WO2008066257A1

WO2008066257A1 - Apparatus and method for hierarchical modulation transmission and reception of scalable video bitstream

Info

Publication number: WO2008066257A1
Application number: PCT/KR2007/005472
Authority: WO
Inventors: Dong-San Jun; Hae-Chul Choi; Jae-Gon Kim; Jong-Soo Lim; Jin-Woo Hong
Original assignee: Electronics And Telecommunications Research Institute
Priority date: 2006-11-30
Filing date: 2007-10-31
Publication date: 2008-06-05

Abstract

Provided is an apparatus and method for hierarchical modulation transmission and reception of a scalable video bitstream. A transceiver for hierarchical modulation transmission and reception of a scalable video bitstream includes a splitter generating a (High Priority) HP bitstream having HP based on a base layer among a plurality of scalable layers included in the scalable video bitstream and a (Low Priority) LP bitstream having LP based on an enhancement layer among the plurality of scalable layers included in thescalable video bitstream.

Description

APPARATUS AND METHOD FOR HIERARCHICAL MODULATION TRANSMISSION AND RECEPTION OF

SCALABLE VIDEO BITSTREAM

Technical Field

[1] The present invention relates to an apparatus and method for hierarchical modulation transmission and reception of a scalable video bitstream, and more particularly, to an apparatus and method for hierarchical modulation transmission and reception of a scalable video bitstream in order to provide a high quality video service in advanced Terrestrial Digital Multimedia Broadcasting (T-DMB). This work was supported by the IT R&D program of MIC/IITA.[2006-S017-01, Development of advanced transmission technology for the terrestrial DMB system] Background Art

[2] Since the advent of digital broadcasting technology, various next-generation digital multimedia transmission methods of providing a High Definition (HD) digital television (DTV) service and an additional data service including high quality audio and video have been tried.

[3] In addition, according to the variety of broadcasting media, the expansion of programs, and the taste of users, social and technical variation of a digital broadcasting service has been rapidly accomplished, and a broadcasting environment has been changed from an independent/fixed use environment providing a single information type (video/audio/text) service to an integrated/mobile use environment providing an integrated information type (multimedia) service.

[4] As a part of this broadcasting environment change, the development of Digital

Multimedia Broadcasting (DMB) technology for providing a Compact Disc (CD)-level high quality audio service, various additional data services, such as traffic and advertisement, and a clear video service in a mobile environment has been rapidly accomplished.

[5] DMB is a next generation digital broadcasting service for providing CD-level high audio quality, various bi-directional data services, and excellent mobile reception quality by exceeding conventional Amplitude Modulation (AM) and Frequency Modulation (FM) radio technology according to digitalization of audio broadcasting.

[6] Furthermore, DMB expands the concept of 'audio broadcasting' of conventional radio broadcasting to 'audio/visual broadcasting' and can broadcast music and various kinds of multimedia information, such as news, traffic information, weather information, geographical position information, and video information, as graphics and images. [7] Accompanying this, Digital Audio Broadcasting (DAB) in Korea has expanded its concept from an audio and data service initially to a video multimedia service, and its name was changed from DAB to DMB in early 2003.

[8] However, only if international standardization is derived from research and development of technology providing a a convergence (high-capacity and high-quality communication and broadcasting) mobile multimedia service through various terminals, which considerably exceeds quality and functions provided by existing T- DMB, the competitiveness of T-DMB technology can be maintained.

[9] As described above, development of high quality mobile multimedia service technology maintaining compatibility with exiting T-DMB and meeting requirements of users according to the popularization of a better image quality digital broadcasting service and a broadband network is needed. Disclosure of Invention Technical Problem

[10] In exiting T-DMB, since maximum screen resolution is limited to Common Intermediate Format (CIF) 352 ' 288 due to a limited data rate, users can not receive a high-resolution video service.

[11] H.264 (ITU-T Rec. H.264 I ISO/IEC 14496-10 Annex A.21), which is a video compression standard used in existing T-DMB, has a 50% or greater compression rate than H.263 or MPEG-4 Part 2 visual simple profile at most bit-rates.

[12] H.264 can provide a high-quality video service by using a deblocking filter and a

1/4-pixel motion vector and has improved error robustness by performing motion compensation using multiple reference frames and by using SP (Switching P) and SI (Switching I) frames.

[13] In addition, since H.264 adopts a Network Abstraction Layer (NAL), an H.264 bitstream can be easily transmitted via various networks.

