JPH04337568A - Digital recording and reproducing device for moving image data - Google Patents

Abstract

PURPOSE:To facilitate the sure high speed reproducing and the ultra high speed searching of a moving image data subjected to data compression. CONSTITUTION:In accordance with a record starting signal or a scene changing signal, one frame data by one is pulled out from the moving image data subjected to data compression by a frame pulling out circuit 5. A same image data signal is recorded continuously for or by preliminarily set time or the number of frame to one side or both sides of optional tracks by a recording head 8 for high speed reproducing through a signal processing part 6 for high speed reproducing and a recording and reproducing circuit 7 for high speed reproducing. In such a case, a signal for program searching to indicate the generation of record starting or scene changing is recorded to the header part of the image data for high speed reproducing and a non data area signal to indicate it is recorded to a area where no image data for high speed is recorded.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention relates to a digital recording and reproducing device for moving image data, and in particular to a moving image recording device that uses a helical scan recording type digital tape recorder to reproduce moving image data at high speed. The present invention relates to a recording/reproducing device.

0002

[Prior art] Digital audio tape (DAT)
was originally developed for audio use, but recently its application as an external storage device for computers has become widespread, and it has become popular in the DATA/DAT format and DATA format.
It has been standardized as the DS format.

By the way, when playing back moving images digitally recorded on such a helical scan recording type digital tape recorder at high speed, the bit rate of the playback signal needs to be the same as the bit rate during normal playback. It is necessary to control the rotation speed of the cylinder with high precision according to the playback speed. Furthermore, since the trajectory of the head during high-speed reproduction is oblique to the recorded track, recorded moving image data cannot be completely detected.

0004

Generally, when decoding data such as a moving image that has been compressed by high-efficiency encoding, it is extremely difficult to restore the image if there is any data loss.

For example, when moving image data is recorded on DATA/DAT, data for one frame is continuously recorded over several to several tens of tracks. When attempting to reproduce this data at high speed, the locus of the magnetic head becomes oblique to the track, and the data obtained from the reproduction head becomes intermittent. For this reason, it is not possible to recognize and reproduce all of the recorded moving image data, and it becomes difficult to restore the image, especially with variable length coded image data.

[0006] The present invention has been made in view of the above points, and is a method of moving image data that can recognize and reproduce recorded images even when compressed moving image data is played back at high speed. The purpose of the present invention is to provide a digital recording and reproducing device.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the moving image data digital recording and reproducing apparatus of the present invention includes a magnetic tape for recording image data for normal speed reproduction. a first recording means; a second recording means for recording image data for high-speed reproduction in a different area on the same tape as the magnetic tape; a third recording means for recording a no-data area signal to indicate that no image data is recorded in a different area on the same tape as the magnetic tape; and high-speed reproduction by the second recording means. Recording of image data for normal speed playback is started almost simultaneously with the start of recording of image data for normal speed playback by the first recording means, and when a certain period of time has elapsed after the start of recording, or after a certain number of frames have been recorded. stops the recording of the image data for high-speed reproduction, and when the image data for high-speed reproduction is not recorded by the second recording means, the second recording means is added to the third recording means. and recording control means for recording the no-data area signal in the area where recording is to be performed.

[0008]

[Operation] That is, in the digital recording and reproducing apparatus for moving image data according to the present invention, the second recording means records image data for high-speed reproduction on the same magnetic tape as the magnetic tape on which recording is performed by the first recording means. Record to a different area, such as an optional track. In this case, the recording of image data for high-speed reproduction by the second recording means is controlled by the recording control means. That is, the recording of image data for high-speed reproduction by the second recording means starts almost simultaneously with the start of recording of the image data for normal-speed reproduction by the first recording means. Then, when a certain period of time has elapsed after the start of recording, or after a certain number of frames have been recorded, recording is stopped. When the second recording means is not recording image data for high-speed reproduction, the recording control means controls the third recording means to control the magnetic field to be recorded by the second recording means. A no-data area signal indicating that no image data is recorded is recorded in a different area on the same tape.

