JP4826407B2 - Recording / playback device - Google Patents

Description

  The present invention relates to a playback device for playing back a data stream.

In recent years, there are many digital devices such as television broadcast receivers and personal computers that can record a television broadcast on a recording medium such as a hard disk (hereinafter abbreviated as HDD) or a Blu-ray disc and view it later. In order to efficiently process enormous amounts of data such as television broadcasts, data compression / decompression techniques are indispensable. In Japanese broadcasting, MPEG (Moving Picture Experts Group), which is an international standard for compression and decompression, adopts MPEG2 system, which is considered to be applied to communication systems and broadcasting systems. A format called MPEG2 transport stream (hereinafter abbreviated as MPEG2-TS) suitable for transmission / storage in an error-prone environment is used. In MPEG2-TS, a reference reference value program clock reference (PCR) of the system is embedded and transmitted so as to be reproducible on the receiving side as intended by the transmitting side. Similarly, data such as time management information program time stamp (PTS) referred to at the time of reproduction and time management information decoding time stamp (DTS) referred to at the time of decoding are embedded and transmitted.

The operation of receiving and reproducing the broadcast wave by the receiver is as follows. That is, the program association table (PAT) / program map table (PMT) is acquired from the input transport stream (TS), and the target program identifier (PID) is determined. Obtain TS packets with the identified PID and separate them into video, audio and PCR. The initial value of the system time clock (STC) is set using the received PCR, and the PCR value and STC value that are received periodically are compared, and the error of the 27 MHz system clock frequency that is the decoding time base Adjust. An STC counter that creates a clock inside the playback device increases the STC value constantly according to the system clock frequency. Decoding is performed at the time when the STC value and the DTS attached to each video data match, and the display is performed at the time when the PTS attached to the video or audio data matches.

In the recording medium, only TS packets of contents to be recorded are extracted and recorded from a stream transmitted in a state where a plurality of programs are multiplexed in accordance with the MPEG2-TS format. In addition to recording video and audio data for playback from a recording medium, time information such as PTS indicating display time and DTS indicating decoding time, PCR which is time information on the transmission side
It is necessary to record.

When playing a TS from a recording medium, the time information recorded as described above
The TS can be output and reproduced at the same timing as the TS input timing. In addition, a technique for reproducing data by a reproduction method that monitors the amount of data stored in the buffer of the decoder and adjusts the input from the recording medium in accordance therewith is disclosed (Patent Document 1). In the latter playback method, the STC value of the decoder is used as the operation reference value, and MPEG (Moving P
This is effective for special playback as defined by the (icture Encoding Group) standard. For example, when only I pictures are sequentially displayed, it is easily realized by increasing the STC value, which originally increases continuously, stepwise in accordance with the time interval of the I picture.

JP-A-8-331560

When playing back a TS recorded on a medium such as an HDD in the same procedure as playing a broadcast wave, the TS output method from the HDD monitors the amount of data stored in the decoder buffer, A problem arises in the reproduction method (hereinafter referred to as flow control reproduction) in which the input from the recording medium is adjusted accordingly. This will be described with reference to FIG.

FIG. 1 is a schematic diagram showing a difference between a reproduction method (hereinafter referred to as time stamp reproduction) in which TS is output from the HDD at the same timing as the TS input timing at the time of recording and flow control reproduction. Reference numeral 101 denotes a difference in input between time stamp reproduction and flow control reproduction with respect to an operation in which the MPEG decoder performs reproduction. The arrow written at the top indicates the time sequence for the reproduction by the MPEG decoder, and the data output timing in the time stamp reproduction is indicated by the right oblique line below it. In time stamp reproduction, data is output in small increments in the same manner as the input timing at the time of recording. On the other hand, as indicated by the left diagonal line below, in the case of flow control reproduction, data is always output as long as the decoder request continues. 102
FIG. 3 is a diagram schematically showing TS output from a recording medium in a sequence of packets. TS on the right
Assuming that packets are output in order from packet 1, in the case of time stamp playback, preparation for setting PCR in the STC by the part indicated by arrow A is completed, and TS packet X, which is PCR data, is sent to the decoder. In contrast to substituting PCR for the STC value at the input timing, in the case of flow control playback, since the data input speed is high, it is output up to the part indicated by arrow B, and TS packet Y which is PCR data is input If so, the STC value is set. As a result, when decoding is started, the video and audio data from TS packets 1 to Y-1 buffered before packet Y is not decoded because the DTS / PTS is smaller than the set STC counter value. Or it is forcibly decoded and output without being able to acquire correct time information and output in a state where the video and audio cannot be synchronized, causing the viewer to feel uncomfortable. 103 is a diagram showing a case where the data amount up to packet y-1 is larger than the data amount in which the MPEG decoder buffer fails in flow control reproduction. 1 to 4 in 103
As shown in FIG. 4, when the near overflow is detected, the MPEG decoder requests the TS controlling the output from the recording medium to stop the TS input. Then, since the recording medium stops outputting, it is possible that the decoder cannot set the PCR as the STC value and the reproduction operation stops.