[14] However, a scalability function for providing various screen resolutions/time resolutions/image qualities cannot be provided in H.264, and due to this, a one-source multi-use service for a high-quality video service in advanced T-DMB cannot be provided. Technical Solution

[15] The present invention provides an apparatus and method for hierarchical modulation transmission and reception of a scalable video bitstream in order to provide a high quality video service in advanced Terrestrial Digital Multimedia Broadcasting (T-DMB) while maintaining downlink compatibility with existing T-DMB.

[16] According to an aspect of the present invention, there is provided a transmitter for a scalable video bitstream, the transmitter comprising a splitter for hierarchical modulation transmission of a scalable video bitstream, the splitter comprising: a High Priority (HP) channel generator generating an HP bitstream having HP based on a base layer among a plurality of scalable layers included in the scalable video bitstream; and a Low Priority (LP) channel generator generating an LP bitstream having LP based on an enhancement layer among the plurality of scalable layers included in the scalable video bitstream.

[17] The splitter in the transmitter for a scalable video bitstream may further comprise a splitter header parser splitting the scalable video bitstream into the base layer and the enhancement layer by analyzing a Network Abstraction Layer (NAL) header included in a NAL unit of the scalable video bitstream.

[18] According to another aspect of the present invention, there is provided a receiver for a scalable video bitstream, the receiver comprising a compositor for a hierarchical- modulated scalable video bitstream, the compositor receiving a High Priority (HP) bitstream having HP and a Low Priority (LP) bitstream having LP by splitting the scalable video bitstream and reconstructing the scalable video bitstream.

[19] The compositor in the receiver for a scalable video bitstream may comprise: a bitstream receiver receiving the HP bitstream and the LP bitstream; a compositor header parser analyzing a Network Abstraction Layer (NAL) header and a slice header, which are included in NAL units of the HP bitstream and the LP bitstream; and a bitstream reconstructor reconstructing and outputting the scalable video bitstream for each Access Unit (AU), which is a set of NAL units in the same time axis.

[20] According to another aspect of the present invention, there is provided a transceiver for a scalable video bitstream, the transceiver comprising: a transmitter, which comprises a splitter for: hierarchical modulation transmission of a scalable video bitstream, the splitter generating a plurality of bitstreams having different transmission priority, which are generated based on specific layers among a plurality ofscalable layers, by splitting the scalable video bitstream, and a receiver, which comprises a compositor fora hierarchical-modulated scalable video bitstream, the compositor receiving a plurality of bitstreams having different transmission priority, which are generated based on specific layers among the plurality of scalable layers and reconstructing the scalable video bitstream.

[21] The splitter in the transmitter of the transceiver for a scalable video bitstream may comprise: a High Priority (HP) channel generator generating an HP bitstream having HP based on a base layer among the plurality of scalable layers; a Low Priority (LP) channel generator generating an LP bitstream having LP based on an enhancement layer among the plurality of scalable layers; and a splitter header parser splitting the scalable video bitstream into the base layer and the enhancement layer by analyzing a Network Abstraction Layer (NAL) header included in a NAL unit of the scalable video bitstream.

[22] The compositor in the receiver of the transceiver for a scalable video bitstream may comprise: a bitstream receiver receiving the HP bitstream having HP, which was generated based on the base layer among the plurality of scalable layers, and the LP bitstream having LP, which was based on the enhancement layer among the plurality of scalable layers; a compositor header parser analyzing a Network Abstraction Layer (NAL) header and a slice header, which are included in NAL units of the HP bitstream and the LP bitstream; and a bitstream reconstructor reconstructing and outputting the scalable video bitstream for each Access Unit (AU), which is a set of NAL units corresponding to the same time axis.

[23] According to another aspect of the present invention, there is provided a method of transmitting a scalable video bitstream, the method comprising splitting the scalable video bitstream as follows: generating a High Priority (HP) bitstream having HP based on a base layer among a plurality of scalable layers included in the scalable video bitstream; and generating a Low Priority (LP) bitstream having LP based on an enhancement layer among the plurality of scalable layers included in the scalable video bitstream.

[24] The splitting of the scalable video bitstream may further comprise a splitter header parsing process, wherein the scalable video bitstream is split into the base layer and the enhancement layer by analyzing a Network Abstraction Layer (NAL) header included in a NAL unit of the scalable video bitstream.

[25] According to another aspect of the present invention, there is provided a method of receiving a scalable video bitstream, the method comprising a process of compositing a hierarchical-modulated scalable video bitstream, wherein the scalable video bitstream isreconstructed by receiving a High Priority (HP) bitstream having HP and a Low Priority (LP) bitstream having LP by splitting the scalable video bitstream.

