WO2006011426A1

WO2006011426A1 - Receiving device, receiving program and recording medium with receiving program recorded therein

Info

Publication number: WO2006011426A1
Application number: PCT/JP2005/013494
Authority: WO
Inventors: Makoto Adachi
Original assignee: Sharp Kabushiki Kaisha
Priority date: 2004-07-30
Filing date: 2005-07-22
Publication date: 2006-02-02
Also published as: JP3881992B2; JP2006049941A

Abstract

A receiving device (2) is provided with a data accumulating means (23) for sequentially accumulating received data, a data outputting means (24) for sequentially fetching the data when a data quantity of the data accumulating means (23) exceeds a first reference value, and a count means (26), which sets a data fetching speed to a prescribed speed so as to increase the data quantity of the data accumulating means (23) and increases the data fetching speed by a prescribed time when the data quantity of the data accumulating means (23) exceeds a second reference value. Therefore, since there is no need for avoiding underrun, the quantity of data accumulation prior to reproduction start can be small.

Description

RECEIVING DEVICE, RECEIVING PROGRAM, AND RECORDING MEDIUM CONTAINING RECEIVING PROGRAM

TECHNICAL FIELD [0001] The present invention relates to a receiving device, a receiving program, and a recording medium recording the receiving program, and in particular, a receiving device, a receiving program, and a receiving device that receive data transmitted from a transmitting device via a communication network. The present invention relates to a recording medium on which a program is recorded.

Background art

[0002] In recent years, IP (Internet)

Protocol) packet transfer technology is spreading. In this case, the amount of data transmitted per unit time differs from the amount of data to be reproduced due to the difference in clock between the encoder (code decoder) and the decoder (decoder circuit). There was a possibility of causing problems such as deterioration.

[0003] In MPEG2-TS, which is generally used in digital data real-time stream transmission, as shown in FIG. 17, a synchronization signal called a PCR signal is transmitted from a transmission device 51 to a reception device 52 together with data. Send. The decoder in the receiving device 52 uses a clock synchronization circuit called a PLL circuit based on the value included in the PCR signal and the information about the time when the PCR signal is input. To reproduce. As a result, the clock difference between the transmitting device 51 and the receiving device 52 is eliminated.

[0004] However, the synchronization method using the PLL circuit is effective when the delay variation (jitter) in the network is small, and is not effective in a network with a large jitter such as an IP data communication network. In order to solve such problems, a method called the adaptive clock method is generally used.

In this method, as shown in FIG. 18, on the receiving device 53 side, before receiving the received data to the decoder, all the data is buffered and the receiving side clock (generally a decoder). The clock is input to the decoder in synchronization with a clock different from the internal clock. As a result, the decoder is synchronized with time information for driving the reception buffer of the reception device 53. For this reason, the transmission device 51 transmits the data and the reception device 53 This is different from the speed at which the data is output to the decoder. For this reason, the data in the receive buffer increases or decreases over the long term, but the data accumulated in the buffer is monitored and the data output speed is increased when the accumulated data amount exceeds the upper limit. By speeding up and slowing down the output speed when the amount of accumulated data falls below the lower limit, it is possible to avoid the phenomenon of overflow of noffer (overrun) and lack of data (underrun) (for example, Japanese Patent Laid-Open No. 20002). — See publication 165148).

FIG. 19 is a time chart illustrating a change in the buffer amount of the reception buffer. In Fig. 19, when buffering of received data is started, the buffer capacity of the receive buffer increases at a constant rate. When the buffer amount reaches the playback start position, the data in the receive buffer is output to the decoder. When the data output speed is faster than the input speed, the buffer amount decreases. If this is left as it is, an underrun will occur, so the data output speed will be slower than the input speed in response to the amount of nother reaching the lower limit to avoid underrun. If the data output speed is slower than the input speed, the buffer amount increases. If this is left unattended, an overrun occurs, so the output speed of the data is made faster than the input speed in response to the amount of nother reaching the upper limit to avoid overrun. In this way, overruns and underruns are avoided.

