JP2002269897A - Device and method for recording and reproducing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an overflow and underflow in a buffer arranged in a MPEG-2 decoder. SOLUTION: A selecting means 15 selects data of prescribed data group from an input data stream by each transmission unit. A counter 20 counts time information corresponding to the data selected by the selecting means 15. An adding means 23 adds the count value of the counter 20 at the time when the data are selected by the selecting means 15, to the data selected by the selecting means 15, and supplies the result to a recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a recording / reproducing apparatus and a recording / reproducing method for recording / reproducing digital broadcast program (program) data transmitted by a transport stream.

[0002]

2. Description of the Related Art In recent years, MPEG (Moving Picture Exper
ts Group) 2 (MPEG2 standard)
Digitalization of television broadcasts has been implemented. In digital broadcasting using the MPEG2 standard, encoded data such as video, audio, and text (PES: Packetized
Elementary Stream format, Section format, etc.)
Is divided into a structure called a packet shown in FIG. 5, and a transport stream (T
S).

As shown in FIG. 5, a packet conforming to the MPEG2 standard (MPEG-TS packet) is mainly composed of a header and an adaptation field.
Field) and payload (Payload). FIG. 5 is a structural diagram when byte alignment is performed. For simplicity, each byte (8 bits) data is numbered from 0 to 187 in order from the leading byte.
ber (BN).

[0004] As shown in FIG. 5, an MPEG-TS packet has a length of 188 bytes. The header has a length of 4 bytes and is a data part always added to each packet. This header includes a sync (synchronization) byte indicating the beginning of the packet and a PID (Program ID
tifier).

The adaptation field contains the PCR
It includes time reference information for reproducing a time axis on the transmission side called “Program Clock Reference” on the reception side. This PCR is periodically transmitted from the transmission side.

The payload includes a PES or a section.
Data is split or multiplexed. The presence or absence of the adaptation field and the payload is described in an adaptation field flag: adff of the header. When the adaptation field is included, the adaptation field length is described in the first byte: adf-len. The receiving side, this adf-le
The boundary between the adaptation field and the payload can be detected based on n.

In addition, since the role of each data shown in FIG. 5 is well known, only the name is shown here, and the description is omitted.

Err: error indicator, unit:
Unit Start indicator, pri: priority indicator, scrm: scramble flag, cc: Continuity
Counter, tbdis: Time Base Discontinuity, p
crf: pcr flag.

On the receiving side, the MPEG2 decoder (decoding device) refers to the PID from the transport stream structure as described above, and extracts the packet of the same PID, thereby only the desired program (program) from the transmission stream. Can be decoded. Therefore, the MPE
A television receiver compliant with the G2 standard can take out only one desired program even when a transport stream including coded data of a plurality of programs A, B, and C is input, for example.

By the way, only desired packets are extracted from the transport stream including the coded data of a plurality of programs and recorded on a recording medium such as a tape, a hard disk, a DVD (Digital Versatile Disk) or a memory. Can be considered. In the digital broadcasting standard and the like, the extracted packet group is called a partial TS, and a state before extraction in which packets of a plurality of programs are multiplexed is called a full TS in a sense to distinguish it from the partial TS. Therefore, recording or reproducing only a desired packet group (program) on a recording medium is referred to as “partial TS”.
Recording / playback ".

FIG. 6 is a diagram for explaining the partial TS recording / playback processing. FIG. 6A shows a received stream (full TS or transport stream), FIG. 6B shows a packet (partial TS) extracted from the received stream, FIG. 6C shows a packet reproduced from a recording medium, and FIG. d) indicates the buffer capacity, respectively. FIG. 7 shows a packet recorded on a recording medium.

The receiving stream shown in FIG. 6 (a) encodes three types of programs A, B, and C on the transmitting side, and
B and C are further packetized as A1, A2,... And B1, B2,.
It is assumed that the data has been transmitted as a transport stream of two standards.

