JP5441650B2 - Media receiver - Google Patents

Description

  The present invention relates to a media receiver that can synchronize an operation frequency and a reception operation of a transmission side of a media signal.

In recent years, an IP network is relatively inexpensive and can be easily constructed as compared with data transfer using a dedicated line. Therefore, the IP network has been widely developed and the transmission speed has been increased.
Digital broadcasting, video distribution services, surveillance camera systems, etc. require high transmission rates and stable quality when packetizing and transmitting data streams that are multiplexed by encoding video and audio media signals. Conventionally, a transmission system using a dedicated line has been used.
On the other hand, services for transmitting and viewing media signals via an IP network have become widespread due to recent improvements in IP network transmission quality and cost reduction.
In addition, from the viewpoint of interoperability with existing applications that use a dedicated line and reuse of development resources, the IP network media multiplexing employs a method compliant with the MPEG-2 Systems standard to transmit packets. Often configured.

On the other hand, in IP network transmission, various information can be transmitted, but a variety of communication protocols are defined and can be used together. In order to make it easier, the overhead in transmission is also increased, for example, header information is required in each communication protocol layer.
For this reason, in order to improve transmission efficiency, a plurality of media packets are collectively transmitted as one transmission packet. As a result, the timing may change to an output timing different from the timing generated individually as a media packet, resulting in burst transfer.
In addition, transmission delay is not guaranteed in IP network transmission. For this reason, transmission jitter that is not allowed in the MPEG-2 Systems standard also occurs.
Since packet transmission via an IP network has such transmission characteristics, there is a drawback that it is difficult to match the operating frequency between the media transmission device and the media reception device.

Therefore, conventionally, transmission / reception is performed by comparing the transmission time counter value added to the transmission packet on the transmission side with the time counter value on the reception side, or by monitoring the remaining amount transition in the packet reception buffer on the reception side. A technique for correcting the operating frequency of the media receiving device by calculating the operating frequency difference between them is disclosed.
However, if there is a bias in the arrival timing of the transmission packet, or if the media packet to be transmitted is transmitted at irregular intervals, that is, the amount of media information generated is irregular, On the side, the remaining amount of the packet staying in the packet reception buffer does not transit to a constant value, and there is a problem that it is not possible to calculate an accurate operation frequency difference between transmission and reception.

  For example, in the receiving devices disclosed in Patent Document 1 and Patent Document 2, a media packet is stored in a buffer called a fluctuation absorbing buffer or a dejittering buffer, and a time counter value in the received transmission packet and its own time counter value are stored. The difference in operating frequency between the transmission and reception is calculated, and the own time counter value or the operating frequency is corrected based on the difference in operating frequency. As a result, the timing of transmitting the media packet to the media decoding processing unit included in the device is adjusted.

  In IP network transmission, transmission paths and transmission processing are not uniform, and therefore transmission delays are not constant. In Patent Document 1, in order to compensate for transmission fluctuations caused by this, the transmission time count extracted from the transmission packet is normalized with its own time counter value at the start of reception in the fluctuation absorption calculation, or for a certain period of time. Minute transmission time counter values are averaged by the square error estimation method.

  Further, in Patent Document 2, when the difference between the transmission time counter value extracted from the received transmission packet and the time counter value of the receiving device itself is significantly different from other timings, it is determined that the reception timing is abnormal. By excluding from the calculation target of the operating frequency difference, a significant fluctuation in transmission delay peculiar to IP network transmission is eliminated.

JP 2008-118549 A JP 2003-258894 A

When media packets are actually stored in transmission packets and transmitted, a plurality of media packets are stored in the transmission packets. In this case, since it is in a state like so-called burst transfer, the transmission time counter value assigned to the media packet and the time counter value of the receiving apparatus itself do not necessarily satisfy a certain relationship.
Accordingly, since a large jitter occurs in the difference between the time counter value on the transmission side and the time counter value on the reception side, an error tends to occur in the calculation of the operating frequency difference between the media transmission device and the media reception device.

