KR20010010468A - Method and Telephone for still picture transport - Google Patents

Abstract

PURPOSE: A method for transmitting static picture and a picture transmission terminal are provided to transmit desired static picture to the other party by using a motion picture terminal, so as to transmit high-quality static picture. CONSTITUTION: A core unit(300) extracts static picture by the frame from motion picture, and encodes the extracted static picture frame. A frame memory(301) restores the encoded static picture frame, to store original static picture. A variable length coder(302) is included. A channel buffer(303) stores encoded bit string for motion picture. A bit string memory(304) stores encoded bit string for static picture. A multiplexer(305) transmits bit string according to user's selection, in the bit string for motion picture or static picture.

Description

Still image transmission method and video transmission terminal {Method and Telephone for still picture transport}

The present invention relates to image transmission of a mobile terminal, and more particularly, to a still image transmission method and an image transmission terminal adapted to transmit a high quality still image using a video terminal.

With the advent of the multimedia communication era, a video terminal capable of transmitting voice and video together has been implemented and will be commercialized soon.

Such a video terminal includes an encoder and a decoder capable of processing a video, and transmit or display a continuous image frame to or from a counterpart in real time.

However, up to now, video terminals cannot transmit / receive high quality still images.

Therefore, in general, a digital camera, a scanner, and a computer are used to transmit still images to the counterpart. In other words, by connecting a digital camera to a computer or a scanner to a computer, a still image is transmitted to the other party.

This, a brief description of the still image transmission method using a digital camera, a scanner and a computer.

1 is a view showing a system configuration for transmitting a conventional still image.

Referring to FIG. 1, first, a desired still image is captured by using the digital camera 100.

Subsequently, the captured still image is input to the computer 102 and stored, and the computer 102 transmits the stored still image to the counterpart through a wired or wireless network.

On the other hand, if there is no digital camera 100, after taking a picture by using a general camera, the scanner 101 may capture a still image through the picture.

However, the conventional video terminal cannot transmit a video having a high picture quality due to a limitation of channel bandwidth for transmitting a real-time video. For this reason, video that requires real-time transmission is transmitted with low quality. However, in the case of a still image, it is difficult to transmit a still image from a video terminal that transmits a real time / low quality image because of its high quality.

As a result, a method of transmitting a still image using a digital camera, a scanner, and a computer can be considered as in the related art, but this is expensive, and it is cumbersome and inconvenient to use.

Accordingly, there is a constant demand for a video terminal capable of transmitting not only a moving picture but also a high quality still picture.

Accordingly, an object of the present invention is to provide a still image transmission method and an image transmission terminal capable of transmitting a high quality still image using a video terminal in view of the above-mentioned problems of the prior art.

According to a first aspect of the present invention for achieving the above object, a still image transmission method is a video terminal for encoding and transmitting a moving image, extracting a still image in a frame unit from the moving image, the extracted still image Encode and send.

According to a second aspect of the present invention for achieving the above object, the still image transmission method is a video terminal for encoding and transmitting a moving image, and stores a still image of the input frame unit, the still image of the stored frame unit The encoding of the image is performed according to the state of the channel buffer.

According to a third aspect of the present invention for achieving the above object, in a video terminal for encoding and transmitting a video, the video transmission method, and stores a still image of the input frame unit, the same stop of the stored frame unit The encoding process for the image is repeated.

According to another aspect of the present invention for achieving the above object, the image transmission terminal is an arbitrary frame memory for storing the image input in the frame unit, and discrete cosine for discrete cosine transform the image input from the frame memory And a quantization unit for quantizing the signal output from the discrete cosine transform unit.

Advantageously, said arbitrary frame memory uses a decoder's motion compensation frame memory.

1 is a diagram showing a system configuration for transmitting a conventional still image.

2A is a block diagram illustrating an encoder of a conventional video terminal.

2B is a block diagram illustrating a decoder of a conventional video terminal.

3A is a block diagram illustrating an encoder according to a first embodiment of the present invention.

3B is a block diagram illustrating a decoder in accordance with a first embodiment of the present invention.

4A is a block diagram illustrating an encoder according to a second embodiment of the present invention.