That is, in the present invention, for example, data for normal speed playback is transferred to the main track by a rotary head, and data for high speed playback is multiplied to one or both of the optional tracks on both sides of the main track. Recording is started on multiple tracks using a fixed track head almost simultaneously with the start of recording of image data for normal speed playback, or when a scene change occurs, and automatically after a certain period of time or after a certain number of frames have been recorded. The recording of high-speed reproduction data is stopped.

[0010] Here, the data recorded for high-speed reproduction is image data constructed using a part of the image data recorded on the main track, or data recorded for high-speed reproduction based on the image data recorded on the main track. Image data processed for playback, additional information representing the title, time information, frame number, etc. of the image data recorded on the main track, and an ID signal etc. to indicate the start of recording of image data for high-speed playback. be.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, taking as an example a case where compressed moving image data is recorded in DATA/DAT.

FIG. 2 shows a DAT (Digital Aud).
io Tape) is a diagram showing the track format. In the figure, 21 is a track for helical scan recording, and 22 and 23 are optional tracks (I) and (II) for recording with a fixed head, which will be described later.

FIG. 3 shows the track format of the optional track (I) 22 in this embodiment. Note that the track format of the optional track (II) 23 is also the same as this, so it is not particularly illustrated. Optional track (I) 2
2 and (II) 23 each have a track width of 55 μm,
It consists of 7 tracks with a track pitch of 70 μm.

The recording head for high-speed reproduction described later uses a thin film coil head with a track width of 55 μm, and the read head for high-speed reproduction described later uses a thin film coil head with a track width of 40 μm.
Use R head.

If the shortest recording wavelength is 0.7 μm, DA
Since the standard tape speed of T is 8.15 mm/sec, the recording rate when all 14 tracks of optional tracks 22 and 23 are used is 312 Kbytes/sec.

FIG. 4 is an explanatory diagram of group format 1 (streaming mode) in DATA/DAT. One group consists of 45 frames (90 tracks). Video data, audio data, system data, etc. are recorded in the data area after being added with C1 and C2 codes for error detection and correction using, for example, the Reed-Solomon error correction method. Furthermore, a C3 code (layered ECC) for error detection and correction is recorded in the C3 parity area. FIG. 5 shows the hierarchical structure of moving image data handled in this embodiment. Layer (a) is a video sequence layer and is a frame data string of an original signal.

Layer (b) shows a frame string of compressed data obtained by compressing the original signal and rearranging the frame order. Here, an I frame is encoded only by DCT (discrete cosine transform) on the data of that frame, followed by adaptive/weighted DCT coefficient quantization,
A frame whose data is compressed by zigzag scan encoding and entropy encoding, and is also called a core frame. In addition, a P frame is a frame that is subjected to motion compensated interframe prediction based on the previous (past) I frame or P frame, resulting in a small difference value, and then subjected to DCT conversion and high efficiency encoding. be. A B frame is a frame that is subjected to motion compensated interframe prediction based on past or future I frames or P frames, and then similarly compressed with high efficiency. Layer (c) indicates a group of pictures (GOP) layer, and in this example, there are 9 layers.
One group consists of frames.

FIG. 1 is a block diagram of this embodiment. The moving picture compression circuit 1 performs compression encoding on the original signal of a moving picture given from point A, and outputs a motion vector signal. During recording, the normal playback signal processing section 2 performs the following:
Adds C3 code necessary for error correction, adds C1 and C2 codes, and converts data to DATA/DAT format (interleaving) to data input from the video compression circuit 1. Also, during playback, , performs deinterleaving, error correction, etc.

During recording, the normal playback recording and playback circuit 3 records and modulates the data signal-processed by the normal playback signal processing section 2, and outputs the data to the normal playback recording and playback head 4 through a recording amplifier (not shown). do. Also, when playing,
After amplifying the data from the recording/reproducing head 4 for normal reproduction, it is subjected to equalization, detection, demodulation, etc., and is then supplied to the signal processing section 2 for normal reproduction.

The high-speed playback frame extracting circuit 5 extracts the video image from the moving image compression circuit in response to a recording start signal in response to pressing a recording start switch (not shown) or a scene change signal from a scene change detection circuit 16 (to be described later). 1
This circuit extracts core frame data that needs to be recorded for high-speed playback from data compressed and encoded. During recording, the high-speed reproduction signal processing unit 6 adds C1 and C2 codes to the data extracted for high-speed reproduction by the frame extraction circuit 5, adds C1 and C2 codes necessary for error correction, and Performs conversion (interleaving) to a high-speed playback format. Also, during playback, deinterleaving, error correction, etc. are performed.