Patent Document 1: Japanese Patent Laid-Open No. 2002-165148

Disclosure of the invention

Problems to be solved by the invention

[0007] As described above, in a communication network having jitter in the network, buffering is necessary to prevent the reproduction data from being lost. If the data transmission speed and playback speed are exactly the same, it is common to start playback by buffering an amount of data according to the maximum jitter value before playback starts.

However, when the reproduction speed is faster than the transmission speed due to clock shift, the buffer amount decreases in the long run. In fact, the buffer amount decrease due to the clock shift is very small compared to the buffer fluctuation due to the network jitter, so it is difficult to detect the clock shift within the range where the buffer amount moves with the network jitter increase / decrease.

On the other hand, the state of the network suddenly deteriorates locally due to various factors, and the arrival of a packet. The arrival may be delayed (= jitter becomes large), and if data is buffered only for the jitter of the network by the time playback starts, the amount of data that has been reduced due to clock deviation + reduced by the jitter of the network However, the amount of data will be lost from the buffer, resulting in an underrun. Therefore, in order to avoid the occurrence of underrun, it is generally necessary to buffer a larger amount of data before starting playback so that underrun does not occur due to clock misalignment. Then, as shown in Fig. 20, the required buffer amount is double that when there is no clock shift.

[0010] Therefore, in the conventional technique, there is a problem that a long buffering is required before the reproduction is started, and the response to the user operation is bad.

[0011] In addition, a large-capacity buffer for buffering is required, which increases the cost.

[0012] Therefore, a main object of the present invention is to provide a receiving apparatus, a receiving program, and a recording medium on which the receiving program is recorded, capable of reducing the amount of data stored before starting reproduction. .

Means for solving the problem

[0013] A receiving device according to the present invention is a receiving device that receives data transmitted from a transmitting device via a communication network, and includes a data storage unit that sequentially stores received data, and a data storage unit. The data output means for sequentially taking out the data accumulated in the data accumulating means and the data accumulating means increase in response to the accumulated data amount exceeding a predetermined first reference value. When the data output speed of the data output means is set to a predetermined speed and the data amount of the data storage means exceeds a predetermined second reference value higher than the first reference value, And a control means for increasing the data extraction speed of the data output means by time.

[0014] Further, a reception program according to the present invention is a reception program for causing a computer to execute a reception method in a reception apparatus that receives data transmitted from a transmission apparatus via a communication network, and that receives the received data. The first step of sequential storage in the device buffer and the amount of data stored in the buffer exceeded a predetermined first reference value. In response to the second step of sequentially extracting the data stored in the buffer, the data extraction speed in the second step is set to a predetermined speed so that the amount of data of the buffer increases. When the value exceeds a predetermined second reference value higher than the first reference value, the third step of increasing the data extraction speed of the second step for a predetermined time is executed.

[0015] Further, a computer-readable recording medium according to the present invention records the above reception program.

The invention's effect

[0016] In the receiving apparatus and the receiving program according to the present invention, the data extraction speed is set to a predetermined speed so as to increase the data accumulation amount. Therefore, if data is accumulated by absorbing the jitter of the communication network. It ’s enough. Therefore, the amount of data stored before the start of playback can be reduced compared to the conventional case of storing the amount of data necessary to avoid underrun due to jitter and clock shift in the communication network. Therefore, since the data accumulation time before the start of reproduction can be shortened, the response to the user's operation becomes faster. In addition, since the data storage capacity is small, low cost can be achieved.

[0017] In addition, when the data accumulation amount exceeds the second reference value, the data retrieval speed is increased for a predetermined time. Therefore, even when the data accumulation amount fluctuates greatly due to the influence of jitter, the data retrieval speed is frequently increased. There is no need to control.

Brief Description of Drawings

FIG. 1 is a block diagram showing a configuration of a network system according to an embodiment of the present invention.

2 is a block diagram showing a configuration of a transmission device and a reception device shown in FIG.