[26] The process of compositing may comprise: a bitstream receiving process, wherein the HP bitstream and the LP bitstream are received; a compositor header parsing process, wherein a Network Abstraction Layer (NAL) header and a slice header, which are included in NAL units of the HP bitstream and the LP bitstream, are analyzed; and a bitstream reconstructing process, wherein the scalable video bitstream is reconstructed and output for each Access Unit (AU), which is a set of NAL units corresponding to the same time axis.

[27] According to another aspect of the present invention, there is provided a method of transmitting and receiving a scalable video bitstream, the method comprising: a transmitting process forhierarchical modulation transmission of a scalable video bitstream, wherein a plurality of bitstreams having different transmission priority are generated based on specific layers among a plurality of scalable layers; and a receiving process for a hierarchical-modulated scalable video bitstream, wherein the scalable video bitstream is reconstructed by receiving a plurality of bitstreams having different transmission priority based on specific layers among the plurality of scalable layers.

[28] The transmitting process may comprise: a High Priority (HP) channel generating process, wherein an HP bitstream having HP is generated based on a base layer among the plurality of scalable layers; a Low Priority (LP) channel generating process, wherein an LP bitstream having LP is generated based on an enhancement layer among the plurality of scalable layers; and a splitter header parsing process, wherein the scalable video bitstream is split into the base layer and the enhancement layer by analyzing a Network Abstraction Layer (NAL) header included in a NAL unit of the scalable video bitstream.

[29] The receiving process may comprise: a bitstream receiving process, wherein the HP bitstream having HP, which was generated based on the base layer among the plurality of scalable layers, and the LP bitstream having LP, which was based on the enhancement layer among the plurality of scalable layers, arereceived; a compositor header parsing process, wherein a Network Abstraction Layer (NAL) header and a slice header, which are included in NAL units of the HP bitstream and the LP bitstream, are analyzed; and a bitstream reconstructing process, wherein the scalable video bitstream is reconstructed and output for each Access Unit (AU), which is a set of NAL units corresponding to the same time axis.

[30] As described above, the present invention suggests an apparatus and method for hierarchical modulation transmission and reception of a scalable video bitstream, in which in order to generate and reconstruct two sub-bitstreams (an HP bitstream and an LP bitstream) in advanced T-DMB, a transmitter end splits the scalable video bitstream and a receiver end reconstructs the scalable video bitstream. Advantageous Effects

[31] As described above, according to the present invention , an apparatus and method for hierarchical modulation transmission and reception of a scalable video bitstream provides a high-quality service in advanced T-DMB while maintaining downlink compatibility with existing T-DMB. Description of Drawings

[32] The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

[33] FIG. 1 is a conceptual diagram of hierarchical modulation used in advanced

Terrestrial Digital Multimedia Broadcasting (T-DMB);

[34] FIG. 2 is a conceptual diagram of Scalable Video Coding (SVC); [35] FIG. 3 is a configuration diagram of a conventional T-DMB service;

[36] FIG. 4 is a configuration diagram of a useful data rate in advanced T-DMB;

[37] FIG. 5 is a configuration diagram of advanced T-DMB to which scalable video is applied according to an embodiment of the present invention; [38] FIG. 6 is a block diagram of a transmitter for hierarchical modulation transmission of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention;

[39] FIG. 7 is a configuration diagram of a scalable video bitstream to which a hierarchical modulation method according to an embodiment of the present invention is applied; [40] FIG. 8A is a block diagram of a splitter for hierarchical modulation transmission of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention; [41] FIG. 8B is a diagram for explaining an operation of a splitter for hierarchical modulation transmission of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention; [42] FIG. 8C is a flowchart illustrating a method of splitting a scalable video bitstream using a splitter for hierarchical modulation transmission of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention; [43] FIG. 9 is a block diagram of a receiver for hierarchical modulation reception of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention; [44] FIG. 1OA is a block diagram of a compositor for hierarchical modulation reception of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention; [45] FIG. 1OB is a diagram for explaining an operation of a compositor for hierarchical modulation reception of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention; and [46] FIG. 1OC is a flowchart illustrating a method of reconstructing a bitstream using a compositor for hierarchical modulation reception of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention.

Best Mode [47] FIG. 6 is a block diagram of a transmitter for hierarchical modulation transmission of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention. [48] Referring to FIG. 6, the transmitter according to the current embodiment of the present invention includes a transmission standard of an MPEG-4/MPRG-2 systems method, outer coding (Reed Solomon), and an outer convolutional interleaver as in existing T-DMB and additionally includes a splitter 600 in a video encoder at an input side.

[49] The splitter 600 encodes scalable video having a hierarchical structure and splits a scalable video bitstream encoded per channel.