By the way, generally, the decoding time in the MPEG2 decoder differs depending on the contents of data.
Therefore, in order to absorb the difference in processing time, the MPEG2 decoder temporarily stores the received (encoded) data in a buffer. The capacity of this buffer is defined in the MPEG2 standard. For this reason, on the transmitting side, the transmission stream (receiving side or MPEG) is used to prevent overflow or underflow from occurring in this buffer.
2 decoder). That is, the transmitting side determines the number of consecutive packets of the same type (program) and the transmission clock in consideration of the decoding time of each packet.

For example, as shown in FIG. 6A, in order to transmit three types of programs as one transport stream, it is necessary to transmit three times or more the data amount of one program per unit time. No. Therefore, in order to transmit one program by one transport stream, a frequency that is at least three times the minimum required transmission clock is required.

The received stream shown in FIG. 6A has an input time for three packets from the end of the input of the packet A2 to the end of the input of the packet A3. This indicates that the decoding process of the packets A1 and A2 may require three packets of decoding time.

Now, consider a case where only packets A1, A2,... Based on program A are extracted and recorded as shown in FIG. This extracted packet group is referred to as partial A for convenience. When the partial A is recorded (written) as recording data on the recording medium, as shown in FIG. 7, the packets A1, A2,... By recording continuously in this manner, the storage capacity of the recording medium can be reduced.

When reproducing (reading) the partial A from the recording medium, in order to prevent overflow or underflow from occurring in the buffer, the reproduction data rate is returned to the original transmission rate, and thereafter, the data is supplied to the MPEG2 decoder. There must be. The method of restoring the rate of the reproduced data includes outputting the reproduced packets A1, A2,... At equal intervals, and outputting the packets A1, A2,... In a burst arrangement as shown in FIG.

For reference, an example of how to determine the supply rate to the MPEG2 decoder (restoration method) will be described. PCR (Pr
gram Clock Reference)
(N) and the number N of coded data between A (n + k) and this 2
PCR (n) and PCR multiplexed into one packet
Check (n + k). That is, approximately N / (PCR
By (n + k) -PCR (n)), an average transmission rate indicating the amount of transmission data per unit time of the program A, that is, a supply rate can be obtained.

When reproduced data is output using a supply (or output) clock obtained from this supply rate, packets are equally spaced. If the reproduced data is output using a supply clock having a higher frequency than all predetermined transmission clocks, the packet becomes bursty. In both cases, the supply rates averaged within a certain time (for example, one second) are the same.

However, as described above, MPEG
The two decoders need to use the transmission times of the programs B and C to decode the program A without overflow or underflow of the buffer, and the transmitting side takes into account the time required for the decoding process of the MPEG2 decoder. Partial A
The transmission interval was controlled. However, when the partial A is once recorded on the recording medium and then reproduced, the packets A1, A2,... Are supplied to the MPEG2 decoder at intervals different from those at the time of transmission. As a result, the buffer may overflow or underflow.

This situation will be described with reference to a graph shown in FIG. La (thin line) shown in FIG.
The partial A shown in (b) is not recorded on the recording medium, but is supplied to the MPEG2 decoder as it is, and the transition of the data amount occupying the buffer when decoded is shown.

Lc (thick line) shown in FIG.
The partial A is temporarily recorded on the recording medium, and is reproduced at the time of reproduction as shown in FIG.
As shown in (c), a change in the amount of data occupying in the buffer when the data is supplied to the MPEG2 decoder in a burst and decoded is shown.

In order to facilitate comparison, the time (delay amount) from recording to reproduction is neglected, and both are assumed to start supplying Partial A to the MPEG2 decoder (buffer) at time 0. The time axis of Lc is adjusted.

[0024]

As shown in FIG. 6 (d), when an extracted packet is supplied to an MPEG2 decoder by a packet interval at the time of transmission and a transmission clock, La
Decoding can be continued without exceeding (underflow) or exceeding (underflow) the buffer capacity as shown by (thin line). That is, when the partial A is stored in the buffer according to the packet interval at the time of transmission, the partial A in the buffer is subjected to the decoding process according to the packet interval at the time of transmission. The occupancy of the partial A in the buffer decreases each time the decoding process of the partial A ends. Therefore, the buffer does not overflow or underflow.