3 is a diagram for explaining the operation of the processing means shown in FIG. 2.

4 is a block diagram for explaining the operation of the reception processing unit shown in FIG. 2.

FIG. 5 is a flowchart showing data reception processing shown in FIG.

FIG. 6 is a diagram showing a notor included in the data storage means shown in FIG. 4.

7 is a flowchart showing the buffering process shown in FIG.

8 is a flowchart showing the data output process shown in FIG. FIG. 9 is a part of a flowchart showing a clock count process shown in FIG. 4.

FIG. 10 is the remaining part of the flowchart shown in FIG.

FIG. 11 is a time chart for explaining a method of calculating a correction end time shown in FIG.

FIG. 12 is another time chart for explaining a method of calculating the correction end time shown in FIG.

FIG. 13 is a time chart illustrating the operation of the receiving apparatus shown in FIGS.

FIG. 14 is another time chart illustrating the operation of the receiving apparatus shown in FIGS.

FIG. 15 is a time chart illustrating the operation of a receiving device as a comparative example.

FIG. 16 is a diagram showing a modification of this embodiment.

FIG. 17 is a block diagram showing a configuration of a conventional network system.

FIG. 18 is a block diagram showing a configuration of another conventional network system.

FIG. 19 is a time chart illustrating the buffer amount of the reception buffer shown in FIG.

FIG. 20 is a time chart for explaining problems of the network system shown in FIG.

Explanation of symbols

[0019] 1, 51 transmitting device, 2, 30, 52, 53 receiving device, 3 communication network, 4, 5 device, 1 1 encoder, 12, 25, 29 clock generating means, 13 encoding means, 14 transmission processing unit , 15 processing means, 16, 22 network connection means, 21 reception processing section, 23 data storage means, 24 data output means, 26 counting means, 27 decoder, 28 decoding means, 31 computer main body, 32 display device, 33 FD drive , 34 FD, 35 keyboard, 36 mouse, 37 CD-ROM device, 38 CD-ROM, 39 Network communication device.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a network system according to an embodiment of the present invention will be described. In this embodiment, in real-time communication via a communication network with large delay variation, the time from the start of communication to the start of playback is shortened.

In the present embodiment, the present invention passes through an IP (Internet Protocol) network. Next, an example applied to MPEG2 real-time stream transmission using RTP (Real Time Protocol) is described. However, the present invention is not limited to this.

FIG. 1 is a block diagram showing a configuration of a network system according to an embodiment of the present invention. This network system is a network to which various household devices such as a television, a hard disk recorder (hereinafter referred to as HDR), and a digital tuner are connected. In this network system, for example, communication is performed using a network protocol such as IP (Internet Protocol).

[0023] The transmission device 1 is a real-time data transmission device that performs real-time stream transmission with a reception device (for example, a television) 2, and is, for example, a video, HDR, digital tuner, or the like having a communication function. The transmission device 1 is connected to the reception device 2 via the communication network 3. Devices 4 and 5 are other devices connected to the communication network 3.

FIG. 2 is a block diagram showing configurations of the transmission device 1 and the reception device 2. In FIG. 2, the transmission device 1 includes an encoder 11 and a transmission processing unit 14, and the reception device 2 includes a reception processing unit 21 and a decoder 27.

The encoder 11 is a coding device that performs coding on a predetermined input according to a coding rule defined by MPEG2 and outputs MPEG2 data. The encoder 11 includes clock generation means 12 that generates a clock signal that serves as a reference for the time of the encoder 11, and code key means 13 that performs data sign synchronization in synchronization with the clock signal.

[0026] The transmission processing unit 14 includes a processing unit 15 and a network connection unit 16, and converts the data output from the encoder 11 into a format that can be transmitted on the network 3, and outputs the data to the network 3. The processing means 15 adds the RTP header, TCP header, and IP header to the MPEG2 data output from the encoder 11, as shown in FIG. The RTP header includes a sequence number, a time stamp, and the like. As a result, MPEG-2 data can be transmitted over the IP network. Returning to FIG. 2, the network connection means 16 outputs the IP packet generated by the processing means 15 to the communication network 3, and is, for example, an Ethernet (registered trademark) card.