4B is a block diagram illustrating a decoder in accordance with a second embodiment of the present invention.

5 is a block diagram illustrating an encoder according to a third embodiment of the present invention.

6 is a diagram illustrating a still image transmission and storage system between video terminals adopting a still image transmission method according to a first embodiment of the present invention.

7 is a diagram illustrating a still image transmission and storage system between video terminals employing a still image transmission method according to a second or third embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

300: core portion 301: frame memory

302 variable length encoder 303 channel buffer

304: bit string memory 305: mux

Hereinafter, a configuration and an operation according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

The present invention proposes three still image transmission methods and video transmission terminals, respectively, so that a high quality still image can be transmitted using a video terminal.

The first still image transmission method extracts a still image in units of frames from a video, encodes the extracted still image frame in I image coding, and stores the generated bit sequence in a separately added bit string memory. Is a method of transmitting to the receiver at a desired time.

The second still image transmission method receives a still image in units of frames from a camera and performs encoding of I image coding, and then transmits the image to the receiving side, and prevents overflow and underflow of a channel buffer. A separate control signal is additionally generated for this purpose.

The third third image transmission method has the same concept as the still image transmission method described above. However, the control unit does not add a control signal and encodes the same still image several times, thereby gradually obtaining a high quality image.

All three still image transmission methods as described above are performed using an encoder and a decoder provided in a conventional video terminal, and the structures of the encoder and the decoder are modified differently according to the transmission method.

First, the encoder and decoder provided in the conventional video terminal will be described in detail before describing the still image transmission method according to the present invention.

2A is a block diagram illustrating an encoder of a conventional video terminal, and FIG. 2B is a block diagram illustrating a decoder of a conventional video terminal.

Referring to FIG. 2A, a core part 210 for compressing and encoding an input continuous image frame, a frame memory 220 for restoring and storing an encoded image frame, and a variable length encoder (VLC) 230 and channel buffer 240.

Here, the core unit 210 reconstructs the encoded image frame with the DCT 200 and the quantization unit 202 for compressing and encoding the image frame to the original image frame, and displays a motion difference between the image frame which is continuously input. It is composed of an inverse quantization unit 203, an IDCT 204, a motion compensator 205, and a motion estimator 206 for estimating.

The operation of the encoder configured as described above is as follows.

First, a variable length encoder 230 is passed through a discrete cosine transformed DCS (Discrete Cosine Transform, DCT) 200 through a cosine transformed compression, and then a quantizer 202 for discarding a high frequency term. Encodes into bit strings with various bit lengths. The encoded bit string is stored in the channel buffer 240 and then transmitted to the receiver through the wireless network.

In this case, the encoder decodes the encoded image frame through the inverse quantization unit 203 and the IDCT 204, restores the original image frame, and stores the image in one frame. Save the restored image. This is to calculate the motion difference between the image frames that are continuously input and the previous image frame. The motion estimation unit 206 estimates the motion difference according to the correlation between adjacent image frames, and the motion compensation unit 205 estimates the motion difference. By rewarding the real-time video can be transmitted.

Here, in order to abstract and compensate for the motion difference between adjacent image frames, at least the first frame of the input image sequence should be encoded using only its own frame regardless of correlation with the adjacent frame. Such a coding method is called I picture coding, and a method of using correlation with adjacent frames is called P picture coding. I image coding may be described with the same concept as a method of encoding still images, such as JPEG.

On the other hand, the decoder shown in Figure 2b performs the operation opposite to the encoder.

That is, the encoded video frame input through the channel buffer 250 is dequantized and inverse discrete cosine transform (IDCT) through the core unit 270 to restore the original image, and then reproduce the same. The video is stored in the frame memory 280 and the real-time video is reproduced by using correlation with the video frames continuously input.

The still image transmission method using the encoder and the decoder of the conventional video terminal as described above will now be described separately by each embodiment.

First embodiment

The still image transmission method proposed in the first embodiment is a method of extracting a still image in a frame unit from an input video, and encoding and transmitting the extracted still image. Stored in the column memory to transmit the stored bit string at the time selected by the user.

