JPS631160A - Transmission system for digital still picture signal - Google Patents

Abstract

PURPOSE:To reduce a large transmission time by applying phase inversion type sub Nyquist sampling to a digital still picture signal and applying differential predicating coding to the signal so as to send the result. CONSTITUTION:The digital still picture signal is subjected to phase inversion type sub Nyquist sampling, picture elements are sampled at each other line, a picture element corresponding to a picture element not sampled on the preceding line is sampled on the next line at each other line and the processing above is repeated. Then pre-filter is applied, a picture element Z(x, y) is replaced into a picture element Z'(x, y) expressed by the linear combination comprising the picture element Z(x, y) and eight picture elements therearound aud then the differential predicting coding is applied. The element Z'(x, y) is replaced into a picture element Z''(x, y) expressed by the linear combination comprising the picture element Z'(x, y) and 2 picture elements therearound, A digital picture element signal subject to 1/4 compression processing is formed into a packet and sent with respect to the original digital picture element signal in this way. The processing above is repeated at each packet.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a digital still image signal transmission system.

[Summary of the invention]

The present invention relates to a transmission method for digital still image signals, in which the digital still image signals are subjected to phase inversion sub-Nyquist sampling and differential predictive encoding is performed, thereby significantly reducing the transmission time of the digital still image signals. This is a shortened version.

[Conventional technology]

In conventional digital still image signal transmission systems, the digital still image signal is differentially predictive encoded and transmitted, thereby reducing the compression ratio to 1/2.

In this case, 96 bytes of digital still image signal is stored in 760 bytes.
When transmitting using a 00 baud modem, the transmission time is approximately 5
It takes minutes and 20 seconds.

[Problem that the invention seeks to solve]

Even with such conventional digital still image signal transmission methods, the transmission time cannot be said to be sufficiently short.

In view of this, the present invention proposes a digital still image signal transmission system that can significantly shorten the transmission time of digital still image signals.

[Means for solving problems]

The digital still image signal transmission method according to the present invention is characterized in that the digital still image signal is subjected to phase inversion type sub-Nyquist sampling, and differential predictive encoding is performed on the digital still image signal before transmission.

[Effect]

According to the present invention, a digital still image signal is subjected to phase-inverted sub-Nyquist sampling, and the difference numerator,
By performing the tllJll conversion and transmitting, the transmission time is further reduced to 1/2 compared to the above-mentioned conventional technique.

〔Example〕

Below, with reference to FIG. 1, compression processing on the transmitting side of the digital still image signal transmission system according to an embodiment of the present invention will be explained. The digital still image signal stored in the frame memory of the transmitting still image transmission device, which will be described later with reference to FIG.
Similarly, using a CPU (for example, MC68000), which will be described later, signal processing is performed as follows. Phase-inverted sub-Nyquist sampling of the digital still image signal (step 5)
T-11). This will be explained with reference to FIG. FIG. 2 shows pixels of a digital still image signal, where black circles indicate sampled pixels and white circles indicate unsampled pixels. Then, the pixels of a certain line are sampled every 11th time, and in the next line, the pixels corresponding to the unsampled pixels of the previous line are sampled every other time, and this process is repeated.

This phase-inverted sub-Nyquist sampled digital still image signal is applied with a Buri filter (comb-shaped filter) (step ST-12). This will be explained with reference to FIG. An arbitrary pixel Z (x, y) (where X indicates the horizontal position of the pixel, and y indicates the vertical position of the pixel) is expressed by the following equation: Pixel Z' expressed as a linear combination of eight surrounding pixels
(x.

y).

Z' (x, y) = (1/4)Z (x, y) - (
1/8) (Z (x-1, y) +Z (x+1
．． y)” Z (x+ y l) +Z (x, y
+1)) ”(1/16)(Z (x-Ly-1)+
Z (x+1.y-1)+Z (x-1,y+1)+Z
(x↓1.y+1)) ・ ・ ・ ・ (1) The digital still image signal subjected to the Buri filter is differentially predictive encoded (step ST-13).