[50] In detail, since SVC encodes a plurality of video layers to a single bitstream and each video layer independently has a bit rate, a frame rate, an image size, and image quality, a sub-bitstream suitable for each channel is split using the splitter 600 in order to hierarchical modulation transmission.

[51] FIG. 8A is a block diagram of a splitter 810 for hierarchical modulation transmission of a scalable video bitstream in advanced T-DMB according to an embodiment of the present invention.

[52] Referring to FIG. 8 A, the splitter 810 can include a splitter header parser 811, an HP channel generator 812, and an LP channel generator 813.

[53] The splitter 810 splits a single scalable video bitstream into bitstreams suitable for each channel in order to perform hierarchical modulation transmission.

[54] The scalable video bitstream includes a plurality of scalable layers independently having a bit rate, a frame rate, and resolution for a single bitstream.

[55] The splitter header parser 811 parses a Network Abstraction Layer (NAL) header included in a NAL unit of the scalable video bitstream.

[56] The splitter header parser 811 classifies the scalable video bitstream into a base layer and an enhancement layer by parsing the NAL header.

[57] The HP channel generator 812 generates an HP bitstream having HP based on the base layer among a plurality of scalable layers included in the scalable video bitstream.

[58] The LP channel generator 813 generates an LP bitstream having LP based on the enhancement layer among the plurality of scalable layers included in the scalable video bitstream.

[59] Advanced T-DMB uses the hierarchical modulation method by which a useful data rate can be more than doubled compared to existing T-DMB.

[60] In order to apply the hierarchical modulation method, according to the current embodiment, two sub-bitstreams (HP and LP streams) can be generated by splitting a single scalable video bitstream through HP and LP channels in the splitter 810. In addition, according to the current embodiment, the two generated bitstreams can be transmitted by a single transmitter.

[61] FIG. 8C is a flowchart illustrating a method of splitting a scalable video bitstream using a splitter for hierarchical modulation transmission of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention.

[62] Simple pseudo-code of a splitter algorithm will now be described.

[63] Case A) pseudo-code in a case of splitting a bitstream at an SD-class 30-frame rate [64] if ((Dependency_id==O)&&(NAL_unit_type !=6)) write_bitstream_HP; [65] else if (Dependency_id==O)&&(NAL_unit_type ==6)) write_bitstream_LP; [66] else write_bitstream_LP; [67] Case B) pseudo-code in a case of splitting a bitstream at an SD-class 15-frame rate using non-reference pictures

[68] if ((Dependency_id==0)&&(non_ref_pic !=0)&&(NAL_unit_type !=6))// [69] ((Dependency_id==0)&&(NAL_unit_type==7))// [70] ((Dependency_id==O)&&(NAL_unit_type ==8)) write_bitstream_HP; [71] else if (Dependency_id !=0)//(NAL_unit_type ==6)) write_bitstream_LP; [72] else drop; [73] SPS and PPS are parameter NAL Units indicating 'Sequence Parameter Set' and 'Picture Parameter Set' having decoding information of each layer.

[74] SEI stands for 'Supplemental Enhancement Information' and indicates information on scalability.

[75] Lid denotes 'Dependency_id'. [76] SPS and PPS are also indicate a NAL unit type, and SPS/PPS corresponding to a corresponding layer is also output through the splitter.

[77] Each nal_unit_type is defined as illustrated in Table 2. [78] [Table 2] [79] [Table 1] [Table ]

[80] In order to split a scalable video bitstream, a process of analyzing syntax information of an SVC NAL header is necessary, and in this case, necessary syntax elements are as follows. [81] (1) nam_unit_type: indicates a type of a packet including a NAL unit and identifies

SEI, SPS, PPS, and Slice. [82] (2) dependency_id: is information in a NAL header extended from H.264, is used in a decoding process, and indicates a lower layer used for inter-layer prediction. [83] Thus, in a bitstream encoded to two layers, a base layer is indicated by dependency_id=O, and an enhancement layer is indicated by dependency_id=l. In FIG.

7, Lid indicates dependency_id for inter-layer distinction. [84] Referring to FIG. 8C, Nal_unit_type and dependency_id can be obtained by parsing a