To this end, the encoder and the decoder of the conventional video terminal further include a bit string memory and a mux for processing still images.

3A is a block diagram showing an encoder according to the first embodiment of the present invention, and FIG. 3B is a block diagram showing a decoder according to the first embodiment of the present invention.

Referring to FIG. 3A, a core unit 300 extracting a still image in a frame unit from a video, encoding the extracted still image frame, and a frame memory for restoring an encoded still image frame to store an original still image ( 301, a variable length encoder 302, a channel buffer 303 for storing encoded bit strings for video, a bit string memory 304 for storing encoded bit strings for still images, and a video or The mux 305 is configured to transmit a bit string according to a user's selection among bit strings of a still image.

The bit string memory 304 and the mux 305 are components added to the above-described conventional encoder.

The reason why the bit string memory 304 and the mux 305 are added is as follows.

In general, since a still image has a different purpose from a moving image, it requires a higher quality image than a moving image. Therefore, although a single still image is transmitted, a high quality that is not able to feel a difference from the original image should be transmitted.

In this case, since the high quality still image is encoded at a high bit rate (ie, a low compression rate) during encoding, many bits are generated when the still image is compressed by the encoder, and a separate additional memory for storing the generated many bits is required. In the present invention, these bits are stored in the bit string memory 304.

On the other hand, if the bit buffer of the still image can be stored in the channel buffer 303, the encoder can be configured more simply. However, the channel buffer 303 has a limitation in size due to the delay constraint of the video transmission.

That is, in the case of video, a delay of about 300 msec is generally allowed from the transmitting camera to the receiving display, so if the channel buffer 303 pass time of the video bit string is set to 100 msec, considering the video transmission speed of 64 Kbps, the channel buffer The size of 303 becomes 6.4 Kbit at 100 msec x 64 Kbps.

In this case, assuming that a CIF-format still image (ie, 352x288) is compressed at 2 bits / pixel and transmitted, about 300 Kbits are generated when compressing one image (352x288x1.5x2, where 1.5 is 4: 2: 0). In the format, the total image size is 1.5 times the size of the Luminanco image), and the channel buffer 303 having the size of 64 Kbit cannot store all the 300 Kbit bit streams generated when the still image is compressed.

For this reason, the encoder used in the first embodiment further includes a separate bit string memory 304 for storing bits generated when encoding still images in addition to the channel buffer 303.

The still image transmission method using the encoder configured as described above will now be described.

First, unlike video, the encoder maintains a low quantization value with respect to the extracted still picture so as to maintain a high bit rate.

That is, when encoding a video, the quantization value may vary according to the state of the channel buffer 303, but when the still image is encoded, a constant quantization value is maintained.

At this time, the core unit 300 encodes the I image coding using only the first image frame of the input video.

Then, due to the low quantization value, the core unit 300 generates a large number of bits when encoding still images, and the generated bits are bit strings having a variety of bit lengths through the variable length encoder 302. Are stored in.

In this case, the channel buffer 303 is used only when encoding a video.

In this state, when a user desires, a user control signal is generated to transmit a coded bit string of a still image stored in the bit string memory 304 at a predetermined channel rate. In this case, the user control signal is provided to the channel buffer 303, the bit string memory 304, and the variable length encoder 302.

On the other hand, since the channel rate is 64Kbps, and the bit amount of one image is approximately 300Kbit, it takes about 5 seconds to transmit one still image. Since the transmission time decreases as the channel rate increases or the image quality decreases, the user can find an appropriate compromise in consideration of the transmission time of the image quality.

The decoder for restoring the still image transmitted from the encoder will now be described.

Referring to FIG. 3B, a demux 306 for receiving a coded bit stream of a still image or a video and dividing the bit stream of the encoded still picture or a video, and a channel buffer 307 for receiving and storing a bit stream of a video from the demux 306. ), A bit string memory 308 for receiving and storing a bit string of a still image from the demux 306, a mux 309 for selecting and outputting a bit string of a moving image or a still image, respectively, A length decoder 310, a core unit 311 for decoding the bit strings of the still image stored in the bit string memory 308, and a frame memory 312 for storing the decoded image.