Next, the receiving device 2 will be described. The receiving device 2 receives real-time stream data from the transmitting device 1, and is, for example, a television or a liquid crystal equipped with a communication function. Such as a projector. The reception device 2 includes a reception processing unit 21 that receives data transmitted from the network 3 and a decoder 27 that decodes the received data. The reception processing unit 21 includes a network connection unit 22, a data storage unit 23, a data output unit 24, a clock generation unit 25 and a count unit 26, and the decoder 27 includes a decoding unit 28 and a clock generation unit 29.

[0028] The network connection means 22 is for connecting the receiving device 2 and the communication network 3, and is, for example, an Ethernet (registered trademark) card. The data transmitted from the transmission device 1 is received by the network connection means 22. The data storage means 23 includes a buffer for temporarily storing the data received by the network connection means 22 before outputting it to the decoder 27, and a control processing function for controlling the buffer.

The data output means 24 outputs the data stored in the data storage means 23 to the decoder 27 based on the count value counted by the count means 26 and the time information included in the received data.

The clock generation means 25 generates a clock signal used as a reference for determining the output time to the decoder 27. The counting means 26 counts the number of pulses of the clock signal generated by the clock generating means 25 and provides the data output means 24 with a count value adjusted according to a predetermined rule.

The decoding unit 28 performs decoding of the data (MPEG2) output from the data output unit 24. The clock generation means 29 generates time information included in the output data and timing power at which the data is input, and also generates a clock signal for reproducing the received data, and sends the clock signal to the decoding means 28. give.

Next, a detailed operation when the receiving device 2 receives real-time data will be described. As shown in FIG. 4, each means of the reception processing unit 21 has a processing function for causing each means to function therein, and the reception processing is realized by operating in cooperation with each other. The

[0033] When the reception processing unit 21 is activated, data reception processing is activated in the data storage means 23, clock count processing is activated in the counting means 26, and buffering processing is performed in the data output means 24. It is activated. Data reception processing and clock count processing The buffering process is always executed, and the data output process is started and terminated when a predetermined condition is met. The reception processing unit 21 includes a CPU (Central Processing Unit) and a recording medium. The recording medium stores a program for causing the CPU to execute the above processes. The CPU reads the recording medium power program and executes each process.

FIG. 5 is a flowchart showing data reception processing of the data storage means 23. When the data reception process is activated, in step S1, the data storage means 23 determines whether or not it has received a packet from the network connection means 22 (S1), and if received (YES in S1), proceeds to the next step S2. move on. If not received (NO in S1), the determination process in step S1 is performed again. The determination process in step S1 is continued until a packet is received. In step S2, the received packet data is written into the storage buffer.

[0035] As shown in FIG. 6, the data is written into the designated write position (buffer_tail) of the buffer, and is read out by the designated read position (buffer_head) of the buffer. Returning to FIG. 5, when the data writing is completed, the process proceeds to step S3. In step S3, the buffer write position (buffer_tail) is advanced by one, and the RTP header time stamp value of the received packet is written to the variable ta_rtp_ts. When step S3 ends, the process returns to step S1 and a series of processing is repeated.

FIG. 7 is a flowchart showing the buffering process of the data output means 24. When the buffering process is started, in step S11, the data output means 24 determines whether or not the power confirmation that the data of the first packet is written in the buffer in the data storage means 23 is still available. To do. If the data of the first packet has been written to the buffer but has not yet been confirmed, the current count value COUNT obtained from the counting means 26 is written to the variable fr_rtp_ti (reception time of the first packet) (S 12), The time stamp value included in the RTP header of the first packet is written to the variable fr_rtp_ts and the variable he_rtp_ts (time stamp value of the first packet in the buffer) (S13), and the output start time start_ti is calculated (S14).

