JPS6253083A - Picture signal multiplex transmission equipment - Google Patents

Abstract

PURPOSE:To attain a multiplex transmission as suppressing the deterioration of resolution by multiplexing two picture informations in vertical and horizontal directions to cope with the subfield mode and the subsampling mode necessary in case a movement in a picture is for a long distance. CONSTITUTION:Analog signals from input terminals 1 and 2 are band-restricted by low-pass-filters 4 and 5, and digitized by A/D converters 8 and 9 to be written in video memories 10 and 11. Subline circuits 12 and 13 gate every other line of the signals using the reference clock from a memory control circuit 14, and thin the picture elements of each line to 1/2. The signals are synthesized into a sheet of picture and transmitted, which is separated into two pictures by a separator circuit 21 on the reception-side. Line interpolation circuits 22 and 23 takes an average value of picture element for each line to generate a data of one picture. the data is converted to an analog signal by D/A converters 24 and 25 and outputted to a monitor.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical field to which the invention pertains The present invention relates to an apparatus for efficiently transmitting video signals such as those of a video conference using an interframe transmission path.

(2) Prior Art As a method for simultaneously transmitting a plurality of different screens, Document [1], which will be mentioned later, discloses ``Screen reduction synthesis method'' and ``Field multiplexing method.'' ■ in the document [1] thins out the pixels in the vertical and horizontal directions of multiple screens to 1/2 and combines them into one screen, and up to 4 screens can be transmitted simultaneously, but the resolution is reduced to 1/2. It deteriorated to 2 and the screen became smaller to view.

Another disadvantage is that when transmitting two screens, the efficiency is low because the screens are small. Furthermore, in order to efficiently transmit this signal, an inter-frame transmission line is used which takes the correlation between frames and encodes the difference before transmitting it, as shown in Reference [2], which will be described later.

When the movement is large, there will be a lot of difference information between frames, and in subfield mode, pixels in the horizontal direction are only transmitted line by line, reducing the resolution to 1/2; or in subsample mode, pixels in the vertical direction are transmitted. is transmitted only for each sample, and the resolution is reduced to 1/2. In the former case, the resolution is 1/4 in the vertical direction. The resolution becomes 1/2 in the horizontal direction, and in the latter case, the resolution becomes 1/2 in the vertical direction. 1/4 horizontally
The problem was that the image quality deteriorated due to the resolution of .

On the other hand, the method (2) shown in document [1] mentioned below is a method that multiplexes in the time axis direction and simultaneously transmits multiple different screens for each field, and considering jerkiness, up to four screens can be multiplexed. Since the information for each field is different, there is a problem that the difference information between frames increases, causing an overflow of the buffer memory, etc., making it impossible to use the interframe transmission path, and requiring a large-capacity transmission path.

References (1) Sawada et al. “Multipoint video conference system” Tsuken Report, 33. No, 11. pp2731-2741.1
984 Reference [2] Kuroda et al. “1.5°/S frame inter-frame coding device for video conferencing” Tsuken Jitsuho, 33. No, 11. pp271? -2729,
1984 (3) Purpose of the Invention In order to solve the drawbacks of using an interframe transmission path, the present invention provides two frames in the horizontal or vertical direction for the subfield mode or subsample mode that occurs when there is large motion. The object of the present invention is to multiplex transmission while suppressing deterioration of resolution by multiplexing information.

(4) Configuration of the invention (Embodiment 1) Figure 1 shows the configuration of the embodiment, where Figure 1 (A) represents the transmitting side and Figure 1 (B) represents the receiving side. Reference numeral 1 in the figure and 2 is an input terminal of the transmitter, 3 is an output terminal, 4 and 5 are low-pass filters, 6 and 7 are video signal synchronization extraction circuits,
8 and 9 are A/D converters, 10 and 11 are video memories, 12 and 13 are supply circuits, 14 is a memory control circuit, 15 is a synthesis circuit, and 16 is a transmission line interface. 17 is an input terminal of the receiving section, 18 and 19 are output terminals, and 20 is a transmission line interface.

21 is a separation circuit, 22 and 23 are line interpolation circuits, 2
4 and 25 are D/A converters.

The analog signal from the input terminal I is band-limited by a low-pass filter 4 to remove aliasing noise. Further, a synchronization extraction circuit 6 extracts a synchronization signal such as a video frame from this signal, and the A/D converter 8 digitizes the signal and writes it into the video memory 10. On the other hand, the reference clock of the memory control circuit 14 is used to extract a synchronization signal such as a video frame. At the same time, the supply line circuit 12 applies gates to every other line to thin out the pixels in each line to 1/2. In addition, input terminal 2
Similar processing is performed on the signals from .

