KR100978506B1 - Digital video player and the method for controlling buffer the player - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital broadcasting viewing terminal and a buffer control method of the terminal. The present invention relates to audio transmitted in a stream form such as digital multimedia broadcasting (eg, Digital Multimedia Broadcasting, ISDB-T, DVH-H, etc.) or Internet multimedia broadcasting, such as IPTV. When a fluctuation of an input stream occurs in a terminal receiving a video service including a digital broadcasting watching terminal and a buffer control method of the terminal to control the buffer to be a continuous flat video and audio output using the buffer will be.

Digital Broadcasting Player should output audio / audio signal suitable for video image through accurate A / V synchronization method and buffer control so that viewers can more conveniently watch broadcasting in stream form. However, in the case of a broadcast service transmitted in the form of a stream, variations in the time axis of the received packet are severe, and the received packet is buffered and processed. At this time, it is often seen that video and audio are operated separately due to unnatural video playback or A / V synchronization that is not properly performed. In addition, proper buffer control is possible only by compensating for an error in the amount of data due to the difference between the accuracy of the clock used by the broadcast equipment on the transmitting side and the clock used by the terminal on the receiving side. In order to solve the above problems, the present invention implements a buffer control method suitable for receiving a video service including audio transmitted in a stream form in software, and can be effectively applied to a receiver such as a DMB or an IPTV.

According to the present invention, a viewer can be provided with a DMB service in which audio / audio is reproduced in conformity with a natural video image by applying a proper control of a buffer and an A / V synchronization method.

DMB, Buffering, Rendering, Parsing

Description

Digital broadcasting viewing terminal and buffer control method of the terminal {DIGITAL VIDEO PLAYER AND THE METHOD FOR CONTROLLING BUFFER THE PLAYER}

The present invention relates to a digital broadcasting viewing terminal and a buffer control method of the terminal. The present invention relates to a digital broadcasting terminal for controlling a buffer for natural video reproduction and minimizing buffering so that an image can be output quickly by minimizing a delay of video reproduction. A viewer terminal and a buffer control method for the terminal.

Video services transmitted in the form of a stream are typically broadcast (eg, Digital Multimedia Broadcasting, ISDB-T, DVH-H, etc.) or IPTV. In this way, a video service including audio transmitted in a stream form compresses sound and video in MPEG-4 (Moving Picture Experts Group) (MPEG) -4 standard in order to transmit effectively through a transmission medium. It is formatted in the form of MPEG-2 TS (Transport Stream) so as to be suitable for transmission. In case of a broadcast, the MPEG-2 TS parser extracts MPEG-2 TS (Transport Stream) data through the inverse modulation through a modem or receives a packetized MPEG-2 TS stream through the Internet. It is separated into an audio stream signal, and the decoder decompresses MPEG-4 compressed video and audio for playback using a player. In this case, buffering is required for data interworking among the various functional blocks, and the quality of the reproduced video depends on proper control of the buffer.

In the conventional digital broadcasting viewing terminal, when watching a broadcasting service, the A / V synchronization is not played after the first time or a certain time, or in some products, it may be corrected after a considerable time (a few minutes). There is a problem such that the playback continues without being performed. In addition, there is a problem in that it takes a long time until the output because the proper buffer control is not made, or the natural image cannot be output due to the lack of buffering.

The present invention is proposed to improve the problems of the prior art as described above, in the digital broadcasting terminal having a multimedia broadcasting receiving function to control the buffer for the natural video playback, and also to minimize the delay during video playback The goal is to minimize the buffering so that the output is faster.

In addition, an object of the present invention is to reproduce the video image and the audio / audio signal in the digital broadcasting viewing terminal having a multimedia broadcasting reception function.

In order to achieve the above object, the digital broadcasting viewing terminal according to an embodiment of the present invention parses the MPEG-2 TS, and uses the SL (Sync Layer) stage of the MPEG-4 for the MPEG-2 TS. The TSAC parser thread constituting the encoded BSAC ES, the H.264 ES (Elementary Stream), and the DSP (BSAC) codec unit for decoding the BSAC ES and restoring the compressed audio data. DSP (H.264) codec unit for decoding H.264 ES and restoring compressed video data, Audio Ring Buffer for storing audio data in input order, and storing video data in input order A video ring buffer to play audio frames stored in the audio ring buffer in the input order, and audio data stored in the audio ring buffer and video data stored in the video ring buffer. CTS value And a video render thread that synchronizes and reproduces the synchronization of audio data and video data.

According to the present invention, an audio (BSAC) ACK thread for controlling an audio ring buffer to store audio data in the order input from the DSP (BSAC) codec unit and video data in the order input from the DSP (H.264) codec unit. And a video (H.264) ACK thread to control the video ring buffer to store.