During recording, the high-speed reproduction recording/reproducing circuit 7 records, modulates and demultiplexes the data from the high-speed reproduction signal processing section 6, and sends the data through a recording amplifier (not shown) to the high-speed reproduction recording head 8. Output to. In addition, during reproduction, the data from the high-speed reproduction reproduction head 9 is amplified for each track, multiplexed, and subjected to equalization, detection, demodulation, etc. during reproduction, and is processed by the high-speed reproduction signal processing section 6. supply to.

The high-speed reproduction recording head 8 is a multi-track coil type thin film head. Further, the high-speed reproduction reproducing head 9 is a multi-track magnetoresistive thin film head. In addition, in the figure, 10 is a magnetic tape.

A selector 11 for selecting a reproduction signal selects a normal reproduction signal from the normal reproduction signal processing section 2 and a high-speed reproduction signal from the high-speed reproduction signal processing section 6 according to a reproduction speed control signal to be described later. and are selectively output. The moving picture decompression circuit 12 performs decompression processing on the normal playback signal or high-speed playback signal selectively inputted from the selector 11. The system can be switched between normal playback and high-speed playback.

[0024] Playback mode changeover switch (SW) 13
is for selecting a playback mode such as normal playback, high-speed playback, and high-speed search, and outputs the above-mentioned playback speed control signal. Cue signal or no data area signal detection circuit 1
4 is a circuit for detecting a cue signal or a no-data area signal recorded on a recording track for high-speed reproduction. The tape speed switching circuit 15 changes the tape speed to
This circuit switches the speed according to the playback mode such as normal playback, high-speed playback, and high-speed search.

The scene change detection circuit 16 is a circuit that detects the presence or absence of a scene change from changes in the magnitude and direction of the motion vector signal output from the moving image compression circuit 1.

Note that the buffer memory 17 is a memory for recording image data for high-speed reproduction. Further, the tape drive circuit 18 drives the tape 10 at the speed switched by the tape speed switching circuit 15. Next, the operation of the moving image data digital recording/reproducing apparatus configured as described above will be explained.

First, the recording operation of moving image data will be explained. In FIG. 1, the original signal of a moving image input from point A is processed by a moving image compression circuit 1 through I-frame compression, P-frame compression, and B-frame compression, as shown in layer (a) of FIG. Compression is done sequentially. In this example, the code amount of the core frame after compression is 16 Kbytes, and the code amount of one group (9 frames) is 48 Kbytes (Rec.601
The compression ratio for the amount of effective pixel data is approximately 1/130).

Next, in the normal reproduction signal processing section 2, the DA
C for error correction according to the TA/DAT format.
3 codes are added, interleaving is applied, C1 and C2 codes for error detection and correction are added, and DATA/
It is output as main data of DAT based on the format. Then, it is recorded and modulated by the recording/reproducing circuit 3 for normal reproduction, and is recorded in the main data area of the magnetic tape 10 by the recording/reproducing head 4 for normal reproduction via a recording amplifier (not shown).

At the same time, the moving image data compressed by the moving image compression circuit 1 is compressed into one I frame when it is determined that it is necessary to record an image for high-speed playback based on a recording start signal or a scene change signal. The data is extracted by the frame extraction circuit 5 and stored in an internal frame memory (not shown). Next, the image data in this frame memory is supplied to the signal processing section 6 for high-speed reproduction, where it is interleaved, C1 for error correction,
A double Reed-Solomon code consisting of C2 is added and output together with additional information such as a synchronization signal, ID code, and frame address. Then, modulation is performed by the 8-10 conversion method in the recording/reproducing circuit 7 for high-speed reproduction, and a demultiplexer (not shown) sends each channel bit to the recording head 8 for high-speed reproduction via a recording amplifier (not shown). The same image data signal is continuously recorded on one or both of the optional tracks 22 and 23 for a preset time or number of frames. Note that when recording the above-mentioned image data for high-speed playback, a cue signal indicating the start of recording or the occurrence of a scene change is recorded in the header portion of this image data, and the image data for high-speed playback is not recorded. A no-data area signal is recorded in the area to indicate it. Next, the operation of reproducing moving image data recorded on the magnetic tape 10 will be explained.

