KR20020042962A - Encoder and decoder in a wireless terminal for retransmitting a moving picture - Google Patents

Abstract

PURPOSE: A motion picture encoding device is provided to set whether or not to retransmit a transmitted video image with the frequency according to importance of a predictive coding of the image, when an error is generated in the image, and to transmit a re-transmission command to a host system, thereby reducing the amount of re-transmitted data as ensuring the re-transmission frequency. CONSTITUTION: A video encoder(208) encodes a video signal by a predictive coding. A frame storage(212) stores video image frames encoded through the encoder. A re-transmission request processor(218) transmits a re-transmission command to the frame storage in response to a re-transmission request of the encoded video signal transmitted from a wireless terminal. A re-transmission frequency decider(210) differently stores the frequency or a result about whether or not to re-transmit an encoded image within one field, according to importance of the predictive coding of each image and image types, when performing an encoding in response to the re-transmission command. A video image for re-transmission is transmitted to the wireless terminal through a transmitter after being encoded, or the re-transmission command is ignored.

Description

A video encoding device and a video decoding device of a wireless terminal {ENCODER AND DECODER IN A WIRELESS TERMINAL FOR RETRANSMITTING A MOVING PICTURE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to video encoding and its decoding apparatus, and more particularly, to predicting motion of an image when generating a retransmission signal in order to recover an error occurring during transmission of an encoded video using MPEG and a compression technique (eg, H.263, etc.). A video encoding apparatus and a video decoding apparatus of a wireless terminal for classifying the number of retransmission signals according to a degree.

Moving Picture Expert Group (MPEG) is an international standard for the compression of digital video. The MPEG method employs a motion extraction and compensation technique to remove time redundancy when compressing a video, and a DCT (Discrete Cosine Transform) transform that removes spatial redundancy.

Currently, a widely used video compression algorithm uses a motion prediction encoding method. This predictive coding indicates that a signal value of a pixel is represented by an adjacent signal value or a signal value of another time (usually past). In other words, this method is based on one image and differentially encodes the motion from the next image.

The types of images for predictive encoding are largely classified into I image (intra-frame encoded image), P image (inter-frame forward predictive encoded image), and B image (bidirectional predictive encoded image).

The I picture is an intra-frame coded picture with independence of a group of pictures (GOP), and is a picture that usually intra-codes everything on the screen. A P-picture is an inter-frame forward-prediction coded video, and some of the small block units in the picture may include intra coding. The B image is a bidirectional predictive coded image. The I and P images are encoded in the same order as the original image, but the B image is obtained by processing the I and P images first and then encoding the screen between them.

For many images during compression, inter-frame prediction (P-picture) is used, but intra-frame coding (I-picture) is usually used in parts with low correlation between frames such as scene transitions (videos that change scenes suddenly).

On the other hand, when an error occurs in the transmission of the compressed video, a device that receives and decodes the compressed video requires retransmission. According to the retransmission request scheme of the current MPEG technology, the decoding apparatus requests retransmission for all error images. Therefore, even an image that is not a reference in predictive encoding is subject to retransmission, causing an overload of a transmission network wirelessly connected to the decoding apparatus.

Moreover, in the next generation information communication terminals such as IMT-2000 that exchange voice, data, and image information in real time, the amount of retransmission data increases when a transmission error occurs frequently, resulting in delay of video transmission or loss of transmission packets. There was a problem.

An object of the present invention is to set the number of retransmissions in accordance with the importance of the predictive encoding of the image in order to solve such problems of the prior art, to ensure the number of retransmissions of the reference image (I image) of the image from which the transmission error occurs The present invention provides a video encoding apparatus capable of reducing the amount of retransmission data with a wireless terminal by providing a retransmission number determination unit, thereby reducing delay of video transmission or loss of a transmission packet.

Another object of the present invention is to set the number of retransmissions according to the importance of the predictive encoding of the video when a transmission error occurs in a compressed image transmitted wirelessly from the host system, the reference image (I image) By retransmitting the number of retransmission data with the wireless terminal can be reduced, thereby providing a video decoding apparatus of a wireless terminal that can reduce the delay of video transmission or the loss of the transmission packet.

