JPH07193784A - High speed reproducing method for digitally compressed moving picture data - Google Patents

Abstract

PURPOSE:To attain high speed reproducing for digitally compressed moving picture data recorded on a magnetic tape of a VTR. CONSTITUTION:At the time of high speed reproducing for moving picture data recorded on a magnetic tape 6, time rotational speed of a rotary drum 1 is also increased in proportion to the traveling speed of the tape 6, all data are extracted by a detection circuit 11 and only an I picture is extracted from the extracted data through a B/P picture removing filter 12. The I picture is sent at a fixed speed by canceling the frame when a stream buffer 13 is overflowed or sending the same frame in an underflow state and the moving picture is desultorily reproduced by a decoder 14 to reproduce the moving picture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high speed reproducing method for reproducing digitally compressed moving image data recorded on a video tape recorder (VTR) at high speed.

[0002]

2. Description of the Related Art In order to enable high-speed reproduction of digitally compressed moving image data recorded on a VTR, conventionally, a special format is used at the time of recording,
Special encoding was performed for high speed playback. Moreover, it may be necessary to change the decoder for high-speed reproduction.

[0003]

As described above, the compression efficiency has to be sacrificed in order to perform a special format or a special encoding for high-speed reproduction, as described above.
There were problems such as the need to change the decoder.

On the other hand, the standardization of moving image compression methods has advanced, and high-definition televisions and digital VTRs, CDs, etc. capable of recording a large amount of digital methods are becoming reality, but a user-friendly operating environment is not yet available. Issues remain to be considered. Particularly in a helical scan recording type VTR, a method of fast-forward reproduction of moving image data which has been digitally compressed with high efficiency has been a problem.

The present invention has been made in order to solve the above-mentioned problems, and it records a high speed reproduction of moving image data which is recorded on a VTR and which is highly efficient digital compression coded in a special format. Another object of the present invention is to provide a high-speed reproducing method of digitally compressed moving image data that is realized without requiring a specially designed decoder.

[0006]

A high-speed reproducing method of digitally compressed moving image data according to the present invention detects moving image data which is digitally compressed and recorded on a magnetic tape by a magnetic head provided on a rotary drum. In a high-speed reproduction method of a helical scan method of reproducing by a decoder, when the magnetic tape is run at high speed for high-speed playback, the rotational speed of the rotary drum is increased in proportion to the running speed of the magnetic tape to increase the magnetic field. All the data recorded on the tape is taken out, and only the independently reproducible frame signals are selected from the taken out data and sent to the decoder to replay the whole image in a scattered manner.

Further, a buffer is provided immediately before sending independently reproducible frames to the decoder, so that frames are discarded in case of overflow and the same frame is sent again in case of underflow.

[0008]

In the present invention, when the magnetic tape is run at a high speed, the rotation speed of the rotary drum is increased in proportion to the running speed of the magnetic tape. Therefore, all the data recorded on the magnetic tape is taken out and The entire image is reproduced in a scattered manner using only the frame signals that can be reproduced independently from the inside.

In addition, not all the independently reproducible frame signals are used, but in the case of overflow, they are discarded, and in the case of underflow, the same frame is sent again, so that a constant transmission rate is obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments of the present invention, a recording method of digitally compressed moving image data and a recorded recording pattern which are objects of the present invention will be described.

FIG. 3 shows a VT according to the helical scan method.
It is explanatory drawing of the recording principle of R. In this figure, 1 is a rotary drum, and 1 is a magnetic head 2 for recording and reproducing images.
80. Are provided at intervals of. 3 is the rotary drum 1
A driving motor, 4 is a pinch roller, 5 is a capstan, and 6 is a magnetic tape.

During recording, the magnetic tape 6 advances in the direction of the arrow by the pinch roller 4 and the capstan 5. At the same time, the rotary drum 1 rotates in the direction opposite to the direction in which the magnetic tape 6 advances, whereby the magnetic head 2 crosses the magnetic tape 6 diagonally and records one after another.

FIG. 4 is a block diagram showing an example of the configuration of a conventional recording circuit, 7 is an encoder, 8 is a drive circuit, 2 is the magnetic head shown in FIG. 3, and 6 is a magnetic tape. Also,
FIG. 5 is a diagram showing a recording pattern of a frame signal recorded on the magnetic tape 6 by the recording circuit of FIG.
Is an output pattern of.

Next, the operation will be described. Video signal S
V is input to the encoder 7, where data compression is performed, the drive circuit 8 applies it to the magnetic head 2, and recording is performed on the magnetic tape 6. It should be noted that description of the recording of the audio track and the control track is omitted.

Next, the data compression of the video signal SV in the above will be described. In high-efficiency digital compression coding of moving images, various measures have been taken to remove redundant portions and suppress the generated coding amount. The redundancy included in the moving image includes temporal redundancy in addition to spatial redundancy and redundancy regarding the occurrence frequency. In the standard proposal, in order to remove this temporal redundancy, a method is used in which prediction is performed in frames before and after, and only the difference from that is encoded. There are two methods of prediction: forward prediction and bidirectional prediction.

