KR20090055399A - Broadcasting system and method of processing audio data - Google Patents

Abstract

A broadcasting system and an audio data processing method are provided to supply a viewer with a high sound quality service through mobile broadcasting by achieving a multi channel audio service in terrestrial DMB. An audio data processing method of a broadcasting system comprises the following steps. A mobile broadcasting signal including multi channel audio data is received. By using identification information included in the mobile broadcasting signal, the multi channel audio data is extracted. The extracted multi channel audio data is decoded and outputted. The identification information for identifying the multi channel audio data is included in an object descriptor.

Description

Broadcasting system and method of processing audio data}

The present invention relates to a broadcast system, and more particularly, to a mobile broadcast system and an audio data processing method for supporting a multi-channel audio service.

Digital multimedia broadcasting (DMB) of mobile broadcasting that can provide high quality voice and video services anytime and anywhere has evolved from listening broadcasting to watching broadcasting. Based on the excellent mobile reception characteristics, various contents such as music, text, and video are delivered through mobile terminals such as mobile phones and PDAs, thereby establishing a complementary relationship with digital terrestrial TV broadcasting pursuing high quality and high sound quality.

The DMB is based on Eureka-147 Digital Audio Broadcasting (DAB), which has been adopted as the European terrestrial radio standard. That is, the Eureka-147 was created for digital audio broadcasting (DAB), but is also used as a ground-based DMB technology that serves a small screen size video using a narrow frequency bandwidth of 2 MHz.

In addition to the MPEG-4 data transmission, the DMB can transmit other types of data such as TPEG and BWS (Broadcast Website), thereby supporting multimedia broadcasting of mobile reception. This can be said that the industrial ripple effect can be very large in that it can be applied not only to the DMB receiver itself but also to existing mobile devices such as PDAs, portable DVDs, and mobile phones. The MPEG-4 method uses an image expression method based on contents, and processes the screen into video objects having attributes of shape information, motion information, and texture information. The content-based image representation method establishes the interrelationship between objects in various multimedia applications to facilitate their access and manipulation. In other words, the object-oriented interactive function in MPEG-4 handles the object elements of a picture or sound independently in multimedia data access, and combines them by linking with each other so that the user can freely configure the picture or sound. For example, processing such as replacing only the main character with the background on the screen previously possible only in the production stage, but in the MPEG-4 user stage.

An object of the present invention is to provide a terrestrial DMB broadcasting system and an audio data processing method for supporting a multi-channel audio service.

Another object of the present invention is to provide a terrestrial DMB broadcasting system and an audio data processing method for supporting an MPEG surround audio service.

In the broadcasting system according to the present invention, a method for processing audio data in a receiving system includes: receiving a mobile broadcast signal including multichannel audio data; extracting multichannel audio data using identification information included in the mobile broadcast signal; And decoding and outputting the extracted multi-channel audio data.

The present invention enables the multi-channel audio service in the terrestrial DMB, thereby providing a higher-quality sound service to viewers through mobile broadcasting.

The present invention provides a multi-channel audio signal such as a 5.1 channel in a transmission system capable of transmitting terrestrial DMB, and to receive and output the multi-channel audio signal in a reception system capable of receiving terrestrial DMB. .

1 shows an embodiment of a terrestrial DMB packet structure according to the present invention.

In FIG. 1, an MPEG-4 system in a transmission system for DMB broadcasting uses an MPEG-4 sync layer to perform audio / video elementary streams (A / V ES) that are each compressed and coded with a predetermined compression algorithm. Packetize (Layer; SL).

For example, video can be compressed and encoded using MPEG-4 / AVC (Advanced Video Coding) (MPEG-4 Part 10) and packetized into MPEG-4 Sync Layer (SL), which provides object-oriented interactive functionality. To support this, MPEG-4 BIFS (Binary Format for Scenes) interactive content can also be packetized in MPEG-4 SL.

The audio may be compressed and encoded using MPEG-4 / BSAC (Bit Sliced Arithmetic Coding), and then packetized into MPEG-4 SL, or compressed and encoded using MPEG surround, and then packetized into MPEG-4 SL. . As another example, an audio ES combined with MPEG-4 BSAC and MPEG Surround may be packetized into MPEG-4 SL. For convenience of description, the MPEG-4 BSAC audio signal will be referred to as main audio data.