However, when the extracted packet is once recorded on a recording medium and then reproduced and supplied to the MPEG2 decoder, an overflow at time T0 or an underflow at time T1 occurs as shown by Lc (thick line). That is, since the partial A is supplied to the buffer regardless of the packet interval at the time of transmission, an overflow or an underflow occurs.

In order to solve this problem, a method of recording the number of packets deleted between extracted packets is disclosed in
-138316. However, in the conventional technique disclosed in this publication, the transmission clocks of all transport streams to be recorded must be constant. For this reason, when broadcasting using different transmission clocks is mixed, for example, when one or more desired programs are recorded in a state where BS digital broadcasting and terrestrial digital broadcasting can be received, this technology is applied. Could not.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to prevent overflow and underflow of a buffer provided in a decoder, and to reproduce reproduced data. An object of the present invention is to provide a recording / reproducing device and a recording / reproducing method capable of reliably decoding.

[0028]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a recording apparatus according to the present invention converts a plurality of types of data groups each including data from an input data stream obtained by time-dividing a predetermined transmission unit into a predetermined data group. Selecting means for selecting data for each transmission unit, and a counter for counting time information corresponding to the data selected by the selecting means,
An adding unit that adds the count value of the counter when the data is selected by the selection unit to the data selected by the selection unit and supplies the data to a recording medium.

Further, the reproducing apparatus of the present invention records the data on a recording medium in a state where a count value corresponding to time information when the data is selected is added to each of a plurality of data constituting a data group, A reproducing apparatus for reproducing the data from the recording medium, comprising: extracting means for extracting a count value of the data read from the recording medium; and a time count with the first count value extracted by the extracting means as an initial value. A counter for counting information, a count value of the counter is compared with a count value extracted by the extracting means, and when the extracted count value is larger than the count value of the counter, data of the data from the recording medium is read. A comparator that outputs a stop signal for stopping reading.

Further, according to the recording method of the present invention, data of a predetermined data group is selected for each transmission unit from an input data stream obtained by time-dividing a plurality of types of data groups each including data, and A count value corresponding to the time when the data is selected is added to the data selected for each unit, and the data with the added count value is supplied to a recording medium.

Further, according to the reproducing method of the present invention, a plurality of data constituting a data group are recorded on a recording medium in a state where a count value corresponding to time information when the data is selected is added, A reproduction method for reproducing the data from the recording medium, wherein a count value of data read from the recording medium is extracted, and time information is counted with the extracted first count value as an initial value,
Comparing the counted count value with the extracted count value, if the extracted count value is greater than the counted count value, stop reading data from the recording medium; When the count value is equal to or less than the counted value, data is read from the recording medium.

[0032]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the recording apparatus of the present invention.

The antenna 11 receives a digital television signal of a BS digital broadcast or a terrestrial digital broadcast. The output signal of the antenna 11 is supplied to a tuner 12. The tuner 12 selects a desired channel. The transport stream TS of the selected channel output from the tuner 12 is an MPEG2
The signal is supplied to the first switch 14 of the decoder 13. The first switch 14 selects an output signal of the tuner 12 at the time of recording a program and a recording / reproducing device 21 described later at the time of reproduction.
Select the output signal of

A data selector 15 is connected to an output terminal of the first switch 14. This data selector 15
Selects one program to be recorded from the transport stream TS supplied from the first switch 14. That is, the data selection unit 15 determines the transport stream TS according to the PID in the packet.
, A packet corresponding to one desired program is extracted.
The output of the data selector 15 is connected to a decoder 16 for decoding a packet. The decoding unit 16 is provided with a buffer 17 for storing packets.

Further, a PCR extraction unit 18 is connected to an output terminal of the data selection unit 15. The PCR extraction unit 18 extracts the time reference information PCR shown in FIG. 5 included in the packet output from the data selection unit 15. The extracted PCR is time information set for each program as described above, and indicates the packet transmission timing.