As a method for solving these problems, a method of sufficiently increasing the STD buffer of the decoder can be considered, but it is not realistic.

The present invention has been made in view of the above problems, and an object of the present invention is to reproduce video and audio well .

In order to solve the above problems, an embodiment of the present invention is configured as described in, for example, the claims.

According to the present invention, video and audio can be reproduced satisfactorily .

In the following embodiment, an explanation will be given by taking as an example an apparatus for recording and reproducing MPEG2-TS used for transmission of current broadcasts on an HDD. The following is an example for explaining the present invention, and is not intended to limit the scope of the present invention only to this modification. The present invention can be implemented in various digital recording / reproducing apparatuses other than the following embodiments.

Since a plurality of programs are multiplexed and transmitted in one TS in the broadcast wave, PSI (Program Specific I) representing the relationship between the included programs and the elementary streams constituting the TS.
nformation). The decoder can extract an arbitrary program by analyzing the PSI. There are no clear rules on how to record TS to HDD, so various methods can be considered. In this example, multiple programs are multiplexed according to the MPEG2-TS format as described above. It is assumed that recording is performed in a format (hereinafter referred to as partial TS) in which only a stream constituting one program to be recorded is extracted from the broadcast wave.

FIG. 2 is a block diagram showing an example of the configuration of the playback apparatus. The operation until the predetermined TS is decoded from the recording medium in the present embodiment will be described with reference to FIG. In FIG. 2, the playback apparatus includes a recording medium 201, an output control unit 202, a separation unit 203, an MPEG decoder 204, a control unit 205, and a system bus 206. Further, the output control unit 202 includes a reading unit 2021,
It comprises a decoding unit 2022, an output unit 2023, and a counter 2024. Further, although not clearly shown in the figure, a buffer for absorbing an error in processing speed exists in the preceding stage of each processing unit.
The MPEG decoder 204 includes a PCR acquisition unit 2041, an STC counter 2042, and an audio parser 20.
43, audio buffer 2044, audio decoder 2045, video parser 204
6, a video buffer 2047 and a video decoder 2048. Although not clearly shown in the figure, there is a buffer before the output stage.

In this embodiment, it is assumed that a broadcast wave is received at an input unit not shown in FIG. 2 and is recorded on the recording medium 201 in an encrypted partial TS format. 201 is a recording medium for recording a partial TS, but by recording and managing the GOP head position of a stream to be stored at the same time, various special displays such as not only normal reproduction but also continuous display of I pictures, for example. Record for playback.

Reference numeral 202 denotes an output control unit for outputting a partial TS from a recording medium. The TS to be played back is read from the recording medium 201 and sent to the separation unit 203. An arbitrary partial TS is transferred from the recording medium 201 to the subsequent stage by the reading unit 2021. Decoding is performed in the decoding unit 2022. The output unit 2023 outputs the decoded data by either time stamp reproduction or flow control reproduction. The counter 2024 counts up time information during reproduction, and becomes a reference time for time stamp reproduction.

In the case of time stamp reproduction, the time information of the partial TS to be reproduced and the counter 2024
Are compared with the time information generated by the, and sequentially output the PES having the same time.

