JP2000217080A - Compressed information reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device that solves a conventional problem due to reproduction of time information from transmission compressed information read from a storage medium and realizes more accurate reproduction of the transmission compressed information. SOLUTION: Time information is not reproduced from transmitter side time information (PCR) included in an MPEG bit stream read from a storage medium 3. An MPEG decoder 5 is operated by using a reference signal generating circuit 9 that is a self oscillation circuit. Then the read MPEG bit stream is separated into video information and audio information and the video information is fed to a post-stage decoder 7 via a memory 6. Then a memory residual amount detection circuit 8 detects a residual amount of the video information stored in the memory 6 and a read drive system (a servo circuit 1 and a drive circuit 2) of a storage medium 3 is controlled so that the residual amount is constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressed information reproducing apparatus for reproducing compressed transmission information (to which transmission-side time information is added) read from a storage medium, for example, a digital broadcast transport stream. Is a digital VTR (video tape recorder) that records and reproduces as it is. It is another object of the present invention to provide a compressed information reproducing apparatus for realizing more accurate reproduction of the transmission compressed information once stored and read.

[0002]

2. Description of the Related Art In digital broadcasting, a technique for multiplexing information such as compressed video, audio and data and transmitting the multiplexed information as a bit stream has been established. In this transmission system, the receiving side must reproduce a system clock synchronized with the transmitting side and perform signal processing. Therefore, information for reproducing the system clock is inserted into the bit stream at an appropriate interval and transmitted, and information for reproducing the system clock is extracted from the bit stream on the receiving side and PLL is applied. A clock synchronized with the system clock on the transmitting side is obtained.

[0003] As digital broadcasting, ISO / IEC
13818 (hereinafter referred to as MPEG2) compliant broadcasting is emphasized. In this MPEG2 system, compressed video
Information such as voice and data is packetized and multiplexed, and transmitted as a transport stream (referred to as an MPEG bit stream on the receiving side).

[0004] A program clock reference (hereinafter referred to as PCR) is inserted into the transport stream at appropriate intervals as time information for reproducing a clock synchronized with a system clock on the transmitting side on the receiving side. Is done. The value of this PCR becomes the value of the counter that operates with the system clock.

[0005] There is a digital VTR in which a transmitted transport stream can be recorded as it is on a magnetic tape and then reproduced and decoded. In this digital VTR, at the time of reproduction / decoding, the time information on the transmission side is reproduced by the time information processing circuit based on the PCR reproduced from the magnetic tape.

[0006]

When a transport stream (MPEG bit stream) with PCR is reproduced from a magnetic tape in a digital VTR, the transmission added at the time of transmission is caused by fluctuations in the magnetic tape drive system or the like. In some cases, a difference occurs between the time information on the side and the time information reproduced by the digital VTR. If this difference occurs, the MPEG decoder built in the digital VTR will cause abnormal operations such as overflow and underflow, and the transport stream will not be correctly decoded.

The present invention solves the problem of reproducing time information from transmission compressed information read from a storage medium (problem based on the asynchrony between the time information transmitting side and the reproducing side) and provides more accurate compression. It is an object of the present invention to provide a compressed information reproducing device for reproducing information.

[0008]

In order to solve the above-mentioned problems, the present invention accumulates transmission compressed information in which compressed video information and audio information are multiplexed and transmission side time information is added. In a compressed information reproducing apparatus for reproducing the transmission compressed information read from a storage medium, the transmission compressed information read from the storage medium is separated into video information and audio information, and the time on the transmission side is separated. A separation circuit that deletes information, a storage circuit that temporarily stores the separated video information and outputs the information to a subsequent circuit, and detects an information amount of the video information stored in the storage circuit, and the information amount is constant. And a self-oscillation circuit for generating a reference signal serving as a reference for the operation timing of the entire apparatus. Device, there is provided a.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, a transmission side stream included in a transmission bit stream (compressed transmission information in which compressed video information and audio information are multiplexed and time information is added) read from a storage medium is described. The reproducing device is operated using the self-oscillation circuit without operating the reproducing device based on the time information reproduced by the time information. At the same time, the transmission bit stream read from the storage medium is separated into video information and audio information, and the video information is supplied to a subsequent video information processing circuit via a storage circuit.

Then, the remaining amount of the video information stored in the storage circuit is detected, and the read drive system of the storage medium is controlled so that the remaining amount becomes constant. Thus, the compressed information reproducing apparatus of the present invention can eliminate the difference between the time information transmitting side and the reproducing side (asynchronism between the time information transmitting side and the reproducing side) and solve the problem.

An embodiment of the compressed information reproducing apparatus according to the present invention will be described with reference to FIG. This embodiment is applied to a digital VTR capable of storing and reproducing a transport stream (MPEG bit stream), which is transmitted transmission compression information, as it is on a storage medium (magnetic tape).