In practice, a frame (hereinafter referred to as P picture) signal encoded by forward prediction and a frame (hereinafter referred to as B picture) signal encoded by bidirectional prediction are used in combination. It is necessary to encode the reference image which is the source of the frame only within the frame. For example, it is common to insert a frame (hereinafter referred to as I picture) signal by such intra-frame encoding every 15 frames. Is. This I picture is the only frame that can be reproduced independently. However, the frame here does not refer to only a so-called frame in an interlaced image, but refers to one frame of an image used for a moving image.

In normal recording and reproduction, first, at the time of recording, sequentially input images are encoded by the encoder 7 in the order of the frame signals I1, P4, B2 and B3, and are recorded on the tracks of the magnetic tape 6 in the same order. Record. This state is shown in FIG.

In FIG. 6, I1, P4, B2, B3,
P7, B5, B6, P10, B8, B9, I13, ...
Are frame signals, respectively, the first intra-frame coded image data, the fourth forward predictive coded image data, the second bidirectional inter-frame predictive coded image data,
Third bidirectional inter-frame predictive encoded image data, seventh forward predictive encoded image data, fifth bidirectional inter-frame predictive encoded image data, sixth bi-directional inter-frame predictive encoded image data, 10 The third forward predictive encoded image data, the eighth bidirectional inter-frame predictive encoded image data, the ninth bidirectional predictive encoded image data, and the thirteenth intraframe encoded image data are shown. However, in the following description, pictures are used for I, P, and B, respectively.

During normal reproduction, which is not high-speed reproduction, first, the frame signal I1 is decoded, the P picture P4 is decoded by using that image as a reference image, and the P picture P4 is expanded into two frame buffers, respectively, and then only the I picture I1 is decoded. Is displayed. These two decoded images are used as reference images for predicting B pictures B2 and B3. This is shown in FIG. B picture B2 and B
After 3 is decoded and displayed, the last remaining P picture P4 is displayed. For the fifth and subsequent images, P picture P7 is read and P picture P4 is read.
After being decoded as a reference image, the I picture I1 is expanded on the frame buffer in which the I picture I1 has been expanded. That is, the I picture I1 is overwritten. The image on this frame buffer is the B picture B to be read next, along with the already existing P picture P4.
Used as a reference image for decoding 5 and B6. When B pictures B5 and B6 are read, decoded and displayed respectively, P picture P7 is displayed,
The next P picture P10 is read. It is to be noted that, in FIG. 6, I pictures I1 and I13 are each shown by three tracks, two pictures are recorded in one track for the B picture, and one picture is schematically recorded for the P picture. Shows.

Next, a case of high speed reproduction according to an embodiment of the present invention will be described. FIG. 1 is a block diagram showing an example of a high-speed playback device for carrying out the present invention. In this figure, 1 to 6 are the same as those in FIG. 3, 9 is a drum rotation control unit that controls the speed of a motor 3 that drives a rotating drum 1 to which the magnetic head 2 is attached, and 10 is the magnetic tape 6 A tape running controller for driving the capstan 5 for running the tape, 11 a detection circuit to which the output of the magnetic head 2 is applied, 12 a B / P picture removing filter for passing the I picture and removing the B and P pictures, 1
Reference numeral 3 denotes a stream buffer, which discards the frame when the input bit stream overflows, and sends the same frame at the time of underflow, thereby sending out the frame at a constant speed. Reference numeral 14 is a decoder, which interlaces and reproduces from the transmitted I picture to reproduce a moving image. However, as with the case of including all I, B, and P pictures, the I picture alone does not erase the syntax of the stream, so that the conventional decoder can be used as it is.

An embodiment of the high-speed reproducing method of the present invention will be described with reference to the high-speed reproducing apparatus shown in FIG. First, as shown in FIG. 5 and FIG. 6, recording data signal-compressed using I, B, and P pictures is I1, P4, B2, B3.
P7, B5, B6, P10, B8, B9, I13, B1
It is assumed that the recording data encoded in the order of 1, B12, P16, ... And recorded on the magnetic tape 6 at a normal speed is reproduced at high speed by the high speed reproducing apparatus of FIG.

During high speed reproduction, the tape running control unit 10 increases the running speed of the magnetic tape 6, and the magnetic tape 6 is taken out from the detection circuit 11 at high speed. At this time, if the ratio of the running speed of the magnetic tape 6 in FIG. 3 to the rotating speed of the rotary drum 1 is kept constant by the drum rotation control unit 9, all the data recorded on the magnetic tape 6 even in the helical scan recording method. Data can be retrieved. FIG. 2 shows an output pattern of the detection circuit 11.