In the case of flow control playback, the MPEG decoder 204 sends a partial through the control unit 205.
When a TS output request is received, data is sequentially read from the recording medium. In this case, the added time stamp is ignored and output is performed at a higher speed than time stamp reproduction. MPEG decoder 2
If there is a request to stop the partial TS output from 04, reading from the recording medium is stopped. By repeating this, data output corresponding to the reproduction processing capability of the MPEG decoder 204 is realized.

The separation unit 203 analyzes the TS sent from the recording / output control unit 202 and separates it into video, audio, time information, and other additional information. The separated data is sent to the MPEG decoder 204.

In the MPEG decoder 204, the following processing is performed by using the data signal separated by the separation unit 203 as an input. The PCR acquisition unit 2041 acquires the time stamp of the TS,
Set to system time information. The STC counter 2042 periodically counts up the set time information, and the audio decoding unit 2045 and the video decoding unit 20
48. The video data input by the video PES parser 2046 is analyzed and stored in the video buffer 2047. The video decoding unit 2048 performs decoding when the time information transmitted from the STC counter 2042 and the DTS of the video data match, and performs PTS If it matches, it is output to the subsequent video output stage. The audio data is analyzed by the audio PES parser 2043 and stored in the audio buffer 2044. The audio decoding unit 2045 outputs audio when the time information transmitted from the STC counter 2042 matches the PTS of the audio data.

In the MPEG decoder 204, a setting is made to determine whether or not to transmit a flow control signal used for flow control reproduction. There is no difference in the reproduction procedure depending on whether or not the flow control signal is transmitted. After the reproduction procedure is started, the first acquired PCR is set as the STC value, and thereafter, the STC counter counts up at a constant speed. The decoding unit performs decoding / output based on the time information of the STC counter. When a flow control signal is transmitted, the data amount of one or both of the video buffer 2047 and the audio buffer 2044 of the MPEG decoder is constantly monitored, and the amount of data accumulated in the buffer is greater than or equal to a certain threshold value. In the case of a failure, a partial TS output stop request is issued to the output control unit 202 through the control unit 205. Similarly, a TS output start request is issued to the output control unit 202 when the amount of data in the buffer is less than or equal to a certain threshold value or less than the threshold value. By repeating the above operation alternately, a state where decoding is always possible is maintained, and video and audio are output in synchronization.

The control unit 205 controls each of the above modules and controls the entire system. For switching between time stamp reproduction and flow control reproduction, an instruction is sent from the control unit 205 and executed. The system bus 206 transmits instructions from the control unit to each unit and information from each unit. A playback procedure for outputting the partial TS input from the recording medium 201 in synchronization with video and audio using the apparatus described above will be described.

An operation for starting normal reproduction will be described.
FIG. 3 is a flowchart showing the operation of the apparatus at the start of reproduction. For example, when the reproduction of an arbitrary partial TS recorded on the recording medium 201 is instructed from an external input device such as a remote controller, the control unit notifies the output control unit 202 of information on the target stream.

In step (hereinafter abbreviated as S) 301, the output control unit 202 sets time stamp reproduction, and the process proceeds to S302. The recording medium 201 manages the position of the I picture, and the partial TS is output from the I picture.

In step S302, the output control unit 202 determines a program to be played back based on information received from the higher-level task, starts outputting a partial TS from the recording medium 201 by time stamp playback, and switches to flow control playback. Is set and the process proceeds to S303. The waiting time to be set is set to a value longer than the time required for the MPEG decoder to start playback. Although there is no regulation on the processing time required to start decoding for reproduction from a recording medium, a time during which decoding can be reliably performed is checked in advance, and a certain waiting time such as one second is set.

In S303, a playback start command is issued from the control unit 205 to the MPEG decoder 204. The MPEG decoder 204 starts decoding and outputting video and audio, and proceeds to S304. In S304, when the time corresponding to the timer set in S302 elapses, the control unit 205 switches the operation of the output control unit 202 from time stamp reproduction to flow control reproduction, and the process ends.

In the above flowchart, the output control unit 202 sets a waiting time, and the output control unit 202
The MPEG decoder 204 operates asynchronously, but instead of this operation, the MPEG decoder 204
The same effect can be obtained by notifying the output control unit 202 through the control bus 206 / control unit 205 that the video and audio have started to be output in synchronization, and receiving it and switching the partial TS output method to flow control playback. Can be realized. FIG. 4 shows a flowchart when processing is replaced.