Drive circuit 2 controlled by servo circuit 1
The received transport stream (MPEG bit stream including PCR (time information)) is temporarily stored in the storage medium (magnetic tape) 3 driven by the.

A storage medium (magnetic tape) 3 driven by a servo circuit 1 also serving as a read drive system and a drive circuit 2
The amount of code transmitted per unit time of the MPEG bit stream read from the MPEG-2 is not constant due to fluctuations of the drive circuit 2, the servo circuit 1, and the like.

The read MPEG bit stream is separated by a separation circuit 4 into video data and audio data. At this point, the transmission-side time information included in the MPEG bit stream read from the storage medium,
R is deleted.

The separated video data is supplied to a decoding integrated circuit of the built-in MPEG decoder 5. Normally, a buffer memory 6 exists inside the decoding integrated circuit. The video data is temporarily stored in the memory 6, read out, and supplied to the decoder 7.

The state of use of the memory 6 is detected by a remaining memory detecting circuit 8. More specifically, the memory remaining amount detection circuit 8 sequentially detects the remaining amount of video data in the memory 6.

The remaining memory detecting circuit 8 supplies a detection signal of remaining data to the servo circuit 1. The detection signal is used to control the servo circuit 1 and the drive circuit 2 which are the read drive system of the storage medium (magnetic tape) 3 so that the read control is performed so that the remaining amount of video data on the buffer memory 6 becomes constant. I do.

On the other hand, the operation timing of the MPEG decoder 5 is controlled only by the reference signal from the reference signal generation circuit 9 which is a self-oscillation circuit (for the MPEG bit stream read from the storage medium (magnetic tape) 3). Time information is not reproduced from the included PCR, and PCR is not used for operation timing control.) The operation timing of the decoder 7 consuming the contents stored in the memory 6 is also controlled only by the reference signal from the reference signal generation circuit 9.

As a result of the above-described control of the read drive system by the remaining memory detection circuit 8 and the control of the operation timing of the decoder 7 by the reference signal generation circuit 9, the decoder 7
Is determined only by the reference signal from the reference signal generation circuit 9, and a fixed amount of video data is supplied to the decoder 7. (That is, the code transmission amount of video data per unit time supplied to the decoder 7 is constant.)

Therefore, the present embodiment solves the conventional problem (problem based on the non-synchronism between the transmission side and the reproduction side of the time information) caused by reproducing the time information from the MPEG bit stream read from the storage medium. Thus, it is possible to prevent the malfunction of the MPEG decoder and to reproduce the MPEG bit stream more accurately.

Further, since the cycle of reproducing video data and audio data is controlled only by the oscillation cycle of the reference signal generating circuit 9 which is a self-oscillation circuit, synchronous operation of a plurality of digital VTRs can be performed, and editing can be performed. Work such as is easy.

[0022]

As described above, the compressed information reproducing apparatus according to the present invention has the conventional problem (the asynchronous operation between the time information transmitting side and the reproducing side) caused by reproducing the time information from the transmission compressed information read from the storage medium. Problem based on performance) can be solved, and more accurate reproduction of the compressed information for transmission can be realized.

Furthermore, in the present compressed information reproducing apparatus, the operation timing of reproducing the compressed information for transmission is controlled by the self-oscillation circuit, so that a plurality of units can be operated synchronously and the work of editing and the like becomes easy.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Servo circuit 2 Drive circuit 3 Storage medium (magnetic tape) 4 Separation circuit 5 MPEG decoder 6 Buffer memory 7 Decoder 8 Remaining memory detection circuit 9 Reference signal generation circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C018 HA06 HA16 5C053 FA14 FA20 GB06 GB38 HA33 JA03 JA07 JA12 JA22 KA01 KA06 LA05 5K028 EE03 EE08 KK03 KK32 NN00 SS15 SS24 5K047 CC01 CC08 CC11 DD01 DD02 GG02 MM24 MM49

Claims (1)

[Claims] 1. Compressed information for reproducing compressed transmission information read from a storage medium storing compressed transmission information to which compressed video information and audio information are multiplexed and transmission-side time information is added. In the playback device, a separation circuit that separates the transmission compressed information read from the storage medium into video information and audio information and deletes the transmission side time information, and temporarily stores the separated video information. A storage circuit for outputting to a subsequent circuit; and an information amount detection for detecting an information amount of video information stored in the storage circuit and controlling a read drive system of the storage medium so that the information amount is constant. A compressed information reproducing apparatus comprising: a circuit; and a self-oscillation circuit that generates a reference signal serving as a reference for operation timing of the entire apparatus.