KR19980067062A - Active Picture Size Control Method According to Channel Condition and Its Apparatus - Google Patents

Abstract

Disclosed is a method and an apparatus for controlling an active picture size according to a channel state to support a high quality screen by actively adjusting a picture size according to a channel state in a video conference system. The present invention recognizes the current frame rate from the encoded video data amount of the frame unit composed of a picture size of a certain format, compares the current frame rate and the preset frame rate, and determines the state of the channel based on the comparison result, According to the result, the current picture size is controlled to be reduced or increased. Accordingly, the present invention can use the channel more efficiently by actively adjusting the picture size in response to the change of the channel, and provides an effect capable of supporting a high quality large and small screen at all times.

Description

Active Picture Size Control Method According to Channel Condition and Its Apparatus

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video conference system, and in particular, an active picture according to a channel state in which a picture size transmitted in response to a change in a channel condition is controlled to always support a high quality screen. A size control method and apparatus therefor.

With the official recommendation of ITU-T H.263, the international standard for digital moving picture compression, the era of video communication is in full swing. H.263 is mainly used in multimedia communication terminals that are commercialized as a standard for video telephony and conferencing systems, and is based on the camera input signal of the current TV. However, since the transmission speed is limited to about 10 Kbps to 30 Kbps, the common resolution of the resolution (720 pixels x 240 lines x 60 fields and 720 pixels x 288 lines x 50 fields) of NTSC or PAL-specific camera signals is reduced in advance. Format it. This is a common intermediate format called Common Intermediate Format (CIF), which is 352 pixels by 288 lines of pixels, up to 30 frames per second. As described above, the format of the video signal in H.263 is CIF (Common Intermediate Format) and QCIF (Quarter CIF: ¼CIF) in which the number of vertical and horizontal pixels is ½. In general, video codecs are coded for QCIF, Sub-QCIF, 16CIF, 4CIF, and CIF, are mandatory to decode QCIF, Sub-QCIF, and are set to selectively decode 16CIF, 4CIF, and CIF. have.

However, in a conventional video conference, a picture size transmitted when a conference is started is limited to one of CIF, QCIF, and Sub-QCIF. This maintains the same picture size regardless of channel changes, so when the channel deteriorates, almost still transmission occurs, resulting in poor image quality.

Accordingly, an object of the present invention is to provide an active picture size control method according to a channel state capable of transmitting a small screen of good quality even if the channel deteriorates by actively adjusting the picture size in response to a change in the channel.

Another object of the present invention is to provide an apparatus for implementing an active picture size control method according to the channel state in hardware in a video conference system.

1 is a block diagram showing a preferred embodiment of a video conference system to which the present invention is applied.

Explanation of symbols for main parts of the drawings

11: Video input device 12: Format organizer

13: video codec 14: controller

15: Audio input unit 16: Audio codec

17: multiplexer

The active picture size control method according to the channel state of the present invention for achieving the above objects is a method for controlling the picture size of the video data input according to the channel state in the videoconferencing system, the (1) constant format Recognizing the current frame rate of the transmission channel from the encoded video data amount of the frame unit consisting of the picture size of (2) and compares the recognized current frame rate and the predetermined frame rate, based on the comparison result Determining the state; (3) controlling the picture size to be reduced or increased in accordance with the channel state determination result; and (4) video data inputted in the format of the reduced or increased picture size according to the control. Configuring.

An active picture size control apparatus according to a channel state of the present invention for achieving another object of the present invention is a video conferencing system that compresses and encodes input video data and audio data and multiplexes them with other data. A controller for recognizing a current frame rate from the encoded video data amount in a frame unit configured of a picture size of a format to determine a current state of a transmission channel, and controlling the picture size to be adjusted based on the determination result, and a control of the controller And a format composer constituting video data input in a format corresponding to a picture size adjusted according to the method.

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

1 is a configuration diagram showing a video conference system to which the present invention is applied. As shown, the system of FIG. 1 is an H.324 system that implements a video conferencing system using a general telephone line of a PSTN, which includes all the original configurations of the H.324 system, and further includes a frame in the video codec 13. And a controller 14 for recognizing the current frame rate from the amount of video data encoded in units to determine the current state of the transmission channel, and controlling the picture size to increase or decrease based on the determination result. In addition, according to the control of the controller 14 is composed of a modified format configurator 12 for outputting the video data input in the format of the increased or decreased picture size and output to the video codec (13).