The MPEG-2 system in the transmission system packetizes the MPEG-4 SL packet packetized in the MPEG-4 system in the form of a packetized elementary stream (PES), and then the packet in an MPEG-2 transport stream (TS). Make up. The MPEG-2 TS packet is composed of a header and a payload. The MPEG-2 system performs Reed-Solomon encoding on the MPEG-2 TS packet, attaches a Reed-Solomon code having a size of 16 bytes to the TS packet, and then byte interleaving. After performing, the result is transmitted to the receiving system.

As described above, the transmitting side of the terrestrial DMB transmits audio / video objects using the MPEG-4 system standard, and transmits scene description information indicating the arrangement of these AV objects in time and space. After the scene is composed in the receiving system, it can be rendered and displayed for a two-dimensional display. In reality, the scene description information has a tree structure, and each node of the tree represents an A / V object. An object descriptor (OD) is connected to an end node of the tree. The OD includes information indicating various attributes of an object and the location of actual data corresponding to the object. Therefore, the reception system first refers to the scene configuration information, determines the position in each object's space time and space, finds object data using the OD, and arranges the object data in the scene according to a specified attribute.

In addition, the transmitting side transmits a PAT (Program Association Table) of MPEG-2 TS and an Initial Object Descriptor (IOD) of the MPEG-4 system standard in a multiplexed stream. In this case, the IOD is included in a program map table (PMT) of the MPEG-2 TS.

That is, when packetizing MPEG-4 compressed and encoded multimedia into MPEG-2 TS, the above-described PMT syntax includes IOD and SL (Sync Layer) descriptor defined in MPEG-4.

The IOD informs the profile and level information of the transmitted MPEG-4 content. It also includes the ES (Elementary Stream) ID of the OD stream and the ES ID information of the Scene Description (SD) stream. That is, information on the OD stream and information on the SD stream is described in the ES descriptor of the IOD. The IOD serves as a pointer connecting the BIFS and the OD of the SD. Therefore, when the IOD is analyzed in the MPEG-4 system of the receiving system, a logical channel (ES_ID) for transmitting information about scene description and information about each object can be obtained. Each logical channel can then be accessed to compose a scene, and after obtaining information about the object, the logical channel for sound or video can be obtained.

The OD includes an ES descriptor, and the ES descriptor includes an ES_ID and a DecoderConfigDescriptor. The DecoderConfigDescriptor includes stream type information indicating a type of a stream to be transmitted, an objectTypeIndication indicating an object type, and a Decoderspecific info indicating decoding information for each stream.

In the present invention, in order to receive and correctly output a multi-channel audio signal in a reception system, a value that can uniquely distinguish MPEG surround audio data is assigned to a stream type value transmitted through the PMT. That is, if the stream to be transmitted is an MPEG surround audio stream, 0x1C is assigned to the stream type value as shown in FIG. 2. The 0x1C value is one embodiment and can be changed to another value by the system designer.

As described above, the present invention defines a stream type value for multi-channel extension audio for signaling MPEG surround audio data through PMT.

The reason for defining the stream type is that it is necessary to distinguish subchannel data for main audio data and multichannel audio data. For example, some systems may not support multichannel audio depending on the specifications of terrestrial DMB receiving system. In this case, it is necessary to decode only main channel audio and ignore stream type data defined as multichannel extension audio.

3 to 5 illustrate embodiments of a method of packetizing multi-channel audio data (eg, MPS audio data) into MPEG SL according to the present invention.

FIG. 3 shows an example of a method of inserting an MPS ES into an ancillary data (ie, BSAC Extencion) field in the current audio ES and packetizing it into MPEG SL. That is, both the BSAC ES and the MPS ES are inserted into the payload in one SL packet. At this time, the ES_ID of each SL packet transmitting the audio ES has the same value (eg, 0x101) without distinguishing between the BSAC ES and the MPS ES.

4 shows an example of a method of allocating a separate ES_ID to the MPS ES and distinguishing the SL packet from which the BSAC ES is transmitted and transmitting the separate SL packet.

If the ES_ID of the BSAC ES is 0x101, the ES_ID of the MPS ES may be assigned a value other than 0x101, for example, 0x105. At this time, since the MPS has a low bitrate, the MPS inserts a plurality of access units (AUs) into the payload in the SL packet in a super frame unit. FIG. 4 shows an example in which an MPS super frame that combines three MPS AUs is inserted into a payload in one SL packet.

