KR20080069035A - Ip settop box for reducing zapping time and method thereof - Google Patents

Abstract

An IP(Internet Protocol) set top box for reducing a channel conversion delay time and a control method thereof are provided to decode low definition images existing in a data PES(Packet Elementary Stream) before receiving an HD I frame during channel conversion, thereby firstly outputting a screen without decoding delay time of the I frame. A packet receiver receives an MPEG TS(Moving Picture Expert Group Transport Stream) including HD(High Definition) image data and low definition image data configured with only an I frame. A decoding controller(140) receives a channel conversion request from a user, and selectively transmits the HD image data or the low definition image data to a decoder(150) according to whether HD image data of I frame is received. The decoder decodes the image data transmitted from the decoding controller.

Description

IP Settop Box for Reducing Zapping Time and Method Thereof}

1 is a flowchart illustrating a channel switching method according to a general IP broadcasting system.

2 is a block diagram illustrating a configuration of an IP set-top box for reducing channel switching latency according to an embodiment of the present invention.

3 is a flowchart illustrating a channel switching method for reducing channel switching waiting time according to another embodiment of the present invention.

4 is an exemplary diagram illustrating a structure of an MPEG transport stream transmitted using IP broadcasting according to the present invention.

5 is an exemplary diagram showing a structure of a header for distinguishing PES in an MPEG2 transport stream in the present invention.

<Description of the symbols for the main parts of the drawings>

100: IP set-top box 110: packet receiving unit

120: demultiplexer 130: cue

140: decoding control unit 150: decoding unit

160: output interface unit

The present invention relates to channel switching and channel decoding in an IP set-top box using Internet Protocol (IP) streaming, and more particularly, to an IP set-top box for reducing channel switching latency and a control method thereof.

1 is a flowchart illustrating a channel switching method according to a general IP broadcasting system.

As shown in FIG. 1, a typical IP set-top box attempts channel switching using an Internet Group Management Protocol (IGMP) technique. FIG. 1 illustrates an operation example of a case in which an IP set-top box is currently displaying channel number 1 and receives a switch to channel 100 from a user. On the other hand, DSLAM (DSL Access Multiplexer) is a type of router for multicasting IP broadcast data to a large number of homes and corresponds to the case of receiving channels 1 to 50 from the headend.

The IP set-top box sends an IGMP Join message to DSLAM requesting multicasting of channel 100. Currently, since the DSLAM only receives packets for channels 1 to 50, the DSLAM transmits an IGMP join message for channel 100 to the first router.

The first router transmits a Protocol Independent Multicast-Sparse Mode (PIM-SM) Join message for channel 100 to the third router receiving channel 100 from the headend. Of course, the PIM-SM protocol is used in this process, but the protocol used in the present invention is not limited to the PIM-SM. In addition, if the second router was performing multicasting of channel 100, the first router would transmit the PIM-SM Join message only to the second router.

As such, when the IGMP join is completed, the headend starts streaming for channel 100. At this time, the streaming server streams each screen into I, B, and P frames by H.264 encoding. The set-top box decodes the data of the I frame and stores the picture in the video frame buffer for replay.

In response to a channel switching request of the user, the IP set-top box transmits an IGMP Leave message for channel 1 to the DSLAM, and the DSLAM stops multicasting of channel 1 to the IP set-top box to terminate channel switching.

On the other hand, in order to be displayed as a screen on a TV, images of frame units are continuously played in the frame of the screen size. Among them, I frame is a frame having data of the entire image, and B and P correspond to compressed frames including only data of a moving part. On TVs, the compression rate of the data can be increased by separately outputting these frames.

In the IP set-top box using the I, B, P frame, such as IGMP Leave to switch the channel, the delay time (delay time) is required until IMGP Join has been described in FIG. In the case of H.264 HD (High Definition) content, the IP set-top box must receive an I frame in order to switch channels and display a TV screen. This is because the I frame is data for one entire screen. If the set-top box receives only frames including only compressed motion information such as B or P frames after channel switching, the set-top clap cannot configure the screen. In other words, the waiting time for receiving the next I frame increases the channel switching waiting time, and there is a problem that no image can be displayed on the TV.

