JP2006238175A - Communication control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication control method capable of restoring an image immediately to realize stress-free transmission environment even if a packet loss arises, in an image communication system using an image difference compression method codec. <P>SOLUTION: The communication control method controls a communication system for communicating a real time video data using an image difference compression method codec with an RTP (real-time transport protocol). The communication control method comprises a process for transmitting a basic frame by a transmitting side, a process for transmitting a difference frame difference compressed and encoded based on the basic frame by a transmitting side, a process for receiving the basic frame by a receiving side, a process for receiving the difference frame and decoding and image outputting based on the basic frame by the receiving side, and a process for requesting transmission of the basic frame using an RTCP (RTP control protocol) packet when loss of an RTP packet is detected by the receiving side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a communication control method.

  There is a technology for constructing a videophone system in which moving images and sounds obtained by a video camera and a microphone are image-compressed and voice-compressed and communicated as real-time data through a communication line such as the Internet.

  In a videophone system, it is necessary to always cope with communication line conditions that change state. For example, even if a packet loss occurs and an image is disturbed, it is necessary to recover immediately.

  RTP (Realtime Transport Protocol) is known as such a communication protocol. In RTP, RTP (RTP Data Transfer Protocol) is used for transmission / reception of video and audio data, and RTCP (RTP Control Protocol) is used for transmission / reception of control data.

  In such a communication system, control information is periodically transmitted and received. For example, in RTP, the RTPC transmission interval is recommended about once every 5 seconds. For this reason, there is a problem in that when the communication line situation deteriorates and packet loss or the like occurs, detection of the change in the situation is delayed.

Therefore, in the cited reference 1, in the control method for transmitting the control signal for grasping the situation on the network at a predetermined time interval, the frequency of sending the control information according to the detected change in the situation of the network is detected. Is adjusted.
JP 11-284659 A

  However, even if the control method described in the cited document 1 is used, the recovery time differs depending on whether the basic frame or the differential frame is lost for the image differential compression codec. For example, when the differential frame is lost, The problem arises that the video cannot be recovered until the basic frame arrives.

  The present invention has been made to solve the above problems, and in an image communication method using an image differential compression method codec, communication that realizes a stress-free communication environment by immediately restoring an image even when packet loss occurs. An object is to provide a control method.

To achieve the above object, the present invention provides a communication control method for controlling a communication system that communicates real-time video data using an image differential compression codec using RTP.
Transmitting a basic frame on the transmitting side;
Transmitting a differential frame encoded by differential compression based on the basic frame on the transmission side;
Receiving the basic frame on the receiving side;
Receiving the difference frame on the receiving side, decoding the difference frame based on the basic frame, and outputting an image;
And a step of requesting transmission of a basic frame using an RTCP packet when detecting a lost RTP packet on the receiving side.

  At this time, when transmitting the basic frame on the transmission side, the parameter value of the bit rate, frame rate or size set in the encoder can be changed according to the frequency of occurrence of packet lost.

  Further, when a lost packet is detected on the receiving side, it can be displayed that a packet lost has occurred.

  In addition, when the lost packet is detected on the receiving side, the PTCP packet can be transmitted immediately.

  In addition, the transmission side that has received the RTCP of the packet lost can change the video image frame to be transmitted from a difference frame to a basic frame and transmit the frame to the reception side.

  Further, the transmission side that has received the RTCP of the packet lost can indicate that the packet lost has occurred.

  According to the present invention, in a real-time video communication using an image differential compression method codec, even when a video stream packet is lost, a normal image without distortion can be provided to the user earlier.

  Hereinafter, the best embodiment of the present invention will be described. The present invention is not limited to these embodiments and can be used in various ways.

  FIG. 1 is a diagram showing an example of a protocol stack configuration of a commercial application used in the communication control method of the present invention.

  As shown in FIG. 1, in this protocol stack configuration, a UDP / IP (OS) layer is constructed on a hardware (Hardware) layer. On top of this UDP / IP layer is a SIP / SDP layer, G.P. A 711 codec layer, an audio input / output layer, an RTP / RTCP layer, an MPEG-4 codec layer, and an image input / output (DirectShow) layer are constructed. On these layers, a signaling layer, a Voice layer, and a Video layer are constructed. On top of these layers, an application layer is built.

  In the communication control method of the present invention, in such a protocol stack configuration, real-time video data using an image differential compression method codec is communicated using RTP.

  FIG. 2 shows an example of a communication flow when packet loss occurs in video communication using the image differential compression method codec showing the communication control method of the present invention.

  First, the transmitting side transmits a basic frame, the transmitting side transmits a differential frame that is differentially compressed and encoded based on the basic frame, the receiving side receives the basic frame, and the receiving side receives the differential frame. The system is configured to decode the difference frame based on the frame, output an image, and request the transmission of the basic frame using the RTCP packet when the receiving side detects the lost RTP packet.