In order to achieve the above object, the present invention provides a host system for encoding a video signal and transmitting the video signal wirelessly to a terminal, comprising: a video encoder encoding a video signal by predictive encoding; and a frame storing video image frames encoded through the encoder. A storage unit, a retransmission request processor for transmitting a retransmission command to the frame storage unit in response to a retransmission request of the encoded video signal transmitted from the wireless terminal, and an image type and each when encoding in response to the retransmission command transmitted to the frame storage unit. A retransmission number determination unit storing different retransmissions of the encoded image in one field according to the importance of predictive encoding and the number of retransmissions, and encoding the retransmission video image through the video encoder according to the determination of the retransmission number determination unit. Back to the wireless terminal via the transmitter Or it characterized in that it ignores the retransmission command.

In order to achieve the above object, the present invention provides a wireless terminal for decoding an encoded video signal, comprising: a video decoder for receiving a compressed video signal from a host system that sends encoded video information and decoding the video signal; A frame storage unit for storing the video signal, an error check / correction unit for checking an error of the video signal decoded by the video decoder, and correcting the error; If the error is not restored by the retransmission comparison / request unit and the retransmission comparison / request unit, which determines the presence / absence and the number of retransmissions of the error image according to the compressed video type and the importance of the set video image, the error is detected. Transmitter for transmitting the retransmission signal of the generated video, retransmission comparison / request A video decoder, a frame storage unit, and an output unit for displaying a video signal obtained by decoding and correcting an error through an error check / correction unit are received by receiving the encoded video image transmitted back from the host system in response to a request for retransmission of the unit and the transmitter.

1 is a circuit block diagram showing a video decoding apparatus of a wireless terminal according to an embodiment of the present invention;

2 is a circuit block diagram showing an encoding apparatus for retransmitting a video in a host system according to an embodiment of the present invention;

3 is a diagram for describing a retransmission video image in which a transmission error occurs in a video encoding apparatus and a video decoding apparatus of a wireless terminal of the present invention.

<Description of the code | symbol about the principal part of drawing>

10: wireless communication unit 100: video decoding device

102: transmitting and receiving unit 104: signal separation unit

106: audio decoder 108,118: output unit

110: video decoder 112: previous frame

114: error check unit 116: retransmission comparison / request unit

200: video encoding device 202: audio input unit

204: audio encoder 206: video input

208: Video encoder 210: Retransmission number determination unit

212: frame storage unit 214: signal integration unit

216: transceiver unit 218: retransmission request processing unit

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a circuit block diagram illustrating a video decoding apparatus of a wireless terminal according to an embodiment of the present invention.

Referring to FIG. 1, the video decoding apparatus 100 of the wireless terminal of the present invention includes a transceiver 102, a signal separator 104, an audio and video decoder 106 and 110, an audio output unit 108, and a frame storage unit. 112, an error check / correction unit 114, a retransmission comparison / request unit 116, and a video output unit 118.

Here, the signal separator 104 receives the compressed video signal transmitted through the wireless communication unit 10 from the host system (not shown) by the receiver 102 and divides the compressed video signal into a compressed audio signal and a compressed video signal.

The audio decoder 106 receives a compressed audio signal from a host system that sends compressed video information, decodes the compressed audio signal, and the video decoder 110 receives a compressed video signal from a host system that sends compressed video information. Takes input and decodes it.

The frame storage unit 112 stores the video signal decoded by the video decoder 110.

The error check / correction unit 114 checks an error of a video signal decoded by the video decoder 110 and corrects the error.

The retransmission comparison / request unit 116 sets the type of the video image (I image, P image, B image) when the error is not recovered by the transmission error among the video signals in which the error is corrected through the error check / correction unit 114. ), And whether or not the number of retransmissions of an error-produced image is determined according to the importance of the predictive encoding) and the retransmission signal is not transmitted or transmitted to the transmitter 102 according to the set value. Accordingly, the transmission unit 102 transmits a retransmission signal of an image in which an error occurs according to the signal of the retransmission comparison / request unit 116. Furthermore, the retransmission comparison / request unit 116 of the present invention determines retransmission of an error-produced image according to the predictive encoding type (I image, P image, B image) of the image. Video) sets the maximum number of retransmissions, but does not retransmit or sets the number of retransmissions less than the number of retransmissions of the reference video.