The output terminal of the PCR extraction unit 18 is connected to the comparator 1
9 is connected to one input terminal. An output terminal of an STC (System Time Counter) 20 is connected to the other input terminal of the comparator 19. The STC 20 is a counter capable of counting time information corresponding to a program for 24 hours. The comparator 19 compares the time information supplied from the PCR extraction unit 18 with the count value supplied from the STC 20, and detects these errors. The error signal output from the comparator 19 is supplied to a loop filter 21 constituting a PLL (Phase Locked Loop) circuit. This loop filter 21 generates a voltage corresponding to the error signal,
This is supplied to a VCO (voltage controlled oscillator) 22. The VCO 22 generates a system clock signal having a frequency according to the voltage supplied from the loop filter 21. The system clock signal output from the VCO 22 is supplied to the STC 20. This STC20 is VCO2
The system clock signal supplied from 2 is sequentially counted. In this way, control is performed so that the count value of the STC 20 matches the time reference information PCR.

The output terminal of the STC 20 is supplied to a second switch 23 as a multiplexer. The second switch 23 adds a start code SC and a count value output from the STC 20 to a packet supplied from the data selection unit 15. The output terminal of the second switch 23 is connected to a recording / reproducing device 24. The recording / reproducing device 24 is, for example, a video tape recorder, a hard disk device, a DVD (Digital Versatil
e Disk) or a recording medium such as a memory. The signal output from the second switch 23 is sequentially recorded in the recording / reproducing device 24. The output terminal of the recording / reproducing device 24 is connected to the first switch 14.

In the above configuration, the recording operation of the program will be described with reference to FIG.

At the time of the recording operation, the first switch 14 selects the output signal of the tuner 12. The selected transport stream TS output from the tuner 12 is
It is supplied to the MPEG2 decoder 13. This MPEG2
In the decoder 13, the transport stream TS that has passed through the first switch 14 is supplied to a data selection unit 15. The data selection unit 15 determines whether the PI
According to D, a packet corresponding to one desired program is extracted from the transport stream TS. The extracted packet is supplied to the decoding unit 16 and the PCR extraction unit 18. The decoding unit 16 sequentially stores and decodes the supplied packets in the buffer 17, and outputs the packets as a video signal and an audio signal.

On the other hand, the PCR extracting unit 18 extracts time reference information PCR from the supplied packet. The extracted PCR is supplied to the comparator 19 together with the count value output from the STC 20. The comparator 19 detects an error between the PCR and the count value, and supplies the detected error signal to the rope filter 21. The loop filter 21 generates a voltage corresponding to the error signal and supplies it to the VCO 22. Therefore, the VCO 22 generates a system clock signal having a frequency corresponding to the supplied voltage. This system clock signal is supplied to the STC 20. Therefore, the STC 20 is controlled by the PLL circuit so that the count value is always equal to the PCR. The change in the count value indicated by the broken line in FIG. 2 schematically indicates the operation of the STC 20.

As is clear from FIG. 2, the count value output from the STC 20 matches the PCR. Therefore, this count value indicates the time when the packet arrives at the MPEG2 decoder 13.

On the other hand, the second switch is a data selector 1
When a packet is output from No. 5, the extracted packet is added to the count value of the STC 20 at that time and supplied to the recording / reproducing device 24. That is, the start code SC indicating the head of the packet, the count value output from the STC 20, and the packet output from the data selection unit 15 are supplied to the second switch 23. When a packet extracted from the data selection unit 15 is output, the second switch 23 adds the start code SC and S at this time to the packet.
The count value of TC20 (shown as STC in FIG. 2) is added.

The packet of the unique format having the generated start code SC and count value is supplied to the recording / reproducing device 24 and recorded. Hereinafter, similarly, the start code SC and the count value are added to the packet extracted in the data selection unit 15 and the packet is sequentially and continuously recorded in the recording / reproducing device 24.

The recording data shown in FIG.
4 shows a unique format packet continuously recorded.

Each packet sequentially recorded in the recording / reproducing device 24 has a count value indicating time information when the packet arrives at the MPEG2 decoder 13. For this reason, the original packet interval can be reproduced using this count value.

FIG. 3 shows an embodiment of the reproducing apparatus of the present invention, and the same parts as those in FIG. 1 are denoted by the same reference numerals.

