JPH01125186A - Picture communication equipment - Google Patents

Abstract

PURPOSE:To improve a transmission efficiency by applying an error correcting code only to a low frequency component to which most of an energy is centralized to orthogonally converted data. CONSTITUTION:An encoding side provided with a TV camera 1, a video input device 2, a video encoder 3, an error correcting code applying device 4, a digital modulator 5, a power amplifier 6 and a wave transmitter 7 and a decoding side provided with a wave receiver 8, a receiving amplifier 9, a digital demodulator 10, an error correcting device 11, a picture decoder 12, a picture output device 13 and a monitor 14 are provided. The error correcting code applying device 4 receives encoding picture data for every block from the picture encoder 3 and applies the error correcting code for every block. The error correcting code is applied only to the low frequency area in which most of the energy is centralized. Thereby, the transmission efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image communication device, and more particularly to an image communication device that orthogonally transforms and encodes image data and transmits the same through a narrowband transmission path.

[Conventional technology]

When transmitting image data captured by a television camera to a receiving side, the transmission path is often limited to a narrow band. In such cases, image data is basically transmitted using digital transmission means with a compressed transmission band.
Orthogonal transform coding is often used as one of such band compression coding methods.

With this orthogonal transform encoding method, image data is transformed from time domain to frequency domain data. Various types of conversion means are available, such as Fourier transform, Hadamard transform, Karhunen-Loeve transform, and discrete CoS transform which has the characteristic of asymptotic to Karhunen-Loeve transform as the order increases.

In this orthogonal transform encoding method, a plurality of sample values are usually combined into a set and a predetermined orthogonal transform is performed on the set. In this case, taking into account the degree of effect of decoding on image reproduction, coarse quantization bits are assigned to less important frequency domain components to compress image data. In other words, when looking at the acquired image data in the frequency domain, most of the energy is concentrated in the DC component to the relatively low frequency component, and this region is also important for image reproduction. A large number of quantization bits is assigned to this range with low redundancy, and a significantly reduced number of bits is assigned to high frequency regions where the energy distribution becomes extremely small, or the image data is deleted entirely. We are trying to compress the

[Problem that the invention seeks to solve]

In the above-described conventional image communication device using orthogonal transform coding, a larger number of quantization bits is assigned to a lower frequency component, and a smaller number of quantization bits is assigned to a higher frequency component.

However, only the error correction code to be added after orthogonal transform encoding is uniformly added over the entire frequency domain, which has the disadvantage that efficient encoding is hindered and transmission efficiency is reduced.

An object of the present invention is to provide an image communication device that can significantly improve transmission efficiency by eliminating the above-mentioned drawbacks and adding an error correction code only to low frequency components where energy is concentrated. .

[Means for solving problems]

The device of the present invention is an image communication device that orthogonally transform encodes image data and transmits the image data through a narrowband transmission path. It is configured to include means for adding an error correction code only to the data.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

The embodiment shown in Fig. 1 is an example of a case where underwater image data captured using a TV camera is sent and received via a transmission line using a combination of a transmitter and a receiver, and is reproduced and displayed on a monitor. , its configuration is a TV camera 1, a video input device 2, a video encoder 3, an error correction code adder 4, a digital modulator 5,
The encoding side includes a power amplifier 6, a transmitter 7, and a receiver 8.
, reception amplifier 9, digital demodulator 10, error corrector 1
1, a decoding side equipped with an image decoder 12, an image output device 13, and a monitor 14.

First, the encoding side will be explained. The image data captured by the TV camera 1 is supplied to the image input device 2 as three components of RGB for each frame.

The image input device 2 samples the input image data at a sampling rate set in consideration of the highest frequency in image reproduction, digitizes it with a predetermined number of bits, and stores it in a memory frame by frame and for each RGB element.

The data stored in the image input device includes RGB color elements in pixel units of 256 bits in each horizontal and vertical direction for each frame.

The image encoder 3 receives R for each frame from the image input device 2.
Data including each element of GB is read out and subjected to orthogonal transform encoding using DCT. By this DCT, time domain data for each frame is converted into frequency domain data in each of the horizontal and vertical directions. Assume that the conversion frequency in the horizontal direction is from DC to fxmax, and in the vertical direction is from DC to fymax, and when encoding and transmitting this, these frequency ranges in the horizontal and vertical directions are
The lower frequency region of the region determined by this division is assigned a larger number of bits for encoding.

