）关联表给出花束名和服务列表SDT 服务描述表对服务的描述-服务名、服务提供商EIT事件信息表描述事件的名、开始时间、长度不同的事件可用不同的描述子,服务信息描述-SI（续）,RST 事件运行状态表TDT 当前时间和日期的信息描述表TOT 当前时间和当地时间的时差信息表ST 填充表SIT 可选信息表（存储时用）DIT 断续信息表（存储时用）,服务信息表,所有的表都以数据段的形式插入TS流中不是任何TS需要所有的表除EIT表外，其他所有的表不能被加密段做为语法语义结构将SI表映射到TS流中SI的语法结构应符合MPEG2中定义的私用段的语法,SI表的PID分配,PAT CAT TSDT reserved NIT,ST SDT,BAT,ST EIT,ST RST,ST TDT,TOT,ST network synchronization reserved for future use DIT SIT,0 x00000 x00010 x00020 x0003 to 0 x000F0 x00100 x00110 x00120 x00130 x00140 x00150 x0016 to 0 x001D0 x001E0 x001F,table_id的分配,0 x00 program_association_section0 x01 conditional_access_section0 x02 program_map_section0 x03 transport_stream_description_section0 x04 to 0 x3F reserved0 x40 network_information_section-actual_network0 x41 network_information_section-other_network0 x42 service_description_section-actual_transport_stream0 x43 to 0 x45 reserved for future use0 x46 service_description_section-other_transport_stream0 x47 to 0 x49 reserved for future use0 x4A bouquet_association_section0 x4B to 0 x4D reserved for future use0 x4E event_information_section-actual_transport_stream,present/following0 x4F event_information_section-other_transport_stream,present/following,table_id的分配（续）,0 x4F event_information_section-other_transport_stream,present/following0 x50 to 0 x5F event_information_section-actual_transport_stream,schedule0 x60 to 0 x6F event_information_section-other_transport_stream,schedule0 x70 time_date_section0 x71 running_status_section0 x72 stuffing_section0 x73 time_offset_section0 x74 to 0 x7D reserved for future use0 x7E discontinuity_information_section0 x7F selection_information_section0 x80 to 0 xFE user defined0 xFF reserved,NIT表的定义,network_information_section()table_id 8 uimsbfsection_syntax_indicator 1 bslbfreserved_future_use 1 bslbfreserved 2 bslbfsection_length 12 uimsbfnetwork_id 16 uimsbfreserved 2 bslbfversion_number 5 uimsbfcurrent_next_indicator 1 bslbfsection_number 8 uimsbflast_section_number 8 uimsbfreserved_future_use 4 bslbfnetwork_descriptors_length 12 uimsbffor(i=0;iN;i+)descriptor()reserved_future_use 4 bslbftransport_stream_loop_length 12 uimsbf,NIT表的定义（续）,for(i=0;iN;i+)transport_stream_id 16 uimsbforiginal_network_id 16 uimsbfreserved_future_use 4 bslbftransport_descriptors_length 12 uimsbffor(j=0;jN;j+)descriptor()CRC_32 32 rpchof,SDT表的定义,service_description_section()table_id 8 uimsbfsection_syntax_indicator 1 bslbfreserved_future_use 1 bslbfreserved 2 bslbfsection_length 12 uimsbftransport_stream_id 16 uimsbfreserved 2 bslbfversion_number 5 uimsbfcurrent_next_indicator 1 bslbfsection_number 8 uimsbflast_section_number 8 uimsbforiginal_network_id 16 uimsbfreserved_future_use 8 bslbf,SDT表的定义（续）,for(i=0;iN;i+)service_id 16 uimsbfreserved_future_use 6 bslbfEIT_schedule_flag 1 bslbfEIT_present_following_flag 1 bslbfrunning_status 3 uimsbffree_CA_mode 1 bslbfdescriptors_loop_length 12 uimsbffor(j=0;jN;j+)descriptor()CRC_32 32 rpchof,EIT表的定义,event_information_section()table_id 8 uimsbfsection_syntax_indicator 1 bslbfreserved_future_use 1 bslbfreserved 2 bslbfsection_length 12 uimsbfservice_id 16 uimsbfreserved 2 bslbfversion_number 5 uimsbfcurrent_next_indicator 1 bslbfsection_number 8 