JP2791022B2 - Video signal processing device - 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 sub-sampling video data and outputting the video data.
The present invention relates to a video signal processing device that inputs subsampled video data. [Prior Art] A video signal has a large amount of information per unit time, and when a video signal having such a large amount of information is digitized, it becomes an extremely high bit rate signal. However, this digital signal will be transmitted using a communication system. In this case, a large-capacity line is required, which causes a shortage of the line capacity or an increase in transmission cost. Further, when such a high bit rate digital signal is to be recorded on a recording medium such as a magnetic recording medium, there is a problem that the recording head cannot be used and the recording time becomes extremely short. Therefore, in order to reduce the data amount of a digital signal, various band compression techniques are generally proposed. So-called offset subsampling is considered as one of the band compression techniques. Offset subsampling is a technique in which oblique components of an image that are not so important in visual characteristics are removed in advance by a spatial filter, and high-frequency components are arranged in the removed frequency region to lower the sampling frequency. Such offset subsampling includes line offset subsampling (LOSS) in which the sampling position is shifted between adjacent scanning lines in the same field, and sampling between adjacent scanning lines in two adjacent fields. There is a field offset subsampling (FOSS) in which the position is shifted, but in any case, before the offset sampling is performed, the above-mentioned spatial filter as a pre-filter is used.
Two-dimensional band limiting must be performed. When decoding an offset subsampled digital signal, spatial interpolation must be performed by a spatial filter as a postfilter. [Problems to be Solved by the Invention] By the way, this spatial filter has a relatively large circuit scale. For example, as a spatial filter, in order to realize a 25-tap filter for assigning coefficients to 25 pixels near the center pixel as shown in FIG. 7, a coefficient unit, a multiplier and an adder constituted by a RAM or ROM table , And a signal processing circuit having digital delay lines according to the number of taps. Therefore, in a magnetic recording / reproducing apparatus such as a VTR for performing offset subsampling, such a large space filter must be provided for recording and reproduction, respectively, and the circuit becomes large. Similarly, in a transmitter / receiver for a communication line, it is necessary to provide a spatial filter on the transmission side and the reception side, and the circuit becomes large. In FIG. 7, x and y indicate the pixel intervals in the horizontal and vertical directions, respectively. The present invention has been made in view of the above-mentioned problems, and has a video signal recorded or transmitted in a video signal processing device that subsamples and outputs video data and inputs the subsampled video data. And to simplify the circuit configuration. [Means for Solving the Problems] According to the present invention under such a purpose, a recording or transmitting unit for subsampling and outputting video data,
A video signal processing device having a reproduction or reception unit for inputting subsampled video data,
Using the sample of interest and samples around it, the sub-sampled video data input from the reproduction or reception unit can be input to a spatial filter that limits the band of video data to be sub-sampled in the recording or transmission unit. In addition to the configuration, the video data sub-sampled in the recording or transmission unit can be returned to the original number of pixels, and then can be output to the outside through a filter that uses a smaller number of peripheral samples than the spatial filter. And [Operation] As described above, by providing a small-scale filter for the monitor, one spatial filter can be used for both the pre-filter in the recording or transmitting unit and the post-filter in the reproducing or receiving unit. It is possible to reduce the number of spatial filters. Accordingly, the circuit can be reduced in size, and the size and cost of the device can be reduced. Embodiment FIG. 1 is a diagram showing a VTR in which a pre-filter for subsampling is used also as an interpolation filter, wherein 1 is an analog-digital (A / D) converter, and 2 and 4 are recording / reproducing. Switching switch, 3 is a spatial filter, 5 is a band compressor, 6
Is an error correction code adder, 7 is a modulator, 8 is a demodulator, 9 is an error corrector, 11 is a band extender, and 15 is a digital-analog (D / A) converter. An image signal input at the time of recording is converted into a digital signal by an A / D converter 1, cut by a spatial filter 3 in a two-dimensional band where interference occurs due to aliasing, and is subjected to offset subsampling by a compressor 5. After pixel thinning and compression such as DPCM are performed and an error correction code is added by an error correction code adder 6, the data passes through a digital modulator 7 and is recorded on a recording medium T from a head Hr. On the other hand, at the time of reproduction, the signal read from the medium T by the head Hp is digitally demodulated by the demodulator 8, error-corrected by the error corrector 9, and 0 is added to the pixels thinned out by the band extender 11 Performs bandwidth expansion such as data insertion and DPCM decoding. Here, the output of this expander is the PB of the switch.
