JP2001244969A - Method and device for receiving data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce received real time data without communication failure even when any reproducing time information is added on the side of transmission. SOLUTION: Communication delay is detected by a communication delay detecting circuit 102. An offset value for controlling the reproducing time of real time data is found by a DSP 300 while counting delay for reception processing in addition to the detected communication delay. The offset value is set to correction registers 103 and 107. The set offset values are respectively added to the received reproducing time data or output value of real time data by adders 205 and 108. Thus, fine adjustment is adaptively applied to the reproducing time of data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data receiving method and a data receiving apparatus, and more particularly, to a data receiving apparatus for receiving real-time data such as a video signal transmitted via a communication network or the like.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for immediately transmitting and reproducing a video (for example, a video shot for live broadcasting or monitoring) to a side receiving information. For example, there are distribution of moving images via a network such as the Internet, and two-way communication in satellite broadcasting.

When transmitting time-series data such as audio data, image data or performance data via a network or the like in real time, signal delays in a transmission path cannot be ignored, and the communication system does not become a completely synchronous communication system. There are cases.

In such a case, in order to guarantee reproducibility on the time axis of transmitted data, reproduction time data (time stamp) indicating a time at which the data is to be reproduced is added to the data itself. Then, the receiving side refers to the time stamp (information indicating the data reproduction time) and reproduces the data when the specified time is reached.

[0005]

In realizing transmission and reception in which reproduction time information (time stamp) is added to data, the reproduction time information includes communication delay, jitter or processing delay on the receiving side of a wired or wireless medium. It is necessary to determine in consideration of the buffer capacity and the like.

In reality, it is difficult for the transmitting side to predict these in advance, and after all, if the transmission delay in the communication medium and the processing delay on the receiving side are taken into account, the time until reproduction must be made sufficiently long. Absent.

However, in this case, the capacity of the data buffer on the receiving side becomes insufficient, and an overflow may occur. Conversely, if the time until playback is set to a small value, a delay in the receiving process on the receiving side, etc.
There is also a possibility that the playback time has passed halfway and the received data is regarded as a past time and cannot be played back.

The present invention has been made in view of such considerations, and it has become possible to reproduce received data without causing communication failure, regardless of what reproduction time information is added by the transmitting side. The purpose is to do.

[0009]

According to the present invention, a delay of a transmission line is detected on the receiving side, and the detection result is taken into consideration.
The reproduction time data (reproduction time information) or the value of the timer on the receiving side is corrected. On the receiving side, the reproduction time is adaptively fine-tuned in consideration of the transmission delay (further, the delay of the reception processing, etc.), so that whatever the reproduction time information is added by the transmitting side, the communication is broken. It is possible to reproduce the received data without the need.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One aspect of the present invention is a receiving unit for normal packet reception, a communication delay detecting circuit for detecting a network delay time of a communication medium, a value of this value and a processing delay of a receiver. Register for storing correction data in consideration of the above, an adder for adding the correction data, a reception buffer for buffering the reception data until the reproduction time, and a real-time counting real time on the network It includes a timer, a correction register for correcting when the reproduction time data added to the received data is too large, and a comparator for comparing the reproduction time data with real time until the reproduction time is reached.

The time data to be corrected is large reproduction time data to which received packet data is added so as to exceed the communication delay and jitter of the wired / wireless medium, the processing delay on the receiving side, and the buffer capacity. The delay and jitter of the communication medium can be obtained by a communication delay detection circuit. This communication delay detection circuit, when receiving a real-time packet from any device on the network,
The time lag is detected by comparing with the value of the real-time timer. The detected shift amount is used to determine the value of each correction register.

When the receiving section receives the packet to which the reproduction time data has been added, the packet header is analyzed, the number of data is counted from the beginning of the packet, and the data of the correction register is added to the packet field having the reproduction time data by the adder. I do. Thereby, even when the reproduction time data is smaller than the processing delay on the receiving side, normal reproduction can be performed by setting the value of the correction register to the time lag and the processing delay time on the receiving side. Can be. On the other hand, when the reception rate of the packet data received by the receiving unit is low and the added reproduction time data exceeds the capacity of the reception buffer, an appropriate value is set in the correction register, and the value of the real-time timer is set. By comparing the reproduction time data with the comparator based on the value added by the adder, normal reproduction can be performed.

Next, embodiments of the present invention will be described more specifically with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a data receiving apparatus according to the present embodiment.

As shown in the figure, the data receiving apparatus includes a receiving section 101 and a delay detecting circuit 102 (a subtractor 30).
1), an adder 104 (including an adder 205), a reception buffer 105 (built-in a register 206 for storing reproduction time data), correction registers 103 and 107, and a real-time timer 106. , An adder 108, a comparator 109, and a reproduction processing unit 20.
And 7. The reception buffer 105 is provided to buffer the received data until the reproduction time comes.