In S401, the same operation as S301 is performed. In S402, as in S302, the output control unit 202 starts outputting a partial TS, but the process proceeds to S403 without setting a timer. In S403, the same control as in S303 is performed, and the MPEG decoder 204 starts an output operation, and the process proceeds to S404. In step S404, the MPEG decoder 204 notifies the control unit 205 that video and audio output has started. In step S405, as in step S304, the operation of the output control unit 202 is switched from the control unit 205 to flow control reproduction, and the process ends.

If the MPEG decoder 204 continues in the non-decoding state for a long time after the output from the recording medium 201 is started, either or both of the video buffer 2044 and the audio buffer 2047 will overflow. In case of overflow, the MPEG decoder 20
4 may be an operation such as discarding excess data sequentially from the oldest, but if the output from the recording medium 201 is started by time stamp reproduction as described above, the input bit rate is the same as the broadcast wave. Alternatively, if the playback start operation of the control unit 205 and the MPEG decoder 204 is the same sequence as that when the broadcast wave is played back, the video buffer 2044 is used.
Even if the size of the audio buffer 2047 is not changed, reproduction can be performed without the buffer breaking down.

Once the playback method has been set to flow control playback by the above operation, until the user needs to re-synchronize by stopping playback or switching the playback method, or unless the partial TS input from the recording medium is stopped Is operated by flow control reproduction.

A control for switching the playback state by a remote control operation from the user after starting normal playback will be described. FIG. 5 shows a procedure in the case of transition from the normal reproduction to the search operation for displaying only the video of the I picture that does not perform audio output.

In S501, if the current reproduction method is time stamp reproduction, the process proceeds to S502, and if it is flow control reproduction, the process proceeds to S503. In S502, the operation of the output control unit 202 is switched to flow control reproduction, and the process proceeds to S503. In step S503, the buffer included in the output control unit 202, the video buffer 2044 and the audio buffer 2047 in the MPEG decoder are cleared from the control unit 205, and the process proceeds to step S504. In step S504, the output control unit 202 changes the TS output method from the recording medium, and the process advances to step S505. The position of the next I picture to be output is acquired every time, and the data is changed so that data of a size including one I picture is output to the decoder from the obtained position. In step S505, the reproduction method of the MPEG decoder is changed from the control unit 205 so that only the I picture is decoded and output for the video, and the audio is not decoded and output, and the process ends. Even when transitioning to a special playback other than the above, that is, when transitioning from a state in which playback is performed by synchronizing video and audio to a playback state that does not require synchronization, flow control playback is performed in the same procedure. Switch to.

FIG. 6 is a flowchart showing a procedure for switching from special reproduction, which outputs only an I picture without audio output, to normal reproduction. In S601, the partial TS output is stopped, and S602
Transition to. In S602, the buffer in the output control unit 202 and the buffer in the MPEG decoder are cleared, and the process proceeds to S603. If switching to normal playback without clearing the buffer, the stream of only the I picture remaining in the buffer at the time of switching is decoded and output, giving the viewer a sense of incongruity. Therefore, by clearing the buffer, the transition to normal reproduction in which all the I, P, and B pictures are smoothly decoded and output without any remaining data is realized. In step S603, the operation of the output control unit 202 is switched to time stamp reproduction, and the process proceeds to step S604. In S604, the output control unit 202 changes the setting of the output method of the partial TS from the recording medium 201 so that all I, P, and B pictures are output.
Transition to 05. In S605, the output of the partial TS is started and the process proceeds to S606. S6
In 06, the control unit 205 changes the reproduction method of the MPEG decoder 204 so that normal decoding is performed, and the process ends. For example, a playback state that requires synchronization of video and audio from a special playback state that does not synchronize video and audio other than the above, including high-speed playback using only I and P pictures and slow playback without audio output. In the case of transition to, the time stamp reproduction is switched in the same processing procedure.

Other than the examples shown so far, for example, in a transition where only the playback speed is changed while the video and audio are synchronized and output, such as normal playback to 1.5-speed fast forward playback with audio, the output is performed. Since there is no change in picture type / order, there is no need to clear the buffer and there is no need to re-synchronize the video and audio. Therefore, in this case, there is no need to switch from flow control playback to time stamp playback. However, you can also change to time stamp playback.