That is, the DC 0 to fxmax is divided into 8 equal parts, and each is divided sequentially from the DC component by X,,X2゜X,...
...X. Further, in the fymax direction, Yl, Y2 . Ys......Y, then Xl
Assign the maximum number of encoding bits to the range occupied by In this way, the number of encoding bits to be sequentially deleted is assigned to the entire block as eight blocks.

In this way, the reason why it is possible to reduce the number of encoding bits as a whole by allocating the number of encoding bits to each block as it moves from the low frequency region to the high frequency region is because, as mentioned above, the energy of image data is greater at low frequencies. Taking this and the redundancy of image data into consideration, it is based on the background that it is practically sufficient to store the necessary information during image reproduction by allocating such coded bits.

When image data is converted into frequency domain data by orthogonal transformation in this way, the highest frequency naturally differs depending on the sampling rate of the image input device 2, but in the case of this embodiment, it is approximately 1 of each of f xmax and f ymax. Energy is concentrated in a low frequency region of about /2 or less.

Now, the error correction coding adder 4 receives encoded image data for each block from the image encoder 3 for each of RGB and adds an error correction code to each block.

In this embodiment, this error correction code is not added to each block, but is applied to the low frequency region where most of the energy is concentrated, in this case approximately 1/2 of the maximum frequency in orthogonal transformation. An error correction code is added only to the blocks up to the range, and this is sent to the digital modulator 5.
supply to.

The digital modulator 5 modulates a predetermined carrier wave using the input data in a predetermined digital modulation format, in this embodiment, a PSK modulation format, and supplies the modulated signal to the power amplifier 6.

The power amplifier 6 amplifies the power of the input to a predetermined level,
This is supplied to the transmitter 7.

The transmitter 7 converts the input into an acoustic signal, radiates it into the water as a transmission line 15, and sends it to the receiver 8 on the decoding side.

Next, processing on the decoding side will be explained. The receiver 8 captures the output of the transmitter 7 input via the transmission line 15, converts it into an electrical signal, and supplies it to the receiving amplifier 9.

The receiving amplifier 9 amplifies the input and supplies it to the digital demodulator 10 .

The digital demodulator 10 demodulates the PSK modulation performed on the encoding side, obtains an image code added with an error correction code, and supplies this to the error corrector 11.

The error corrector 11 performs error detection based on the error correction code, corrects detected code errors, and supplies the corrected code to the image decoder 12.

The image decoder 12 performs decoding processing of the image encoding performed on the encoding side and supplies the decoding process to the image output device 13 as digitized image data for each frame.

This digitized image data is stored in a memory for each RGE element of the frame, and then read out, subjected to D-A conversion, and reproduced into analog data, which is supplied to the monitor 14 and displayed as an image.

In this way, by assigning error correction codes only to the low frequency components where most of the energy is concentrated,
Transmission efficiency can be improved while image deterioration can be suppressed to a level that does not pose a practical problem.

The present invention provides an error correction code only for low frequency components where most of the energy is concentrated, and improves transmission efficiency without applying error correction codes to other frequency components. It has the basic characteristics of
Various modifications of the illustrated embodiment are also conceivable.

For example, in this embodiment, DO is used as the orthogonal transform encoding method.
Although T is used, other orthogonal transform encoding transformation methods such as Fourier transform and Karhunen-Loeve transform may also be used.

Also, PSK is used as digital modulation, but
Of course, other digital modulation formats may also be used.

The error correction code may basically be any algebraic code as a block code or a convolutional code as a non-block code, and all of the above can be easily implemented without detracting from the gist of the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, in an image communication device that orthogonally transforms and transmits image data, an error correction code is applied only to the low frequency component where most of the energy is concentrated in orthogonally transformed data. This has the effect of realizing an image communication device that can significantly improve transmission efficiency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention. 1...TV camera, 2...Image input device, 3...Image encoder, 4...Error correction code adder, 5... ...Digital modulator, 6.
...Power amplifier, 7...Transmitter, 8...
...Receiver, 9...Reception amplifier, 10...
...Digital demodulator, 11...Error corrector, 12...Image decoder, 13...
Image output device, 14...Monitor, 15...
・Transmission line. Agent Patent Attorney Otoo Uchihara/Illustration

Claims (1)

[Claims] In an image communication device that orthogonally transform-encodes and transmits image data via a narrowband transmission path, error correction is performed only on preset low-frequency components where most of the energy is concentrated in the orthogonally transform-encoded data. An image communication device comprising means for assigning a code.