In FIG. 3, an STC extraction unit 31 is connected to an output terminal of the first switch 14. This ST
The C extracting unit 31 extracts the count value added to the packet read from the recording / reproducing device 24. This S
The output terminal of the TC extraction unit 31 is the STC 20 and the comparator 32
It is connected to the. This comparator 32 is an STC extraction unit 31
Is compared with the count value output from the STC 20. The output terminal of the comparator 32 is connected to the recording / reproducing device 24. This comparator 32
Outputs a stop signal for stopping the reproducing operation of the recording / reproducing device 24 when the extracted count value STC1 is larger than the count value STC2 output from the STC 20.

The input end of the decoder section 16 is connected to a packet separating section 33. This packet separation unit 3
3 removes the start code SC and the count value from the packets reproduced from the recording / reproducing device 24 and supplied through the first switch 14, and supplies only the packets to the decoding unit 16.

In the above configuration, a reproducing operation will be described with reference to FIG.

At the time of reproduction, the first switch 14 is switched to the reproduction side as shown in FIG. In this state, the first packet is read from the recording / reproducing device 24. That is, the start code SC and the count value STC of the first packet are sequentially read out.
2 decoder 13. The STC extraction unit 31 extracts a count value from the data supplied via the first switch 14. The first extracted count value is supplied to the STC 20 as an initial value.

During reproduction, the STC 20 runs by a system clock signal of a predetermined frequency defined by the MPEG2 standard, and counts up using the set count value as an initial value.

The comparator 32 compares the count value STC1 supplied from the STC extractor 31 with the count value STC2 supplied from the STC 20. In the case of the first packet, the comparison result is STC1 ≦ STC2. For this reason, the packets subsequently read from the recording / reproducing device 24 are subjected to the start code S
C and the count value are removed and supplied to the decoding unit 16.

When reading a subsequent packet from the recording / reproducing device 24, the comparator 32 operates as follows. That is, the comparator 32 compares the count value STC1 extracted by the STC extraction unit 31 with the count value STC2 of the STC20. As a result, when STC1> STC2,
The comparator 32 outputs a stop signal. Therefore, the recording / reproducing device 24 stops the read operation, and the packet is not read.

The STC 20 is self-running. For this reason,
After a lapse of a predetermined time, the count value STC2 of the STC 20 becomes:
It becomes larger than the extracted count value STC1. When the comparison result satisfies STC1 ≦ STC2, the comparator 32 releases the stop signal. Therefore, the recording / reproducing device 24 starts reading the packet. The read packet is supplied to the decoding unit 16 via the packet separating unit 33. Hereinafter, by the same operation, when the count value STC1 read from the recording / reproducing device 24 becomes equal to or larger than the count value STC2 of the SCT 20, the packet is read from the recording / reproducing device 24. This read packet is
The data is supplied to the decoding unit 16 and subjected to a decoding process.

The packet reproduced from the recording / reproducing device 24 in this manner is such that the packet is recorded in the MPEG-2 format at the time of recording.
It is supplied to the decoding unit 16 at the time interval at which it arrives at the decoder 13. Therefore, the decoding unit 16
7, the decoding process can be reliably performed without causing overflow or underflow.

When the reproduced transport stream is to be output to the outside, the output signal of the packet separating section 33 may be output as it is.

According to the above embodiment, when recording, the STC
20 counts the elapsed time of the selected program, and
When a packet is output from the data selection unit 15, the switch of the selected
A count value of 20 is added and supplied to the recording / reproducing device 24. For this reason, the packet recorded in the recording / reproducing device 24 is recorded in the recording / reproducing device 24 with a count value indicating the time when the packet arrives at the MPEG2 decoder 13 added. Therefore, the time when the packet reaches the MPEG2 decoder 13 can be reproduced by the added count value.

The PCR extracting section 18 extracts the time reference information PCR added to the packet, and the loop filter 21 and the VCO 22 constituting the PLL circuit generate a system clock signal based on the PCR and supply it to the STC 20. are doing. For this reason, since the STC 20 can be synchronized with the PCR, the count value of the STC 20 can be calibrated. Therefore, the count value added to each packet can be accurately matched with the packet time interval set on the transmitting side.