In addition, when a transition is made from a forward search that displays only I pictures to a playback state that does not require synchronization from a playback state that does not synchronize video and audio, such as a reverse search that displays only I pictures. Will clear the buffer as needed while still in flow control,
Change the playback method.

As described above, it is possible to determine whether or not to perform time stamp reproduction by considering the reproduction state before and after the operation. If the playback state has a “pause” state, it is not possible to determine whether or not to change to time stamp playback during playback simply by checking the playback state before transition. For example, if the user's operation is “play” → “pause” → “play”, the flow control playback may be left without clearing the buffer, but “search” → “pause”
→ If the transition is “playback”, the buffer must be cleared and timestamp playback must be started. Therefore, either make “pause” not recognized as a playback state, or “
When in the “pause” state, the previous playback state is managed.

In reproduction from a randomly accessible recording medium, it is possible to move to a position designated by a user operation during reproduction and resume normal reproduction. When normal playback is performed from the specified position, it is necessary to synchronize video and audio at the start of playback after operation regardless of the playback state before the operation because time information is surely skipped. , Must restart with time stamp playback. FIG. 7 is a flowchart for explaining an operation of starting to reproduce a partial TS from a designated position by a user operation or the like during normal reproduction or special reproduction.

In step S701, the control unit 205 searches for an I picture in the vicinity of the designated time. If the target I picture is found, the process proceeds to S702. If the target I picture is not found because the specified time is out of the range of the stream, the process is terminated without doing anything. In S702, the same operation as that in the flowchart shown in FIG. 6 is performed to start the time stamp reproduction, and the process ends.

With the playback method shown in the above embodiment, it is possible to perform playback while maintaining AV synchronization without causing a buffer failure at the start of normal playback in partial TS playback recorded on a storage medium. Increasing the size of the video buffer 2044 and the audio buffer 2047 of the decoder is also effective in preventing overflow when a partial TS is input from the HDD. Therefore, it is possible to reduce the waiting time set in S302 by combining with the above embodiment. Ultimately, there is no waiting time set in S302, that is, the operation of the output control unit using the input as the flow control reproduction from the beginning. MPEG decoder 2
The waiting time set in S302 can also be shortened by preparing a flow control procedure during the 04 decoding procedure and shortening the processing time. However, both methods are not realistic due to disadvantages such as an increase in resources to be prepared or a new program being built, resulting in an increase in development man-hours.

The processing described above is effective regardless of the type of recording medium, provided that the TS input to the decoder has time information and can perform time stamp reproduction. In the above example, playback from the HDD was used, but other examples include DVD discs and Blu-Ray.
For example, playback from a disc. Further, the present invention is not limited to a television broadcast receiver, and can be applied to all devices that have the same configuration and can reproduce video and audio.

As described above, according to the present invention, when the TS recorded on the recording medium is read and playback that requires AV synchronization is performed, the stop of the input stream due to the overflow of the STD buffer is avoided, and the elements constituting the program (video It is possible to perform playback while maintaining good audio synchronization without preparing a dedicated flow control procedure and without increasing the amount of memory used by the decoder.

It is a schematic diagram for demonstrating the subject which this invention solves. It is a schematic diagram which shows the system configuration | structure of the reproducing | regenerating apparatus in one Example of this invention. 4 is a flowchart illustrating a reproduction start method according to an embodiment of the present invention. FIG. 3 is a flowchart for explaining that the same effect can be achieved even if a part of the processing of the flowchart shown in FIG. 2 is changed. It is the flowchart which showed the transition procedure to the flow control reproduction | regeneration in one Example of this invention. It is the flowchart which showed the transfer procedure to the time stamp reproduction in one execution example of this invention. It is the flowchart which showed the reproduction | regeneration start procedure from the arbitrary places of the partial TS in one Example of this invention.