A feature of the present embodiment is that a communication delay detecting circuit 102 detects a network transmission delay and, in consideration of the detection result, corrects reproduction time data added to a transmission packet, or In other words, the reproduction time is optimized by correcting the count value of a real timer incorporated in the receiving device.

The correction data is calculated, for example, by the DSP 300 and set in the correction registers 103 and 107. The correction register 103 holds correction data to be added to the reproduction time information (reproduction time information) in order to slightly extend the reproduction time when the value of the data indicating the reproduction time set by the transmission side is too small.

On the other hand, when the value of the data indicating the reproduction time set by the transmitting side is too large, the correction register 107
It holds correction data to be added to the count value of the real-time timer built in the receiving device.

The correction data set in the correction register 103 is added to the reproduction time information by the adder 205. The correction data set in the correction register 107 is added by the adder 108 to the real-time timer 10.
6 is added to the output value.

Hereinafter, the overall configuration and operation of the receiving apparatus shown in FIG. 1 will be described step by step.

The receiving unit 101 has a function of receiving a packet transmitted via the network 10 and a function of detecting reproduction time data added to the received data.

As shown in FIG.
It includes a header analysis unit 201, a reception processing unit 202, a data counter 203, and an error check unit 204.
Header analysis section 201 analyzes the packet header section of the received data packet, and outputs the received data to reception processing section 202.

The received data input to the reception processing unit 202 is counted by a data counter (packet counter) 203 and an error check unit 204 to check whether there is an error in the received data. If there is an error, invalidate the received data.

On the other hand, if the received data is valid,
The following processing is performed. When transmitting real-time data, first, a real-time packet indicating the real time in the system (system) is transmitted, and subsequently, a data packet to which reproduction time data is added is transmitted.

Therefore, in the reception processing unit 202, the real-time data transmitted from the header analysis unit 201 in the form of a real-time packet (this packet is issued every communication cycle) Function as the data indicating the transmission time in), this is sent to the communication delay detection circuit 102.

In the case of transmitted real-time data (communication data to which reproduction time data is added),
The packet field of the real-time data is counted from the beginning of the packet, the position where the reproduction time data is added is detected, and a signal indicating the detected position is supplied to the adding unit 104. Further, it supplies the real-time data (communication data) to the adder 205 in the adder 104.

The communication delay detection circuit 102 uses a built-in subtractor 301 to convert the count value of the real-time timer 106 and the real-time data (data indicating the transmission time on the transmission side) transmitted from the reception processing unit 202. Take the difference from the value. As a result, the time required from transmission to reception,
That is, the delay time of the communication network can be detected.

The real-time timer 106 counts the actual time on the network, and operates on the operating clock of the receiving device. Each device (each receiving device) connected to the network 10 has a built-in real-time timer, and performs its own time counting.

Then, a real-time packet is issued from one device on the network (that is, a transmitting device that performs packet transmission), and when this is received, the time data contained in the received real-time packet is transmitted. Then, the value of the real-time timer of each receiving device is set. In other words, in order to ensure synchronization between the transmission side and the reception side, the system is such that the real timer on the reception side is adapted to the real time on the transmission side.

The communication delay detecting circuit 102 calculates a difference between the value before the real-time timer 106 is set and the value of the real-time data sent from the reception processing unit 202. That is, the real time on the network is stored and compared with the real time on the network before the real time timer built in the receiving device is corrected by the real time packet issued for each communication cycle. Therefore, the transmission delay in the network can be reliably obtained.

The DSP 300 includes a communication delay detection circuit 102
In consideration of the detection result of the above, if the time until the reproduction time set by the transmission side is too short (or the reproduction time has already passed), for example, "+1" is set in the correction register 103, for example. The set correction value is added by the adder 205 of the adder 104 to the reproduction time data added to the transmitted data. At this time, the adding unit 104 determines, based on the detection signal indicating the position of the reproduction time data supplied from the reception processing unit 202,
The reproduction time data position added to the received data is recognized, and correction data is added.

As described above, the correct value is set in the correction register 10.
By writing to 3, the reproduction time can be appropriately delayed by adding an offset value to the reproduction time data. That is, the reception side adds the actual reception processing delay and the communication delay on the network to the reproduction time data added to the real-time data such as the received video and audio signals. Thus, it is possible to ignore a reception processing delay and a communication delay on the network.

When the time until the reproduction time set by the transmission side is too long and the reception buffer 105 overflows, the offset value (for example, "") is set in the correction register 107 so that the reproduction time becomes appropriate. +2 ”) is set.

The reception buffer 105 stores reception data waiting for reproduction, and a register 206 incorporated in the reception buffer 105 stores data indicating the reproduction time (more specifically, data until the reproduction time is reached). Time data) is retained.

The comparator 109 compares the data of the remaining time up to the reproduction time set in the register 206 with the real time counted by the real time timer.