FIG. 5 shows an example of a method of allocating an independent subchannel for the MPS ES and transmitting the MPS ES to the assigned subchannel.

For example, video, BSAC audio, and system information (eg, PMT, PAT, etc.) may be transmitted through subchannel A, and only MPS audio may be transmitted through newly allocated subchannel B. In this case, the ES_ID of the MPS ES transmitted to the subchannel B may have the same value as the ES_ID of the BSAC ES or may have a different value.

As described above, in order to support the multi-channel audio service, ES_ID and OD_ID should be defined, and DecoderConfigDescriptor for MPS should be defined. In addition, it is necessary to define a super frame structure for optimizing the TS rate when transmitting the MPS to an independent ES.

Here, the ES for transmitting spatial audio data is identified by an Audio Object Type "MPEG Surround" (An elementary stream carrying spatial audio data is identified by the Audio Object Type "MPEG Surround"). At this time, the audio object type ID of MPEG surround is assigned as an embodiment (Object Type ID 30). And AudioSpecificConfig () for the object transmits SpatialSpecificConfig () data and sacPayloadEmbedding flag. The audioSpecificConfig () for this object carries the SpatialSpecificConfig () data and a sacPayloadEmbedding flag that indicates whether or not the SpatialFrame () payload is transmitted as ES or inserted into downmix data. the SpatialFrame () payload is conveyed as an elementary stream or embedded into the downmix data).

Data corresponding to SpatialSpecificConfig () in AudioSpecificConfig () is carried in DecoderConfigDescriptor and transmitted.

Each MPS ES is packed by a syntax called SpatialFrame (), which is transmitted through SL-> PES-> TS packetization. If the MPS ES is transmitted as shown in FIG. 4, the ES_ID of the MPS ES has a value different from that of the BSAC ES.

The size of the SpatialFrame () is so small that a super frame structure can be used for efficient TS trunk. At this time, if a plurality of MPS ES can be inserted in one SL packet, the syntax of super frame need not be defined separately. There may be several BSAC ESs corresponding to one MPS SL. Therefore, the number of SLs packetizing the BSAC and the SLs packetizing the MPS may not match, but may have a multiple relationship.

6 to 24 show examples of an AudioSpecificConfig () structure for supporting a multi-channel audio service according to the present invention.

In this embodiment, the Audio Object Type ID of the MPEG-4 BSAC is 22 and the Audio Object Type ID of the MPEG Surround is 30.

Also transmitted to DecoderConfigDescriptor for audio is AudioSpecificConfig () as defined in FIGS. 6 to 24.

Here, it is divided into a descriptor for BSAC and a descriptor for MPEG surround (hereinafter referred to as MPS) according to the ObjectType ID. 6 to 24, the data field present in the DecoderConfigDescriptor for the BSAC is represented by 10, and the data field present in the DecoderConfigDescriptor for the MPS is represented by 20, and in common when represented by 30. do.

That is, according to the ObjectType ID, it is classified into a type of calling GASpecificConfig () in case of BSAC and SpatialSpecificConfig () in case of MPS.

In case of combining BSAC + SBR or BSAC + MPS to one ES, it transmits descriptor information about BSAC and SBR or MPS through one AudioSpecificConfig () through contents related to extensionAudioObjectType of AudioSpecificConfig (). Can be. The field used for this is indicated by 40.

At this time, the samplingFrequencyIndex in the descriptor for MPS cannot be different from the descriptor for BSAC. ChannelConfiguration in the descriptor for MPS is meaningless. The bsSamplingFrequencyIndex in the descriptor for the MPS cannot be different from the samplingFrequencyIndex on the MPS and BSAC descriptors. Therefore, as duplicated data, one can be defined to be ignored. The bsFrameLength value in the MPS should be configured to point to a multiple of 1024 samples, the frame size of the BSAC. You can use this information to use the superframe concept. Up to 8192 samples can be defined as one MPS frame, which corresponds to eight BSAC frames. When using this field, the actual concept is not a super frame, but a single MPS frame corresponds to multiple BSACs. In this case, in order to correspond to the plurality of BSAC frames (ES) to one MPS frame, an identifier, sync information, timing information, etc. indicating a relationship between each other may be required. Several parameters in SpatialSpecificConfig () can limit the scope of their operation for a target app. For example, bsTreeConfig can be restricted or bsArbitraryDownmix, bsMatrixMode, bs3DaudioMode, etc. can be limited to a specific value in order not to support multichannel mode of 5.1 channels or more.