The TS parser thread may include a program association table (PAT), an adaptation field (ADT), a program map table (PMT), and the like of an MPEG-2 TS (Transport Stream) using a SL layer of MPEG-4. Parse a packetized elementary stream (PES).

In a buffer control method of a digital broadcasting viewing terminal according to another embodiment of the present invention, (a) receiving an audio frame decoded by a DSP (BSAC) codec unit and storing the decoded audio frame in an audio ring buffer; (B) checking whether the buffer is full or not, if the audio ring buffer is full, deleting (c) at least one frame of the oldest audio frame among the previously stored audio frames, and the audio ring buffer is empty. In the case of the state (Empty), it is determined whether the audio ring buffer is full at the time when the audio callback occurs, and if the audio ring buffer is full in the step (d), the audio frame And (e) adjusting a sync of a video frame input from the video ring buffer.

As a result of the checking in step (d), when the audio ring buffer is empty, the method may further include filling at least one frame of data values of the audio frames stored in the audio ring buffer.

Step (e) includes checking whether the video ring buffer is empty.

According to the present invention, step (e) includes filling the data value of the audio frame with at least one frame when the video ring buffer is empty.

In addition, step (e) includes checking whether the audio ring buffer is full at the time of recording a time when the video ring buffer is full.

According to the present invention, the digital broadcasting viewing terminal having a multimedia broadcasting reception function controls the buffer for natural video reproduction, and minimizes the buffering so that the video can be output quickly by minimizing the delay during video reproduction.

In addition, according to the present invention, there is an effect of reproducing a video image and an audio / audio signal in a digital broadcasting viewing terminal having a multimedia broadcasting reception function.

Hereinafter, a digital broadcast viewing terminal and a buffer control method of the terminal according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

A broadcast viewing terminal according to a preferred embodiment of the present invention includes a broadcast receiver for receiving broadcast signals and a DVP processor for controlling buffering of data. Here, the broadcast receiver is a TV. It may vary depending on IPTV. In addition, since the focus of the present invention is how to process the TS stream, a detailed description of the broadcast receiver is omitted, and the configuration of the present invention will be described on the assumption that a signal is received later.

Analyzing the fluctuations in the number of frames along the time axis of the received broadcast data, it can be observed that the broadcasters vary greatly around a specific average value. The viewing terminal absorbs this and needs proper buffering for continuous, natural video playback. Although the size of the buffer may be larger than the fluctuation in the worst case, the delay increases in proportion to the size of the buffer, and there is a problem in that it takes a long time for the received signal to be reproduced. In addition, even if an appropriate buffer size is allocated, if the buffering is not properly performed, there is a problem in that an empty state due to lack of data or a full state in which the buffer cannot be filled can occur.

Accordingly, in the present invention, a new type of digital system capable of appropriately controlling the size of data to be actively buffered according to the size of fluctuation of input streams different for each broadcaster does not occur and minimizes the delay. Propose a broadcast viewing terminal.

In addition, proper buffer control is possible only by compensating for an error in the amount of data due to a difference between the accuracy of the clock used by the broadcasting equipment on the transmitting side and the accuracy of the clock used by the terminal on the receiving side. Therefore, the digital broadcasting viewing terminal according to the present invention controls the buffer for the accuracy of such a clock.

FIG. 1 is a diagram illustrating a result of measuring and displaying the number of data frames of a broadcast stream input to a digital broadcast viewing terminal along a time axis.

More specifically, FIG. 1 illustrates a form in which fluctuation occurs and a result of measuring a rendering buffer by displaying the number of data frames of a stream input to a digital broadcasting terminal according to a time axis.

As shown in FIG. 1, the degree of occurrence of variation (Fluctuation) is measured differently for each broadcaster. That is, some broadcasters are able to compensate sufficiently with a small amount of buffering 100 due to the low degree of variation, while some broadcasters require a considerable amount of buffering due to the high degree of mutation. It can be seen. Accordingly, the digital broadcasting viewing terminal should be able to actively control the buffer according to the reception characteristics of each broadcasting company to minimize the DMB reproduction delay through the compensation of the appropriate variation, and to absorb the degree of occurrence of the variation.

2 is a block diagram illustrating a digital broadcast viewing terminal according to an example of the present invention.

According to the present invention, the DVP processing unit 200 is a block for performing all functions of the digital broadcasting viewing terminal. The TS parser thread 210 separates and assembles audio ES and video ES units from TS streams packetized in units of 188 bytes. The DSP (BSAC) codec unit 221 and the DSP (H.264) codec unit 231 restore the compressed signal. To store the decoded stream, the audio (BSAC) ACK thread 222 includes an audio render buffer therein, and the video (H.264) ACK thread 232 includes a video render buffer. In addition, an audio callback unit 224 and a video render thread 234 are output through the output unit 300.