Explanation of symbols

101 Schematic diagram showing difference between time stamp playback and flow control playback 102 Schematic diagram of input stream (TS packet) 103 Explanation of a procedure for stopping input by flow control playback 201 Recording medium 202 Output control unit 203 Separating unit 204 MPEG decoder 205 Control unit 206 System bus 2021 Reading unit 2022 Decoding unit 2023 Output unit 2024 Counter 2041 PCR acquisition unit 2042 STC counter 2043 Audio PES parser 2044 Audio buffer 2045 Audio decoding unit 2046 Video PES parser 2047 Video buffer 2048 Video decoding unit

Claims (7)

A recording unit for recording a data stream including video data and audio data;
A decoder for decoding the data stream;
A control unit for controlling reproduction of the data stream recorded in the recording unit,
The decoder temporarily holds the input data stream as buffer data before decoding,
Wherein the control unit includes a special playback not synchronize the video data and audio data, to switch the special playback and to synchronize the video data and audio data, without outputting the buffered data remaining in the decoders, the decoder When the playback speed is switched while synchronizing and reproducing the video data and the audio data, the remaining buffer data is output to the decoder. recording and reproducing apparatus and controls. The decoder temporarily stores video data and audio data included in the input data stream as video buffer data and audio buffer data before decoding, respectively, and decodes the video buffer data and the audio buffer data, respectively. ,
Wherein, when switching the special playback is not synchronized with said video data and audio data, special reproduction and synchronizing said video data and audio data, remaining with the video buffer data remaining in the decoders wherein no audio buffer data and the output each of the decoders or al, and controlling so as to decode outputs video data and audio data included in the newly input data stream to said decoder The recording / reproducing apparatus according to claim 1. A recording unit for recording a data stream including video data and audio data;
A decoder for decoding the data stream;
A controller that performs reproduction of the data stream recorded in the recording unit by switching between special reproduction in which video data and audio data are not synchronized and special reproduction in which video data and audio data are synchronized;
The decoder temporarily holds the input data stream as buffer data before decoding,
The control unit sends an instruction to clear the buffer data to the decoder when sending an instruction to switch from special reproduction that does not synchronize the video data and audio data to special reproduction that synchronizes the video data and audio data. feed Ri, when sending commands to change the playback speed during playback in synchronization with video data and audio data recording and reproducing apparatus characterized by not sending instructions to clear the buffer data to the decoder. The decoder temporarily stores video data and audio data included in the input data stream as video buffer data and audio buffer data before decoding, respectively, and decodes the video buffer data and the audio buffer data, respectively. ,
The control unit sends video buffer data and audio buffer data to the decoder when sending a command to switch from special reproduction that does not synchronize the video data and audio data to special reproduction that synchronizes the video data and audio data. The recording / reproducing apparatus according to claim 3, wherein a command for clearing each of the above is sent. A recording unit for recording a data stream including video data and audio data;
A decoder for decoding the data stream;
The data stream recorded in the recording unit is input, and the output of the input data stream to the decoder in the special playback is synchronized with the output by the control not synchronizing the video data and the audio data with the video data and the audio data. An output unit that performs switching to output by control
A controller that controls the recording unit, the decoder, and the output unit;
The decoder includes a buffer unit that temporarily holds an input data stream, and a decoding unit that decodes the data stream output from the buffer unit,
Wherein, in the special reproduction, when sending a command to switch from not synchronous control and the video data and audio data to a control for synchronizing said video data and audio data to the output unit, of said decoders Ri send instructions buffer clear the buffer portion, when sending commands to change the playback speed during playback in synchronization with video data and audio data, that do not send the instruction buffer clear the buffer of the decoder A characteristic recording / reproducing apparatus. The buffer unit of the decoder is a plurality of buffer units, and includes at least a video data buffer unit that temporarily holds the video data and an audio data buffer unit that temporarily holds the audio data,
The decoding unit of the decoder is a plurality of decoding units, and includes a video data decoding unit that decodes output data from the video data buffer unit and an audio data decoding unit that decodes output data from the audio data buffer unit ,
In the special reproduction, the control unit sends a command to the output unit to switch from control for not synchronizing the video data and audio data to control for synchronizing the video data and audio data to the output unit. 6. The recording / reproducing apparatus according to claim 5, wherein a command for clearing each of the buffer data of the video data buffer unit and the buffer data of the audio data buffer unit is sent.   The recording / reproducing apparatus according to claim 1, wherein the data stream is recorded in a transport stream format.

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