The decoder configured as described above stores the bit string of the encoded still image transmitted from the encoder in the bit string memory 308, and decodes the bit string stored at a desired time point to reproduce the still image.

For this purpose, a user control signal is provided to the channel buffer 307, the bit string memory 308, and the mux 309, similarly to the encoder.

As described above, in the still image transmission method according to the first exemplary embodiment, since the compressed bit sequence for the still image is stored in the bit string memory 308, a plurality of still images can be stored, thereby replacing the video terminal with a digital camera. Can be used.

Second embodiment

The still image transmission method proposed in the second embodiment receives a still image in a frame unit from a camera, and encodes and transmits the input still image.

In order to perform the still image transmission, the encoder further includes a separate frame memory for storing a still image in a frame unit input to the front end of the encoder described in FIG. 2, and also performs operations of the core unit and the variable length encoder. A control signal for controlling is further generated.

An encoder having such a structure is shown in FIG. 4A and its operation is as follows.

Referring to FIG. 4A, first, a still image of a frame unit is received from a camera and stored in the added first frame memory 400. At this time, the camera input may be turned on / off to receive a still image in a frame unit.

Therefore, one frame of the still image is stored in the first frame memory 400 according to an on / off operation of the camera.

Then, the core unit 401 performs I picture coding on the image stored in the first frame memory 400 with the fixed quantization value as described in the first embodiment. In this case, since the quantization value is kept low, a large amount of bits are generated during encoding, which may cause an overflow in the channel buffer 404.

In order to prevent such an overflow, the channel buffer 404 generates a control signal (that is, a wait signal) to the core unit 401 and the variable length encoder 403 for pausing the encoding. ) Temporarily stops encoding of the still image frame stored in the first frame memory 400.

Subsequently, when the state of the channel buffer 404 is stabilized, the core unit 401 restarts encoding, encodes the still image frame stored in the first frame memory 400, and transmits the encoded picture to the receiver.

In this way, the encoder can transmit the still image of high quality by appropriately adjusting and encoding the still image frame stored in the first frame memory 400 according to the state of the channel buffer 404.

The decoder will now be described.

Referring to FIG. 4B, the decoder has the same structure as the decoder shown in FIG.

The operation of the decoder is as follows.

First, the bit string of the still image encoded and input from the encoder is first stored in the channel buffer 405. At the same time, the core unit 407 starts decoding the bit string stored in the channel buffer 405.

At this time, since the decoding speed of the core unit 407 is faster than the channel transmission rate, an underflow may occur in the channel buffer 405. In order to prevent this, the channel buffer 405 generates a control signal (that is, a wait signal) for stopping the decoding operation of the core unit 407 to the core unit 407 and the variable length decoder 406.

When the bit string of the still image encoded above the predetermined reference value is input to the channel buffer 405, the variable length decoder 406 and the core unit 407 restart decoding to reproduce the still image.

The decoder described above may be used in connection with the encoder proposed in the first embodiment.

Third embodiment

In the image transmission method proposed in the third embodiment, a still image in a frame unit is received from a camera, and an encoding and transmission procedure of the input still image is repeatedly performed.

To this end, the encoder is a structure in which a control signal (that is, a wait signal) is missing from the encoder described in the second embodiment, and is shown in FIG. 5A.

Referring to FIG. 5A, first, a still image input from a camera in a frame unit is stored in the first frame memory 500, and the camera input is turned off so that the image is no longer input. Accordingly, one frame of the still image is stored in the first frame memory 500 according to an on / off operation of the camera.

Next, the core unit 501 and the variable length encoder 503 encode the still image frame stored in the first frame memory 500.

In the third embodiment, unlike the above-described first and second embodiments, the quantization value is not fixed to the input image of the still image of one frame, and is variably encoded according to the state of the channel buffer 504. The encoder performs the same operation as the encoding of the video, and the encoder encodes the image stored in the first frame memory 500 and transmits the same to the receiving side as in the case of processing the normal video.

Then, the decoder having the same structure as that of the decoder shown in Fig. 2 restores and reproduces the still image of low quality once.

