JPH10164573A - Image transmission method and image transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the effects of other images of transmission errors and to switch and display the images at a sure timing by adding the identifier of the image and the identifier of a minimum coding unit(MCU) to a transmission unit, performing transmission and decoding coded data and substitutive data, when the image identifier of received data is changed on a reception side. SOLUTION: Normal coded data from an image coding means are stored worth one screen, the coded data of the MCU are segmented from there as the transmission unit, an image ID and an MCUID are added in front of the coded data, and they are outputted to a communication control means as transmission data. After an image transmission control means outputs the coded data of the final MCU of the final image, data to which the image ID=99, for example of a dummy for reporting transmission end to the reception side p set are transmitted. At that time, a communication control procedure detects an error as the transmission data for one unit. Thus, even when the plural images are continuously transmitted, the generated transmission error is prevented from affecting other screens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image transmission method and an image transmission apparatus used for image transmission, and more particularly, to transmission of a screen even if a transmission error occurs during continuous image transmission. The present invention relates to an image transmission method and an image transmission apparatus capable of switching images at a certain timing and displaying a transmission image without an error affecting other screens.

[0002]

2. Description of the Related Art First, FIG.
I will explain using. FIG. 6 is a configuration block diagram of a conventional image transmission device. As shown in FIG. 6, in a conventional image transmission apparatus, a transmission side apparatus 1 'includes an image input unit 11, an image encoding unit 12, a communication control unit 14', and a transmission unit 1 '.
5 and the receiving device 2 ′
, A communication control unit 22 ′, an image decoding unit 24, and an image output unit 25.

Next, each section of the conventional image transmission apparatus will be specifically described. The image input unit 11 is an NTSC output from a camera having a solid-state imaging device (Charge Coupled Device: CCD or the like) or a video storage device such as a VTR.
(National Television System Committee) Composite signal, Y / C signal, PAL (PhaseAlternation by Li)
ne) A general-purpose video signal such as a signal is fetched, converted into digital image data by A / D conversion, and the image data is stored in units of one screen.

As shown in FIG. 7, the image encoding means 12 sequentially cuts out image data of one screen in a rectangular area, compresses and codes the rectangular area as one encoding unit, and outputs encoded data. It is. Generally, a rectangular area is called a minimum coded unit (MCU).
FIG. 7 is an explanatory diagram showing an outline of a general image encoding method.

As a typical compression encoding method, JPEG
(Joint Photographic Experts Group: ITU-T T.81) is known, but in the JPEG system, digitally converted image data is first converted to an MCU (for example, 8 × 8 pixels or 1 pixel).
Discrete Cosine in units of 6 × 16 pixels
Transform: DCT) transform and output DCT coefficient,
The number of effective coefficients is reduced by quantizing the T coefficient, entropy coding (Huffman coding) as variable length coding is performed, and coded data is output.

In Huffman coding, in particular, in the coding of the DC component, the difference from the DC component of the MCU immediately before (to the left) is coded. For details of the JPEG method, see "Latest MPEG Textbook 1994.8.1
It is described on pages 53 to 67 issued by ASCII Corporation.

[0007] The communication control means 14 'controls communication with the receiving side. The transmission means 15 is a communication control means 1
The data is transmitted to the transmission line 3 by modulating the transmission frame from 4 '.

The receiving means 21 is for demodulating data from the transmission line 3 and outputting the received data to the communication control means 22 '. The communication control means 22 'controls communication with the transmitting side.

[0009] The image decoding means 24 comprises an image coding means 1
In the JPEG system, the received encoded data in MCU units is entropy-decoded (Huffman-decoded).
The image data is inversely quantized and inversely DCT-transformed to output image data in MCU units.

[0010] The image output means 25 comprises an image decoding means 24.
Is stored in units of one screen, and the digital image data is converted into an analog video signal by D / A conversion, output, and displayed.

Next, the operation of the conventional image transmission apparatus will be described with reference to FIG. In a conventional image transmission apparatus, when a video signal is input to a transmission side apparatus 1 ', the image signal is converted into image data by an image input unit 11, stored for one screen, and cut out by the image encoding unit 12 in MCU units. The encoded data compressed and encoded by the communication control means 14 ',
The data is transmitted to the transmission path 3 via the transmission means 15.