[0037] The output start time start_ti is set after a predetermined time MAX_SAVE has elapsed since the first packet was received. MAX_SAVE is normally set to the maximum jitter time expected on the network. For example, 300 msec. NO in step S11 If the process of step S14 is completed, the process proceeds to step S15. In step S15, when the count value COUNT obtained from the counting means 26 exceeds the output start time start_ti, the buffering process is terminated and the process proceeds to data output process.If the output start time start_ti is not reached, the process returns to step S11 Repeat a series of processes. Once the processing from step S12 to step S14 is completed, the confirmation of the first packet is completed, so the determination processing in step S11 is always NO.

FIG. 8 is a flowchart showing the data output process of the data output means 24. When the data output process is started, in step S21, the data output means 24 takes out the head position of the noffer (packet at the position of buffer_head) from the buffer. Next, the RTP time stamp of the extracted packet is compared with the count value COUNT acquired from the counting means 26 to confirm whether or not the extracted packet has reached the output start time starUi (S22).

[0039] When the output start time start_ti is reached (YES in S22), the extracted packet is written to the decoder 27 (S23). If the output start time start_ti is not reached, the process of step S22 is performed until the output start time starUi is reached. repeat. When the packet is written to the decoder 27, the reading position (buffer_head) from the buffer is incremented, and the time stamp value of the data of the first packet is written to the variable he_rtp_ts (S24).

[0040] When the processing in step S24 is completed, it is determined in step S25 whether or not the buffer correction operation is in progress, that is, whether or not the flag BUF_REVISE force STRUE. If the flag BUF_REVISE is TRUE! /, The count up speed is increased more than usual in order to prevent the buffer overrun in the clock counting process of the counting means 26 !. If BUF_REVISE force is TRUE (YES in S25), the process returns to step S21, and if FALSE (NO in S25), it is determined whether the amount of koffer exceeds a predetermined threshold (ADJUST_BORDER). Here, the buffer amount is calculated by subtracting the time stamp value he_rtp_ts of the first packet of the buffer from the time stamp value (ta_rtp_ts) of the last packet of the buffer. If the buffer amount exceeds the predetermined threshold (YES in S26), buffer correction is started by setting BUF_REVISE to TRUE in step S27. If not exceeded (FALSE in S26), go back to step S21. FIG. 9 and FIG. 10 are flowcharts showing the clock count processing of the counting means 26. When the clock count process is started, the count unit 26 acquires the pulse of the reference clock signal from the clock generation unit 25 in step S31. When the reference clock signal pulse is obtained, the variable CO for counting the number of pulses of the reference clock signal is incremented in step S32.

Next, the flag BUF_REVISE is checked to determine whether or not the buffer correction process is in operation (S33). If the flag BUF_REVISE is FALSE (NO in S33), the correction to avoid overrun is not performed and the adjustment amount totaLadjust per unit time for the reference clock count value CO is set to S_ADJUST. (S34).

This correction is performed to prevent a buffer underrun from occurring in the data storage means 23 after the output from the data output means 24 is started. S_ADJUST is a value calculated based on the error range between the clock generator 12 of the transmitter 1 and the clock generator 25 of the reception processor 21 of the receiver 2. The count-up speed of the count value COUNT is adjusted so as to be slower than the count-up speed of the count value obtained by the output of the clock generation means 12 of the transmitter 1. For example, if the operation clock of the clock generator 12 of the transmitter 1 is 27 MHz ± 30 ppm specified in the MPEG2 specification, and the clock generator 25 of the reception processor 21 of the receiver 2 is also the same 27 MHz ± 30 ppm, S_ADJUST = 1620 or more must be set. After step S34 ends, the process proceeds to step S38.

[0044] On the other hand, if the BUF_REVISE force is TRUE (YES in S33), correction to avoid overrun is required. First, in step S35, it is determined whether or not the variable end_adjust indicating the correction end time is zero. If end_adjust is zero, it is determined that the buffer amount needs to be corrected in step S26 of the data output process immediately before this step is executed, and the correction end time is determined from the current buffer status. Set to end_adjust (S36).