6A through 6E illustrate an embodiment of a syntax structure of an AudioSpecificConfig according to the present invention. AudioSpecificConfig () extends the abstract class DecoderSpecificInfo, as defined in ISO / IEC 14496-1, when DecoderConfigDescriptor.objectTypeIndication refers to streams complying with ISO / IEC 14496-3 in this case the existence of AudioSpecificConfig () is mandatory.

7 shows an embodiment of the GetAudioObjectType () syntax structure according to the present invention.

8A and 8B illustrate an embodiment of the GASpecificConfig () syntax structure according to the present invention.

9 illustrates an embodiment of a bsac_payload () syntax structure that is a top level payload of an audio object type ER BSAC according to the present invention.

10 shows an embodiment of a bsac_lstep_element () syntax structure according to the present invention.

11A and 11B illustrate an embodiment of a bsac_raw_data_block () syntax structure according to the present invention.

12 shows an embodiment of a bsac_base_element () syntax structure according to the present invention.

13 shows an embodiment of a bsac_header () syntax structure according to the present invention.

14 illustrates an embodiment of a general_header () syntax structure according to the present invention.

15 shows an embodiment of a bsac_layer_element () syntax structure according to the present invention.

16 shows an embodiment of an extended_bsac_raw_data_block () syntax structure according to the present invention.

17 shows an embodiment of an extended_bsac_base_element () syntax structure according to the present invention.

18 shows an embodiment of an extended_bsac_sbr_data () syntax structure according to the present invention.

19 shows an embodiment of a bsac_sbr_data () syntax structure according to the present invention.

20 shows an embodiment of an extended_bsac_data () syntax structure according to the present invention.

21 shows an embodiment of an extended_bsac_sac_data () syntax structure according to the present invention.

Meanwhile, MPEG surround according to the present invention may include SpatialSpecificConfig () and SpatialFrame ().

22A and 22B illustrate an embodiment of a SpatialSpecificConfig () syntax structure according to the present invention.

23 illustrates an embodiment of a SpatialFrame () syntax structure according to the present invention.

24 shows an embodiment of the FramingInfo () syntax structure according to the present invention.

25 shows an embodiment of a receiving system for receiving and outputting multi-channel audio data according to the present invention.

25 includes a DAB system, deinterleaver, RS decoder, TS demux, SL depacketizer, video decoder, BSAC parser, MPEG surround parser, OD / BIFS decoder, IOD parser, BSAC decoder, and multichannel audio decoder can do. If the receiving system is a conventional terrestrial DMB receiver, only BSAC audio data can be decoded.

The DAB system may include a tuner and a baseband signal processor (not shown). The baseband signal processing unit may include an analog / digital (A / D) converter, a synchronizer, an OFDM demodulator, a deinterleaver, a Viterbi decoder, and an audio decoder (not shown). The audio decoder in the baseband signal processor decodes and outputs existing DAB audio data. For example, the audio decoder decodes and outputs a DAB audio signal by a masking pattern adapted universal sub-band integrated coding and multiplexing (MUSCAM) scheme.

If the data processed in the DAB system is the data transmitted in the stream mode, the data stream is output to the deinterleaver of FIG. 25, deinterleaved, and then output to the RS decoder.

The RS decoder performs additional error correction on the data stream and outputs the TS demux. The TS demux performs transport stream depacketizing and packetized element stream (PES) depacketizing on the error corrected data stream and outputs the depacketizer to the SL depacketizer. The SL depacketizer performs SL (Sync Layer) depacketization on PES depacketized data and divides it into one of video ES, BSAC audio ES, MPEG surround audio ES, OD / BIFS, IOD, and JPEG ES. do. That is, in order to receive and correctly output a multi-channel audio signal in a receiving system, the SL depacketizer first distinguishes MPEG surround data from main audio data (ie, BSAC audio data).