[0012] Then, in the receiving side device 2 ', the M from the transmission path 3 via the receiving means 21 and the communication control means 22'.
Receiving the encoded data in units of CU, and
In step 4, the image data is decompressed and decoded and output in MCU units. When the image data for one screen is stored in the image output means 25, the image data is converted into a video signal and output.

[0013]

However, in the above-described conventional image transmission method and image transmission apparatus, particularly when the JPEG system is used as the encoding system, the difference between the DC components is encoded. When an error occurs, not only the MCU included in the frame of the transmission error,
There has been a problem that the error affects other MCUs following it.

In the above-described conventional image transmission method and image transmission apparatus, particularly when the JPEG method is used as the encoding method, the encoding method must be decoded in order from the beginning of the encoded data. Once decoding becomes impossible due to the error, there is a problem that a situation occurs in which the encoded data thereafter cannot be decoded at all.

As a method for solving this problem, one or a plurality of MCUs are transmitted as a transmission unit by inserting an MCU identifier indicating the position of the MCU in an image and transmitting the code according to the MCU identifier on the receiving side. A method has been proposed in which the effect of errors is minimized by arranging encoded data at an appropriate position in an image and then decoding the decoded data. In this method, each MCU is an MCU in the same screen. There is a problem that it is not possible to determine whether or not an MCU of another screen is included in the screen to be displayed and displayed.

Further, in the above-mentioned method, since the encoded data of the image is not decoded and displayed for each screen, the image cannot be switched and displayed at a certain timing for each screen. was there.

The present invention has been made in view of the above circumstances, and by adding an image identifier and an MCU identifier for each transmission unit and transmitting the image, the receiving end identifies image breaks based on the image identifier. It is another object of the present invention to provide an image transmission method and an image transmission apparatus capable of preventing a transmission error in a certain screen from affecting another image and switching and displaying an image at a certain timing for each screen. And

[0018]

According to a first aspect of the present invention, there is provided an image transmission method, comprising the steps of: Coded data, and one or a plurality of the coded data is used as a transmission unit, and an error detection code is added by adding an image identifier and a minimum coding unit identifier attached to a screen unit to the transmission unit. The received data to which the same image identifier is added is stored on the receiving side, and the encoded data that is normally received is stored, and the transmission error detected portion and the missing portion are provided in advance. Replaced with alternative data and stored, characterized in that when the image identifier of the received data changes, the stored encoded data and alternative data are decoded, even if a plurality of images are transmitted continuously. , Without being affected by the transmission error can be displayed by switching the images in a reliable timing.

According to a second aspect of the present invention, there is provided an image transmission apparatus, comprising:
Image encoding means for encoding the input image as an information source in minimum encoding units to create encoded data, and one or more of the encoded data as a transmission unit, and an image identifier attached to a screen unit; Image transmission control means for creating transmission data by adding an identifier of a minimum coding unit, communication control means for performing error detection encoding of the transmission data to create error detection encoded data, and A transmission unit for transmitting the error detection encoded data, wherein a receiving side receives the transmission data and the error detection encoded data, and performs an error detection from the received transmission data and the error detection encoded data. Communication control means, the part in which the error is detected is replaced with alternative data provided in advance, and the normally received encoded data and the alternative data are stored in units of image identifiers, Image reception control means for outputting the stored encoded data and alternative data when the identifier of the image of the transmitted data changes, and image decoding means for decoding the output encoded data and alternative data. It is characterized in that even if a plurality of images are continuously transmitted, the images can be switched and displayed at a certain timing without being affected by transmission errors.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the claimed invention will be described with reference to the drawings. The image transmission method and the image transmission device according to the present invention, on the transmission side, using the encoded data of one or a plurality of MCUs as a transmission unit, adding an image identifier and an MCU identifier attached in a screen unit, Error detection is coded and transmitted, and if an error is detected on the receiving side, it is replaced with alternative data, and one screen of encoded data or alternative data is stored. When the identifier of the image of the received data changes, the data is stored. Since the encoded data and substitute data for one screen have been decoded, the transmission error generated in one screen does not affect the other screen.
Images can be switched and decoded at a certain timing for each screen.