This will be explained with reference to FIG. An arbitrary pixel Z' (x, y) subjected to the Buri filter is expressed as the following two-dimensional prediction formula:
and a pixel Z expressed by a linear combination of two pixels in its vicinity
” (X+y).

Z" (x, Y) - (1/2) (Z' (x+
1゜y-1)+Z' (Zx-2,y))...
(2) The digital pixel signal compressed to 1/4 of the original digital pixel signal is packetized and transmitted (step ST-14). The above process is repeated for each packet. In this case, if a 760-byte digital still image signal is transmitted using a 9600 baud modem, the transmission time will be approximately 2 minutes and 40 seconds, which is half of the conventional method.

Next, with reference to FIG. 5, the decompression process on the receiving side of the digital still image signal transmission system according to an embodiment of the present invention will be explained. The received still image data stored in the frame memory of the receiving side still image transmission device (step 5T
-21) The differentially predictively encoded digital still image signal expressed by equation (2) above is subjected to signal processing as follows using a CPU (for example, MC6800), which will also be described later.

This received digital still image signal is subjected to differential predictive decoding (step 5T-22). This differential predictive decoding is the inverse calculation of the secondary side equation of equation (2) above.

An interpolation filter is applied to this differentially predictively decoded digital still image signal (step 5T-23).

This will be explained with reference to FIG. Any pixel Z(x,y) to be interpolated (where X is the horizontal position of the pixel and y
[indicates the vertical position of the pixel] is expressed as a linear combination of 12 pixels surrounding the pixel Z (x, y), as shown in the following equation.

Z (x, y) = 0. 428 CZ (x-1
,Y')+Z (x+1.y))+0. 077
(Z (x-3, y) + Z (x+3. y))
-O,005(Z (x-5,y) +Z (x
+5. y))+0. 25(Z (x, y-
1)+Z (x, y'-,1))-0,125(
Z (x-2, y-1)+Z (x+2. Y-
1)+Z (x-2,)'+1)+Z (X+2.
y+1)) ・ ・ ・ ・ (3) Thus, the original digital still image signal is obtained. This signal processing is repeated for each packet.

Hereinafter, an example of a still image transmission device to which the present invention is applied will be explained in detail with reference to FIG. (1) is an input terminal for a still image signal. For example, an object is photographed using an electronic camera and recorded on a magnetic disk as a still image signal. This magnetic disk is reproduced by a still image reproducing device (2), and the still image signal is supplied to an input terminal (1). Note that instead of the still image reproducing device (2), a still image signal from another still image reproducing device such as a VTR may be supplied to the input terminal (1).

The still image signal from the input terminal (1) is sent to the A/D converter (3).
After being converted into an 8-bit digital still image signal, the signal is sent to a 768x483x8x2-bit frame memory (field memory is also possible) (video memory).
(4) and are written separately for the luminance signal and color difference signal. The digital still image signal read from the frame memory (4) is supplied to the D/A converter (5) and system bus SB. The still image signal obtained from the D/A converter (5) is supplied through an amplifier 5 (6) to a monitor receiver (7) using, for example, a CRT, and the still image is displayed.

(8) is a CPU (MC6) that controls the entire still image transmission device.
8000), (9) and (10) are the respective CPUs (8000), (9) and (10).
) related ROM (firmware) and RAM
(work memory), both of which are connected to the system bus SB. (11) is caption memory (RAM
(10) can also be used], each character and number of the caption (explanatory text) entered using the keyboard (13) or tablet (15), which will be described later, is stored as a code signal, and the system bus SB connected to. (12) is an external storage device, such as a Flor Novy disk drive, a hard disk drive, a writable optical disk recording/playback device, and a still image.

It can be a recording/reproducing device (using a magnetic disk), a VTR, etc., and is connected to the system bus SB.

(13) is a keyboard, which is connected to the system bus SB through an interface (14).

(15) is a tablet, which is connected to the system bus SB through an interface (16).

(17) is a printer, which is connected to the system bus SB through an interface (18).