At the time of reproduction, the STC extraction unit 31
Extracts the count value added to each packet, and the comparator 32 compares the extracted count value with the self-running STC 20.
And the extracted count value is ST
If it is larger than the count value of C20, the recording / reproducing device 24
When the count value of the STC 20 becomes equal to or greater than the extracted count value, the packet can be read from the recording / reproducing device 24. Therefore, the reproduced packet is supplied to the MPEG2 decoder 13 at a time interval when the packet arrives at the MPEG2 decoder 13 during recording. Therefore, it is possible to prevent the buffer 17 from overflowing or underflowing, and it is possible to reliably perform the decoding process.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0062]

As described in detail above, according to the present invention,
It is possible to provide a recording / reproducing apparatus and a recording / reproducing method capable of preventing overflow and underflow of a buffer provided in a decoder and capable of reliably decoding reproduced data.

[Brief description of the drawings]

FIG. 1 shows the first embodiment of the present invention, and is a configuration diagram showing a configuration at the time of recording.

FIG. 2 is a view shown for explaining the operation of FIG. 1;

FIG. 3, showing the first embodiment of the present invention, is a configuration diagram showing a configuration at the time of reproduction.

FIG. 4 is a view shown for explaining the operation of FIG. 3;

FIG. 5 is a view for explaining the structure of a packet.

FIG. 6 is a view for explaining a partial TS recording / playback process.

FIG. 7 is a view for explaining a packet recorded on a recording medium.

[Explanation of symbols]

13 MPEG2 decoder, 14 first switch, 1
5 data selection unit, 16 decoding unit, 17 buffer, 18 PCR extraction unit, 19 comparator, 20 ST
C, 23: second switch, 24: recording / reproducing device, 31
... STC extraction unit, 32 ... comparator, 33 ... packet extraction unit

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (6)

[Claims] 1. A selecting means for selecting, for each transmission unit, data of a predetermined data group from an input data stream obtained by time-dividing a plurality of types of data groups each including data in a predetermined transmission unit; A counter for counting time information corresponding to the data, and adding the count value of the counter when the data is selected by the selection means to the data selected by the selection means and supplying the data to a recording medium A recording apparatus comprising: an adding unit. 2. An extracting unit for extracting time information included in the data selected by the selecting unit, and comparing the time information extracted by the extracting unit with a count value of the counter, and obtaining an error signal. A voltage generating means for generating a voltage corresponding to the error signal output from the comparing means, a clock signal having a frequency corresponding to the voltage supplied from the voltage generating means, 2. The recording apparatus according to claim 1, further comprising an oscillator that supplies the counter. 3. A plurality of data constituting a data group are recorded on a recording medium in a state where a count value corresponding to time information when the data is selected is added to the recording medium. A reproducing apparatus for reproducing, wherein an extracting means for extracting a count value of data read from the recording medium, a counter for counting time information with an initial count value extracted by the extracting means as an initial value, The count value of the counter is compared with the count value extracted by the extracting means. If the extracted count value is larger than the count value of the counter, a stop signal for stopping reading data from the recording medium is output. A reproducing apparatus comprising: a comparator for outputting the signal. 4. The reproducing apparatus according to claim 3, further comprising a separating unit configured to separate the count value from data read from the recording medium. 5. A data of a predetermined data group is selected for each transmission unit from an input data stream obtained by time-dividing a plurality of types of data groups each including data in a predetermined transmission unit, and the data selected for each transmission unit is selected. And a count value corresponding to the time when the data is selected, and supplying the data with the count value to a recording medium. 6. A plurality of data constituting a data group are recorded on a recording medium in a state where a count value corresponding to time information at the time when the data is selected is recorded on a recording medium. A reproduction method for reproducing, wherein a count value of data read from the recording medium is extracted, time information is counted with the extracted first count value as an initial value, and the counted value and the counted value Comparing with the extracted count value, if the extracted count value is larger than the counted count value, stop reading data from the recording medium, and change the extracted count value to the counted count value. When the value is equal to or less than the value, data is read from the recording medium.