First, the configuration of an image transmission apparatus for realizing the image transmission method according to the present invention will be described with reference to FIG.
FIG. 1 is a configuration block diagram of an image transmission device according to the present invention. Parts having the same configuration as in FIG. 6 are described with the same reference numerals.

In the image transmitting apparatus (this apparatus) of the present invention, the transmitting apparatus 1 has the same parts as the conventional image transmitting apparatus,
It is composed of an image input unit 11, an image encoding unit 12, a communication control unit 14, and a transmission unit 15. An image transmission control unit 13 is provided as a characteristic part of the present invention. However, the communication control procedure of the communication control means 14 of the present invention is different from that of the conventional communication control means 14 '.

The receiving side apparatus 2 of the present apparatus includes a receiving unit 21, a communication control unit 22,
The apparatus comprises an image decoding means 24 and an image output means 25.
Is provided. However, the communication control means 22 of the present invention is different from the conventional communication control means 22 'in the communication control procedure.

Next, each part of the present apparatus will be described in detail. The image input means 11, the image encoding means 12, the transmitting means 15, and the receiving means 21 of the receiving apparatus 2 of the transmitting side apparatus 1 , Image decoding means 24 and image output means 25
Is exactly the same as in the prior art, so that the description is omitted here, and only the features of the present invention will be described.

The image transmission control means 13 includes, for each coded data transmission unit, an image identifier (image ID) assigned for each screen and an identifier (MCUID) for the smallest coding unit indicating the position of the MCU within the screen. ) And the communication control means 14
Is output to

More specifically, as shown in FIG. 2, the image transmission control means 13 internally stores the coded data from the image coding means 12 for one screen, and stores one coded data from the stored coded data.
The encoded data of one or a plurality of MCUs is cut out as a transmission unit, and an image ID (for example, an image number) and an MCU ID
(For example, the MCU number) is added before or after the encoded data (in the example of FIG. 2), and output to the communication control means 14 as transmission data. FIG. 2 is an explanatory diagram showing the operation of the image transmission control means of the present invention.

After outputting the coded data of the last MCU of the last image, the image transmission control means 13 outputs a dummy image ID (image ID = 99 in the example of FIG. 2) to notify the receiving side of the end of transmission. ) Is output and transmitted.

The communication control means 14 includes the image transmission control means 1
3 is incorporated into a transmission frame conforming to the communication control procedure and output to the transmission means 15. As a communication control procedure, any procedure may be used as long as transmission data composed of one or more MCUs' encoded data, an image ID, and an MCU ID during communication is defined as one unit and an error can be detected in that unit. As a general procedure, an HDLC (High level Data Link Control) procedure is known.

The HDLC procedure is capable of transmitting data of variable length in bit units and using an error detection code such as CRC.
A code is added and transmitted. The details of the HDLC procedure are described in "Computer Communication and Network", Kunio Fukunaga, Kyoritsu Shuppan Co., Ltd., pp. 113-130.

The communication control means 22 detects an error in the received data demodulated by the receiving means 21, discards the data in which the error is detected, and outputs only the normally received transmission data to the image reception control means 23. Is what you do.

The image reception control means 23 controls to receive the coded data normally received and to decode the coded data in units of one screen. Here, the internal configuration of the image reception control means 23 will be described with reference to FIG. FIG. 3 is a block diagram showing a configuration inside the image reception control means 23 of the present invention.

The inside of the image reception control means 23 comprises an image reception control section 231, a temporary storage section 232, and an alternative MCU storage section 233.

The temporary storage unit 232 stores the coded data for one screen, and as shown in FIG. 4, an MCU storage area 232a for storing the coded data for one MCU in one screen, and each MCU. MC that stores the encoded data length of
And a U data length storage area 232b.
FIG. 4 is an explanatory diagram showing a configuration inside the temporary storage unit 232 of the present invention.

In the MCU storage area 232a, the MC
The storage area for each U is an area required when the image data length of one MCU, that is, when the image data is compressed to 1/1. For example, when the MCU is 16 × 16 pixels and has a gradation of 24 bits, 16 × 16 × 24 bits per MCU = 6144 bits = 1 MCU
An area of 768 bytes is secured.

