KR100724867B1 - Method for generating and reproducing multi channel for transmitting for the multi channel in digital multimedia broadcasting system - Google Patents

Abstract

According to the present invention, a packetized elementary stream (PES) packet of each of a plurality of channels for multi-channel transmission has the same PID (Packet Identifier), and a PTS (Presentation Time Stamp) of each PES packet uses the same PID. In addition to indicating that it is a multi-channel PES packet, it is reset to have a predetermined PTS difference between channels to distinguish between multiple channels using the same PID. As such, instead of using different PIDs for each channel, multi-channel transmission is realized by using only one PID by using a PTS difference.

Digital multimedia broadcasting (DMB), multi channel, PID, PTS.

Description

METHOD FOR GENERATING AND REPRODUCING MULTI CHANNEL FOR TRANSMITTING FOR THE MULTI CHANNEL IN DIGITAL MULTIMEDIA BROADCASTING SYSTEM}

1 illustrates an MPEG-4 TS.

2 is a block diagram illustrating a packetizer for multi-channel audio transmission according to an embodiment of the present invention;

3 is a diagram illustrating multi-channel audio generation according to an embodiment of the present invention;

4 is a flowchart illustrating a multi-channel audio generation process according to an embodiment of the present invention;

5 is a block diagram illustrating a PES processor for multi-channel audio reproduction according to an embodiment of the present invention;

6 is a flowchart of a multi-channel audio reproduction process according to an embodiment of the present invention.

The present invention relates to a digital multimedia broadcasting (DMB) system, and more particularly to a method for transmitting a multi-channel.

In DMB, multiple cases of voice multicasting are required. For example, in addition to the audio according to the broadcasting program, voice multicasting provides a visual description of the current scene for the visually impaired. For example, there may be voice broadcasting for foreigners or foreign language learners. Multi-channel audio transmission should be performed for such voice multicasting. That is, an audio channel for additional voice transmission is required in addition to an audio channel for basic voice transmission.

In case of caption broadcasting not only in audio multicast but also in video, an additional channel for transmitting text information is required.

Meanwhile, in the DMB system, broadcast channels are distinguished by different PIDs (Packet Identifiers). The PID classifies TS packets multiplexed into TSs according to the TS (Transport Stream) method of the MPEG-4 (Moving Picture Expert Group-4) system used for broadcasting transmission by DMB.

For reference, the generation of the TS in the MPEG-4 system is as follows. The audio information, video information, and data information are pre-processed, encoded, and converted into bit streams called ESs (elementary streams). Each of the audio, video and data ESs are converted into packets in order to distinguish the compression units. The converted packets are called packetized elementary stream (PES) packets.

A PES packet consists of a header and a payload. The header contains information about the payload as well as an indication that a unit of compression has begun. The audio PES, the video PES, and the data PES in which these PES packets are contiguous are respectively time-division multiplexed and converted into TS.

For example, in the case of generating a TS by multiplexing the audio PES and the video PES, first, the audio PES is divided and cut by 184 bytes, and the video PES is divided and cut by 184 bytes. Next, four bytes of headers are added to each of the 184 bytes to form a 188-byte TS packet. TS is generated by time division multiplexing the audio TS packets and the video TS packets.

The structure of a TS packet defined in the MPEG standard will be described with reference to FIG. Each TS packet constituting the TS as shown in FIG. 1A has a header of 4 bytes and a payload of 184 bytes following the header and has a size of 188 bytes as shown in FIG.

The header includes an 8-bit sync byte, a 1-bit transport error indicator, a 1-bit payload unit start indicator, and 1 as shown in FIG. 13 bits of transport priority, 13 bits of PID (Packet Identifier), 2 bits of transport scrambling control, 2 bits of adaptation field control, 4 bits of traversal counter (continuity counter).

The adaptation field control indicates whether the adaptation field and / or payload follows after the header. If the adaptation field control value is '0', it means that there is no adaptation field after the header. This means that only the payload exists after the header. In contrast, when the adaptation field control value is '1', the adaptation field follows the header. Thus, when there is an adaptation field after the header, the adaptation field may or may not have an option field. The option field is a field used as an extension of the header.