NAL header of an input bitstream in operations S 801 and S 802. [85] Exceptionally, in a case of an SEI message, since the SEI message is used when an extractor supported in SVC extracts a bitstream and not needed in an actual decoding process, the SEI message is not transmitted when the splitter splits the bitstream, in operation S803. [86] A bitstream having two layers can have dependency_id of a base layer having CIF resolution to be 0 and dependency_id of an enhancement layer having 4CIF resolution to be 1. Thus, the bitstream can be split using dependency_id in operation S804. [87] As a reference, two PPSs for the enhancement layer are generated to separately apply an Intra_BL MB mode to a Key-picture and a non Key-picture in single loop decoding. [88] As described above, two bitstreams corresponding to the base layer and the enhancement layer of a scalable video bitstream can be obtained using the method according to the current embodiment and are transmitted through an HP channel and an LP channel, respectively, in operations S805 and S806. [89] FIG. 9 is a block diagram of a receiver for hierarchical modulation reception of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention. [90] Referring to FIG. 9, the receiver according to the current embodiment of the present invention includes a compositor 900 that places in front of a decoding end, the compositor 900 reconstructing two sub-streams (HP bitstream and LP bitstream) received through HP and LP channels in order to receive a high-quality/high-resolution

AV service. [91] The compositor 900 receives two sub-streams and reconstructs a decodable single scalable video bitstream. [92] An existing T-DMB terminal can provide an existing service by receiving only an

HP channel. That is, the current embodiment provides downlink compatibility with existing T-DMB. [93] An advanced T-DMB terminal must include the compositor 900 placing in front of a decoding end and reconstructing two sub-bitstreams (HP and LP bitstreams) received through HP and LP channels in order to receive a high-quality/high-resolution AV service. [94] FIG. 1OA is a block diagram of a compositor 1010 for hierarchical modulation reception of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention. [95] A scalable video bitstream includes a plurality of scalable layers each independently having a bit rate, a frame rate, and a resolution. [96] In order to apply the hierarchical modulation method, a transmitter according to an embodiment of the present invention can generate two sub-bitstreams (HP and LP bitstreams) by splitting a scalable video bitstream through HP and LP channels in a splitter (Referring to FIGS. 8A and 8B). [97] The compositor 1010 receives the two sub-bitstreams in a front end of a video decoding end of a bitstream receiver 1011 and reconstructs and outputs a decodable scalable video bitstream. [98] Referring to FIG. 1OA, the compositor 1010 according to the current embodiment of the present invention includes the bitstream receiver 1011, a compositor header parser

1012, and a bitstream reconstructor 1013.

[99] The bitstream receiver 1011 receives an HP bitstream and an LP bitstream.

[100] The compositor header parser 1012 analyzes a NAL header and a slice header, which are included in NAL units of the HP bitstream and the LP bitstream. [101] The bitstream reconstructor 1013 receives the two sub-bitstreams (HP and LP bitstreams) and reconstructs a decodable scalable video bitstream for each Access Unit

(AU), which is a set of NAL units in the same time axis. [102] FIG. 1OC is a flowchart illustrating a process of reconstructing a bitstream using a compositor for hierarchical modulation reception of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention. [103] The compositor provides a function of reconstructing two bitstreams transmitted through an HP channel and an LP channel to form a decodable scalable bitstream. [104] In order to reconstruct the scalable bitstream, syntax element information used in a splitter and frame_num element information in a slice header are used. Syntax elements used in the compositor are as follows. [105] (1) nal_unit_type

[106] (2) frame_num: is used as an ID of each picture and used in a slice header. [107] The compositor sequentially acquires NAL units from a buffer in which they are temporarily stored through HP and LP channels, in operation SlOOl. [108] Nal_unit_type can be obtained through a process of parsing a NAL header of two input bitstreams split by a splitter in operation S 1002.

[109] After each NAL unit is read from the two input bitstreams, a bitstream is reconstructed in operation S 1009 by obtaining parameter NALs, such as an SPS and a PPS, from nal_unit_type of a NAL header using a first conditional statement

(operation S 1003) and selecting packets of the HP and LP channels in operation

S 1004. [110] However, since two PPSs are used in a case of an enhancement layer, a bitstream can be reconstructed in operation S 1009 using the packet of the LP channel by using a second conditional statement (operation S 1005) in order to obtain a second PPS. [I l l] Since other cases correspond to NAL units containing actual slice information, a bitstream can be reconstructed in operation S 1009 by parsing a slice header of each

NAL unit in operation S 1007 and obtaining frame_num in operation S 1008. [112] Frame_num indicates a POC corresponding to an actual display time of a bitstream. [113] As described above, the POC can be calculated by analyzing dependency_id of a

NAL header of an input NAL unit and frame_num of a slice header of the input NAL unit (parsing a NAL header and a slice header). [114] A bitstream can be reconstructed according to dependency_id by gathering NAL units corresponding to the same POC, and a bitstream can be reconstructed from NAL units having small frame_num of slice NAL units obtained from HP and LP. [115] In this case, a NAL unit having low dependency_id for each AU can go before a bitstream. [116] When a bitstream is reconstructed, SEI/SPS/PPS can be located in the beginning of the bitstream by identifying nal_unit_type, and reconstructed NAL units corresponding to actual data can be located next to the SEFSPS/PPS.

