Data reception device
A data reception device having a reception data buffer unit storing a plurality of packets contained in a data packet, a reception data amount measuring unit measuring the data amount stored in the reception data buffer unit, a variable clock generation unit generating a clock having a variable frequency, a time information output unit outputting second time information counted in accordance with the frequency of the clock generated by the variable clock generation unit, and a first time information comparison unit comparing the first time information added to the packets with the second time information outputted from the time information output unit and controlling the timing of outputting the packet stored in the reception data buffer unit. The reception data amount measuring unit controlling the frequency of the clock generated by the variable clock generation unit in accordance with measured values obtained by the reception data amount measuring unit.
1. A data reception device for receiving a data packet containing a plurality of packets, each packet of the plurality of packets having first time information added thereto, and the first time information regarding a time at which the plurality of packets are generated, the data reception device comprising:
a receive data buffer unit for storing the plurality of packets contained in the data packet;
a receive data amount measuring unit for measuring an amount of data stored in the receive data buffer unit to obtain a measured value;
a variable clock generation unit for generating a clock having a variable frequency;
a time information output unit for outputting second time information that is counted in accordance with a frequency of the clock generated by the variable clock generation unit; and
a first time information comparison unit for comparing the first time information added to the plurality of packets with the second time information outputted from the time information output unit, the second time information indicating a time that is behind by a predetermined offset time, and for controlling a timing of outputting the plurality of the packets stored in the receive data buffer unit,
wherein the receive data amount measuring unit controls the frequency of the clock generated by the variable clock generation unit in accordance with the measured value obtained by the receive data amount measuring unit, and
wherein the time information output unit comprises:
a timer unit for outputting third time information that is counted in accordance with the frequency of the clock generated by the variable clock generation unit;
a time information extraction unit for extracting the first time information added to the plurality of packets stored in the receive data buffer unit;
an initialization unit for coinciding the third time information outputted by the timer unit with the first time information extracted by the time information extraction unit; and
an offset unit for delaying, by the predetermined offset time, the third time information output by the time unit to obtain the second time information and for outputting the second time information.
2. The data reception device according to claim 1 , wherein the offset unit changes the predetermined offset time in accordance with a condition of a transmission line to which the data reception device is connected.
3. The data reception device according to claim 1 , wherein the offset unit changes the predetermined offset time in accordance with an amount of data accumulated in the receive data buffer unit.
4. The data reception device according to claim 1 , wherein the offset unit changes the predetermined offset time in accordance with a type of a communication protocol.
5. The data reception device according to claim 1 , further comprising a second time information comparison unit for comparing the third time information outputted by the timer unit with the first time information extracted by the time information extraction unit and for controlling, based on a result of the comparison, the frequency of the clock generated by the variable clock generation unit.
6. The data reception device according to claim 5 ,
wherein, until a predetermined time from a time point of starting the reception of the data packet has passed, the frequency of the clock generated by the variable clock generation unit is controlled by the second time information comparison unit, and
wherein after the predetermined time from the time point of starting the reception of the data packet has passed, the frequency of the clock generated by the variable clock generation unit is controlled by the receive data amount measuring unit.
7. The data reception device according to claim 1 , wherein after a predetermined time has passed, the receive data amount measuring unit starts controlling the frequency of the clock generated by the variable clock generation unit.
8. The data reception device according to claim 1 , wherein the receive data amount measuring unit controls the frequency of the clock generated by the variable clock generation unit by using an average value of data amounts accumulated in the receive data buffer unit, the average value being used as the measured value.
9. The data reception device according to claim 1 , wherein the plurality of packets contained in the data packet are packets that are in an MPEG2-2TS format.
10. The data reception device according to claim 1 ,
wherein as the data packet, audio signals and video signals are encoded to be generated as a plurality of packets that are in an MPEG2-TS format, each of the packets having the first time information regarding a time of the encoding added thereto, and
wherein the packets that are in the MPEG2-TS format and that have the first time information added thereto are combined and transmitted from the data transmission device which is operable to generate the data packet.
11. An integrated circuit for receiving a data packet containing a plurality of packets, each packet of the plurality of packets having first time information added thereto, and the first time information regarding a time at which the plurality of packets are generated, the integrated circuit comprising:
a receive data amount measuring unit for measuring an amount of data stored in a receive data buffer unit that is connected to the integrated circuit and that stores the plurality of packets contained in the data packet, the measured amount of data being used to obtain a measured value;
a variable clock generation unit for generating a clock having a variable frequency;
a time information output unit for outputting second time information that is counted in accordance with a frequency of the clock generated by the variable clock generation unit; and
a first time information comparison unit for comparing the first time information added to the plurality of packets with the second time information outputted by the time information output unit, the second time information indicating a time that is behind by a predetermined offset time, and for controlling a timing of outputting the plurality of packets stored in the receive data buffer unit,
wherein the receive data amount measuring unit controls the frequency of the clock generated by the variable clock generation unit in accordance with the measured value obtained by the receive data amount measuring unit, and
wherein the time information output unit comprises:
a timer unit for outputting third time information that is counted in accordance with the frequency of the clock generated by the variable clock generation unit;
a time information extraction unit for extracting the first time information added to the plurality of packets stored in the receive data buffer unit;
an initialization unit for coinciding the third time information outputted by the timer unit with the first time information extracted by the time information extraction unit; and
an offset unit for delaying, by the predetermined offset time, the third time information output by the time unit to obtain the second time information and for outputting the second time information.