Since the header structure and each field of the TS packet as described above are well known in accordance with the MPEG standard, further description thereof will be omitted. However, as described above, it can be seen that the PID includes a PID used for distinguishing each of the broadcast channels in the DMB.

As described above, when multi-channel transmission is required for voice multicasting and subtitle broadcasting, different PIDs are needed as the number of additional channels. The information to be maintained for managing one PID is basically a payload unit start indicator and a traversal counter in the header shown in FIG. 1, which must be managed separately as many PIDs for multiple channels.

In addition, since several TS packets constitute one PES packet, the receiving side needs to buffer the received TS packet by using a memory until at least one PES packet is received for each PID. Accordingly, in the process of parsing the header data of the packet, the receiving side generates overhead for managing data for an additional channel, that is, overhead for managing a memory area and various variables.

As a result, an increase in the number of channels for multi-channel transmission leads to an increase in PID, which incurs a lot of overhead in maintenance.

Accordingly, the present invention provides a multi-channel generation and reproduction method capable of transmitting a multi-channel using only one PID without using an additional PID.

In addition, the present invention provides a multi-channel generation and playback method that can transmit multi-channel using a PTS (Presentation Time Stamp) difference between channels without using additional PID.

The multi-channel generating method of the present invention comprises the steps of converting a bit stream of each of the plurality of channels into PES packets having the same PID, and the PTS (Presentation Time Stamp) of the PES packets of the multi-channel using the same PID Resetting to have a predetermined PTS difference between channels to distinguish between multiple channels using the same PID as well as indicating that the packet is a PES packet; And outputting.

The multi-channel reproducing method of the present invention indicates that the PTS difference between the current PES packet and the previous PES packet among the PES packets having the same PID is a multi-channel PES packet using the same PID and uses the same PID. Checking a predetermined PTS difference to distinguish them from each other; if the PTS difference is not a predetermined PTS difference, storing the current PES packet as a previous PES packet; and if the PTS difference is a predetermined PTS difference, Changing the PTS of the PES packet to the PTS of the current PES packet.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the annexed drawings, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted. For convenience of explanation, an example of a case in which two audio channels of two channels are transmitted using only one PID will be described.

2 is a block diagram illustrating a packetizer 100 for multi-channel audio transmission according to an exemplary embodiment of the present invention, and shows an example of transmitting two audio channels without using a separate PID. An example of generating a TS by multiplexing audio and video is shown. The packetizer 100 receives audio bit streams and video bit streams of channels 1 and 2.

The packetizer 100 converts the audio bit streams of the two channels into PES packets having the same PID, that is, PID1 in the example of FIG. 2, and outputs the audio PES, and converts the video bit stream into a PID different from the audio PES, That is, in the example of FIG. 2, the video PES is output by converting the packets into PES packets having PID2. As such, the packetizer 100 assigns different PIDs to the audio PES packet and the video PES packet, whereas the packetizer 100 assigns the same PID to the audio PES packet of the audio channel 1 and the audio packet of the audio channel 2.

Referring to FIG. 4, which shows the audio PES generation processing flow of the packetizer 100 in steps 200 and 204, the packetizer 100 receives the audio bit streams of the audio channels 1 and 2 in step 200. Convert PES packets with the same PID to each other. In operation 202, the PTSs of the PES packets are reset to have a predetermined PTS (Presentation Time Stamp) difference between the audio channels 1,2.

The reason for resetting the PTS of the PES packets is to indicate that the PES packet is a PES packet of a multi-channel using the same PID and to distinguish audio channels 1 and 2 that are not distinguished by PID only by using the same PID. . The packetizer 100 outputs the audio PES in which the PES packets of the audio channels 1 and 2 in which the PTSs are reset are alternately continued by time division multiplexing in step 204.

Typically, the PES packet has a PTS in the header, which is relative time information on which data in the payload of the corresponding PES packet should be reproduced, and the PTS interval between the audio PES packets is constant according to the sampling rate of the audio data. . For example, if stereo audio needs to be reproduced at a sampling rate of 8 Hz, the PTS difference between audio PES packets is constant at about 43 Hz.