In order to solve this problem, it is also possible to apply a technique for smoothing a time counter value for a certain period as in Patent Document 1 or a technique for eliminating a time counter value that has changed extremely as in Patent Document 2. It is done.
However, the fluctuations that occur in IP network transmission are large, and the absorption contributes to a high-cost structure.
Further, when the amount of media packets generated is not constant, the buffer transition itself is not constant. For this reason, as in Patent Documents 1 and 2, in the technique of monitoring the buffer state and controlling clock recovery using all received packets, the time of each transmission time counter value included in a plurality of media packets is determined. There is a problem that the correspondence between the transition and the temporal transition of the time counter value of the receiving apparatus cannot be accurately grasped, and it is difficult to completely absorb jitter.

  The present invention has been made to solve the above-described problems. Even when transmission fluctuations caused by IP network transmission and the transmission interval of media packets are not constant, the operating frequency difference with the transmission apparatus is reduced. It is an object of the present invention to obtain a media receiving apparatus that can accurately calculate and properly synchronize its own time counter value with the time counter value on the transmission side.

A media receiving apparatus according to the present invention includes a transmission packet receiving unit that receives a transmission packet transmitted from a media transmitting apparatus, an operating frequency that is an operation reference of the own apparatus, and a time counter generation that generates a time counter value synchronized with the operating frequency. And the time counter value at the time when the transmission packet is received by the transmission packet reception unit from the time counter generation unit as the reception time counter value, and from the plurality of media packets stored in the transmission packet, the media transmission device The media time counted corresponding to the operating frequency of the media transmitting apparatus involved in the generation of the encoded media information stored in the media packet, for each of the transmission time counter values indicating the transmission timing of the media packet If a counter value is assigned, the media A time counter value extraction unit for extracting a time counter value, and a transmission time counter value, a reception time counter value, and a media time counter obtained by the time counter value extraction unit for transmission packets sequentially received by the transmission packet reception unit A time counter value accumulation unit that sequentially stores values, and a time transition amount of each value in the transmission time counter value, reception time counter value, and media time counter value stored in the time counter value accumulation unit is converted into a frequency difference, Based on the operating frequency difference calculated by the inter-transmission / reception operating frequency difference calculator, the operating frequency of the media transmitting device is calculated based on the operating frequency difference calculated by the operating frequency difference calculator. An operation frequency control unit that corrects the generation of the operation frequency by the time counter generation unit so as to match, The counter value extraction unit holds the media time counter value and the transmission time counter value extracted from the media packet to which the media time counter value is assigned, and is the latest among the plurality of media packets stored in the transmission packet. A value obtained by adding the difference value between the transmission time counter value of the generated media packet and the transmission time counter value extracted from the media packet to which the media time counter value is assigned to the media time counter value is calculated as a virtual value for the transmission packet. As a media time counter value, a difference value of a reception time counter value of each transmission packet received continuously in time from a reception time counter value stored in a time counter value accumulation unit is a predetermined value. A reception time counter value exceeding the threshold is detected, and the detected reception time counter value A selection unit that selects a virtual media time counter value of a transmission packet corresponding to the transmission packet from the time counter value accumulation unit, and the operating frequency difference calculation unit between transmission and reception is a virtual media time counter value selected by the selection unit And the time transition amount of each value of the transmission packet reception time counter value is converted into a frequency difference to calculate an operating frequency difference between transmission and reception.