The correction end time is calculated as follows, for example. As shown in Fig. 11, assuming that the correction duration is t and the change in the output speed from the buffer accompanying the change in the clock increase speed is Δ 増加, the increase in the output amount compared to the case without correction D Is given by D = AV X t It is done. Since the amount of change in the clock count per unit time during correction is B_ADJUST, AV = B_ADUST X (number of bytes per time stamp) can be set.

[0046] On the other hand, the number of bytes of data remaining in the buffer can be calculated by (ta_rtp_ts he_rtp_ts) X (number of bytes per time stamp). It is sufficient to leave enough data to absorb the data, that is, MAX_SAVE worth of data. In other words, as shown in Figure 12, Dmax = (ta_rtp_ts-he_rtp_ts MAX.SAVE) X (number of bytes per time stamp) data can be reduced from the buffer.

[0047] Here, when the increase D in the output data amount due to correction becomes Dmax, the maximum correction duration t is obtained. From AVXt = D, the correction duration t = DmaxZ AV is set to Get. The correction end time is calculated by adding t obtained in this way to the current time.

[0048] If YES is determined in step S35, or if the end time is set in step S36, the adjustment amount totaLadjust per unit time for the reference clock count CO is set to S_ADJUST—B_ADJUST in step S37. .

[0049] Thereby, the count-up speed of the count value COUNT counted by the counting means 26 is adjusted so as to be faster than the count-up speed of the count value obtained by the output of the clock generating means 12 of the transmitter 1. The For example, if the operation clock of the clock generation means 12 of the transmission device 1 is 27 MHz ± 30 ppm specified in the MPEG2 specification, and the clock generation means 25 of the reception processing unit 21 of the reception device 2 is also the same 27 MHz ± 30 ppm, B_A DJUST = 3240 must be set.

[0050] Next, in step S38, a period T for correcting the clock is calculated. The period T is obtained by dividing the count number K per second counted by the reference clock by the clock adjustment number t otaLadjust per second (T = K / total_adjust). In step S39, it is determined whether the remainder obtained by dividing the reference clock count value CO by the period T is zero or not. If it is not zero, it is counted without correction in step S40 (COUNT = COUNT + l ), If it is not, go to step S41.

[0051] In step S41, it is determined whether or not the clock speed is increased or decreased, that is, whether T> 0. If T> 0 is not satisfied, the clock is advanced faster than usual in step S42 (COUNT = COUNT + 2), and the process proceeds to step S43. If T> 0, the process proceeds to step S43.

[0052] In step S43, it is determined whether the correction end time is reached (COUNT> end_adjust and BUF_REVISE = TRUE). If it is not the correction end time, the process returns to step S31, and if it is the correction end time, step S44 is performed. To complete the correction (end_adjust = 0, BUF_REVISE = FALSE) and return to step S31.

FIG. 13 is a time chart illustrating an example of a change in the buffer amount of the reception buffer included in the data storage unit 23. In FIG. 13, when buffering of received data is started, the buffer amount of the receive buffer increases at a constant rate. When the buffer amount reaches the playback start position, the data in the receive buffer is output to the decoder 27. The playback start position is lower than before.

The data output speed is always set slower than the data input speed. Therefore, the buffer amount increases. If this is left unattended, an overrun occurs, so the data output speed is increased by a predetermined time according to the fact that the amount of koffa has reached the upper limit for avoiding overrun. As a result, the amount of koffa decreases. In this way, the amount of koffa is maintained near the upper limit.

FIG. 14 is a diagram showing a temporal change in the number of packets output from the data output means 24 to the decoder 27 per unit time (1 second). FIG. 15 shows the time variation of the number of packets output to the reception buffer power decoder per unit time (1 second) in the conventional receiving apparatus shown in FIG. 18 and FIG. 19 as a comparative example. FIG.

