JP3263625B2 - Digital video recorder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an MPEG2 (Moving Picture Experts Group 2) which is an international standard for image compression.
The present invention relates to a digital VCR (video cassette recorder) for recording and reproducing a TS (Transport Stream) signal as digital data on a recording medium such as a magnetic tape.

[0002]

2. Description of the Related Art As a digital VCR system capable of recording a DVB (Digital Video Broadcast) broadcast signal which is an MPEG digital broadcast in Europe, there is a DVB format standardized by the HD Digital Council.

[0003] This standard, as shown in FIG. 3, defines an MPEG transport stream packet (1 byte) of 187 bytes.
Two of the 88 bytes (one byte of the synchronization byte is not recorded) are recorded using five packets called sync blocks, each of which has 77 bytes unique to the digital VCR as one data block. In FIG. 3, TP
-1 and TP-2 indicate different MPEG transport streams.

As shown in FIG. 3, each MPEG transport stream packet has a TSP extra header (3 bytes) for storing time information (hereinafter referred to as "time stamp") when the packet is input to the VCR. I have. FIG. 4 shows the structure of the TSP extra header.

In the DVB broadcasting, one transponder has a recording rate of 25 Mbps, which is the recording rate of the digital VCR video data of the HD Digital VCR Council standard.
A plurality of programs are multiplexed and transmitted at a transmission rate of about 30 Mbps, which exceeds the above.

[0006] Therefore, a program to be recorded is selected on the digital VCR side, unnecessary MPEG transport stream packets are removed, and the recording is suppressed to within 25 Mbps so that recording can be performed in the DVB format.

[0007] In order to record data transmitted at about 30 Mbps at a rate of 25 Mbps as described above, if only MPEG transport stream packets are simply recorded, the original MPEG transport stream packet at the time of reproduction is used.
The time axis of the transport stream cannot be restored. Therefore, in the DVB format, the time axis is restored based on the time stamp.

In other words, the time axis is restored by reproducing the time intervals of the preceding and succeeding MPEG transport stream packets by the value indicated by the time stamp. Assuming that the reproduced bit stream is output to the MPEG decoder at the same transmission rate as the input, the time interval between the preceding and following MPEG transport stream packets is an integer number of MPEG transport stream packets. This interval is set when a packet discarded at the time of recording in the bit stream data input by multiplexing a plurality of programs,
During playback, by inserting a null packet here,
A reproduced MPEG transport stream that does not violate the MPEG syntax can be obtained.

[0009]

In the time axis restoration method according to the prior art, when an error that cannot be corrected in reproduced data occurs, the time stamp of the MPEG transport stream packet included in the error correction block is used. There is a possibility that the information is incorrect. Therefore, there is a problem in that correct time axis restoration cannot be performed by using the incorrect time stamp information.

Accordingly, an object of the present invention is to solve such a problem.

[0011]

In order to solve the above-mentioned problem, a flag bit indicating an error state occurring in the reproduced MPEG transport stream packet is added to each of the reproduced MPEG transport stream packets. In the state of (1), when it is indicated that the error correction code block including the corresponding MPEG transport stream packet is uncorrectable, the time axis restoration process using the time stamp of this packet is not performed.

Further, when the error flag indicates that the error cannot be corrected, the packet is output at a predetermined data transfer rate following the corresponding MPEG transport stream packet. At this time, the first 4 of the corresponding uncorrectable MPEG transport stream packet
"Transport error indic" of fixed bit length header of byte
ator "area is rewritten to" 1 "and output.

According to the above method, when restoring the time axis, it is selected not to perform the time axis restoration processing according to the state of the flag bit, and the error at the time axis restoration is limited to the corresponding packet, and the subsequent reproduction is performed. It is possible to avoid affecting the time axis restoration processing of the bit stream.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a reproduction system of a digital video recorder embodying the present invention. A signal of a format as shown in FIG. 2 reproduced from a video tape (not shown) is subjected to error correction processing by an error correction circuit 1. The packet conversion circuit 2 converts the sync block structure into MPEG packet blocks in units of 192 bytes.

Next, an error flag is added to the output of the packet conversion circuit 2 in accordance with the result of the correction processing in the error correction circuit 1 and stored in the rate buffer 4.

FIG. 3 shows the form of a signal output from the error flag adding circuit 3, in which 3 bytes of time stamp information and 187 bytes of MPEG data (of 188 bytes, one byte of a synchronization byte is not recorded) ), A total of 192 bytes of a 2-bit error flag and a 14-bit reserved area are defined as one block.

The contents of the error flag are "00" for no error, "01" for error and corrected, "10".
Is an error and cannot be corrected (SB1, 3, 4), "1
1 "indicates that there is an error and cannot be corrected (SB0, 2). Here, SB0, SB1, SB2, SB
3 and SB4 are the sync block numbers in FIG.