According to this invention, the time counter value extraction unit holds the media time counter value and the transmission time counter value extracted from the media packet to which the media time counter value is assigned, and stores a plurality of times stored in the transmission packet. A value obtained by adding, to the media time counter value, a difference value between the transmission time counter value of the media packet generated most recently and the transmission time counter value extracted from the media packet to which the media time counter value is assigned. As a virtual media time counter value for the transmission packet, and from the reception time counter value stored in the time counter value accumulation unit, the reception time counter of each transmission packet received continuously in time Detected the reception time counter value where the difference value of the value exceeds a predetermined threshold, and detected A selection unit that selects a transmission time counter value and a virtual media time counter value of a transmission packet corresponding to the transmission time counter value from the time counter value accumulation unit, and the operating frequency difference calculation unit between transmission and reception is a virtual unit selected by the selection unit. The amount of time transition between each of the media time counter value and the reception time counter value of the transmission packet is converted into a frequency difference to calculate an operating frequency difference between transmission and reception.
With this configuration, in order to increase transmission efficiency, a plurality of media packets are stored and transmitted in one transmission packet, and even if the transmission interval and TS rate of media packets are not constant, the operation between transmission and reception is performed. It is possible to appropriately select a packet to be used for calculating the frequency difference, and it is possible to extract a time transition equivalent to the time interval at which the media packet is generated and output by the media transmission device. As a result, there is an effect that it is possible to realize a media receiving apparatus with good reception quality by synchronizing the operating frequency between transmission and reception with high accuracy even for packet transmission via the IP network.

It is a block diagram which shows the structure of the media receiver by Embodiment 1 of this invention, and its peripheral device. It is a figure which shows the structure of the network packet handled by this invention. It is a block diagram which shows the structure of the time counter value extraction part of FIG. It is a figure which shows an example of the structure of a media packet. It is a figure which shows the relationship of each time counter value with respect to a transmission packet and a media packet. It is a figure which shows the relationship between the transmission time counter value with respect to a media packet, and a reception time counter value. It is a flowchart which shows the flow of the calculation process of the virtual MCT value by a time counter value extraction part. It is a figure which shows an example of the time counter value which the time counter value extraction part 9 handled by this invention calculated. It is a block diagram which shows the structure of the peak packet selection part of the media receiver by Embodiment 2 of this invention. It is a figure which shows an example of the relationship between the transmission packet used as the isolation | separation object in a network packet, and another transmission packet. It is a figure which shows an example of the relationship between a reception time counter value and a media time counter value. It is a figure which shows an example of the relationship between a reception time counter value and the difference value of an adjacent reception time counter value. It is a block diagram which shows the structure of the media receiver by Embodiment 3 of this invention, and its peripheral device.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing the configuration of a media receiving apparatus and its peripheral devices according to Embodiment 1 of the present invention. In FIG. 1, a media transmission device 1 is a device that receives media information such as video, audio, and data, encodes them, packetizes them, and outputs them to an IP network. The media receiver 3 according to Embodiment 1 receives a network packet 2 including encoded media information transmitted via an IP network, and separates media information such as video, audio, and data from the network packet 2. Decrypt. The video display device 4 is a device that displays video media among the media information decoded by the media reception device 3. The audio reproduction device 5 is an apparatus that reproduces audio media among the media information decoded by the media reception device 3.

Further, the media receiver 3 includes, as an internal configuration, a time counter generation unit 6, a transmission packet reception unit 7, a time counter value extraction unit 9, a media packet transmission unit 11, a media separation / decoding unit 13, and an MCT / RCT value accumulation unit. (Time counter value accumulation unit) 16, peak packet selection unit 18, operating frequency difference calculation unit 20 between transmission and reception, and operation frequency control unit 22.
The time counter generation unit 6 is a configuration unit that generates a clock signal and a time counter value that are the operation reference of the media reception device 3. The transmission packet receiving unit 7 is a component that receives the network packet 2 output from the media transmission device 1 through communication connection with the IP network. Further, the transmission packet receiving unit 7 extracts the transmission packet 8 from the network packet 2.

  The time counter value extraction unit 9 inputs a real time time counter value 14 at the time when the transmission packet reception unit 7 receives the transmission packet 8 from the time counter generation unit 6 as a reception time counter value (hereinafter referred to as RCT value as appropriate). At the same time, the media packet 10 is extracted from the transmission packet 8 and the transmission time counter value (hereinafter referred to as SCT value) and media time counter value (hereinafter referred to as MCT value) given to the media header information are described as appropriate. ).