In FIG. 14 and FIG. 15, MPEG2-TS packets are used as packets, the content bit rate is 24 Mbps, the maximum frequency Fmax is 27 MHz + 1620 Hz, and the minimum frequency Fmin is 27 MHz-1620 Hz. In Fig. 14, the initial buffering amount is 2.4 Mbit, and the upper threshold of the buffering amount is 2.88 Mbit. In Fig. 15, the upper threshold of the buffering amount is 4.8 Mbit, and the lower limit of the buffering amount is 2.4 Mbit.

[0057] The number of packets per second S is S = (original frequency) Z (frequency used for output) X (content bit rate) Z (number of bytes per packet) Z8. Therefore, 1 second The maximum value Smax of S is Smax = 27 (MHz) / Fmin X 24 (Mbps) / 1 88 (byte) Z8 (bit) = 133868 (number of Z seconds). The minimum value Smin of the number of packets S per second is Smin = 27 (MHz) / Fmax X 24 (Mbps) / 188 (byte) / 8 (bit) = 133854 (number of Z seconds).

[0058] In FIG. 14, the period T1 at which the number of packets increases or decreases is Tl = {[(upper threshold) (initial amount of noffering)] Ζ2} Ζ (content bit rate) Z (l Deviation of time per second) X 2 = 0.24 (Mbit) Ζ 24 (Mbps) Ζ 60 s) X 2 = 333 (s). In Fig. 15, the period T2 when the number of packets increases or decreases is T2 = {(upper threshold) (lower threshold)} Ζ (content bit rate) Z (time per second) Deviation) X 2 = 2.4 (Mbit) / 24 (Mbps) / 60 (s) X 2 = 3333 (s).

Therefore, in the present invention, the output number S of packets per unit time is switched from the maximum value Smax to the minimum value Smin or from the minimum value Smin to the maximum value Smax in units of several minutes, whereas in the conventional technology, Switch in sufficient units. This means that the present invention controls the buffering amount in small increments in order to reduce the buffering amount as compared with the prior art.

[0060] When comparing the prior art and the present invention, the total buffering amount of the present invention is smaller than that of the prior art. The time until the start of reproduction is shorter in the present invention than in the prior art. In the prior art, the packet output speed at the start of playback is not particularly determined, whereas in the present invention, the packet output speed at the start of playback is determined to be the minimum value Smin. The period for switching the packet output speed is shorter in the present invention than in the prior art. The threshold of the upper limit of the buffering amount when switching the packet output speed is lower in the present invention than in the prior art. The present invention is different from the prior art in these points.

[0061] In the present embodiment, the output speed is controlled by correcting the count value obtained by the clock signal power having a constant frequency generated by the clock generating means 25. For example, VCO (voltage An example of controlling the output speed by changing the operating frequency of the clock generating means 25 using a controlled oscillator) is also conceivable.

[0062] In the present embodiment, the correction value per unit time is set for execution of the correction process. Although the example of fixing and calculating the duration of correction has been shown, an example in which the correction time is fixed and the correction value is varied is also conceivable.

[0063] In the present embodiment, the receiving device 2 is exemplified as a television. However, for example, the receiving device 2 may be configured as a communication control circuit built in the television, or may be configured separately from the television. It may be configured as a device.

FIG. 16 is a diagram showing an external appearance of such a receiving device 30. In FIG. 16, the receiving device 30 includes a computer main body 31, a display device 32, an FD drive 33 on which an FD (Flexible Disk) 34 is mounted, a keyboard 35, a mouse 36, a CD-ROM (Compact Disk-Read Only Memory). ) Includes CD-ROM device 37 on which 38 is installed, and network communication device 39. A program for realizing the function of the receiving device 30 (hereinafter referred to as a receiving program) is supplied by a recording medium such as the FD 34 or the CD-ROM 38. When the reception program is executed by the computer main body 31, the above-described reception operation is executed. The reception program may be supplied to the computer main body 31 from another computer via the communication line and the network communication device 39.