The audio output unit 108 outputs the audio signal decoded by the audio decoder 106, and the video output unit 118 in the host system in response to the retransmission request of the retransmission comparison / request unit 116 and the transmitter 102 A video signal obtained by decoding and correcting an error is displayed through the video decoder 110, the frame storage unit 112, and the error check / correction unit 114 by receiving the compressed video image transmitted again.

Therefore, the video decoding apparatus 100 of the present invention configured as described above has the type (I picture, P picture, B picture) of the decoded video picture in which the error is not recovered in the retransmission comparison / request unit 116, and the importance of predictive encoding. In this case, the retransmission signal is transmitted (not sent) to the host system by determining the presence / absence and the number of retransmissions of each error image. That is, the video decoding apparatus of the present invention does not require retransmission for all of the video in which an error occurs, but in real time by determining the presence / absence and the number of retransmissions according to the importance of the video that is the reference code and the video that is not. When decoding video data, the load on the transmission network can be reduced by reducing the amount of retransmitted data.

2 is a circuit block diagram illustrating an encoding apparatus for retransmitting a video in a host system according to an exemplary embodiment of the present invention.

Referring to FIG. 2, an example of an encoding apparatus for retransmitting a video according to the present invention includes an audio input unit 202, an audio encoder 204, a video input unit 206, a video encoder 208, a retransmission number determination unit 210, The frame storage unit 212, the signal integrating unit 214, the transceiver unit 216, and the retransmission request processing unit 218 are configured.

Here, the audio encoder 204 compresses the audio data by encoding the audio signal input through the audio input unit 202 by a compression algorithm.

The video encoder 208 compresses the video data by encoding the video signal input through the video input unit 206 by a predictive encoding technique of an image according to the motion compensation of the image frame.

The retransmission count determiner 210 determines whether or not to retransmit an encoded image in a field according to the image type and the predictive encoding importance of each image when encoding in response to the retransmission command transmitted to the frame storage unit 212. Set the retransmission count differently.

The frame storage unit 212 stores video image frames encoded by the video encoder 208.

The signal integrator 214 integrates the encoded audio and video signals through the audio encoder 204 and the video encoder 208, respectively.

The transceiver 216 transmits the compressed video data (encoded audio and video data) to a wireless terminal (not shown) through the wireless communication unit 10, and receives wireless data transmitted from the wireless terminal.

The retransmission request processing unit 218 transmits a retransmission command to the frame storage unit 212 in response to a retransmission request of the encoded video signal transmitted from the wireless terminal through the reception unit 216.

Therefore, in the video encoding apparatus of the host system configured as described above, the retransmission number determining unit 210 determines the type of the image and the importance of predictive encoding in advance when the wireless terminal requests retransmission of the encoded video signal for transmission error. According to determine whether or not and the number of retransmission, and after encoding the video image for retransmission through the video encoder 208, and transmits wirelessly through the transmitter 216 or ignores the retransmission request of the wireless terminal. That is, the encoding apparatus of the present invention also does not retransmit all of the error-producing images, but transmits the retransmission to the decoding apparatus or ignores the retransmission request by varying the number of retransmissions of each image retransmitted according to the type of the image and the motion prediction encoding. By reducing the amount of data retransmitted in real time, it is possible to reduce the load on the transmission network.

3 is a diagram for describing a retransmission video image in which a transmission error occurs in a video encoding apparatus and a video decoding apparatus of a wireless terminal according to the present invention.

Referring to FIG. 3, the present invention considers the degree of motion prediction compensation between images in a retransmission number determining unit of a video encoding apparatus and a retransmission comparison / request unit in a video decoding apparatus of a wireless terminal, and a reference image having a large error effect. Presence or absence of retransmission according to the image and the number of retransmissions are set in advance. Therefore, when there is an image that cannot be restored due to a transmission error in the input error corrected video image, the video decoding apparatus determines whether or not retransmission is performed according to the information set according to the importance of the error image, and the corresponding image that is good within the set number of retransmissions is determined. Send a resend command to the transmitter until it is sent. Accordingly, the video encoding apparatus receives a retransmission command (video signal) of the wireless terminal and uses the retransmission number determination unit for retransmission within the number of retransmissions of different images determined according to the type of the image determined before encoding the video image and the importance of the predictive encoding. In the case of an image which is encoded and transmitted to a wireless terminal or does not need to be retransmitted, the video apparatus ignores the request of the decoding apparatus and does not retransmit.