Mode for Invention [117] FIG. 1 is a conceptual diagram of hierarchical modulation used in advanced

Terrestrial Digital Multimedia Broadcasting (T-DMB). [118] As existing wireless Local Area Networks (LANs) are replaced by Wireless

Broadband Internet (Wibro) and existing mobile communication networks are replaced by High Speed Downlink Packet Access (HSDPA) networks, T-DMB also must provide a high transmission efficiency/high quality service in the future by overcoming the service limit of existing technology. [119] Advanced T-DMB for providing a high transmission efficiency/high quality service uses a hierarchical modulation method for roughly doubling a useful data rate provided in existing T-DMB. [120] Referring to FIG. 1, if the hierarchical modulation method is used, by splitting a bitstream into High Priority (HP) and Low Priority (LP) channels, two sub-bitstreams

(an HP bitstream and an LP bitstream) can be generated. [121] That is, if the hierarchical modulation method is used, two sub-bitstreams (an HP bitstream and an LP bitstream) can be transmitted by a single transmitter. [122] In advanced T-DMB, which is next generation T-DMB, data can be transmitted at around 2 Mbps compared to 1.062 Mbps that is a useful data rate used in existing T- DMB, and a high quality/high resolution video service can be provided based on the increased useful data rate.

[123] In advanced T-DMB using the hierarchical modulation method, an existing T-DMB service providing screen resolution of a Common Intermediate Format (CIF) 352 ' 288 class at maximum can be provided through an HP channel, and a T-DMB service providing screen resolution of a high quality (high resolution) Standard Definition (SD) 720 ' 480 class can be simultaneously provided through an LP channel.

[124] FIG. 2 is a conceptual diagram of Scalable Video Coding (SVC).

[125] The present invention applies SVC, which is being standardized in Joint Venture Team (JVT) (MPEG & VCEG), to advanced T-DMB in order to maintain compatibility with existing T-DMB while serving higher quality (higher resolution) multimedia content than that served in existing T-DMB.

[126] SVC, which is extended coding technology of H.264, is a new extended coding technology developed to solve problems of hierarchical coding based scalability tried in conventional MPEG-2, MPEG-4, and so on, such as low compression efficiency, no composite scalability support, and high implementation complexity, at once.

[127] Referring to FIG. 2, SVC encodes a plurality of video layers to a bitstream. each video layer includes a base layer and at least one enhancement layer, which can be continuously layered.

[128] Each enhancement layer can express a maximum bit rate, a maximum frame rate, and maximum resolution allowed thereto based on lower layer information. In SVC, as more enhancement layers are continuously layered, more various selections of a bit rate, a frame rate, and a resolution can be supported.

[129] As described above, SVC is coding technology suitable for a multimedia content service of a Universal Multimedia Access (UMA) environment, which can compositely solve problems in a variety of bandwidths, varieties of reception terminal performance and resolution, varieties of preference of content consumers, and so on occurring in a heterogeneous network environment.

[130] The present invention suggests an apparatus and method for hierarchical modulation transmission and reception of a scalable video bitstream in order to provide a high quality service in an advanced T-DMB while maintaining downlink compatibility with existing T-DMB.

[131] In more detail, the present invention suggests an apparatus and method for hierarchical modulation transmission and reception of a scalable video bitstream, in which in order to generate and reconstruct two sub-bitstreams (an HP bitstream and an LP bitstream) in an advanced T-DMB, a transmitter end splits the scalable video bitstream and a receiver end reconstructs the scalable video bitstream. [132] FIG. 3 is a configuration diagram of a conventional T-DMB service. Referring to

FIG. 3, in existing T-DMB, a service provider can have a data rate of 1.536 Mbps remaining from a maximum data rate of 2 Mbps, due to interference between channel frequencies. [133] By excluding outer coding, such as channel coding, from the data rate of 1.536

Mbps, the service provider can actually use a useful data rate of around 1.062 Mbps. [134] Thus, each service provider in existing T-DMB can provide a two-CIF(352 ' 288) class Audio- Visual (AV) program service, a Compact Disc (CD)-quality level audio service, and a data service using the useful data rate. [135] A provided AV program uses the H.264 video compression standard and is encoded up to 512-548 Kbps per service provider. [136] FIG. 4 is a configuration diagram of a useful data rate in advanced T-DMB.