[0065] In addition, the reception method performed in the above-described reception device 30 can be provided as a program. Such a program can be recorded on a computer-readable recording medium such as the FD 34 or CD-ROM 38 attached to the computer main body 31 and provided as a program product. Alternatively, the program can be provided by being recorded on a recording medium such as a hard disk built in the computer main body 31. The program can also be provided by downloading via a network.

[0066] The provided program product is installed in a program storage unit such as a hard disk and executed. The program product includes the program itself and a recording medium on which the program is recorded. The recording media are not limited to FD34 and CD-ROM38. Magnetic tape, MO (Magnetic Optical disk), MD (Mini Disk), DVD (Digital Versatile Disk), IC (Integrated Circuit) cards, etc. There may be.

[0067] The embodiments disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims, and includes meanings equivalent to the scope of claims and all modifications within the scope. Intended.

Claims

The scope of the claims

[1] A receiving device (2) for receiving data transmitted from a transmitting device (1) via a communication network (3),

Data storage means for sequentially storing received data (23),

Data output means (24) for sequentially taking out the data stored in the data storage means (23) in response to the amount of data stored in the data storage means (23) exceeding a predetermined first reference value ),and

The data output speed of the data output means (24) is set to a predetermined speed so that the data amount of the data storage means (23) increases, and the data amount of the data storage means (23) is set to the first value. And a control means (25, 26) for increasing the data output speed of the data output means (24) for a predetermined time when a second predetermined reference value higher than the reference value is exceeded. apparatus.

[2] The receiving device according to claim 1, wherein the first reference value is a data amount necessary to absorb jitter of the communication network (3).

[3] The receiving device according to claim 1, wherein the predetermined speed is set so that a data amount of the data storage means (23) increases in proportion to time.

[4] The receiving device according to claim 1, wherein the data output speed of the data output means (24) increased by the predetermined time is faster than the data transmission speed of the transmitting device (1).

[5] The receiving device according to claim 1, wherein the predetermined time becomes longer according to a difference between a data amount of the data storage means (23) and the first reference value.

[6] The product of the predetermined time and the increase amount of the data output speed of the data output means (24) is equal to the difference between the data amount of the data storage means (23) and the first reference value. The receiving device according to claim 5.

[7] The control means (25, 26)

A clock generating means (25) for generating a clock signal having a predetermined frequency, a counting means (26) for counting the number of pulses of the clock signal and determining a data extraction timing based on the count value;

The count value of the counting means (26) is increased by the predetermined time and the data The receiving device according to claim 1, further comprising: a count value changing means (26) for accelerating the take-out timing.

[8] The predetermined speed is determined based on the data transmission speed error range of the transmission device (1) and the clock signal frequency error range, based on the data storage means (23). The receiving device according to claim 7, wherein the amount is determined to increase.

[9] The control means (25, 26)

The receiving apparatus according to claim 1, further comprising clock changing means (26) for increasing the frequency of the clock signal by the predetermined time to thereby advance the data extraction timing.

[10] The data received by the receiving device (1) includes a time stamp value for each predetermined data unit,

The amount of data stored in the data storage means (23) is determined based on a difference between a time stamp value of the stored first data and a time stamp value of the last data, according to claim 1. Receiver device.

[11] A reception program for causing a computer to execute a reception method in a reception device (2) that receives data transmitted from a transmission device (1) via a communication network (3),

A first step (S11 to S15) for sequentially storing received data in the buffer (23) of the receiver (2);

A second step (S21 to S27) for sequentially taking out the data stored in the buffer (23) in response to the amount of data stored in the buffer (23) exceeding a predetermined first reference value. ),and

The data extraction speed in the second step is set to a predetermined speed so that the data amount of the buffer (23) increases, and the data amount of the buffer (23) is higher than the first reference value A reception program for executing a third step (S31 to S44) for increasing the data extraction speed of the second step for a predetermined time when a predetermined second reference value is exceeded. A computer-readable recording medium on which the receiving program (SI 1 to S15, S21 to S27, S31 to S44) according to claim 11 is recorded.