The operation of the present invention in the videoconferencing system configured as described above will be described in detail.

First, in the H.324 system implementing the video conferencing system, the video input unit 11 inputs video data obtained through a camera or the like into the format configurator 12. The format configurator 12 configures the input video data into a format such as CIF, which is a standard input image, or QCIF obtained by dividing the CIF into four, and outputs it to the video codec 13. The size of the CIF is 352 × 288, and the QCIF is 176 × 144 since it is ¼ of the CIF. The video codec 13 compresses and encodes video data having a size of CIF or QCIF based on the H.263 recommendation, and outputs it to the multiplexer 17. Meanwhile, the audio input unit 15 inputs audio data obtained through a microphone or the like into the audio codec 16. The audio codec 16 compresses and encodes the input audio data based on the G. 723 recommendation, and outputs it to the multiplexer 17. The multiplexer 17 multiplexes the compressed-coded video data and audio data together with other data according to H.223 recommendations and transmits them to the counterpart system via a general telephone line of the PSTN. Here, the picture size information for the video data to be compressed and coded exists in the stream. That is, picture size information and video data of a coded bitstream of the picture are loaded starting with the picture start code (PSC). Here, the code amount of the encoded video data varies in units of frames according to the complexity of the image or the violent motion. Thus, the controller 14 recognizes the current frame rate on the transmission channel of a certain capacity from the video data amount encoded in units of frames and compares the current frame rate with the preset frame rate. As a result of the comparison, if the current frame rate is less than or equal to the preset frame rate, the controller 14 determines that the channel condition is worsened and adjusts the current picture size of the format configurator 12 to be reduced. For example, if the current picture size is QCIF, if the channel deteriorates, the sub-QCIF is adjusted. On the contrary, if the current frame rate is greater than or equal to the preset frame rate, the controller 14 determines that the channel condition is good and adjusts the current picture size of the format configurator 12 to increase. For example, if the current picture size is Sub-QCIF, if the channel is good, it is adjusted to QCIF. The format configurator 12 configures the picture size of the video data input from the video input unit 11 under reduced or increased format under the control of the controller 14 and outputs the picture size to the video codec 13.

As described above, the present invention relates to a method for controlling an active picture size according to a channel state and an apparatus thereof, and compared to a conventional frame video coded by using a single picture size regardless of a channel change. It recognizes the current frame rate from the amount of data and determines the current state of the transmission channel.It controls the picture size to be actively adjusted based on the determination result. The channel can be used more efficiently.

Claims (7)

In a video conference system, a method for controlling the picture size of video data input in accordance with a channel state, (1) recognizing the current frame rate of the transport channel from the encoded video data amount in the frame unit composed of a picture size of a certain format; (2) comparing the recognized current frame rate with a preset frame rate and determining a channel state based on a comparison result; (3) controlling the picture size to decrease or increase according to the channel state determination result; And (4) a method of controlling an active picture size according to a channel state, comprising constructing video data input in a format of reduced or increased picture size according to the control. The method of claim 1, wherein the step (2) determines that the channel state is deteriorated when the current frame rate is less than or equal to the preset frame rate, and determines that the channel state is good when the current frame rate is greater than or equal to the preset frame rate. An active picture size control method according to a channel state, characterized in that. 3. The active picture size according to the channel state of claim 2, wherein the step (3) controls the picture size to be reduced when the channel state is deteriorated, and to increase the picture size when the channel condition is deteriorated. Control method. In a videoconferencing system which compresses and encodes input video data and audio data and multiplexes them with other data, A controller for recognizing a current frame rate from the encoded video data amount in a frame unit having a picture size of a predetermined format to determine a current state of a transmission channel, and controlling the picture size to be adjusted based on a determination result; And And a format configurator for configuring video data input in a format corresponding to a picture size adjusted according to the control of the controller. The apparatus according to claim 4, wherein the controller compares the recognized current frame rate with a preset frame rate and determines a channel state based on a comparison result. The active picture size control according to the channel state according to claim 5, wherein the controller determines that the channel state is deteriorated if the current frame rate is less than or equal to the preset frame rate. Device. The apparatus according to claim 5, wherein the controller determines that the channel state is good when the current frame rate is greater than or equal to the preset frame rate, and controls the current picture size to increase. .