For example, if a transmission error occurs in the intra image (I image) 1, which is the reference of the first field, as shown in the figure, images 2 to 4 (P image, B image, P image) using image 1 as a predictor Are all affected by errors. Similarly, if an error occurs in images 5 and 10, which are the reference images (I images) of the second and third fields, this error also affects P images B and B images 6 to 9 and 11 to 12, respectively. .

In order to recover such a transmission error, the decoding apparatus of the wireless terminal of the present invention requests retransmission to the host system. As in the prior art, the importance of predicting an image in which an error occurs is not required to retransmit all the images in error. According to (I video, P video, B video), the presence / absence of retransmission and the number of retransmissions are determined, and a retransmission reception command is generated. That is, in the decoding apparatus of the present invention, when a transmission error occurs in the first field part, the retransmission comparison / request unit issues a retransmission command for the first image having a larger predicted importance than another image, and the number of retransmissions is 5 at maximum. The retransmission comparison / request unit also retransmits the second image, and sets the number of retransmissions up to three. However, retransmission command is not performed for images 3 and 4, or 1 or 2 even if retransmission command is performed.

Similarly, the encoding apparatus of the host system also sends an encoding signal for retransmission to all the images in which an error occurs as in the prior art, and determines the presence / absence and the number of retransmissions according to the predicted importance of the image in which the error occurs. Resend different images.

As described above, the present invention determines the presence / absence of the retransmission and the number of retransmissions according to the importance of the prediction encoding of the image and the reference image during the prediction encoding, and sends a retransmission command to the host system. In accordance with the present invention, retransmission of the encoded video having an error in the presence / absence of the retransmission and the number of times or ignore the retransmission request. Therefore, the amount of retransmission data can be reduced, and the overload of the transmission network wirelessly connected to the decoding apparatus can be greatly reduced.

In addition, the present invention can guarantee the maximum retransmission of the reference video when the transmission error occurs frequently in the next-generation information communication terminal, such as IMT-2000 that exchanges telephone and image information in real time, so that delay or transmission of the video transmission Real-time video generated by packet loss can be decoded as it is.

On the other hand, the present invention is not limited to the above-described embodiment, various modifications are possible by those skilled in the art within the spirit and scope of the present invention described in the claims to be described later.

Claims (3)

In the host system for encoding a video signal and transmitting to the terminal wirelessly, A video encoder for encoding the video signal by predictive encoding; A frame storage unit which stores video image frames encoded by the encoder; A retransmission request processor for transmitting a retransmission command to the frame storage in response to a retransmission request of an encoded video signal transmitted from the wireless terminal; And And a retransmission count determining unit storing different retransmissions of the encoded video in one field and the number thereof according to the video type and the importance of predictive encoding of each video when encoding in response to the retransmission command transmitted to the frame storage unit. , And retransmitting the video image for retransmission through the video encoder according to the determination of the retransmission number determination unit, and then transmitting the retransmission command to the wireless terminal or disregarding the retransmission command. A wireless terminal for decoding an encoded video signal, A video decoder which receives a compressed video signal from a host system that sends the encoded moving picture information and decodes it; A frame storage unit storing a video signal decoded by the video decoder; An error check / correction unit for checking an error of a video signal decoded by the video decoder and correcting the error; If the error is not recovered from the video signal whose error is corrected through the error check / correction, determining whether or not and how many times the error occurs is retransmitted according to the compressed video type and the importance of the set video image. Retransmission compare / request; A transmitter for transmitting a retransmission signal of an image in which an error occurs in response to a signal of the retransmission comparison / request unit; And In response to the retransmission request of the retransmission comparison / request unit and the transmission unit, the encoded video image transmitted back from the host system is input, and a video signal obtained by decoding and correcting the error is displayed through a video decoder, a frame storage unit, and error check / correction. An apparatus for decoding a video of a wireless terminal, comprising: an output unit. The method of claim 2, wherein the retransmission comparison / request unit sets a maximum number of retransmissions of a video that is a reference when encoding when a transmission error occurs in a video image encoded according to a motion prediction encoding technique, and the non-standard video The apparatus for decoding a video of a wireless terminal, wherein the number of retransmissions is not set or the number of retransmissions is set smaller than the number of retransmissions of the reference video.