The substitute MCU storage unit 233 stores an area in which substitute coded data that can be replaced with an MCU in which a transmission error has occurred or a missing MCU and a length of the substitute coded data are stored in advance as substitute data. It is.
As the substitute coded data, coded data obtained by coding MCUs of the same color, such as one color of white and one color of black, is used.

The image reception control unit 231 receives the coded data normally received, and actually performs control for decoding one screen unit. Specifically, the alternate MCU storage unit 2
The temporary storage unit 232 is initialized with the substitute data stored in the storage unit 33, the encoded data in the normally received reception data is stored in the area of the temporary storage unit 232 corresponding to the MCU ID, and the image ID of the reception data is When it changes, the contents of the temporary storage unit 232 are output to the image decoding unit 24.

The specific processing operation of the image reception control section 231 will be described with reference to FIG. FIG. 5 is a flowchart showing the flow of the process of the image reception control unit 231 of the present invention.

The reception control process in the image reception control unit 231 is performed as an initializing process as an alternative MCU storage unit 233.
The temporary storage unit 232 is initialized with the substitute data stored in the image data (100), and the old image ID for checking image switching is initialized with the first image ID (for example, 1) (102).

Then, it is determined whether or not there is an input of the received data normally received from the communication control means 22 (110). If there is no input (No), the reception control process ends, and if there is an input (Yes). Determines whether the image ID of the received data is the same as the old image ID (112).

The image ID of the received data is the old image I
If it is the same as D (Yes), the process jumps to step 130; if it is not the same (No), all the coded data stored in the
4 (120), and initializes the temporary storage unit 232 with the alternative data stored in the alternative MCU storage unit 233 (122).

In the output process of the encoded data in the process 120, the encoded data length is first read from the MCU data length storage area 232b in order from MCUID1, and the encoded data is read from the MCU storage area 232a by the data length. Is output to the image decoding means 24, and this operation is performed for the number of MCUs.

The encoded data of the received data is represented by M
The coded data length is stored in the location corresponding to the MCUD in the CU storage area 232a (130), and the coded data length is stored in the location corresponding to the MCUD in the MCU data length storage area 232b (132).

Next, the operation of this apparatus will be described with reference to FIG.
I will explain using. In this apparatus, when a video signal is input to the transmission side apparatus 1, the image signal is converted into image data by an image input unit 11 and stored for one screen, and is cut out in units of MCU by an image coding unit 12 and compression-coded. And MC
The encoded data in U units is output to the image transmission control means 13 and stored for one screen.

Then, the coded data of one or a plurality of MCUs is cut out as a transmission unit by the image transmission control means 13, added with the image ID and the MCU ID, output to the communication control means 14, and output to the communication control means 14. And an error detection code is added to the transmission path 3 via the transmission means 15.

Then, the receiving device 2 receives the received data from the transmission line 3 via the receiving means 21, detects an error in the communication control means 22, and outputs only the normally received data to the image reception control means 23. Is done.

Then, in the image reception control means 23,
The coded data and its data length are stored in the portion of the temporary storage unit 232 initialized with the substitute data corresponding to the MCUID of the received data.

When the image ID of the received data is switched, the coded data and the substitute data stored in the temporary storage unit 232 are output to the image decoding unit 24 in MCU units, and the image decoding unit 24 performs decompression decoding. MCU
When a unit of image data is output and the image data for one screen is stored in the image output means 25, the image data is converted into a video signal and output.

In the present invention, the method of encoding / decoding an image is not limited to the JPEG method, but may be the MPEG1 method,
MPEG2 system, H.264. H.261 system, H.264. The H.263 system may be used.

According to the image transmission method and the image transmission apparatus of the present invention, on the transmission side, the image ID assigned to the compression-encoded data by the image transmission control means 13 for each transmission unit on a screen basis. The encoded data normally received in the temporary storage unit 232 initialized with the substitute data is sequentially stored in association with the MCUID on the receiving side, and the image ID of the received data is switched. sometimes,
This is for decoding the coded data for one screen stored in the temporary storage unit 232, so that even if a plurality of images are continuously transmitted, a transmission error occurring on one screen may affect another screen. There is an effect that an image can be switched and displayed at a certain timing without causing the image to be displayed.