The MCT value is a time counter value counted corresponding to the operating frequency of the media transmitting apparatus 1 related to the generation of the encoded media information, and is a reference for reproducing the operating frequency related to the generation of the encoded media information. The media receiver 3 refers to the value indicating the time.
The SCT value is a time counter value indicating the transmission timing of the media packet 10 transmitted from the media transmitting apparatus 1, and is a time counter value counted at the same frequency as the MCT value.

In addition, the time counter value extraction unit 9 calculates the difference between the SCT value assigned to each transmission packet 8 received by the transmission packet reception unit 7 and the SCT value assigned to the media packet 10 having the MCT value, A virtual MCT value (hereinafter referred to as a virtual MCT value as appropriate) for the newest media packet 10 stored in the transmission packet 8 is calculated.
Transmission packet time information 15 including the virtual MCT value and the RCT value at the time when the transmission packet 8 is received is output from the time counter value extraction unit 9 to the MCT / RCT value accumulation unit 16.

  The media packet transmission unit 11 is a component that temporarily stores the media packet 10 and controls the output timing of the decoding target media packet 12 according to the SCT value of each media packet. The media separation / decoding unit 13 is a configuration unit that separates and decodes encoded media information from the decoding target media packet 12 and outputs media signals such as video, audio, and data.

The MCT / RCT value accumulation unit 16 is a storage unit that sequentially inputs and accumulates transmission packet time information 15 output from the time counter value extraction unit 9.
The peak packet selection unit 18 calculates the transmission / reception operating frequency difference from the selection target transmission packet time information 17 including the combination of the MCT value to be selected and the RCT value read from the MCT / RCT value accumulation unit 16. It is a structure part which selects the time information to be used. The time information selected by the peak packet selection unit 18 is output to the operating frequency difference calculation unit 20 between transmission and reception as operation target transmission packet time information 19.

The transmission / reception operating frequency difference calculation unit 20 is a component that calculates the transmission / reception operating frequency difference 21 based on the computation target transmission packet time information 19.
The operating frequency control unit 22 is a component that determines the correction amount of the operation clock and the time counter value of the time counter generation unit 6 based on the operating frequency difference 21 between transmission and reception, and a time counter control value indicating the determined correction amount 23 is output to the time counter generator 6.

  FIG. 2 is a diagram showing the structure of a network packet handled in the present invention. The network packet 2 shown in FIG. 2 is transmitted between the media transmission device 1 and the media reception device 3 of the present invention via a transmission path such as an IP network. The network header information 2a is information that is included in the network packet 2 and stores information for specifying a transmission source, a reception destination, or a type of information to be transmitted.

  The transmission packet 8 is included in the network packet 2 and is transmitted in accordance with a transmission procedure applied to applications such as video distribution. The transmission packet 8 includes transmission packet header information 8a and a plurality of media packets 10. In the example shown in FIG. 2, the media packet 10 from the mth to the (m + k) th is included in the transmission packet 8.

  The transmission packet header information 8a is information for specifying a transmission source, a reception destination, and the like of the transmission packet 8. The media packet 10 stores media information and includes media header information 10a and a media packet payload 10b. The media header information 10 a is header information included for each media packet 10 and includes media packet time information 24. The media packet payload 10b stores encoded media information or control information.

  The media packet time information 24 is information related to a time counter among the information included in the media header information 10a, and includes a transmission time counter value (SCT value) 24a and a media time counter value (MCT value) 24b.

  FIG. 3 is a block diagram showing a configuration of the time counter value extraction unit of FIG. In FIG. 3, the time counter value extracting unit 9 includes an RCT value capturing unit 25, a media packet extracting unit 26, an SCT value extracting unit 27, an MCT value extracting / SCT value holding unit 28, a virtual MCT value calculating unit 29, and an MCT value. An RCT value output unit 30 is provided.