First, the case of reproduction at normal speed will be explained. The signal reproduced by the recording/reproducing head 4 for normal reproduction is amplified, waveform-equalized, detected, and demodulated by the recording/reproducing circuit 3 for normal reproduction. Next, after being deinterleaved and error corrected in the normal playback signal processing circuit 2, it is decoded in the moving image decompression circuit 12 via the selector 11, and as a moving image signal from point B to the layer (a) in FIG. ) are output in the order shown.

Next, the case of high-speed reproduction will be explained. The signal reproduced by the high-speed reproduction reproducing head 9 is amplified for each track by the high-speed reproduction recording/reproducing circuit 7, multiplexed by a multiplexer (not shown), and then waveform interference is eliminated by an equalization circuit (not shown). is corrected, separated into data and clock by a PLL circuit (not shown), synchronously detected by a detection circuit (not shown), and then demodulated by 10-8 conversion. Next, after being deinterleaved and error corrected in the high-speed reproduction signal processing circuit 6, it is decoded in the moving image decompression circuit 12 via the selector 11, and recorded in the buffer memory 17 for high-speed reproduction image data. It is output from point B until the next image data arrives.

Next, a high-speed search method will be explained. The tape drive circuit 18 plays back the tape at a tape speed faster than the high-speed playback mode, and when the cue signal/no data area signal detection circuit 14 detects the cue signal, the playback mode changeover switch 13 and the tape The speed switching circuit 15 causes the tape drive circuit 18 to reduce the tape speed to the speed of the high speed playback mode. Then, the recorded image data for high-speed reproduction is reproduced at high speed, and the signal is processed in the same manner as in the case of high-speed reproduction described above, and is recorded in the display buffer frame memory 17 and displayed on a CRT (not shown). It is output from point B to do this.

Further, while the cue signal/no data area signal detection circuit 14 detects the no data area signal, the tape drive circuit 18 again drives the tape 10 at the tape speed for high speed search. A high-speed search state is entered. At this time, the image data in the high speed reproduction image data buffer memory 17 is held until the next cueing signal is detected again.

[0034] In the above embodiment, nine frames were used as one group of picture layer, but the present invention does not necessarily have to be limited to this, and the allocation of I frames, P frames, and B frames is also carried out according to the above embodiment. It doesn't have to be an example.

In the above embodiment, the compression-encoded core frame data of the image data for normal speed playback is used as the image data for high speed playback.
However, the present invention is not limited to this, and for example, in order to reduce the amount of code, for example, pixel thinning processing may be performed on core frame data before compression encoding, and then the compressed data may be used.

In the above embodiment, DATA/DAT was taken as an example, but at least data for normal reproduction is recorded on a track recorded by a helical scan head, and at least data for high speed reproduction is recorded on a track recorded by a fixed head. Any method for recording is fine. The number of tracks and the system of the recording head or reproducing head for high-speed reproduction are not limited to the above embodiments.

In the conventional helical scan method, the head scans diagonally with respect to the direction of the recording track during high-speed playback, so the data obtained during high-speed playback becomes intermittent, making it extremely difficult to restore moving images. However, according to this device, all the data recorded on the track for high-speed reproduction can be reproduced, so it is possible to completely decode the recorded moving image data for high-speed reproduction.

Furthermore, since this device does not use a helical scan head during high-speed playback, there is no need to wind the tape around a rotating drum, and the deterioration of the magnetic material on the tape surface during high-speed playback is much smaller. Become. Furthermore, in high-speed reproduction using a helical scan head, it is necessary to control the rotation speed of the rotating drum with high precision in order to keep the transfer rate constant, but this device eliminates this need.

Furthermore, in this device, image data for high-speed playback is recorded for a certain number of frames almost simultaneously with the start of recording of image data for normal-speed playback, or when a scene change occurs. At the start, a signal for cueing is recorded, and an ID signal indicating this is recorded in areas where image data for high-speed playback is not recorded. Ultra-high-speed searches that cannot be performed at high-speed playback of data can be easily performed.