Accordingly, the present invention is to solve the above-mentioned problems according to the prior art, and receives the MPEG transport stream in which the low-resolution video data is inserted in the data PES, and included in the data PES until receiving the I frame after channel switching An object of the present invention is to provide an IP set-top box for decoding low resolution video data and a control method thereof.

An IP set-top box according to an aspect of the present invention is a packet receiver for receiving an MPEG transport stream including high resolution video data and low resolution video data consisting of only I frames, and after receiving a channel switching request from a user, A decoding controller may be configured to selectively transmit high resolution image data or low resolution image data to the decoding unit according to whether the frame receives high resolution image data, and a decoding unit to decode the image data transferred from the decoding controller.

In this case, if the high resolution image data of the I frame is not received after the channel switching request is received, the decoding control unit transmits the low resolution image data to the decoding unit.

In the present invention, the high resolution image data is inserted into the video PES of the MPEG transport stream, and the low resolution image data is inserted into the data PES of the MPEG transport stream. At this time, the decoding controller checks whether the high resolution image data I frame is received by checking the Picture_Coding_Type field of the video PES.

The IP set-top box may further include a demultiplexer for classifying video PES, audio PES and data PES included in the MPEG transport stream, and a queue for storing each PES classified by the demultiplexer. In this case, the demultiplexer distinguishes a video PES, an audio PES, and a data PES by using a PID field of an MPEG2 transport stream.

According to another aspect of the present invention, there is provided a channel switching method of an IP set-top box, in which an IP set-top box receives a transport stream including high-resolution video data and low-resolution video data composed of only I frames, and the IP set-top box is provided by a user. Checking whether to receive the high resolution image data of the I frame for the switched channel when receiving the channel switching request, if the high resolution I frame of the switched channel is not received, decoding the low resolution image data, When receiving the I frame of, may comprise the step of decoding the high-definition image data.

In this case, the high resolution image data is inserted into the video PES of the MPEG transport stream, and the low resolution image data is inserted into the data PES of the MPEG transport stream. In this case, the step of checking whether the high resolution I frame is received is characterized in that the IP set-top box checks whether the high resolution I frame is received by checking the Picture_Coding_Type field of the video PES.

In addition, the IP set-top box may classify the video PES, audio PES and data PES included in the transport stream using PIDs and store them in a queue, respectively.

According to another aspect of the present invention, an IP TV broadcasting network receives an IP TV server for inserting multicast by inserting low resolution video data into a data PES of an MPEG transport stream and a channel switching request. And an IP set-top box for decoding and outputting low resolution image data included in the data PES of the PES, receiving the video PES including the image information of the I frame, and decoding and outputting the high resolution image data included in the video PES. Can be.

Hereinafter, an IP set-top box for reducing channel switching waiting time and a control method thereof according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram illustrating a configuration of an IP set-top box for reducing channel switching latency according to an embodiment of the present invention.

As shown in FIG. 2, the IP set-top box 100 according to the present invention includes a packet receiver 110, a demultiplexer 120, a queue 130, a decoding controller 140, a decoder 150, and an output interface unit ( 160), and the like.

The packet receiver 110 corresponds to an apparatus for receiving a packet of a joined multicasting group from a server (headend) using a predetermined multicasting protocol. In particular, the packet receiver 110 receives a Moving Picture Experts Group (MPEG) transport stream composed of a plurality of transport packets for IP broadcasting. The received MPEG transport stream data is divided into transport packets and delivered to the demultiplexer 120 in order.

The demultiplexer 120 classifies the MPEG transport packet received from the packet receiver 110 into a video packet, an audio packet, and a data packet. The classification process may be performed by classifying a PID (Program ID) according to a Program Map Table (PMT) and a Program Association Table (PAT). A more detailed process will be described with reference to FIG. 4. The video packets, audio packets, and data packets classified as described above are transferred to the queue 130 and temporarily stored.

The queue 130 is a device for temporarily storing video packets, audio packets, and data packets classified by the demultiplexer 120. The queue 130 may include a video queue 131 for storing video packets, an audio queue 132 for storing audio packets, and a data queue 133 for storing data packets. Unlike the existing invention, the data queue 133 of the IP set-top box 100 may transmit the data packet to the video decoder 151. This is for decoding low resolution video data inserted and inserted into the data PID.