The RCT value capturing unit 25 is a component that captures the RCT value (reception time counter value) 14 at the time of receiving the transmission packet 8 from the time counter generation unit 6.
The media packet extraction unit 26 extracts the media packet 10 from the transmission packet 8 and outputs it to the media packet transmission unit 11, and extracts the media packet time information 24 from the media packet header information 10 a and outputs it to the SCT value extraction unit 27. It is the component which performs.
Further, when there is no media packet 10 to be processed in the transmission packet 8, the media packet extraction unit 26 sends a media packet extraction completion notification 26a indicating that the extraction of the media packet 10 is completed for the transmission packet 8 to the MCT value. Transmit to the RCT value output unit 30.

  The SCT value extraction unit 27 is a component that extracts a transmission time counter value (SCT value) 24a from the media packet time information 24 extracted by the media packet extraction unit 26. In addition to the SCT value extraction process, the SCT value extraction unit 27 Media time count information 24c including a header information part obtained by removing the SCT value 24a of the processing target media packet 10 from the information 24 and the SCT value 24a for the processing target media packet 10 is generated.

The MCT value extraction / SCT value holding unit 28 extracts the media time counter value (MCT value) 24b from the media packet time information 24 extracted by the SCT value extraction unit 27, and is notified at the same time as the extracted MCT value 24b. This is a component that holds the SCT value 24a.
The MCT value extraction / SCT value holding unit 28 also includes virtual MCT value calculation information 28a including the transmission time counter value 24a of the transmission packet 8 to be processed and the latest media time counter value 24b of the transmission packet 8 to be processed. And output to the virtual MCT value calculation unit 29.

  The virtual MCT value calculation unit 29 is based on the SCT value 24a of the media packet 10 to be processed extracted by the SCT value extraction unit 27 and the media time count information 24c generated by the MCT value extraction / SCT value holding unit 28. This is a component that calculates a virtual MCT value (virtual MCT value) 24d for the media packet 10 to be processed.

  The MCT value / RCT value output unit 30 is a component that receives the media packet extraction completion notification 26a from the media packet extraction unit 26, and processes all media packets 10 included in the transmission packet 8 by the media packet extraction completion notification 26a. Is recognized, the virtual MCT value 24d for the media packet 10 (the newest media packet 10 included in the transmission packet 8) last calculated by the virtual MCT value calculation unit 29 in the transmission packet 8, and the transmission Transmission packet time information 15 including the RCT value 14 at the time of receiving the packet 8 is output.

Next, the operation will be described.
The media transmitting apparatus 1 encodes media information such as an input video media signal, audio media signal, and data signal by video encoding, audio encoding, and data encoding according to an encoding method according to the characteristics of each media. Media information is generated.
As the video encoding, for example, a data string encoded in accordance with a video encoding standard such as MPEG-2 Video, MPEG-4 Video, MPEG-4 AVC, or VC-1 is applicable. In addition, examples of audio encoding include a data string encoded in accordance with audio encoding standards such as MPEG-1 Audio, MPEG-2 Audio, MPEG-2 / 4 AAC, Dolby AC-3, and the like.

  In order to aggregate a plurality of pieces of media information into a single transmission data and easily output it to the transmission path, a data string for transmission is formed in a packet structure as shown in FIG. It is transmitted to the media receiver 3. The encoded media information is stored in a media packet payload 10b in a predetermined format, and media header information 10a for specifying what kind of information is added to generate the media packet 10. The media header information 10a is given a transmission time counter value (SCT value) 24a that is the time when the media packet 10 is generated.

  In order to increase transmission efficiency, the transmission packet 8 stores a plurality of media packets 10 together, and is further provided with transmission packet header information 8a for specifying what kind of information it is. Further, the transmission packet header information 8a includes information unique to an application that transmits and receives data stored in the transmission packet 8. This information is assumed to be information related to data transmission between transmission and reception, but is not directly related to the operation of the media reception device 3 according to the first embodiment, and thus detailed description thereof is omitted.