[0050]

According to the first aspect of the present invention, the transmission side uses encoded data of one or a plurality of minimum encoding units as a transmission unit, and an image identifier assigned to a screen unit in the transmission unit and An error detection encoding is performed by adding an identifier of the minimum coding unit and transmitted.At the receiving side, encoded data normally received in the identifier unit of the image and alternative data replaced for a transmission error or omission are output. And an image transmission method for decoding the encoded data and substitute data for one screen stored when the identifier of the image of the received data changes, so that even if a plurality of images are continuously transmitted, When displaying decoded data without affecting transmission errors occurring in one screen to other screens, the data is displayed for each screen, so images are switched at a certain timing and displayed Effect There is.

According to the second aspect of the present invention, on the transmitting side,
The image encoding means generates the encoded data by performing information source encoding on the input image in the minimum encoding unit, and the image transmission control means assigns one or a plurality of encoded data as a transmission unit to each screen. The transmission data is created by adding the identifier of the image and the identifier of the minimum coding unit, the communication control means performs error detection encoding of the transmission data to create error detection encoded data, and the transmission means On the receiving side, the receiving means receives the transmission data and the error detection coded data, the communication control means performs error detection from the received transmission data and the error detection coded data, and receives the image. The control means replaces the portion where the error is detected with the substitute data provided in advance, stores the normally received encoded data and the substitute data for one screen, and changes the identifier of the image of the received data. In this case, the image transmission device outputs encoded data and alternative data when the image is transmitted, and the image decoding unit decodes the output encoded data and alternative data. When the decoded data is displayed without affecting the other screens due to the transmission error that occurred on one screen, it is displayed for each screen, so that the image can be switched and displayed at a certain timing. There is.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of an image transmission device according to the present invention.

FIG. 2 is an explanatory diagram showing an operation of an image transmission control unit of the present invention.

FIG. 3 is a block diagram showing a configuration inside an image reception control unit of the present invention.

FIG. 4 is an explanatory diagram showing a configuration inside a temporary storage unit of the present invention.

FIG. 5 is a flowchart illustrating a flow of processing of an image reception control unit according to the present invention.

FIG. 6 is a configuration block diagram of a conventional image transmission device.

FIG. 7 is an explanatory diagram illustrating an outline of a general image encoding method.

[Explanation of symbols]

1, 1 ': transmitting device; 2, 2': receiving device;
... Transmission path, 11 ... Image input means, 12 ... Image encoding means, 13 ... Image transmission control means, 14, 14 '... Communication control means, 15 ... Transmission means, 21 ... Reception means,
22, 22 '... communication control means, 23 ... image reception control means, 231 ... image reception control section, 232 ... temporary storage section, 232a ... MCU storage area, 232b ... MC
U data length storage area, 233 ... alternate MCU storage unit,
24 image decoding means 25 image output means

Claims (2)

[Claims] 1. A transmission side, wherein an input image is information-source coded in a minimum coding unit to generate coded data, and one or a plurality of the coded data is used as a transmission unit, and a screen unit is used as the transmission unit. The image identifier attached to the image and the identifier of the minimum coding unit are added and error-detection-encoded and transmitted. On the receiving side, the received data to which the same image identifier is added is encoded normally. The data is stored, and the portion where the transmission error is detected and the missing portion are replaced and stored with alternative data provided in advance, and when the image identifier of the received data changes, the stored encoded data and the alternative are stored. An image transmission method characterized by decoding data. 2. An image encoding means, wherein a transmission side encodes an input image as an information source in a minimum encoding unit to generate encoded data, and one or a plurality of the encoded data as a transmission unit and a screen unit Image transmission control means for creating transmission data by adding an identifier of an image and an identifier of a minimum coding unit attached to the transmission data, and communication for performing error detection encoding of the transmission data to create error detection encoded data Control means; and transmission means for transmitting the transmission data and the error detection coded data, wherein a reception side receives the transmission data and the error detection coded data, and the reception side receives the transmission data and the error detection coded data. Communication control means for detecting an error from the encoded data, and a part where the error is detected is replaced with a predetermined substitute data, and the normally received encoded data and the substitute data are imaged. Image reception control means for storing the encoded data and alternative data stored when the identifier of the image of the received data changes,
An image transmission device comprising: an image decoding unit that decodes the output encoded data and the substitute data.