The video ES is output to a video decoder and the BSAC audio ES is output to a BSAC parser. The MPEG surround audio ES is output to an MPEG surround parser, OD / BIFS is output to an OD / BIFS decoder, and the IOD is output to an IOD parser.

The BSAC parser extracts BSAC audio data, and the MPEG surround parser extracts MPEG surround audio data. BSAC audio data extracted by the BSAC parser is output to a BSAC decoder and a multi-channel audio decoder. MPEG surround audio data extracted by the MPEG surround parser is output to a multi-channel audio decoder. The multi-channel audio decoder performs decoding of MPEG surround audio data. The multi-channel audio decoder also decodes audio data combining BSAC and MPEG surround.

A data parsing process for a 5.1 channel audio service including HE-AAC v2 and MPEG surround will be described with reference to FIGS. 26 and 27.

That is, the transmitting side transmits an MPEG-2 TS PAT (Program Association Table) and an Initial Object Descriptor (IOD) of the MPEG-4 system standard in a multiplexed stream. In this case, the IOD is included in a program map table (PMT) of the MPEG-2 TS.

The PAT provides PID information of a TS packet containing information of a program. The PAT is special information transmitted by a packet of PID = 0x00. Each PAT describes a component of the program, and indicates a PID of a transport packet that transmits a program map table (PMT).

That is, a program number and a PID of a PMT are found by parsing the payload of a TS packet having a PID of 0x00.

The PMT obtained from the PAT provides a correlation between the components constituting the program. In this case, since terrestrial DMB is transmitted with MPEG-4 content, IOD is included in PMT. Therefore, IOD descriptor information included in the PMT is extracted. The PID for each ES is searched by mapping the ES_ID of the corresponding ES Descriptor and the ES_ID of the SL Descriptor included in the extracted IOD descriptor.

In the case of an audio stream, a DecoderConfigDescriptor including information on coding characteristics (profile, etc.) of audio is transmitted to each ES descriptor. At this time, DecoderConfigDescriptor is separately defined for the ES (or SL) corresponding to the information about the main channel codec and sub-channel codec.

That is, when packetizing MPEG-4 compressed and encoded multimedia into MPEG-2 TS, the above-described PMT syntax includes IOD and SL (Sync Layer) descriptor defined in MPEG-4. At this time, the IOD descriptor is included in the descriptor () region of the first loop, and the SL descriptor is included in the descriptor () region of the second loop.

As shown in FIG. 27, the IOD informs profile and level information of the transmitted MPEG-4 content. It also includes the ES (Elementary Stream) ID of the OD stream and the ES ID information of the Scene Description (SD) stream.

That is, information about the OD stream and information about the SD stream is described in the ES_descriptor field of the IOD. The IOD serves as a pointer connecting the BIFS and the OD of the SD.

Therefore, by analyzing the IOD, a logical channel (ES_ID) for transmitting information about scene description and information about each object can be obtained. Each logical channel can then be accessed to compose a scene, and after obtaining information about the object, the logical channel for sound or video can be obtained.

In addition, the second loop of the PMT includes a stream_type field for identifying whether a packetized stream is transmitted in a packetized elementary stream (PES) type or a section type in an SL, a PID (elementary_PID) field of each stream, and Contains the ES ID information of the PID. Therefore, when the PMT information is interpreted, the information of all the programs transmitted to the TS can be obtained.

Then, the MPEG-4 SL including the main audio and the subchannel audio is extracted using the PID of the retrieved ES. Each SL is sent to each decoder via an SL depacketizer.

That is, each OD includes an ES descriptor, and the ES descriptor includes an ES_ID field and a DecoderConfigDescriptor field. The DecoderConfigDescriptor field includes a stream type field indicating a type of a stream to be transmitted, an objectTypeIndication field indicating an object type, and a Decoderspecific info field identifying decoding information about each stream.

For example, if the stream type field value is 0x1C, this indicates an MPEG surround audio stream.

Accordingly, the reception system according to the present invention parses the ES_ID and the PID of the stream type (eg, 0x1C) sequentially and processes them together with the basic BSAC data (MUX) to enjoy the extended MPEG surround sound.

The following shows an example of the NewConfigDescriptor () syntax structure according to the present invention.