  In order to finally output to a transmission path such as an IP network, the transmission packet 8 is stored, and the network packet 2 to which the network header information 2a is added is generated. In the network header information 2a, as destination information for accurately transmitting the network packet 2 through various network devices constituting the transmission path, the address indicating the packet transmission source and the packet reception destination and the communication procedure are distinguished. Information such as an identifier to be used.

  As an example of media packetization, a TTS packet (a TS packet with a time stamp) in which a time stamp is added to a TS packet in the TS (Transport Stream) format conforming to the MPEG-2 Systems standard adopted in digital broadcasting, next-generation discs, etc. ). Transmission packetization corresponds to a data string that is packet-multiplexed according to an RTP packet in the RTP (Realtime Transport Protocol) format defined by IETF (Internet Engineering Task Force). The network packet 2 corresponds to a data string that is packet-multiplexed according to a UDP / IP (User Data Protocol / Internet Protocol) UDP / IP packet that is also used on the Internet.

  FIG. 4 is a diagram showing an example of the structure of the media packet 10 stored in the transmission packet 8, and shows a part of parameters in the media packet 10 in the TTS packet format in bit arrangement. The meaning of each parameter is obvious to those skilled in the art and will not be described. The TTS packet has a fixed length of 192 bytes. In the example shown in FIG. 4, the position of the first byte is indicated by “1”, the position of the last byte is indicated by “192”, and the MSB (Most Significant Bit) is indicated by b7, LSB (Least Significant Bit) is indicated by b0, and each bit from MSB to LSB is indicated by b6 to b1, respectively.

In the parameters, information indicated by PCR_Base and PCR_Extension is time information called Program_Clock_Reference.
The PCR_Base part is multiplexed with a counter value of 90 KHz accuracy, and the PCR_Extension part is multiplexed with a counter value of 27 MHz precision.
In order for a device compliant with the MPEG-2 Systems standard to match the operating frequency between transmission and reception, the parameter setting is notified at a constant cycle of PCR and at a transmission interval of 100 msec or less according to the MPEG-2 Systems standard.
The media receiving device 3 according to the first embodiment detects the difference between the transition of the counter value of the PCR and the transition of the counter value in the own device 3, calculates the operating frequency difference between transmission and reception, and based on this By adjusting the operating frequency of the own device 3, the operating frequency can be matched between transmission and reception.

Also for the time stamp set at the head of the TTS packet, the same clock source as the PCR, that is, the counter value counted at the same frequency is stored.
The TTS packet format used in digital broadcast IP network transmission and next-generation discs has differences such as the bit length and additional parameters, but there is no essential difference. Treat as.

  When the TTS packet shown in FIG. 4 is compared with the packet configuration shown in FIG. 2, the transmission time counter value (SCT value) 24a in FIG. 2 corresponds to a time stamp multiplexed at the head of the TTS packet in FIG. The media time counter value (MCT value) 24b corresponds to a PCR (PCR_Base part, PCR_Extension part) multiplexed in the parameter “adaptation_field_control” area of the TTS packet.

As described above, the network packet 2 is configured in accordance with various encoding / transmission standards, and a plurality of media packets 10 are stored and transmitted in the transmission packet 8.
In addition, since network header information 2a and transmission packet header information 8a are multiplexed in network packet 2, if the amount of data stored in network packet 2 is small, the overhead of the header portion increases and transmission efficiency decreases. Will be invited.
Therefore, in order to maximize the transmission efficiency, it is required to increase the amount of data to be stored as much as possible according to the characteristics of the applied network.
On the other hand, the data string to be transmitted is a fixed-length packet as described above, and in the example of FIG. 4, the media packet 10 is a 192-byte fixed-length packet. The packet 10 is stored in the transmission packet 8 and transmitted.

  As an example of a transmission path, the media reception device 3 receives a network packet 2 by a transmission packet reception unit 7 via an IP network. It should be noted that there is no essential difference even if transmission is performed using another communication method that is not an IP network. The transmission packet receiving unit 7 identifies the network packet 2 including media information such as video, audio or data to be processed, extracts the transmission packet 8 from the network packet 2 and outputs it.