By passing through the spatial filter 3 again through the side, the pixels thinned out by the sub-sampling during recording are interpolated. The output of the spatial filter 3 passes through the D / A converter 15 and becomes a reproduced image signal. In the VTR as described above, a recording pre-filter and a reproduction post-filter can be implemented by the same spatial filter 3. Therefore, the circuit configuration is simplified. FIG. 2 is a block diagram showing the configuration of a VTR as one embodiment of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. This embodiment uses the configuration of FIG.
A simple filter 13 is provided so that the system can be monitored, and simple interpolation is performed. At the time of recording, an input video signal passes through an A / D converter 1, a spatial filter 3, a band compressor 5, an error correction code adder 6, and a digital modulator 7, and then through a medium T via a head Hr. Is the same as that of the first embodiment, but after passing through the band compressor of 5, a branch is provided and the switch 10 is connected to the REC side to flow to the band extender 11. 13 via the REC side of the switch 12 through the band extender 11
The data subjected to simple interpolation by the simple filter 13 is output as a monitor analog image signal through the REC-side DMA converter 15 of the switch 14. FIG. 3 shows an example of the configuration of the simple space filter. In the figure, 16, 22, and 23 are delay lines for one sample period (D), and 17, 18, and
21 is a delay line for one horizontal scanning period (H), 19, 24, 27, and 28 are adders, 20, 25 are 1/8 coefficient units, and 26 is a 1/2 coefficient unit. Assuming now that the output data of the D delay line 22 is the data of the central pixel, the coefficients assigned to the five pixels around the central pixel by the filter are shown in FIG. The pixel indicated by a double circle in FIG. 4 is the central pixel. Some degree of band limiting characteristics can also be obtained with the filter of FIG. Further, since a slight deterioration in image quality is allowed for the recording monitor and the transmission monitor, it can be said that the spatial filter of FIG. 3 has sufficient characteristics. All of the filter coefficient units 20, 25 and 26 in FIG. 3 can be realized only by bit shift. Accordingly, the spatial filter of FIG. 3 can be realized at a much lower cost with a much smaller amount of hardware than the spatial filter of FIG. 7 showing coefficients for 25 pixels. Since the simple filter 13 installed in the embodiment shown in FIG. 2 is used for monitoring, it is possible to construct a simpler filter. For example, as shown in FIG. 5, if a simple interpolation using only the preceding pixel is performed by using a pre-interpolation filter in which D flip-flops 19 and 19 'are connected in series, the circuit scale is further reduced. In addition, miniaturization of the cost reduction device can be promoted. The relationship between the input data and the output data in FIG. 5 is as shown, and as shown in FIG. 6, the data of the immediately preceding pixel is taken as the data of the thinned pixel. Generally, in practical use, a circuit monitor at the time of recording only needs to be able to determine whether or not the circuit is in an operating state and whether or not an image signal is being input.
Interpolation is considered to be sufficient with a simple filter as shown in the figure. Although each of the above embodiments has been described using a VTR as an example,
It goes without saying that the present invention is applicable not only to a magnetic recording / reproducing apparatus but also to a transceiver for a communication path. [Effects of the Invention] As described above, according to the present invention, video data is subsampled and output, and the video signal recorded or transmitted by the video signal processing device that inputs the subsampled video data is used. In addition, while simplifying the circuit configuration, it has become possible to reduce the cost and size of the circuit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration of a VTR as one embodiment of the present invention, FIG. 2 is a diagram showing a configuration of a VTR as another embodiment of the present invention, and FIG. FIG. 4 is a view showing an example of the configuration of the simple filter in FIG. 2, FIG. 4 is a view for explaining the operation of the filter in FIG. 3, and FIG. 5 is another configuration of the simple filter in FIG. FIG. 6 is a diagram showing an example, FIG. 6 is a diagram for explaining the operation of the filter of FIG. 5, and FIG. 7 is a diagram showing an example of adding coefficients by a spatial filter. In the figure, 1 is an A / D converter, 3 is a spatial filter, 5 is a band compressor for performing subsampling, 11 is a band expander, and 15 is a D / A converter.

Claims (1)

(57) [Claims] A video signal processing device having a recording or transmitting unit for sub-sampling and outputting video data, and a reproducing or receiving unit for inputting sub-sampled video data, using a sample of interest and samples around it, The recording or transmitting unit is configured so that the sub-sampled video data input from the reproducing or receiving unit can be input to the spatial filter that limits the band of the video data to be sub-sampled in the recording or transmitting unit. A video signal processing apparatus, wherein sampled video data is returned to the original number of pixels, and then output to the outside via a filter that uses a smaller number of peripheral samples than the spatial filter.