uimsbflast_section_number 8 uimsbftransport_stream_id 16 uimsbforiginal_network_id 16 uimsbfsegment_last_section_number 8 uimsbflast_table_id 8 uimsbf,EIT表的定义（续）,for(i=0;iN;i+)event_id 16 uimsbfstart_time 40 bslbfduration 24 uimsbfrunning_status 3 uimsbffree_CA_mode 1 bslbfdescriptors_loop_length 12 uimsbffor(i=0;iN;i+)descriptor()CRC_32 32 rpchof,TDT表的定义,time_date_section()table_id 8 uimsbfsection_syntax_indicator 1 bslbfreserved_future_use 1 bslbfreserved 2 bslbfsection_length 12 uimsbfUTC_time 40 bslbf,SI中用到的描述子和其Tag,network_name_descriptor 0 x40 service_list_descriptor 0 x41 stuffing_descriptor 0 x42 satellite_delivery_system_descriptor 0 x43 cable_delivery_system_descriptor 0 x44 Reserved for future use 0 x45 Reserved for future use 0 x46 bouquet_name_descriptor 0 x47 service_descriptor 0 x48 country_availability_descriptor 0 x49 linkage_descriptor 0 x4A NVOD_reference_descriptor 0 x4B time_shifted_service_descriptor 0 x4C short_event_descriptor 0 x4D extended_event_descriptor 0 x4E time_shifted_event_descriptor 0 x4F component_descriptor 0 x50 mosaic_descriptor 0 x51 stream_identifier_descriptor 0 x52 CA_identifier_descriptor 0 x53 content_descriptor 0 x54,SI中用到的描述子和其Tag,parental_rating_descriptor 0 x55 teletext_descriptor 0 x56 telephone_descriptor 0 x57 local_time_offset_descriptor 0 x58 subtitling_descriptor 0 x59 terrestrial_delivery_system_descriptor 0 x5A multilingual_network_name_descriptor 0 x5B multilingual_bouquet_name_descriptor 0 x5C multilingual_service_name_descriptor 0 x5D multilingual_component_descriptor 0 x5E private_data_specifier_descriptor 0 x5F service_move_descriptor 0 x60 short_smoothing_buffer_descriptor 0 x61 frequency_list_descriptor 0 x62 partial_transport_stream_descriptor 0 x63 data_broadcast_descriptor 0 x64CA_system_descriptor(note 2)0 x65data_broadcast_id_descriptor 0 x66 Reserved for future use 0 x67 to 0 x7Fuser defined 0 x80 to 0 xFEForbidden 0 xFF,内容描述子的定义,content_descriptor()descriptor_tag 8 uimsbfdescriptor_length 8 uimsbffor(i=0;iN;i+)content_nibble_level_1 4 uimsbfcontent_nibble_level_2 4 uimsbfuser_nibble 4 uimsbfuser_nibble 4 uimsbf,内容级与内容的关系,level_1 level_2 Description0 x0 0 x00 xF undefined contentMovie/Drama:0 x1 0 x0 movie/drama(general)0 x1 0 x1 detective/thriller0 x1 0 x2 adventure/western/war0 x1 0 x3 science fiction/fantasy/horror0 x1 0 x4 comedy0 x1 0 x5 soap/melodrama/folkloric0 x1 0 x6 romance0 x1 0 x7 serious/classical/religious/historical movie/drama0 x1 0 x8 adult movie/drama0 x1 0 x90 xE reserved for future use0 x1 0 xF user definedNews/Current affairs:0 x2 0 x0 news/current affairs(general)0 x20 x1 news/weather report0 x2 0 x2 news magazine0 x2 0 x3 documentary0 x2 0 x4 discussion/interview/debate0 x2 0 x5 to 0 xE reserved for future use0 x2 0 xF user defined,内容级与内容的关系（续）,level_1 level_2 DescriptionShow/Game show:0 x3 0 x0 show/game show(general)0 x3 0 x1 game show/quiz/contest0 x3 0 x2 variety show0 x3 0 x3 talk show0 x3 0 x40 xE reserved for future use0 x3 0 xF user definedSports:0 x4 0 x0 sports(general)0 x4 0 x1 special events(Olympic Games,World Cup etc.)0 x4 0 x2 sports magazines0 x4 0 x3 football/soccer0 x4 0 x4 tennis/squash0 x4 0 x5 team sports(excluding