The time counter value extraction unit 9 receives the transmission packet 8 from the transmission packet reception unit 7 and generates a real-time time counter value (RCT) that is generated as needed by the time counter generation unit 6 and serves as a reference time for the media receiver 3. Value) 14 is acquired to obtain the reception time counter value (RCT value).
In consideration of accuracy, the reception time counter value (RCT value) 14 may be acquired from the time counter generator 6 when the transmission packet reception 7 receives the network packet 2.

Further, the time counter value extraction unit 9 extracts the media packet 10 from the transmission packet 8, and obtains the transmission time counter value (SCT value) 24a and the media time counter value (MCT value) 24b added to the media header information 10a. get.
At this time, since the MCT value 24b is not assigned to all the media packets 10 and a plurality of media packets 10 are stored and transmitted in one transmission packet 8, each media packet 10 On the other hand, the relationship between the reception time counter value (RCT value) 14 and the transmission time counter value 24a changes with time.
Due to this change, the reception side cannot accurately grasp the reception time counter value (RCT value) 14 for each media packet 10.

  Therefore, the time counter value extraction unit 9 according to the present invention includes a reception time counter value (RCT value) unique to the transmission packet 8, a transmission time counter value (SCT value) 24a, a virtual media time counter value (hereinafter, in particular, 24b is calculated and applied to the calculation of the operating frequency difference between transmission and reception. Details of the calculation of the virtual MCT value 24b will be described below.

FIG. 5 is a diagram showing the relationship of each time counter value with respect to the transmission packet and the media packet handled in the present invention. As time transitions from the left side to the right side, the media packet and the transmission packet are generated, and the transmission time is generated. This indicates that the counter value (SCT value) advances. In FIG. 5, a transmission packet 8-1 is a transmission packet generated in the “m-th” including a plurality of media packets 10-0 to 10-3.
The media packet 10-0 is an “nth” media packet that does not include a media time counter value (MCT value).

The media packet 10-1 is an “n + 1” th media packet including an MCT value. Further, the media packets 10-2 and 10-3 are media packets generated for “n + 2” and “n + 3”, respectively, which do not include an MCT value.
The media packet 10-3 is a media packet generated at the latest time among media packets multiplexed with the transmission packet 8-1.

The transmission packet 8-2 includes a plurality of media packets 10-4 to 10-7, and is a transmission packet generated “m + 1” th. Here, the media packet 10-7 is a media packet generated at the latest time in the transmission packet 8-2.
The transmission packet 8-3 is a transmission packet generated by “m + 2”, in which a plurality of media packets 10-8 to 10-11 are multiplexed. The media packet 10-11 is a media packet generated at the latest time in the transmission packet 8-3.

For convenience of explanation, each of the media packets 10-0 to 10-11 has a transmission time counter value (SCT value) of SCT [n] = 10, SCT [n + 1] = 20, SCT [n + 2] = 40,. .. SCT [n + 11] = 180 is given. Further, MCT = 20100 is assigned to the media packet 10-1 as a media time counter value (MCT value).
Note that the reception time counter value (RCT value), which is the real-time time counter value at the time when the transmission packets 8-1 to 8-3 are received, is RCT [m] = 20150, RCT [m + 1] = 20225, RCT [m + 2 ] = 20255,... Are obtained.
Further, although four media packets are stored in the transmission packets 8-1 to 8-3, the number of media packets stored in the transmission packet may be one or plural. , It does not have to be a fixed number.

  Media packets 10-0 to 10-3 are multiplexed in the mth transmission packet 8-1, and the transmission time counter value (SCT value) 24a is SCT [n] = 10 and SCT [n + 1] = 20. , SCT [n + 2] = 40 and SCT [n + 3] = 55. That is, the media packet 10-3 to which SCT [n + 3] is assigned is the newest media packet in the transmission packet 8-1.

  The RCT value fetching unit 25 of the time counter value extracting unit 9 obtains a real-time time counter value (RCT [m] = 20150) that is a reference clock of the media receiving device 3 at the time when the mth transmission packet 8-1 is received. The received time counter value (RCT value) 14 is captured.