The decoding control unit 140 performs the following operation when the channel switch request is received. First, the decoding controller 140 determines the frame type of the video packet stored in the video queue 131. The decoding control unit 140 may check which frame among the I, P, and B frames by referring to the Picture_Coding_Type field of the video packet having the MPEG2 format.

As a result of the determination, when the frame of the video packet is B or P, the decoding control unit 140 performs control to drop the video packet of the B or P frame stored in the video queue 131. This is because video packets of B or P frames cannot be normally displayed without receiving I frames. The decoding control unit 140 also controls to decode the low resolution video packet present in the data queue 133.

On the contrary, when the high resolution video packet of the I frame is received, the decoding controller 140 performs control of transmitting the video packet of the I frame stored in the video queue 131 to the decoding unit 150. As described above, after the decoding operation of the I frame is finished, the decoding controller 140 continuously transmits the data stored in the video queue 131 to the video decoder 151. If an I frame is received, the B or P frames transmitted thereafter can be displayed normally.

The decoding unit 150 decodes the high resolution and low resolution video frame and the audio frame received from the queue 130, respectively. The decoding unit 150 selectively receives the high resolution video information and the low resolution video frame under the control of the decoding control unit 140, and decodes the high resolution video information.

The output interface unit 160 corresponds to an apparatus for transmitting a video and audio signal decoded by the decoding unit 150 to a TV. The output interface unit 160 transmits video and audio signals to a TV according to a standard connection standard between an IP set-top box and a TV supporting IP broadcasting.

3 is a flowchart illustrating a channel switching method for reducing channel switching waiting time according to another embodiment of the present invention.

First, an IP TV server transmits a high definition (HD) level video stream and an audio stream through an MPEG transport stream and uses a data PID to stream a stream having a low definition (SD) level using a data PID. It is transmitted to (S301).

The IP set-top box receives a channel switching command from the user (S302). In this case, the IP set-top box receives the IGMP Leave for the old channel and the IGMP Join for the new channel, and then receives the MPEG transport stream for the channel after switching (S303).

The IP set-top box decodes and displays the low resolution stream stored in the data PES of the MPEG transport stream using the demultiplexer (S304). At the same time, the IP set-top box decodes and outputs the audio PES that is synchronized with the data packet elementary stream (PES) of the MPEG transport stream (S305).

The IP set-top box can determine the data packet by matching the PID of the MPEG transport stream with the PAT and PMT. In this case, since the low resolution stream is composed of only I frames, normal screen output is possible.

After that, the IP set-top box checks the Picture_Coding_Type field of the video PES belonging to the received MPEG transport stream to check whether or not a high resolution I frame is received (S306). If the check result does not receive the high resolution I frame, the IP set-top box proceeds to step S304 to maintain the output of the low resolution stream.

When the IP set-top box receives the high resolution image data of the I frame in step S306, the IP set-top box decodes and outputs the high resolution I frame image data (S307). Thereafter, the IP set-top box decodes and outputs high-resolution B and P frames received through the video PES (S308), and also decodes the audio PES that is in sync with it (S309). As a result, the IP set-top box is capable of watching high-definition TV of the switched channel after receiving high-resolution I frames.

4 is an exemplary diagram illustrating a structure of an MPEG transport stream transmitted using IP broadcasting according to the present invention.

As shown in FIG. 4, the MPEG transport stream may be composed of a video PES, an audio PES, and a data PES.

The video PES means a plurality of divided packets in which video data of variable size encoded in MPEG2 has a size of 188 bytes. In the present embodiment, the video PES includes HD data, i.e., high resolution video data. In addition, the video PES belongs to any one frame of I, B, and P frames, respectively.

Audio PES means a plurality of divided packets in which variable-size video data encoded according to the AC3 standard has 188 bytes. Audio PES corresponds to packets with no distinction between high and low resolution.