  That is, the RTCP packet “Sender Report” or “Receiver Report”, which is one of the packet groups constituting the real-time video communication, uses the information “number of packets of lost packets”. When the receiving side detects the RTP packet lost (202) Then, the receiving side notifies the sending side of the occurrence of lost in the next RTCP packet transmitted at random (average constant) intervals (205).

  On the transmitting side, when this RTCP packet is received from the receiving side, it is determined that packet loss has occurred on the receiving side (transmission packet has been lost) (206). Then, on the transmission side, processing such as resetting of the encoder is performed, so that the next frame to be transmitted becomes a basic frame (207).

  At this time, the receiving side that detects the lost stops the screen output so as not to display a distorted image for the user (203, 204). Furthermore, on the receiving side, it is clearly indicated that the reception packet lost has occurred to the receiving-side user by using screen display means such as dedicated item display. The transmitting side transmits the basic frame, and when the receiving side successfully receives the basic frame, the display of the received image is resumed (208).

  In addition, the transmitting side that has detected that the packet lost has occurred on the receiving side (206) may also display the dedicated item to clearly indicate that the transmitting packet lost has occurred to the transmitting side user. At this time, the display side may control the screen display such as the pause of the preview image on the transmission side.

  At this time, when resetting the encoder for basic frame transmission on the transmission side (207), the parameter values such as the bit rate, frame rate, and size to be set are changed according to the communication status (lost occurrence frequency, etc.). Thus, automatic control of the communication global area can be achieved.

  According to this method, when the RTCP packet is received from the receiving side, a normal received image can be restored to the receiving side in a short time as much as the basic frame can be immediately transmitted on the transmitting side (209).

  FIG. 4 shows an example of a communication flow when packet loss occurs in video communication using a conventional image differential compression method codec.

  Here, when the lost RTP packet of a certain image frame occurs (101), the next received difference frame is decoded as it is and displayed on the user screen (103). In this case, the image is distorted because it is not the original difference data. This distortion is recovered when a basic frame is received (104, 105), but several seconds to several tens of seconds or more time elapses until the next basic frame is received (106). The time required for this recovery varies depending on the application specifications and lost occurrence timing. However, when the communication control method according to the present invention is used, the basic packet is transmitted immediately upon receipt of the RTCP packet. Even when compared with the recovery time 106 of the communication control method of FIG.

  FIG. 3 shows an example of a communication flow when packet loss occurs in video communication using an image differential compression method codec relating to another communication control method of the present invention.

  In this example, when using an application whose basic setting of e-no reception interval is shorter than the RTCP packet transmission interval, processing is performed so that the RTCP packet transmission interval, which is usually random, is immediately output only when the received RTP packet lost is detected. (305). As a result, the processing time interval from lost detection to basic frame reception and resumption of provision of normal image display to the user can be realized with less than the basic frame transmission interval (second order) (310). Other control configurations are the same as the communication control means shown in FIG.

It is a figure which shows the example of the protocol stack structure of the common use application used for the communication control method of this invention. It is a figure which shows the example of a communication flow when packet loss generate | occur | produces in the video communication using the image difference compression system codec which shows the communication control method of this invention. It is a figure which shows the example of a communication flow when packet loss generate | occur | produces in the video communication using the image difference compression system codec which shows another communication control method of this invention. It is a figure which shows the example of a communication flow when packet loss generate | occur | produces in the video communication using the image difference compression system codec which shows the conventional communication control method.

Explanation of symbols

201 ... packet lost occurrence 202 ... reception lost detection 203 ... reception lost information 204 ... image output stop 205 ... RTCP packet 206 ... transmission lost information 207 ... basic frame transmission 208 ... image output restart 209 ... image restart time

Claims (6)

In a communication control method for controlling a communication system that communicates real-time video data using an image differential compression codec using RTP,
Transmitting a basic frame on the transmitting side;
Transmitting a differential frame encoded by differential compression based on the basic frame on the transmission side;
Receiving the basic frame on the receiving side;
Receiving the difference frame on the receiving side, decoding the difference frame based on the basic frame, and outputting an image;
And a step of requesting transmission of a basic frame using an RTCP packet when the receiving side detects a lost RTP packet.   2. The communication control according to claim 1, wherein when transmitting the basic frame on the transmission side, a parameter value of a bit rate, a frame rate, or a size set in an encoder is changed according to a frequency of occurrence of packet lost. Method.   2. The communication control method according to claim 1, wherein when a lost packet is detected on the receiving side, a message indicating that a packet lost has occurred is displayed.   The communication control method according to claim 1, wherein when the lost packet is detected on the receiving side, the PTCP packet is immediately transmitted.   2. The communication control method according to claim 1, wherein the transmitting side that has received the packet lost RTCP changes a video image frame to be transmitted from a difference frame to a basic frame and transmits the frame to the receiving side.   The communication control method according to claim 1, wherein the transmission side that has received the RTCP of the packet lost displays that the packet lost has occurred.

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