Referring to FIG. 4, in advanced T-DMB, which is the next generation of existing T-

DMB, each service provider can have a useful data rate double that of before using the hierarchical modulation method. [137] In advanced T-DMB, a conventional T-DMB service can be provided through an HP channel, and a high transmission efficiency/high quality service can be provided through an LP channel. [138] In the case of high transmission efficiency service, around 4 CIF(352 ' 288) class AV programs can be transmitted compared to the conventional service. [139] In the case of high quality service, one CIF(352 ' 288) class AV program and one video service having screen resolution of an SD(720 ' 480) class can be provided compared to the conventional service. [140] FIG. 5 is a configuration diagram of advanced T-DMB to which scalable video is applied, according to an embodiment of the present invention. [141] Referring to FIG. 5, when one AV program is hierarchically encoded by applying scalable video, the AV program is scalable video encoded in a CIF(352 ' 288) class corresponding to a base layer to an HP channel and an SD(720 ' 480) class corresponding to an enhancement layer to an LP channel. [142] While a conventional T-DMB terminal receives a CIF(352 ' 288) class service through the HP channel, an advanced T-DMB terminal additionally receives an

SD(720 ' 480) class video service through the LP channel. [143] As described above, according to an embodiment of the present invention, a high quality DMB service can be provided in advanced T-DMB while maintaining downlink compatibility with existing T-DMB.

[144] FIG. 7 is a configuration diagram of a scalable video bitstream to which a hierarchical modulation method according to an embodiment of the present invention is applied. [145] Referring to FIG. 7, the scalable video bitstream can include a base layer assigned to an HP channel and an enhancement layer assigned to an LP channel. [146] The base layer assigned to the HP channel has a 30-frame rate of the CIF class and is encoded at 384 Kbps in order to keep downlink compatibility with existing T-DMB. [147] The enhancement layer is assigned at the same time as the base layer is assigned to the HP channel. [148] The enhancement layer has a 30-frame rate of the SD class and is encoded at around

900 Kbps. [149] In order to meet a target bit rate assigned to each channel, an H.264 rate control algorithm is applied to SVC, and video coding for the base layer conforms to the

H.264 standard. [150] In advanced T-DMB, a target bit rate according to SVC can be varied within a range not exceeding a total useful data rate for each service provider. [151] The enhancement layer additionally assigned to the LP channel can be encoded at a

15-frame rate using non-reference pictures if a bit rate according to a content type is high. [152] In this case, a splitter must output only reference pictures of the enhancement layer assigned to the LP channel. [153] In addition, in advanced T-DMB, considering terminal performance compared to scalable video complexity, scalability according to Fine Granular Scalability (FGS) is not considered. [154] FIG. 8B is a diagram for explaining an operation of a splitter 820 for hierarchical modulation transmission of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention. [155] In H.264, after video coding is performed, a single bitstream composed of NAL units is generated, each NAL unit having a 1-byte NAL header. [156] Scalable video additionally has a 2-byte header having scalability information besides a 1-byte NAL header in H.264.

[157] Each field in a NAL header is defined by an international standard. [158] Table 1 illustrates major fields of a NAL header. [159] [Table 1] [160] [Table 2] [Table ]

[161] Dependency_id that is one of the major fields of a NAL header is syntax for classifying a base layer and an enhancement layer. [162] Thus, a splitter algorithm performed by the splitter 820 analyzes each input NAL header (NAL header parsing). [163] The splitter 820 can output two sub-bitstreams (HP and LP bitstreams) respectively assigned to HP and LP channels. [164] The splitter 820 generates an HP channel (HP bitstream) having HP based on a base layer among scalable layers included in a single scalable video bitstream. [165] The splitter 820 generates an LP channel (LP bitstream) having LP based on an enhancement layer among the scalable layers. [166] FIG. 1OB is a diagram for explaining an operation of a compositor 1020 for hierarchical modulation reception of a scalable video bitstream in advanced T-DMB, according to an embodiment of the present invention.

[167] Basically, the compositor 1020 determines a Picture Order Count (POC) corresponding to a display order of a corresponding frame (NAL unit) by parsing NAL header information of the NAL units and an additional slice header.

[168] The compositor 1020 uses existing information of Dependency_id, nal_ref_idc, and nal_unit_type of a NAL header and frame_num information of a slice header.

[169] The compositor 1020 finally outputs a decodable scalable video bitstream.

[170] Thus, in order to output a bitstream for each Access Unit (AU), which is a set of

NAL units in the same time axis, POC information is necessarily needed. This POC information can be calculated by applying pseudo-code described below provided by existing SVC.

[171] if(REFERENCE) P0C=(2*frame_num);

[172] else P0C=(2*frame_num)- 1 ;

[173] Consequently, the compositor 1020 can output a decodable bitstream using header information of a corresponding frame used in a splitter.