[0040]

[Effects of the Invention] As detailed above, according to the present invention,
Even when playing back compressed video data at high speed,
It is possible to provide a digital recording and reproducing device for moving image data that can recognize and reproduce recorded images and that can easily perform ultra-high-speed searches.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a digital recording and reproducing apparatus for moving image data according to an embodiment of the present invention.

FIG. 2 is a diagram showing a DAT track format.

FIG. 3 is a diagram showing a track format of an optional track (I) in FIG. 2;

FIG. 4 is an explanatory diagram of group format 1 in DATA/DAT.

FIG. 5 is a diagram showing a hierarchical structure of moving image data.

[Explanation of symbols]

1...Moving image compression circuit, 2...Normal playback signal processing section, 3...
Recording/reproducing circuit for normal playback, 4... Recording/playback head for normal playback, 5... Frame extraction circuit, 6... Signal processing section for high speed playback, 7... Recording/playback circuit for high speed playback, 8... Recording head for high speed playback, 9... Reproduction head for high-speed reproduction, 10...Magnetic tape, 11...Selector, 12...Moving image expansion circuit, 13...Reproduction mode changeover switch (SW), 14...Cueing signal/no data area signal detection circuit, 15...Tape speed switching circuit, 16... scene change detection circuit, 17... buffer memory, 18... tape drive circuit.

Claims (8)

[Claims] Claim 1: A first recording means for recording image data for normal speed playback on a magnetic tape and image data for high speed playback in different areas on the same tape as the magnetic tape. a second recording means for recording, and a non-data area for indicating that no image data is recorded in a different area on the same magnetic tape as the magnetic tape to be recorded by the second recording means. Recording of image data for high-speed reproduction by a third recording means for recording a signal and the second recording means is substantially simultaneous with the start of recording of image data for normal-speed reproduction by the first recording means. When a certain period of time has elapsed after the start of recording, or after a certain number of frames have been recorded, the recording of the image data for high-speed playback is stopped, and the second recording means is used to record the image data for high-speed playback. The third recording means includes recording control means for causing the third recording means to record the no-data area signal in an area to be recorded by the second recording means when image data is not recorded. A digital recording and reproducing device for moving image data. 2. The recording control means causes the second recording means to start recording the image data for high-speed playback in response to reception of a recording start signal in response to pressing of a recording start switch. 2. A digital recording and reproducing apparatus for moving image data according to claim 1. 3. The recording control means records the image data for high-speed playback in the second recording means when the value of the motion vector of the moving image being recorded is larger than a preset value. 2. The digital recording and reproducing apparatus for moving image data according to claim 1, wherein the digital recording and reproducing apparatus for moving image data starts. 4. The moving image according to claim 2 or 3, wherein the second recording means records a cue signal prior to recording the image data for high-speed reproduction. Digital data recording and reproducing device. 5. The recording control means stops recording of the image data for high-speed reproduction when a certain period of time has elapsed after the second recording means started recording the image data for high-speed reproduction; The moving image data according to claim 2 or 3, wherein the third recording means records a no-data area signal for indicating that the image data for high-speed reproduction is not recorded. digital recording and reproducing equipment. 6. In a high-speed search state, detecting means for detecting the no-data area signal and cueing signal, and while the no-data area signal is detected by the detecting means, the magnetic tape a tape drive means for causing the magnetic tape to travel faster than a tape speed during high-speed playback; and when the detection means detects the cue signal, causing the tape drive means to drive the magnetic tape at a tape speed during high-speed playback. When the drive control means and the detection means detect the cue signal, the second recording means records a signal for high-speed reproduction from a different area on the same magnetic tape on which recording is to be performed. 6. The digital recording and reproducing apparatus for moving image data according to claim 4, further comprising high-speed reproducing means for reproducing image data at high speed. 7. In a high-speed search state, when the detection means detects the no-data signal,
7. The digital recording and reproducing apparatus for moving image data according to claim 6, further comprising a buffer memory for recording the image data that has been reproduced at high speed by the high speed reproduction means immediately before that. 8. The digital recording and reproducing apparatus for moving image data according to claim 1, wherein the second recording means has a fixed head for recording the image data for high-speed reproduction.