When an uncorrectable error occurs in SB0 and SB2, time stamp information is present in the error and there is a possibility that the time stamp information on the corresponding MPEG transport stream packet is incorrect. It is distinguished from uncorrectable errors that occur in sync blocks SB1, SB3, and SB4 where no time stamp information exists.

The rate buffer 4 is a memory for converting a processing rate of a DVCR processed based on a transfer rate of 25 Mbps into a transmission rate of an output signal. The MPEG transport stream packets read from the rate buffer 4 at a desired transmission rate are output to an information adding circuit 8 described later after waiting in a delay buffer 5 for a time necessary for time axis restoration.

The time axis restoration processing circuit 6 calculates the difference between the time stamp value extracted from the output signal from the rate buffer 4 and the time stamp value of the MPEG transport stream packet correctly output immediately before.
The delay buffer 5 is instructed to wait for the output of the MPEG transport stream packet for the time corresponding to the difference. In addition, the value of TSL (lower bit of the time stamp) is reset every two track cycles,
As the relative position of the reference signal of the track cycle, the MP
The waiting time of the EG transport stream may be obtained.

Further, the error flag identification circuit 7 performs the following processing depending on the state of the error flag. (1) In the case of “00”, “01”, “10”: The MPEG transport stream packet is output at the timing specified by the time axis restoration processing circuit. (2) In the case of "11": time axis restoration was correctly performed immediately before the corresponding MPEG transport stream packet (the state of the error flag is "00", "01", "1").
0 ″) Outputs the MPEG transport stream packet immediately after the MPEG transport stream packet.

In the case of (2), the MPEG transport stream packet is reproduced several packets earlier in time than the position where it should exist. If the packet is a packet carrying a PCR (Program Clock Reference) value, it has an adverse effect on the MPEG system decoder.
By rewriting the value of "or", this can be dealt with by issuing a warning to the MPEG system decoder. When the packet does not include time management information,
It does not adversely affect the EG system decoder.

After the packet subjected to the process (2), the status of the error flag is "00", "01",
When a packet of “10” comes, the time axis restoration of the packet is performed by using the time stamp of the MPEG transport stream packet that has been correctly time axis restored before the packet subjected to the process (2). Of the time axis.

Finally, the output signal from the delay buffer 5 is subjected to the addition of a synchronization byte (0x47) of the packet of the MPEG transport stream and the rewriting of the "transport error indicator" shown below in the information adding circuit 8.
Output to the outside. "transporterror indicator" is MP
This is a 1-bit area defined by the EG standard (ISO / IEC13818-1), and indicates whether an error is included in the packet. If there is an error, "1" is displayed.

The state of the error flag is "10", "1"
1 ", that is, if an uncorrectable error has occurred, the" transpo "of the MPEG transport stream packet
rt error indicator ”to“ 1 ”,“ 00 ”,
This rewriting is not performed in the case of “01”.

In this embodiment, a magnetic tape is used as a recording medium. However, it is apparent that the same effect can be realized by a tape-shaped or disk-shaped recording medium having magnetic and non-magnetic recording means.

[0028]

According to the present invention, when restoring the time axis of a packet containing an uncorrectable error that has occurred during the recording and reproduction processes, packets with an incorrect time axis are limited to only the packet concerned. It is possible to prevent the subsequent reproduction bit stream from affecting the time axis restoration processing.

[Brief description of the drawings]

FIG. 1 is a block diagram of a reproduction system of a digital VCR embodying the present invention.

FIG. 2 is a diagram showing a configuration of a signal output according to the present invention.

FIG. 3 is a diagram showing a structure of an MPEG transport stream packet.

FIG. 4 is a diagram showing a DVB TSP extra header.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Error correction circuit 2 Packet conversion circuit 3 Error flag addition circuit 4 Rate buffer 5 Delay buffer 6 Time axis restoration processing circuit 7 Error flag identification circuit 8 Information addition circuit

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masahiko Tomikawa 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-8-204584 (JP, A) JP Hei 7-23384 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 5/91-5/956 H04N 7/24

Claims (1)

(57) [Claims] 1. An MPEG transport stream packet is divided into a plurality of blocks on a track on a tape, and the MPEG transport stream packet is recorded together with time stamp information indicating the time when the packet was input to the video recorder. In a digital video recorder which restores the time axis of the MPEG transport stream based on time stamp information, when an uncorrectable error occurs in the block having the recorded time stamp information, ,
An error flag indicating that the error has occurred is set in the MP.
An MPEG transport that has been added to the EG transport stream packet and that has been restored in time just before the MPEG transport stream packet.
A digital video recorder which outputs the MPEG transport stream packet following the stream stream packet.