NewConfigDescriptor ()

{

bsAudioContentsTypeInfo;

bsAudioContentsTypeExtensionInfo;

bsRenderingGuideInfo;

bsDownmixMode;

}

bsAudioContentsTypeInfo indicates the type of audio contents to be transmitted. For example, it distinguishes genres such as news, drama, movie, sports, music, or in combination with bsAudioContetnsTypeExtensionInfo. Tell the details by rock, concert, choir, jazz, pop, ...

The multi-channel audio decoder may utilize such information to perform proper tone control as well as proper redistribution of the 5.1 channel decoded signal. This information can also be used to inform the user via EPG or OSD.

bsRenderingGuideInfo informs the decoder of the desired mode when binaural rendering the transmitted multichannel contents, downmixing to 4.0 channels, such as in a car environment, or downmixing to stereo. Do it. Similarly, bsDownmixMode may be transmitted.

This is useful information considering that the environment using the MPS is a vehicle. Configuration information for mapping a 5.1 channel to a 4.0 channel or a gain term necessary for a downmix process can be transmitted through such a field.

E.g,

If bsDownmixMode = 0,

Lout = L * 1.0 + C * 0.5 + LFE * 0.5

Rout = C * 0.5 + R * 1.0 + LFE * 0.5

Lsout = Ls * 1.0

Rsout = Rs * 1.0

If bsDownmixMode = 1,

Lout = L * 0.7 + C * 0.7 + LFE * 0.7

Rout = C * 0.7 + R * 0,7 + LFE * 0.7

Lsout = L * 0.2 + Ls * 0.9

Rsout = R * 0.2 + Rs * 0.9

As an example, downmixing with different gains is an example.

1 is a diagram showing an embodiment of a terrestrial DMB packet structure according to the present invention;

2 shows an example of a stream type value according to the present invention;

3 to 5 illustrate embodiments of a method for packetizing multi-channel audio data in MPEG SL according to the present invention.

6A-6E illustrate one embodiment of a syntax structure of an AudioSpecificConfig according to the present invention.

7 illustrates an embodiment of a GetAudioObjectType () syntax structure according to the present invention.

8A and 8B illustrate an embodiment of a GASpecificConfig () syntax structure in accordance with the present invention.

9 illustrates an embodiment of a bsac_payload () syntax structure that is a top level payload of an audio object type ER BSAC according to the present invention.

10 illustrates an embodiment of a bsac_lstep_element () syntax structure according to the present invention.

11A and 11B illustrate an embodiment of a bsac_raw_data_block () syntax structure according to the present invention.

12 illustrates an embodiment of a bsac_base_element () syntax structure according to the present invention.

13 is a diagram illustrating an embodiment of a bsac_header () syntax structure according to the present invention.

14 illustrates an embodiment of a general_header () syntax structure according to the present invention.

15 illustrates an embodiment of a bsac_layer_element () syntax structure according to the present invention.

16 is a diagram illustrating an embodiment of an extended_bsac_raw_data_block () syntax structure according to the present invention.

17 illustrates an embodiment of an extended_bsac_base_element () syntax structure according to the present invention.

18 is a diagram illustrating an embodiment of an extended_bsac_sbr_data () syntax structure according to the present invention.

19 illustrates an embodiment of a bsac_sbr_data () syntax structure according to the present invention.

20 illustrates an embodiment of an extended_bsac_data () syntax structure according to the present invention.

21 illustrates an embodiment of an extended_bsac_sac_data () syntax structure according to the present invention.

22A and 22B illustrate an embodiment of a SpatialSpecificConfig () syntax structure according to the present invention.

FIG. 23 illustrates an embodiment of a SpatialFrame () syntax structure according to the present invention. FIG.

24 illustrates an embodiment of the FramingInfo () syntax structure according to the present invention.

25 is a block diagram showing an embodiment of a receiving system for receiving and outputting multi-channel audio data according to the present invention;

26 and 27 illustrate a process of parsing a system information table according to the present invention.

Claims (3)

Receiving a mobile broadcast signal including multi-channel audio data; Extracting multi-channel audio data using identification information included in the mobile broadcast signal; And And decoding and outputting the extracted multi-channel audio data. The method of claim 1, Identification information for identifying the multi-channel audio data is included in an object descriptor (OD). The method of claim 1, And the identification information is stream type information capable of classifying elementary stream types.

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