Finally, in the data PES region, low resolution image data is divided into a plurality of packets having a size of 188 bytes and stored. The IP set-top box according to the present embodiment is to display MPEG-2 decoded low resolution image data in the data PES region.

FIG. 5 is an exemplary diagram illustrating a structure of a header for distinguishing PES in an MPEG2 transport stream according to the present invention.

As shown in FIG. 5, the MPEG2 transport may be composed of a plurality of MPEG2 transport packets having a size of 188 bytes. The MPEG2 transport stream packet may have fields of an MPEG2 transport stream header, an MPEG2 adaptation field, and a payload. The PID field of the MPEG2 transport stream header may be used to determine whether the MPEG2 transport packet is a video PES, an audio PES, or a data PES.

First, the IP set-top box searches for packets with a PID of 0x0000. As described above, a packet having a PID of 0 means PAT, and ID information of a PMT corresponding to each program is stored.

The IP set-top box searches for the PMT using the information of the PAT, and the PMT stores information informing which packet the video and audio data constituting the program is stored and transmitted. The IP set-top box can determine the type of packet by matching the PMT with the PID of each transport packet.

Although the present invention has been described in detail through the representative embodiments, those skilled in the art to which the present invention pertains can make various modifications without departing from the scope of the present invention. I will understand. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the claims below but also by the equivalents of the claims.

As described above, according to the present invention, the IP TV server inserts and multicasts video data including only low-resolution I frames into the data PES of the MPEG transport stream, and the IP set-top box receives high quality I frames during channel switching. By decoding the low resolution image existing in the data PES, there is an advantage that the screen can be output preferentially without having to decode the I frame. The use of a low resolution stream minimizes the overflow of additional data and effectively reduces the channel switching time even during continuous channel switching.

Claims (11)

A packet receiver configured to receive an MPEG transport stream including high resolution image data and low resolution image data composed of only I frames; A decoding control unit for receiving a channel switching request from a user and selectively transferring high resolution image data or low resolution image data to a decoding unit according to whether I frame high resolution image data is received; And IP set-top box including a decoding unit for decoding the image data transmitted from the decoding control unit. The method of claim 1, The decoding control unit, An IP set-top box that delivers low-resolution video data to the decoding unit when receiving high-resolution video data of an I frame after receiving a channel switch request. The method of claim 1, The high resolution image data is inserted into the video PES of the MPEG transport stream, the low resolution image data is inserted into the data PES of the MPEG transport stream IP set-top box. The method of claim 3, The decoding control unit, An IP set-top box, which checks whether a high resolution image data I frame is received by checking a Picture_Coding_Type field of a video PES. The method of claim 3, A demultiplexer for classifying video PES, audio PES, and data PES included in the MPEG transport stream; Wow And a queue for storing each PES classified by the demultiplexer. The method of claim 5, The demultiplexer IP set-top box for distinguishing between video PES, audio PES and data PES using PID field of MPEG2 transport stream. The IP set-top box comprises the steps of: receiving a transport stream including high resolution image data and low resolution image data consisting of only I frames; When the IP set-top box receives a channel switching request from the user, checking whether to receive the high resolution image data of the I frame for the switched channel; Decoding the low resolution video data when the high resolution I frame of the switched channel is not received, and decoding the high resolution video data when the high resolution I frame is received. The method of claim 7, wherein And the high resolution image data is inserted into a video PES of an MPEG transport stream, and the low resolution image data is inserted into a data PES of an MPEG transport stream. The method of claim 8, Receiving the high resolution I frame check step, And checking whether the IP set-top box receives a high resolution I frame by checking the Picture_Coding_Type field of the video PES. The method of claim 8, The IP set-top box further comprises the step of classifying the video PES, audio PES and data PES included in the transport stream using a PID, and storing in the queue, respectively. In the IP TV broadcasting network, An IP TV server for multicasting by inserting low-resolution video data into the data PES of the MPEG transport stream; Wow When receiving a channel switching request, the video data of the low resolution included in the data PES of the multicasted MPEG transport stream is decoded and outputted, and after receiving the video PES including the image information of the I frame, the video PES is included in the video PES. IP TV broadcasting network including an IP set-top box for decoding and outputting high-definition image data.

Images