A distribution control system for distributing data to a communication terminal through a communication network via a communication channel, the distribution control system comprising: a receiver configured to receive, from the communication terminal, transmission delay time information indicating transmission delay time from when the data is distributed by the distribution control system to when the data is received by the communication terminal; and a changing unit configured to change, based on the transmission delay time information received by the receiver, one or more parameters of reproduction quality when the data is reproduced by the communication terminal; characterized in that the parameters include parameters for changing reproduction delay time, target frame rate, resolution or color depth, and the number of channels when the data is video data, wherein the parameters include parameters for changing reproduction delay time, target bit rate, sampling rate, quantization bit rate, and the number of channels when the data is sound data; and wherein the changing unit is further configured to change the one or more parameters in accordance with a priority about which parameter is changed first; and the distribution control system further comprising: a transmitter configured to transmit a channel adaptive control signal including the parameter that has been changed by the changing unit to the communication terminal; wherein the data includes video data and sound data; wherein the changing unit changes parameters relating to video first prior to parameters relating to sound when the data includes the video data and the sound data; and wherein the changing unit changes parameters so that the distribution of the video data is stopped and that only the distribution of the sound data is performed when the data includes the video data and the sound data and when the quality of the communication channel is less than a predetermined threshold, even when the quality of the video data is reduced. a receiver configured to receive, from the communication terminal, transmission delay time information indicating transmission delay time from when the data is distributed by the distribution control system to when the data is received by the communication terminal; and a changing unit configured to change, based on the transmission delay time information received by the receiver, one or more parameters of reproduction quality when the data is reproduced by the communication terminal; characterized in that the parameters include parameters for changing reproduction delay time, target frame rate, resolution or color depth, and the number of channels when the data is video data, wherein the parameters include parameters for changing reproduction delay time, target bit rate, sampling rate, quantization bit rate, and the number of channels when the data is sound data; and wherein the changing unit is further configured to change the one or more parameters in accordance with a priority about which parameter is changed first; and the distribution control system further comprising: a transmitter configured to transmit a channel adaptive control signal including the parameter that has been changed by the changing unit to the communication terminal; wherein the data includes video data and sound data; wherein the changing unit changes parameters relating to video first prior to parameters relating to sound when the data includes the video data and the sound data; and wherein the changing unit changes parameters so that the distribution of the video data is stopped and that only the distribution of the sound data is performed when the data includes the video data and the sound data and when the quality of the communication channel is less than a predetermined threshold, even when the quality of the video data is reduced. a transmitter configured to transmit a channel adaptive control signal including the parameter that has been changed by the changing unit to the communication terminal; wherein the data includes video data and sound data; wherein the changing unit changes parameters relating to video first prior to parameters relating to sound when the data includes the video data and the sound data; and wherein the changing unit changes parameters so that the distribution of the video data is stopped and that only the distribution of the sound data is performed when the data includes the video data and the sound data and when the quality of the communication channel is less than a predetermined threshold, even when the quality of the video data is reduced.