JP2821125B2 - Video signal transmission system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal transmission system, and more particularly to a system capable of transmitting a video signal in a plurality of modes having different data compression ratios. [Related Art] Hereinafter, a digital video tape recorder (VTR) using a magnetic recording / reproducing system as a transmission path will be described in this specification. In the current analog VTR for consumer use,
By setting the tape transport speed to 1/2 or 1/3 that of the standard mode, the track pitch can be narrowed, and the same tape can be recorded twice or three times as long as the standard mode. Some time modes are set. This is to respond to a wide range of user needs by providing a standard mode that emphasizes image quality and a long-time mode that can record for a long time even if the image quality such as S / N ratio and sharpness is slightly reduced. This is an extremely effective method. On the other hand, with the development of digital signal processing technology and integrated circuit technology in recent years, the possibility of realizing a consumer digital recording VTR that performs digital image signal processing is increasing.
Here, a method of setting a plurality of modes for trade-off between image quality and recording time described in the conventional example, that is, a standard mode and a long-time mode in an analog VTR will be considered for this consumer digital VTR. In the case of digital recording, the track pitch of the recording track on the magnetic tape is set to the value that can recover the digital signal at the time of reproduction even in the case of the standard recording time. Cannot be set. Therefore, it has been proposed to set the long-time mode by reducing the data amount by removing the redundancy of the image in the long-time mode as compared to the standard mode, thereby reducing the area required for recording by a fraction. ing. [Problems to be Solved by the Invention] When this data compression is used, if the compression ratio, especially the compression ratio in the time axis direction is increased, the image quality is greatly degraded unless the image is restored using the motion information of the image. I can't stand it. However, in general, the compression ratio cannot be set arbitrarily in image data compression. Therefore, for example, if an attempt is made to provide a mode capable of recording for three times the time, motion detection information is used in addition to the image information compressed to 1/3. It needs to be recorded. On the other hand, in a VTR in which the standard mode and the long-time mode are set, it is meaningless if the signal processing system and mechanism cannot be shared. For example, when trying to share a signal processing system, it is necessary to make the size of the data block to which the sync data is added, the size of the data block to which the error correction code is added, and the like uniform. If a mechanism, such as a rotary head, is to be shared, the amount of data to be recorded per unit time must be an integer ratio between the standard mode and the long-time mode. Therefore, when recording data relating to the above-described motion detection information in the long-time mode, it is necessary to provide a data area for this motion detection information in the standard mode. Therefore, the data area is wasted in the standard mode. An object of the present invention is to provide a system capable of efficiently transmitting data in a plurality of modes having different amounts of data information to be transmitted under the above-described background. [Means for Solving the Problems] For such a purpose, in the video signal transmission system of the present invention, a first transmission mode for transmitting an input video signal, and a compression process of the input video signal for transmission And a second mode, wherein in the second mode,
A part of the scanning line at the end of the screen in the input video signal is deleted, and the second
The processing parameters used in the mode are inserted and transmitted together with the compressed video signal. [Operation] With the above-described configuration, a system capable of transmitting video signals in a plurality of modes having different data compression ratios without any waste of transmission data in the first transmission mode is obtained. [Embodiment] A digital VTR as an embodiment of the present invention will be described below. FIG. 1 is a diagram showing a schematic configuration of a digital VTR as one embodiment of the present invention. In the figure, a video signal input to a terminal 1 is converted into a digital signal by an analog-to-digital (A / D) conversion circuit 2 and input to a distribution circuit 3, pre-filters 4, 5 and a motion detection circuit 6. The output of the motion detection circuit 6 is used as a control input of the volume 7 and is supplied to a terminal b of the switch 9. The outputs of the pre-filter 4 and the pre-filter 5 are weighted and summed by the volume 7 according to the control signal from the motion detection circuit 6, thinned out for each field by the field thinning means 8, and supplied to the terminal a of the switch 9. The switch 9 is a system (not shown)
The timing is controlled by the controller, and a period including a vertical blanking period of the video signal and a predetermined period corresponding to an edge of the screen is connected to the b side, and the other periods are connected to the a side. This switching timing will be described later. As a result, the video signal thinned out for each field and its motion detection information are time-division multiplexed. The output of the switch 9 is supplied to the L side of the switch 11.