Claims

[1] A transmitter for a scalable video bitstream having a plurality of scalable layers, the transmitter comprising a splitter forhierarchical modulation transmission of a scalable video bitstream, the splitter comprising: a High Priority (HP) channel generator generating an HP bitstream having HP based on a base layer among the plurality of scalable layers included in the scalable video bitstream; and a Low Priority (LP) channel generator generating an LP bitstream having LP based on an enhancement layer among the plurality of scalable layers included in the scalable video bitstream.

[2] The transmitter of claim 1, wherein the splitter further comprises a splitter header parser splitting the scalable video bitstream into the base layer and the enhancement layer by analyzing a Network Abstraction Layer (NAL) header included in a NAL unit of the scalable video bitstream.

[3] The transmitter of claim 1, wherein the base layer and the enhancement layer are encoded according to an H.264 standard, the base layer being encoded at a Common Intermediate Format (CIF)-class 30-frame rate and a bit rate of 384 Kbps, and the enhancement layer being encoded at a Standard Definition (SD)-class 30-frame rate and a bit rate of 900 Kbps.

[4] A receiver for a scalable video bitstream having a plurality of scalable layers, the receiver comprising a compositor for a hierarchical-modulated scalable video bitstream, the compositor receiving a High Priority (HP) bitstream having HP and a Low Priority (LP) bitstream having LP by splitting the scalable video bitstream and reconstructing the scalable video bitstream.

[5] The receiver of claim 4, wherein the compositor comprises: a bitstream receiver receiving the HP bitstream and the LP bitstream; a compositor header parser analyzing a Network Abstraction Layer (NAL) header and a slice header, which are included in NAL units of the HP bitstream and the LP bitstream; and a bitstream reconstructor reconstructing the scalable video bitstream for each Access Unit (AU), which is a set of NAL units in the same time axis.

[6] The receiver of claim 4, wherein the HP bitstream is generated based on a base layer among the plurality of scalable layers, and the LP bitstream is generated based on an enhancement layer among the plurality of scalable layers.

[7] The receiver of claim 6, wherein the base layer and the enhancement layer are encoded according to an H.264 standard, the base layer being encoded at a Common Intermediate Format (CIF)-class 30-frame rate and a bit rate of 384 Kbps, and the enhancement layer being encoded at a Standard Definition (SD)-class 30-frame rate and a bit rate of 900 Kbps.

[8] A method of transmitting a scalable video bitstream having a plurality of scalable layers, the method comprising splitting the scalable video bitstream as follows: generating a High Priority (HP) bitstream having HP based on a base layer among the plurality of scalable layers included in the scalable video bitstream; and generating a Low Priority (LP) bitstream having LP based on an enhancement layer among the plurality of scalable layers included in the scalable video bitstream.

[9] The method of claim 8, wherein the splitting of the scalable video bitstream further comprises a splitter header parsing process, wherein the scalable video bitstream is split into the base layer and the enhancement layer by analyzing a Network Abstraction Layer (NAL) header included in a NAL unit of the scalable video bitstream.

[10] The method of claim 8, wherein the base layer and the enhancement layer are encoded according to an H.264 standard, the base layer being encoded at a Common Intermediate Format (CIF)-class 30-frame rate and a bit rate of 384 Kbps, and the enhancement layer being encoded at a Standard Definition (SD)-class 30-frame rate and a bit rate of 900 Kbps .

[11] A method of receiving a scalable video bitstream having a plurality of scalable layers, the method comprising a process of compositing a hierarchical-modulated scalable video bitstream, wherein the scalable video bitstream isreconstructed by receiving a High Priority (HP) bitstream having HP and a Low Priority (LP) bitstream having LP generated by splitting the scalable video bitstream.

[12] The method of claim 11, wherein the process of compositing comprises: a bitstream receiving process, wherein the HP bitstream and the LP bitstream are received; a compositor header parsing process, wherein a Network Abstraction Layer (NAL) header and a slice header, which are included in NAL units of the HP bitstream and the LP bitstream, are analyzed; and a bitstream reconstructing process, wherein the scalable video bitstream is reconstructed for each Access Unit (AU), which is a set of NAL units in the same time axis.

[13] The method of claim 11, wherein the HP bitstream is generated based on a base layer among the plurality of scalable layers, and the LP bitstream is generated based on an enhancement layer among the plurality of scalable layers.

[14] The method of claim 13, wherein the base layer is encoded at a Common In- termediate Format (CIF)-class 30-frame rate and a bit rate of 384 Kbps, and the enhancement layer is encoded at a Standard Definition (SD)-class 30-frame rate and a bit rate of 900 Kbps.

[15] A computer readable recording medium storing a computer readable program for executing the method of any one of claims 8 through 14.