As shown in FIG. 2, the digital broadcasting viewing terminal 1000 according to the present invention includes a broadcast receiving unit 100, a DVP processing unit 200, and an output unit 300.

The broadcast receiving unit 100 receives a broadcast stream signal.

The DVP processing unit 200 processes the broadcast stream signal input from the broadcast receiving unit 100. To this end, the DVP processing unit 200 includes a TS parser thread 210, a BSAC stream processing unit 220, and an H.264 stream processing unit 230.

The TS Parser Thread 210 parses the MPEG-2 TS stream. That is, parsing a program association table (PAT), an adaptation field (ADT), a program map table (PMT), and a packetized elementary stream (PES), and parses the MPEG- 2 Configures the encoded BSAC ES and H.264 ES (Elementary Stream) for TS.

The BSAC stream processing unit 220 controls the sink of the BSAC ES input from the TS parser thread 210. To this end, the BSAC stream processing unit 220 includes a DSP (BSAC) codec unit 221, an audio (BSAC) ACK thread 222, an audio ring buffer 223, and an audio callback unit ( 224).

The DSP (BSAC) codec unit 221 decodes the BSAC ES input from the TS parser thread 210 to restore the compressed audio data.

The audio (BSAC) ACK thread 222 stores the BSAC ES input from the DSP (BSAC) codec unit 221 in the audio ring buffer 223 in order.

The audio ring buffer 223 stores audio frames in the order input from the audio (BSAC) ACK thread 222.

The audio callback unit 224 reproduces the audio frames stored in the audio ring buffer 223 through the output unit 300 in the order of input.

The H.264 stream processor 230 controls the sink of the H.264 ES input from the TS parser thread 210. To this end, for this purpose, the H.264 stream processing unit 230 includes a DSP (H.264) codec unit 231, a video (H.264) ACK thread 232, a video ring buffer (233). And a video render thread 234.

The DSP (H.264) codec unit 231 decodes the H.264 ES input from the TS parser thread 210 to restore the compressed video data.

The video (H.264) ACK thread 232 stores the H.264 ES input from the DSP (H.264) codec unit 231 in the video ring buffer 233 in order. Decode the video frame.

The video ring buffer 233 stores video frames in the order input from the video (H.264) ACK thread 232.

The video render thread 234 synchronizes and synchronizes synchronization with each other using CTS values of audio and video frames stored in the audio ring buffer 223 and the video ring buffer 233. That is, a video frame corresponding to a sync of an audio frame played by the audio callback unit 224 is received from the video ring buffer 233, and the sync is performed by rendering the audio frame and the video frame. Adjust

Therefore, when watching a broadcast received in the form of a stream, it is possible to minimize the phenomenon of a synchronization mismatch between the audio and the video and the delay of the broadcast due to buffering.

FIG. 3 is a flowchart illustrating a process of receiving a tuned broadcast stream by controlling a buffer by a digital broadcasting viewing terminal according to an exemplary embodiment of the present invention.

The broadcast viewing terminal initially does not reproduce video until one frame of video data is input. In addition, the reproduction of the audio signal starts but the operation starts after storing the audio data of 5 frames or more so as to properly buffer the initial stage.

This initial operation of the broadcast viewing terminal is equally applicable to normal signal reception due to loss of video data and when normal signal reception is started again.

There are two reference times for buffer control. The first is Audio Callback, which is the standard of audio signal output, and the second is the time required for A / V synchronous control procedure, which is the standard of video signal output. The audio callback is initially set according to the sampling frequency, and the A / V sync is set using the time obtained through Equation 1 below. First, a composition time stamp (CTS) is obtained by referring to the ISO / IEC 14496-1 2001 (E) standard.

[Equation 1]

CTS = CompositionTimeStamp * 1000 / SL.timeStampResolution

Here, SL.timeStampResolution is fixed to 90,000 in the microwave digital radio broadcasting (terrestrial DMB) video transmission and reception matching standard.

The audio callback unit 224 operates to bring the audio frame stored in the audio ring buffer 223 in accordance with the Audio CTS. The video signal output finds and outputs a frame corresponding to the video CTS in the video ring buffer 233 when the audio signal is output, and skips this process if there is no matching audio frame. Control the buffer.

Referring to the above description, a process of receiving a tuned broadcast stream by controlling a buffer by a digital broadcasting viewing terminal according to an exemplary embodiment of the present invention will be described.

The audio (BSAC) ACK thread 222 receives the decoded audio frame from the DSP (BSAC) codec unit 221 and stores the decoded audio frame in the audio ring buffer 223, and at the time recording time, the audio ring buffer 223 is in a full state. Check whether or not (S301).