On the other hand, the digital video signal input to the distribution circuit 3 is divided into two systems and the S
Supplied to the side terminal. Switches 10 and 11 are switches which are linked and switched with each other. In a mode having a standard recording time (hereinafter referred to as a standard mode), the switch is connected to the S side, and by performing field thinning, time recording twice as long as the standard mode is performed. In the mode that can be performed (hereinafter referred to as double mode)
Connected to the side. The outputs of the switches 10 and 11 are provided with codes for correcting data errors during recording and reproduction by error correction code addition circuits 12 and 12 ', respectively, and are output by modulation circuits 13 and 13' to reduce DC components. After modulation such as -10 modulation, the signals are amplified to appropriate levels by the amplifiers 14 and 14 ', and are recorded on the magnetic tape 17 by the magnetic heads 15 and 16, respectively. FIG. 2 shows a recording pattern in the standard mode, and FIG.
Each of the recording patterns in the double mode is shown. FIG. 2, FIG.
In the figure, 40 is a recording track formed by the head 15,
41 is a recording track formed by the head 16. As is apparent from the figure, in the standard mode, video signals are recorded using both the heads 15 and 16, and in the double mode, recording is performed using only the head 16. The transport speed of the tape by a capstan (not shown) is configured so that the transport speed in the double mode is 1/2 that of the transport speed in the standard mode. The arrows in FIGS. 3 and 4 indicate the head tracing direction. Next, the reproducing system will be described. At the time of reproduction, the image data recorded on the magnetic tape is read out by the magnetic heads 18 and 19, and is amplified to a desired level using the amplifiers 20 and 20 ', and is equalized. The outputs of the amplifiers 20 and 20 'are subjected to demodulation such as 8-10 demodulation by demodulation circuits 21 and 21', and code errors are corrected by error correction circuits 22 and 22 'and applied to switches 23 and 24. Switch 23,24,2
Reference numerals 5 denote switches which are switched to the S side in the standard mode and the L side in the double mode, respectively, and are switched in synchronization with the mode at the time of recording. When the recording is in the standard mode, the two-channel digital video signal divided and recorded by the two heads is supplied to the combining circuit 2 via the S side of the switches 23 and 24.
The digital signal is converted into an analog signal by a digital-analog (D / A) conversion circuit 27 through the S side of the switch 25 and output to an output terminal 28. On the other hand, when the recording is performed in the double mode, the reproducing system from the head 18 to the switch 23 is not used, and the head is not used.
The reproduction output from 19 is the demodulation circuit 21 'and error correction circuit described above.
22 ', added to switch 29 through switch 24. The switch 29 is controlled by the system controller in the same manner as the switch 9 of the recording system, and during the vertical blanking period of the video signal and the period in which the motion information is output from the switch 24 during the period corresponding to the edge of the screen, b During the other period, the image data is sent, so that it is switched to the side a to supply it to the interpolation filters 31 and 32. The output of the motion processing circuit 30 is applied to a volume 33 as a control input. The outputs of the interpolation filters 31 and 32 are weighted and summed by the volume 33 according to the control signal from the motion processing circuit 30, and the D / A conversion circuit 27 is passed through the L side of the switch 25.
Is converted to an analog signal and output to the output terminal 28. Next, the characteristics of the pre-interpolation filter used in the 2 × mode will be described. In the present embodiment, field thinning is performed in order to reduce the amount of image data, a pre-filter is used to prevent aliasing noise due to thinning in the time axis direction, and a field that has not been sent is interpolated. An interpolation filter is used. In the 2 × mode, the transmission rate of the image signal is low. Therefore, unless a motion adaptive filter that adaptively switches the characteristics of the filter according to the image to be transmitted is used, the image is greatly deteriorated and cannot be put to practical use. On the other hand, the pre-filter and the interpolation filter need to have characteristics corresponding to each other, and the control signal of the adaptive filter used in the recording system must be reproduced in the reproduction system. Also, judging the magnitude of movement on the entire screen, if one part of the screen moves, the other part will suddenly blur and it will be unnatural, so divide the effective screen into several blocks,
It is desirable to determine the motion for each block and send the motion information. That is, in this case, motion information that does not need to be recorded and reproduced in the standard mode must be recorded and reproduced in the double mode.