(19) is a communication interface, which is a high level data link control device (HDLC).
ldata 1ink control ) (20
), modem (21) and ta control unit (NCU:
network control unit) (22)
The HDLC (20) is connected to the system bus SB, and the NCU (22) is connected to the subscriber telephone (23). Note that (24) is a telephone line. NCU(2
2) is 2-wire/4-wire switching, inheatance manoching,
It has functions such as isolation, auto dial, and automatic call reception.

Next, the operation of this still image transmission device will be explained. A still image signal from an input terminal (1) is supplied to an A/D converter (3), digitized, and written into a frame memory (4). The digital still image signal stored in the frame memory (4) is read out and supplied to the D/A converter (5) to be converted into an analog still image signal, and then sent to the monitor receiver (
7) and displays the still image on the screen of the CRT.

After the operator presses the caption button (not shown),
While looking at a still image on the screen of this monitor receiver (7), use the keyboard (13) or Kubleso 1-(1, 5) to write a caption corresponding to the still image (date, time and date of shooting of the still image, titles, other memories) and input it as a code signal to the caption memory (1
Write in 1). The caption code signal stored in the caption memory (11) is read out and written to the frame memory (4). In this case, the still image data of the portion of the frame memory (4) where the letters and numbers are written is saved and stored in the RAM (10). In this way, the still image and the caption superimposed thereon are displayed on the screen of the monitor receiver (7). The contents of this frame memory (4) are stored in the storage medium by an external storage device (12) as needed. The contents of the caption memory (11) can also be transferred to the printer (17) as needed.
) can be used to print on recording paper. When the caption button is operated again, the still image data saved and recorded in the RAM (10) is returned to the frame memory (4) and replaced with alphanumeric data, thereby restoring the storage of all still image data.

When the operator operates a transmission button (not shown), the mode is set to transmission, and the still image signal stored in the frame memory (4) and the caption code signal stored in the caption memory (11) are sent to the communication interface. (
19), PCM modulated, and CRC
It is packetized by adding C and sent to the telephone line (24) via the telephone tM (23) at, for example, 9600 ports,
It is transmitted to the still image transmission device on the receiving side (the same as the above-mentioned still image transmission device on the transmitting side). As shown in Fig. 8, a still image signal packet consists of one line consisting of a header, followed by a 5-bit luminance signal Y, a 4-bit red difference signal RY, and a 4-bit blue difference signal B-Y. It consists of 8 lines of signals and the last CRCC code.

In the receiving side still image transmission device, the transmission signal is received by the communication interface (19), and the still image signal and the caption code signal are written into the frame memory (4) and the caption memory (11), respectively. Then, the still image and caption are received by a monitor receiver (7), the still image signal and caption code signal are stored in the storage medium by an external storage device (12), and the caption is sent to a printer (8). Print it on recording paper.

〔Effect of the invention〕

According to the present invention described above, it is possible to obtain a digital still image signal transmission method that can significantly shorten the transmission time of digital still image signals.

[Brief explanation of drawings]

Fig. 1 is a flowchart of compression processing according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of phase inversion type sub-Nyquist sampling, Fig. 3 is an explanatory diagram of a Buri filter, and Fig. 4 is an explanation of differential predictive coding. 5 is a flowchart of the decompression process according to an embodiment of the present invention, and FIG. 6 is an explanatory diagram of the interpolation filter.
FIG. 7 is a block diagram showing an example of a still image transmission device to which the present invention is applied, and FIG. 8 is a diagram showing the data structure of a packet. (3) is an A/D converter, (4) is a frame memory, (5
) is a D/A converter, (8) is a CPU, (9) is a ROM,
(10) is a RAM, and (19) is a communication interface. -Zugi now 111 IE sweeps convex king 1 70 1 hour yard Fig. 1 @O@O@ ○ OO00 @O@O@) ○ @O@O @O@O@ I Tachikari reversal 1 Dimensions 7" 7゛°
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Claims (1)

[Claims] A transmission method for a digital still image signal, characterized in that the digital still image signal is subjected to phase inversion sub-Nyquist sampling, and differential predictive coding is performed before transmission.