As described above, the fact that the correction value set in the correction register 107 is added to the actual count value of the real-time timer 106 by the adder 108 means that the comparator 109 detects the coincidence by the correction value. Means that the timing of the process is advanced. That is,
Thereby, the reproduction time can be advanced.

When the comparator 109 determines a match, the reproduction processing unit 207 extracts the data waiting for reproduction stored in the reception buffer and starts the reproduction process.

FIG. 2 summarizes the operation of the receiving apparatus according to the present embodiment described above.

That is, first, a communication delay (delay of a transmission line) is detected (step 400), and the validity of the reproduction time designated by the transmission side is determined in consideration of the communication delay and the delay of the signal processing on the reception side. (Step 41
0).

If the reproduction time is proper, the received data is buffered until the reproduction time comes, and when the reproduction time comes, the data reproduction process is started (step 450).

On the other hand, if the playback time is not appropriate, it is determined whether the time until the playback time is too short (step 420). If so, the correction value is replaced with data indicating the playback time (playback time). (Data indicating the time until the time is reached) to extend the reproduction time earlier (step 43).
0).

If it is not determined in step 420 that the time until the reproduction time is short, the time until the reproduction time is too long. Therefore, the correction value is added to the output value of the real-time timer (ie,
Offset correction is performed), and the reproduction is started earlier (step 440).

As described above, by adaptively correcting the reproduction time data or the output value of the real-time timer, it is possible to solve all the problems that occur during the reproduction of the real-time data due to the communication delay and the reception processing delay. it can.

The present invention is not limited to the above embodiment, but can be variously modified and applied. For example, in the above-described embodiment, the appropriateness of the “data specifying the reproduction time” is determined. However, when the transmitting side adds and transmits the “data specifying the time range in which the reproduction is permitted”, Can adaptively correct the permissible time range on the receiving side in consideration of actual delays, reception conditions, and the like.

In the above-described embodiment, the offset value is obtained by the DSP. For example, the offset value is stored in a ROM, the ROM is accessed using the delay time information as an address variable, and the offset value is output. (A look-up table method). Further, it is also possible to divide the actual delay amount for each predetermined range into groups and to apply a uniform offset value to delays belonging to one group.

[0046]

As described above, according to the present invention,
Whatever playback time information is attached by the sender,
The reproduction point can be adaptively changed in consideration of the actual communication delay and the reception processing delay. Thus, normal data reproduction is always ensured in the receiving device without communication failure.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a data receiving device of the present invention.

FIG. 2 is a flowchart showing a characteristic operation of the data receiving apparatus of the present invention.

[Explanation of symbols]

 Reference Signs List 101 reception unit 102 communication delay detection circuit 103 correction register 104 addition unit 105 reception buffer 106 real-time timer 107 correction register 108 adder 109 comparator 110 data reception device 201 header analysis unit 202 reception processing unit 203 data counter 204 error check unit 205 adder 206 Register 207 Reproduction processing unit 300 DSP 301 Subtractor

Claims (6)

[Claims] When receiving data requiring real-time transmission which is transmitted with reproduction time information specifying a reproduction time of data, an actual delay in a transmission path is detected, and the detected communication is performed. In consideration of the delay and the delay associated with the reception processing, the validity of the reproduction time information of the data added by the transmission side is determined, and if it is better to delay the reproduction time, an offset is applied to the received reproduction time information. A data receiving method comprising: performing a correction and, if it is better to advance the reproduction time, performing an offset correction on an output of a real-time timer incorporated in the apparatus. 2. A data receiving apparatus for receiving data that requires real-time characteristics, such as video and audio signals, which is transmitted via a network to which reproduction time information specifying a reproduction time of data is added. Communication delay detecting means for detecting a delay time on the network by comparing the information on the real time on the network sent from the transmitting side with the real time information in the own device; Based on the communication delay detected by the communication delay detecting means and the delay associated with the reception processing, an offset value for correcting the reproduction time of the reception data indicated by the reproduction time information is obtained, and the data reproduction time is adaptively adjusted. And a reproduction time adjusting means. 3. The reproduction time adjustment means includes: first offset correction means for performing offset correction on the reproduction time information; and second offset for performing offset correction on a count value of a built-in real-time timer. 3. The data receiving apparatus according to claim 2, further comprising a correction unit. 4. The first offset correction means has a built-in register for holding the offset value, and performs offset correction by adding the offset value set in the register to the reproduction time information. The data receiving apparatus according to claim 3, wherein the data receiving is performed. 5. The offset correction means includes a register for holding the offset value, and calculates the offset value by performing an operation on the offset value set in the register and the count value of the real-time timer. 4. The data receiving apparatus according to claim 3, wherein the correction is performed. 6. The data receiving apparatus according to claim 2, further comprising means for counting the number of data of the received packet and confirming the validity of the received data. .