When a common data format is determined in the two modes, if a dedicated data area for motion information that is not required in the standard mode is secured in the data format of the standard mode, useless data recording is performed. In the standard mode, it is sufficient if the unnecessary data area can be used to improve the image quality. However, considering that the signal processing system is shared with the double mode as described above, the unnecessary data area in the standard mode is improved in image quality. It is difficult to tie. Therefore, in the DVTR of this embodiment, the standard mode is mainly considered,
Based on the information amount to be recorded per unit time and the information amount per unit time for the effective area of the image, the standard mode standard is determined so as not to waste, and the information amount to be recorded in the double mode and the information amount of the image are determined. The motion information for each block that needs to be newly recorded when it becomes 1/2 per unit time is obtained by deleting the data of the pixel at the end of the effective screen and replacing the data of the pixel with the motion information. This data is recorded. Here, FIG. 4 shows an example of a pixel whose motion information is replaced with data. In this case, the top few lines of the effective screen are used as pixel data to be replaced when recording motion information.
For example, considering a case where an image is divided into 500 blocks and two bits of motion information are transmitted for each block, if one horizontal scanning line pixel is 400 pixels and the number of bits for three horizontal scanning lines is sufficient, motion is sufficient. Information can be sent. When an image in the 2 × mode is reproduced, it is desirable that the scanning lines on the corners of the screen used for transmitting the motion information be processed so as to be invisible, for example, by being blackened. Although the description has been made above using the digital VTR, the same effect can be obtained by using this method as long as the image transmission path has a variable compression ratio. [Effects of the Invention] As described above, according to the transmission system of the present invention, even when a video signal is transmitted in a plurality of transmission modes having different information amounts of the video signal to be transmitted, the video signal can be efficiently transmitted. Can be transmitted.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration of a DVTR as one embodiment of the present invention, FIG. 2 is a diagram showing a recording pattern on a tape in a standard mode by the DVTR of FIG. 1, FIG. 3 is a diagram showing a recording pattern on a tape in the double mode by the DVTR in FIG. 1, and FIG. 4 is a diagram showing an example of pixels to be replaced with motion detection information. 4, 5 are pre-filters, 6 is motion detecting means, 7 is a volume, 8 is a field thinning circuit, 9, 10, 11 are switches, 12, 12 'are error correction code addition circuits, and 15 and 16 are recording heads. , 18 and 19 are playback heads, 22, 22 'are error correction circuits, 2
3, 24, 25 are switches, 26 is a synthesis circuit, 29 is a switch, 30
Is a motion processing circuit, 31 and 32 are interpolation filters, and 33 is a volume.

Continued on the front page (72) Inventor Soichi Kashida 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Tamagawa Office of Canon Inc. (72) Inventor Nobutsu Yamashita 3- 30-2 Shimomaruko, Ota-ku, Tokyo In-company (56) References JP-A-62-90092 (JP, A) JP-A-61-201580 (JP, A) JP-A-62-193471 (JP, A) (58) Fields investigated (Int. . ^6, DB name) H04N 7/24 - 7/68 H04N 5/91 - 5/956

Claims (1)

(57) [Claims] An apparatus for transmitting a video signal, comprising: a first transmission mode for transmitting an input video signal; and a second mode for compressing and transmitting the input video signal. In the second mode, And deleting a part of the scanning line at the end of the screen in the input video signal and inserting the processing parameter used in the second mode in place of the deleted scanning line, together with the compressed video signal. A video signal transmission system for transmitting.