According to an embodiment of the present invention, as shown in FIG. 3, in an audio PES in which PES packets of audio channels 1 and 2 are alternately connected, the difference between the PTS of the PES packet of the audio channel 1 and the PTS of the PES packet of the audio channel 2 is different. Reset the PTS to a value other than 43 ms, for example 10. In the example of FIG. 3, 'PTS difference = 10' indicates that the PES packet of the audio channel 2 is a PES packet of a multi channel using the same PID as the PES packet of the audio channel 1, and is an audio channel that is multichannels using the same PID. In order to distinguish one or two from each other, a value determined in advance according to an embodiment of the present invention. As such, in order to distinguish the predetermined PTS difference according to the embodiment of the present invention from the normal PTS difference between audio PES packets of one channel, the following description will be referred to as a 'multi-channel PTS difference' for convenience.

3 illustrates an audio PES output from the packetizer 100 such that PES packets 1, 3, 5, ... of audio channel 1 and PES packets 2, 4, 6, ... of audio channel 2 are alternately connected. An example of a PTS value and a multi-channel PTS difference value of each of the PES packets constituting the PES packet is shown in Table 1 below.

Channel 1 Channel 2 Multichannel PTS car PES Packet 1 (PTS = 7) PES Packet 2 (PTS = 17) 10 PES Packet 3 (PTS = 50) PES Packet 4 (PTS = 60) 10 PES Packet 5 (PTS = 93) PES Packet 6 (PTS = 103) 10 . . . . . . . . .

For reference, in order to facilitate understanding of the present invention, for example, when audio data of audio channels 1 and 2 are transmitted between audio channels by PES having different PIDs instead of the same PID as the present invention, audio channels 1 and 2 PTSs of PES packets of the PES packets are as shown in Table 2 below.

Channel 1 Channel 2  PES Packet 1 (PTS = 7)  PES Packet 2 (PTS = 7)  PES Packet 3 (PTS = 50)  PES Packet 4 (PTS = 50)  PES Packet 5 (PTS = 93)  PES Packet 6 (PTS = 93) . . . . . .

As can be seen from FIG. 3 and Table 1, the PTS difference between PES packets of each channel is 43, which is the same as the PTS difference between typical audio packets shown in Table 2, but the PTS difference between neighboring PES packets is It can be seen that the multi-channel PTS difference value is 10. Therefore, if the PTS difference between neighboring PES packets is not 43, the receiving side receiving the audio PES thus generated may know that the PES packets are data of different channels.

For example, as described above, the packetizer 100 resets the PTSs of the audio packets, whereas the PTSs of the PES packets 1, 3, 5, ... of the audio channel 1 are left as they are. The PTSs of PES packets 2, 4, 6, ... can be reset by adding a multi-channel PTS difference to the PTS of the PES packet of audio channel 1 immediately before each PES packet. This can be easily understood by comparing Tables 1 and 2 above.

As described above, the audio PES output from the packetizer 100, that is, the audio PES multiplexed with audio channels 1 and 2 having PID1 and the video PES of the video channel having PID2 are time-division multiplexed by the TS multiplexer 102. It is converted into TS and transmitted.

FIG. 5 is a block diagram illustrating a PES processor for multi-channel audio reproduction according to an exemplary embodiment of the present invention, wherein a multi-channel audio PES is received by a receiver for receiving a multiplexed PES of the multi-channel audio generated as described above. It shows a block configuration including a PES processor 302 to process. The TS demultiplexer 300 outputs an audio PES and a video PES by inputting and demultiplexing the received TS. In FIG. 5, the PID of the audio PES and the PID of the video PES are PID1 and PID2 as in the example of FIG. 2. In addition, the audio PES of PID1 also shows an example in which the audio PES packets of the audio channels 1 and 2 are multiplexed PES as in the above-described example of FIGS. The PES processor 302 extracts the audio bit streams of channels 1 and 2 from the audio PES, and outputs the video bit stream from the video PES to the coder-decoder 304.

Referring now to FIG. 6, which shows a multi-channel audio reproduction processing flow in steps 400-406 according to an embodiment of the present invention, the PES processor 302 inputs one PES packet from the TS demultiplexer 300. In step 400, it is checked whether the PTS difference between the current PES packet and the previous PES packet is the multi-channel PTS difference T. Here, the current PES packet refers to an audio PES packet currently input, and the previous PES packet refers to an audio PES packet input immediately before the current PES packet.