In this case, when processing a video, image frames continuously input to the encoder are processed. However, in the present invention, since there is no newly input still image by turning off the camera input, the first frame memory 500 encodes and transmits the image frames. The same still picture as the still picture is stored, and it is encoded and transmitted.

In more detail, the second frame memory 502 for the motion compensation unit of the encoder stores the previously encoded image frame (that is, the first image frame processed after the image is input from the camera). However, since the same still image is sent again in the first frame memory 500, when the difference between the input image frame and the image frame stored in the second frame memory 502 is encoded and transmitted, the previously processed image frame ( That is, a smaller amount of bits than the first processed image frame after the image is input from the camera is generated, and accordingly, an image having improved image quality is reproduced for the same kind of still image on the decoder side.

As described above, an operation of repeatedly transmitting one still image by the encoder is stopped when a predetermined time is reached according to a predetermined reference value.

In this case, the reference value may be determined in the user or the encoder and may be set as follows.

The first is to set a predetermined time as a reference value, and the encoder repeatedly transmits a still image for a predetermined time.

The second decision is based on the occupancy of the channel buffer. When the occupancy of the channel buffer falls below a certain value, the repetitive transmission is stopped.

In this way, if the same single still image is repeatedly transmitted, a still image of a desired high quality can be transmitted.

The still image transmission method according to the third embodiment adds only the on / off operation of the camera input and is processed according to the same flow as the conventional video encoding and decoding operations.

Fourth embodiment

In the fourth embodiment, a still image transmission and storage system between video terminals adopting the still image transmission method described above (first to third embodiments) will be described.

6 is a diagram illustrating a still image transmission and storage system between video terminals adopting a still image transmission method according to a first embodiment of the present invention.

Referring to FIG. 6, a video terminal is generally provided with an encoder and a decoder, and since the two-way transmission is performed during video transmission, the encoder and the decoder work together. However, when transmitting and receiving still images, one-way transmission is often performed. In this case, when one of the encoders or decoders operates, the other apparatus does not need to operate. Therefore, the transmission side of the video terminal adopting the still image transmission method as in the first, second, and third embodiments can use the frame memory for motion compensation of the decoder as a substitute for the bit stream memory or the input image frame memory for the transmitter. On the receiving side, the motion compensation frame memory of the encoder can be used as a substitute for the receiving bit string memory or the input image frame memory.

On the other hand, in the first embodiment, when storing a still image on a computer, the image is stored in a bit string. This is because still images are stored in bit strings. However, since the bit string of the still picture stored in the computer is composed of the index words (ie, MPEG, H263) of video encoding, the bit string of the still picture should be converted into the index word (ie, JPEG) of the still picture. In order to perform this function, a computer is provided with code converter software (transcoder software) for translating index words.

7 is a diagram illustrating a still image transmission and storage system between video terminals adopting a still image transmission method according to a second or third embodiment of the present invention.

Referring to FIG. 7, in the second or third exemplary embodiment, image data (ie, image frames) that are not bit strings are transmitted / received, and image data is stored even when stored in a computer.

As described above, the present invention can transmit a desired still image to the counterpart using a video terminal, and thus has the following effects.

First, there is no need to have a variety of equipment such as digital cameras, scanners and computers, reducing costs.

Second, it is possible to conveniently transmit / receive desired still images regardless of time and place, thereby increasing the commercialization of the video terminal.

Third, since multiple still images can be stored, a video terminal can be used as a substitute for a digital camera.

Claims (5)

In a video terminal for encoding and transmitting a video, And extracting the still image on a frame basis from the video, and encoding and transmitting the extracted still image. In a video terminal for encoding and transmitting a video, And storing the input still image in a frame unit, and encoding the stored still image in a frame unit according to a state of a channel buffer. In a video terminal for encoding and transmitting a video, And storing the input still image in the frame unit and repeating the encoding process for the same still image in the stored frame unit. An arbitrary frame memory for storing an image input in units of frames, A discrete cosine transform unit for discrete cosine transforming an image input from the frame memory; And a quantization unit configured to quantize the signal output from the discrete cosine transform unit. The video transmission terminal of claim 4, wherein the arbitrary frame memory uses a motion compensation frame memory of a decoder.