football)0 x4 0 x6 athletics0 x4 0 x7 motor sport0 x4 0 x8 water sport0 x4 0 x9 winter sports0 x4 0 xA equestrian0 x4 0 xB martial sports0 x4 0 xC0 xE reserved for future use0 x4 0 xF user defined,马赛克描述子,马赛克是由一组视频图象组成有效组织信息，使显示屏上同时显示多个视频图象马赛克描述子划分数字视频部件成为基本单元给出基本单元内容和相应信息（服务、事件等）的对应关系,马赛克描述子语法,mosaic_descriptor()descriptor_tag 8 uimsbfdescriptor_length 8 uimsbfmosaic_entry_point 1 bslbfnumber_of_horizontal_elementary_cells 3 uimsbfreserved_future_use 1 bslbfnumber_of_vertical_elementary_cells 3 uimsbffor(i=0;iN;i+)logical_cell_id 6 uimsbfreserved_future_use 7 bslbflogical_cell_presentation_info 3 uimsbfelementary_cell_field_length 8 uimsbffor(i=0;ielementary_cell_field_length;i+)reserved_future_use 2 bslbfelementary_cell_id 6 uimsbfcell_linkage_info 8 uimsbfIf(cell_linkage_info=0 x01)bouquet_id 16 uimsbf,马赛克描述子语法（续）,If(cell_linkage_info=0 x02)original_network_id 16 uimsbftransport_stream_id 16 uimsbfservice_id 16 uimsbfIf(cell_linkage_info=0 x03)original_network_id 16 uimsbftransport_stream_id 16 uimsbfservice_id 16 uimsbfIf(cell_linkage_info=0 x04)original_network_id 16 uimsbftransport_stream_id 16 uimsbfservice_id 16 uimsbfevent_id 16 uimsbf,logical_cell_presentation_info的含义,0 x00 undefined0 x01 video0 x02 still picture(see note)0 x03 graphics/text0 x04 to 0 x07 reserved for future useNOTE:Still picture:A coded still picture consists of a video sequencecontaining exactly one coded picture which is intra-coded.,多语种服务名描述子,主要用于定义服务名和服务提供者名multilingual_service_name_descriptor()descriptor_tag 8 uimsbfdescriptor_length 8 uimsbffor(i=0;iN;i+)ISO_639_language_code 24 bslbfservice_provider_name_length 8 uimsbffor(j=0;jN;j+)char 8 uimsbfservice_name_length 8 uimsbffor(j=0;jN;j+)char 8 uimsbfISO_639_language_code:由ISO 639 Part 2 3 定义的三字节语言码,NVOD参考描述子,提供间隔时间的同一服务描述机制有效描述同一序列不同开始时间的数个服务用户可以访问距开始时间最近的一个服务NVOD参考描述子给出组成NVOD服务的一个服务列表每个服务也在相应的SDT子表中由一个时间间隔描述子定义时间间隔事件描述子用于与时间间隔服务相关的事件描述组成NVOD服务的所有服务可以不在同一TS流中在NVOD所在的所有TS中应包含参考服务描述,NVOD参考描述子语法,NVOD reference descriptorNVOD_reference_descriptor()descriptor_tag 8 uimsbfdescriptor_length 8 uimsbffor(i=0;iN;i+)transport_stream_id 16 uimsbforiginal_network_id 16 uimsbfservice_id 16 uimsbf,基于MPEG-2的 数字电视编码传输系统,数字化广播的优点,抗干扰能力强保真度高采用信源编码技术提高信道利用率采用信道编码技术改善容错性能便于实现收费,应用领域,卫星数字电视广播有线网数字电视广播（同轴或HFC）地面数字电视广播数字电视在微波传输网的应用（MMDS）数字电视在PDH、SDH光传输网的应用数字电视在IP网上的应用,典型的广播编码系统组成示意图,典型的广播编码系统组成示意图,MPEG2编码传输的关键技术,抗干扰RS码交织卷积码高效的调制方法QPSKQAMCOFDM,压缩与解码视频：MPEG-2 MPML音频：MPEG-2 复用MPEG-2系统条件接收节目加解扰控制字加解密,编码传输系统,信源编码与复用,卫星信道适配器,有线系统数字电视,RS编码器(204,188),字节到m位符号的映射,卷积交织 器,信道适配器,8,m,8,8,m,有线系统数字电视,与DVB-S的主要区别调制方式有线数字电视采用16,32或64点的正交调幅调制(QAM)卫星数字电视采用QPSK调制由于传输条件较好，省去了卷积码编码过程由于采用QAM调制，增加了字节到符号的映射为保证得到旋转不变的QAM星座图，对每个符 号的最高两位进行差分处理,PDH，SDH上的数字电视,RS编码器(204,188),信道适配器,G.703接口,交织器,PDH，SDH上的数字电视,由于不用调制，因此能量随机化过程可选信道上主要采用RS编码和交织由于不用调制也不进行字节到符号的映射及差分编码,地面传输系统数字系统,与DVB-S的主要差别采用正交频分复用方式传输由于采用频分复用方式，增加了保护间隔插入,MPEG-2视频压缩方案,MPEG-2视频压缩方法时间冗余运动估计/运动补偿和内插技术空间冗余类似JPEG：DCT、量化、游程及熵编码压缩效果与随机存取的折衷视频图象被分为I图片(Intra Picture)，P图片(Predicted Picture)和B图片(Bidirectional Picture),MPEG-2音频压缩,支持多声道(最多可达五路环绕立体声以 及一路超重低音)、多语种与MPEG-1保持先前以及向后的兼容性采用分层(Layer)的方式压缩，级别越高 则算法越复杂，同时压缩效果也越好。,卫星数字电视转发器结构,卫星数字电视转发器,接收C-波段，Ku-波段卫星数字电视广播支持节目相关的TS流的过滤SPTS流对IEEE1284并口的