If the PTS difference between the current PES packet and the previous PES packet is not a multi-channel PTS difference T, as a result of the check in step (400), the current PES packet is stored as the previous PES packet in step (402), and then (400). Go back to step Accordingly, the above process is repeated with respect to the next PES packet. On the contrary, if the PTS difference between the current PES packet and the previous PES packet is equal to the multi-channel PTS difference T, the PTS of the previous PES packet is changed to the PTS of the current PES packet in step 404. Outputs the audio bit stream according to the changed previous PES packet and the audio bit stream according to the current PES packet to the codec 304.

Accordingly, in step 406, the current PES packet having the same PTS as the PTS changed from the previous PES packet whose PTS is changed is reproduced simultaneously by the codec 304. That is, in the codec 304, the audio of the audio channels 1 and 2 is simultaneously reproduced so that the audio multiplexing is performed.

This will be described with reference to the example of FIG. 3 described above. If the current PES packet is PES packet 3, the PTS difference between PTS = 50 of PES packet 3 and PTS = 17 of PES packet 2 which is the previous PES packet is 43. Then, since the PTS difference is not 10, which is the multi-channel PTS difference T, PES packet 3 is stored as the previous PES packet.

Next, when PES packet 4 is inputted into the current PES packet, the PTS difference between PTS = 60 of PES packet 4 and PTS = 50 of PES packet 3, which is a previous PES packet, becomes 10. Then, since the PTS difference is 10, the multi-channel PTS difference T, PTS = 50 of PES packet 3 is changed to PTS = 60 of PES packet 4. Since the PTSs of the PES packets 3 and 4 of the audio channels 1 and 2 are changed in the same manner, the PES packets 3 and 4 of the different audio channels are reproduced at the same time.

Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications may be made within the scope of the present invention. In particular, although the embodiment of the present invention shows an example of transmitting multi-channel audio, the same applies to the case of transmitting various multi-channels such as subtitle broadcasting or text message transmission using only one PID. Also, for convenience of description, an example in which the number of channels of the multi-channel is 2 has been described, but the same applies to the case where the number of channels increases. Therefore, the scope of the present invention should not be limited by the described embodiments, but should be defined by the equivalents of the claims and claims.

As described above, the present invention implements multi-channel transmission by changing the PTS difference between channels instead of using only one PID without using an additional PID, thereby generating an overhead for increasing PID or maintaining it. There is an advantage in that multi-channel transmission can be performed without making a difference.

In addition, since the multi-channel transmission is implemented using only the PTS difference, the change of the existing system can be minimized, thereby simplifying the implementation.

In addition, it is possible to simply implement whether to reproduce the data of the additional channel according to the receiver user's selection by identifying the channel by identifying the PTS difference.

Claims (5)

In the method for generating a multi-channel in a digital multimedia broadcasting system, Converting the bit streams of each of the plurality of channels into Packetized Elementary Stream (PES) packets having the same PID (Packet Identifier); Representation of the PTS (Presentation Time Stamp) of the PES packets is a multi-channel PES packet using the same PID and reset to have a predetermined PTS difference between the channels to distinguish the multi-channels using the same PID from each other. To do that, And outputting a PES in which a PES packet of each of the channels for which the PTS is reset is alternately connected. The method of claim 1, wherein the multi-channel is a multi-audio channel. In the method of playing a multi-channel in a digital multimedia broadcasting system, Among the Packetized Elementary Stream (PES) packets having the same PID (Packet Identifier), the PTS difference between the current PES packet and the previous PES packet is a multi-channel PES packet using the same PID. Checking a predetermined PTS difference to distinguish the multi-channels using each other; If the PTS difference is not the predetermined PTS difference, storing the current PES packet as a previous PES packet; If the PTS difference is the predetermined PTS difference, changing the PTS of the stored previous PES packet to the PTS of the current PES packet. 4. The method of claim 3, further comprising simultaneously playing a previous PES packet in which the PTS is changed with the current PES packet having the same PTS as the modified PTS. 5. The method of claim 3 or 4, wherein the multi channel is a multi audio channel.

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