The extracted data is passed through a B / P picture removal filter 12 to remove B pictures and P pictures, and only I pictures are stream buffer 13
Send to. This I picture is input at high speed, but it is open between adjacent I pictures, for example, between I1 and I13. The stream buffer 13 closes this interval, outputs at low speed, and sends it to the decoder 14. When an underflow occurs in the stream buffer 13, the same image is sent again, and when an overflow occurs, one frame is discarded, so that the stream is sent to the decoder 14 at a constant transmission rate. Therefore, the decoder 14 may perform decoding in the same manner as when performing normal reproduction.

The reproduction speed is determined by the ratio of the tape running speed during recording and reproduction. However, the rotation speed of the rotary drum 1 during high-speed reproduction is also increased in proportion to the running speed of the magnetic tape 6. The display is completely displayed for one frame, and the conventional VT
As seen during fast playback of R, fragments at different times across frames are not displayed with noise bars. Further, even at the time of high-speed reproduction, the syntax of the stream is not broken and only the contents of the stream are changed. Therefore, high-speed reproduction is possible only by sending it to the decoder 14 conforming to the standard plan which can be normally reproduced.

[0025]

According to the method of high speed reproduction of digitally compressed moving image data according to the present invention, when the magnetic tape is run at high speed for high speed playback, the rotary drum is proportional to the running speed of the magnetic tape. Of all the data recorded on the magnetic tape by increasing the rotation speed of, and select only the independently reproducible frame signal from the extracted data and send it to the decoder to jump over the entire image. Since it is played back, the entire frame at the same time can be displayed neatly at high speed playback, and recording using a special format is also possible,
It can be realized without requiring a special decoder or the like.

Further, when the magnetic tape is run at high speed for high-speed reproduction, all the data recorded on the magnetic tape is increased by increasing the rotation speed of the rotary drum in proportion to the running speed of the magnetic tape. Decoder by extracting only the frame signal that can be independently reproduced from the extracted data, discarding the frame signal in case of overflow, and sending the same frame signal again to the decoder in case of underflow. Since the transmission rate of the data input to is constant, the data is always input to the decoder at a constant transmission rate, so that a normal reproducible decoder can be used as it is.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a high-speed reproduction apparatus for implementing a high-speed reproduction method for digitally compressed moving image data according to the present invention.

FIG. 2 is a diagram showing an example of a reproduction pattern of moving image data which is digitally compressed and recorded.

FIG. 3 is an explanatory diagram of a recording principle of a VTR according to a conventional helical scan method.

FIG. 4 is a block diagram showing an example of a conventional recording circuit.

FIG. 5 is a diagram showing an example of a recording pattern of conventional digitally compressed moving image data on a magnetic tape.

FIG. 6 is a diagram for explaining details of a recording pattern of conventional digitally compressed moving image data.

FIG. 7 is a diagram showing an operation of a frame buffer used for conventional interframe bidirectional predictive coding.

[Explanation of symbols]

1 rotating drum 2 magnetic head 3 motor 4 pinch roller 5 capstan 6 magnetic tape 7 encoder 8 drive circuit 9 drum rotation control unit 10 tape running control unit 11 detection circuit 12 B / P picture removal filter 13 stream buffer 14 decoder I frame Frame signal by coding (I picture) P Frame signal coded by forward prediction (P picture) B Frame signal coded by bidirectional prediction (B picture)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H04N 5/937 (72) Inventor Tomoyuki Shindo 4-36-19 Yoyogi, Shibuya-ku, Tokyo Stock company graphic In SusCommunications Laboratories (72) Inventor Yusumi Wataya 4-36-19 Yoyogi, Shibuya-ku, Tokyo Inside Graphics Communications Laboratories (72) Inventor Hideo Arai 4-chome Yoyogi, Shibuya-ku, Tokyo 36th-19th Stock Company, Graphics Communication Laboratories

Claims (2)

[Claims] 1. A helical scan type high-speed reproducing method in which moving image data which is digitally compressed and recorded on a magnetic tape is detected by a magnetic head provided on a rotary drum and reproduced by a decoder, in order to perform high-speed reproduction. When the magnetic tape is run at high speed, the rotation speed of the rotary drum is increased in proportion to the running speed of the magnetic tape to take out all the data recorded on the magnetic tape, and the data taken out independently of the taken out data. A high-speed reproduction method of digitally compressed moving image data, characterized in that only a reproducible frame signal is selected and sent to the decoder to reproduce the whole image in a scattered manner. 2. A helical scan high-speed reproducing method in which moving image data that is digitally compressed and recorded on a magnetic tape is detected by a magnetic head provided on a rotating drum and reproduced by a decoder, in order to perform high-speed reproduction. When the magnetic tape is run at high speed, the rotation speed of the rotary drum is increased in proportion to the running speed of the magnetic tape to take out all the data recorded on the magnetic tape, and the data taken out independently of the taken out data. Select a reproducible frame signal, discard the frame signal in case of overflow, and send the same frame signal to the decoder again in case of underflow to make the data input to the decoder constant transmission rate and skip Of digitally compressed video data characterized by reproducing the entire image Speed reproduction method.