At this time, when the audio ring buffer 223 is full, the oldest audio frame among the previously stored audio frames is deleted at least one frame to an appropriate size (S302). As another example, the oldest audio frame among the previously stored audio frames is deleted according to the size of the newly input audio frame.

By doing so, the average value of buffering for the audio frame stored in the audio ring buffer 223 is shifted to the center by the size of the deleted audio frame. At this time, if the audio frame is located in a region where the average value of the buffering is full, the process of deleting the oldest audio frame is repeatedly performed. In this way, the audio frame moves away from the full state, ie to the center.

It is checked whether the audio ring buffer 223 is full at the time of the audio callback (S303).

Here, when the audio ring buffer 223 is full, a sync operation is performed on the audio frame and the video frame input from the video ring buffer 233. The video frame is searched for according to the sync operation result (S304). At this time, it is checked whether the video ring buffer 233 is empty (S305).

On the other hand, when the audio ring buffer 223 is empty at the time of the audio callback, the audio frames are bundled and the data of one or more frames is filled. In this case, the buffer state is increased by the size of the filled frame, and the buffering state is moved from the empty state to the center. In this case, when the average value of the buffering occurs frequently at a position close to the empty state, as described above, the average value of the buffering is moved to the center.

As a result of checking the state of the video ring buffer 233 (S305), when it is empty, it is determined that the storage of the audio data is not sufficient, and at least one data value of the audio frame stored in the audio ring buffer 223 is determined. Fill more than the frame (S306). In addition, the size of the audio ring buffer 223 is increased by one frame or more to increase the space for buffering sufficient data.

On the contrary, when the audio ring buffer 223 is full, the video ring buffer 233 checks whether the audio ring buffer 223 is full at time recording time (S301).

Therefore, when the audio signal is reproduced by the audio callback signal according to the A / V synchronization logic, the present invention checks the state of the video ring buffer 233 so that there is no video frame required for reproduction, so that an empty state occurs. The video data is relatively buffered by adjusting the state of the audio ring buffer 223.

In other words. By filling the audio ring buffer 223 more than one frame, the video ring buffer 233 provides time for storing video data. By repeating this process, the buffering is controlled to an appropriate state.

In addition, according to the present invention, if the size of the buffering is continuously more than a certain amount, it is possible to minimize the delay due to the buffering by reducing the amount of buffering by deleting data of one or more frames. Therefore, the average value of the buffering maintains the optimal buffer state so that the minimum data can be stored in the buffer without an empty state.

In the present invention as described above has been described by the specific embodiments, such as specific components and limited embodiments and drawings, but this is provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations are possible from such description.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and all of the equivalents or equivalents of the claims as well as the claims to be described later will belong to the scope of the present invention. .

FIG. 1 is a diagram illustrating a result of measuring and displaying the number of data frames of a broadcast stream input to a digital broadcast viewing terminal along a time axis.

2 is a block diagram illustrating a digital broadcast viewing terminal according to an example of the present invention.

FIG. 3 is a flowchart illustrating a process of receiving a tuned broadcast stream by controlling a buffer by a digital broadcasting viewing terminal according to an exemplary embodiment of the present invention.

<Explanation of symbols on main parts of the drawings>

210: TS parser thread, 231: DSP (H.264) codec unit,

221: DSP (BSAC) codec unit, 232: video (H.264) ACK thread,

222: audio (BSAC) ACK thread, 233: video ring buffer,

223: audio ring buffer, 234: video render thread,

224: audio callback,

Claims (8)

delete delete delete (a) receiving an audio frame decoded by a DSP (BSAC) codec unit and storing the decoded audio frame in an audio ring buffer; (b) checking whether the audio ring buffer is in a full state at the time of recording the time; (c) deleting at least one frame of the oldest audio frame among previously stored audio frames when the audio ring buffer is full; (d) checking whether the audio ring buffer is full at the time when an audio callback occurs when the audio ring buffer is empty; And (e) adjusting the sync of the video frame inputted from the audio frame and the video ring buffer when the audio ring buffer is full in step (d); The buffer control method of the digital broadcasting viewing terminal comprising a. The method of claim 4, wherein As a result of checking in step (d), filling the data value of the audio frame stored in the audio ring buffer at least one frame when the audio ring buffer is empty. The buffer control method of the digital broadcast viewing terminal further comprising. The method of claim 4, wherein In step (e), Checking whether the video ring buffer is in an empty state The buffer control method of the digital broadcasting viewing terminal comprising a. The method of claim 6, In step (e), Filling the data value of an audio frame by at least one frame when the video ring buffer is empty The buffer control method of the digital broadcasting viewing terminal comprising a. The method of claim 6, In step (e), Determining whether the audio ring buffer is full at the time of recording a time when the video ring buffer is full. The buffer control method of the digital broadcasting viewing terminal comprising a.

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