A combining circuit 15 combines both signals to create one screen, and sends it to a transmission line via an interface 16. In this way, the phases of the two video signals, which are not necessarily synchronized, are aligned, the image information is multiplexed in the vertical direction, and the image information is transmitted.

On the receiving side, an interface circuit 20 converts the format, and a nine-separation circuit 21 separates the screen into two screens. Thereafter, line interpolation circuits 22 and 23 take the average value of pixels for each line to create data for one screen, which is converted into analog signals by D/A converters 24 and 25 and output to a monitor or the like.

Image information in video memories 10 and 11, image information synthesized after supplying, and image information after interpolation.

FIG. 2 also shows image information in the case of deterioration caused by the interframe transmission path. In the figure, solid lines indicate line pixels (LA, 2A, . . . ) corresponding to odd-numbered fields.

(IB, 2B, . . .), the dashed line indicates the pixels of the line corresponding to the even field (tA', 2x, . . .), (1
F.

2I3',...). Two pieces of image information are combined vertically, one above the other, to create one screen, which is then separated on the receiving side. At that time, the information of the even field is interpolated by the average value of the line pixels of the odd field.

Therefore, the vertical resolution is 1/2. Furthermore, if the inter-frame transmission path enters sub-sampling mode, pixels will be thinned out horizontally and interpolated using the average value between samples, and the resolution of the output screen will be 1/2 in both the vertical and horizontal directions. can be suppressed to Note that in the figure, white circles and white triangles correspond to true data, and black circles and black triangles correspond to data resulting from interpolation.

[Embodiment 2] As yet another embodiment, the supply line circuits 12 and 13 in the circuit configuration diagram of FIG. 1 are replaced with sub-sample circuits,
Line interpolation circuits 22 and 23 are converted into sample interpolation circuits.
There is a case where the combining circuit 15 and the separating circuit 21 are replaced with circuits that combine and separate horizontally, respectively. However, for reading by the memory control circuit 14, etc., it is necessary to convert the clock to a clock suitable for sub-sampling. Figure 3 shows the image information after subsampling, the image information after interpolation, and the image information degraded by the interframe transmission path in this case. The image information is combined into the left half and right half of the screen in the horizontal direction, separated by one, and then the average value of the pixels for each sample is taken and interpolated.

Therefore, in this case, the resolution in the horizontal direction becomes 1/2. If the subfield mode is established using the interframe transmission path, pixels are thinned out in the vertical direction.

When interpolation is performed using the average value between lines, the deterioration of the resolution in both the vertical and horizontal directions of the output screen can be suppressed to 1/2.

The present invention causes less deterioration in resolution than the conventional screen reduction synthesis method.

(5) As described in detail, according to the present invention, in a system in which two screens are reduced and combined using an interframe transmission path for long-distance transmission, sub-images that occur when the movement of nine screens is large. Deterioration in resolution is small compared to field mode and sub-sample mode, making it possible to suppress deterioration in image quality and enabling efficient multiplex transmission.

[Brief explanation of drawings]

FIG. 1 is an apparatus configuration diagram of Embodiment 1 of the present invention. FIG. 2 is an explanatory diagram for explaining image information in the case of the first embodiment, and FIG. 3 is an explanatory diagram for explaining the image information in the case of the second embodiment. 1.2...Input terminal, 3...Output terminal, 4.5...
・Low pass filter, 6.7... Synchronization extraction circuit, 8.9・
・・A/D converter, 10.11 ・・Video memory, 1
2゜13... Supply line circuit, 14... Memory control circuit. 15...Composition circuit, 16...Transmission line interface. 17...Input terminal, 18.19...Output terminal, 20
...Transmission line interface, 21...Separation circuit, 2
2゜23...Line interpolation circuit, 24.25...D/
A converter.

Claims (2)

[Claims] (1) In a device that encodes a video signal such as a video conference and transmits it through a digital transmission line, a means for extracting video frame signals of two screens on the transmitting side, and at least one frame worth of images for matching the phases of the video signals. It is equipped with two sets of storage means and means for thinning out pixels every other line of each frame of the two screens to reduce the amount of information to 1/2, and combining these outputs to create one frame image and sending it to the transmission path. The receiving side receives the signal from the transmission line, separates the composite signal into two screens of video, interpolates the pixels of each line of each video signal, and converts each into individual television images. 1. An image signal multiplex transmission apparatus, characterized in that the image signal multiplex transmission apparatus has a means for outputting information as an image signal, and multiplexes and separates information for two screens in the vertical direction within one frame. (2) As a means for reducing image information to 1/2 on the transmitting side, pixels are thinned out every other sample in the line direction of the television screen, and at the receiving side, the pixels are interpolated in the horizontal direction within one frame. Claim No. (1) characterized in that information for two screens is multiplexed and separated.
The image signal multiplex transmission device described in 2.