  FIG. 6 is a diagram illustrating the relationship between the transmission time counter value and the reception time counter value for the media packet 10. FIG. 6 schematically shows the relationship between the transmission time counter value and the reception time counter value. As described above, a plurality of media packets are stored in one transmission packet. For this reason, a transmission time counter value (SCT value) indicating an interval until the media transmission device 1 generates and transmits a media packet increases with the passage of time. On the other hand, the intervals at which the media receiving device 3 receives media packets are grouped in units of transmission packets as shown in FIG.

Therefore, the transmission time counter value and the reception time counter value are supposed to be proportional to each other as originally indicated by the broken-line arrows in FIG. 6, but are biased in units of transmission packets, and an accurate reception time counter value cannot be obtained. .
Therefore, in the present invention, a media packet indicated by a black circle symbol in FIG. 6 in which the transmission time counter value and the reception time counter value have a proportional relationship is selected and used for the calculation of the operating frequency difference.

  Returning to the description of FIG. 5, since the media packet 10-1 includes SCT [n + 1] = 20 and MCT = 20100, the time counter value extraction unit 9 determines that the SCT [n + 1] and the transmission packet 8- 1, the difference from SCT [n + 3] = 55 of the latest media packet 10-3 is obtained, and this difference value = 35 is added to MCT = 20100, so that the virtual MCT value 24b for the mth transmission packet 8-1 is obtained. MCT [m] = 20135 is calculated as follows.

Similarly, the time counter value extraction unit 9 obtains a difference value between SCT [n + 1] = 20 and SCT [n + 7] = 120 for the (m + 1) th transmission packet 8-2, and uses this difference value = 100 as a media packet. MCT = 20200 is calculated as the virtual MCT value 24b by adding to the MCT value = 20100 of 10-1, and the reception time counter value RCT [m + 1] = 20225 at this time is fetched from the time counter generation unit 6.
In the m + 2nd transmission packet 8-2, a difference value between SCT [n + 1] = 20 and SCT [n + 111] = 180 is obtained, and this difference value = 160 is added to the MCT value = 20100 of the media packet 10-1. MCT = 20260 is calculated as the virtual MCT value 24b, and the reception time counter value RCT [m + 2] = 20255 at this time is fetched from the time counter generation unit 6.
Thereafter, the time counter value extraction unit 9 repeats the same operation until a new media time counter value (MCT value) is extracted from the media packet.

  The transmission time counter value (SCT value), the reception time counter value (RCT value), and the media time counter value (MCT value) are numerical values held in parameters in the media header information 10a or a counter in the circuit. , It has a property of returning to “0” with a finite value and continuing counting. Even in such a case, the numerical calculation is performed in consideration of the necessary aliasing, and it will be described as being continuously changed.

  FIG. 7 is a flowchart showing the flow of the virtual MCT value calculation process by the time counter value extraction unit. Details of the operation of the time counter value extraction unit 9 will be described with reference to the configuration shown in FIG. 3 along FIG. Here, the m-th transmission packet 8 as shown in FIG.

When the transmission packet 8 received by the transmission packet receiving unit 7 is input, the RCT value fetching unit 25 fetches the real-time time counter value at this time from the time counter generating unit 6 and uses the real-time time counter value RCTm as the real-time time counter value RCTm. It is held (stored) in an RCT memory (not shown in FIG. 3) for sequentially storing time counter values (step ST1).
Thereafter, the RCT value fetching unit 25 outputs the transmission packet 8 to the media packet extracting unit 26, and also receives the reception time counter value RCTm (reception time counter value 14) held in the memory as an MCT value / RCT value output unit. Output to 30.

  The media packet extraction unit 26 checks whether there is a media packet 10 (uninspected media packet 10) that can be processed in the transmission packet 8 input via the RCT value acquisition unit 25 (step ST2). . If there is no unexamined media packet 10 that can be processed in the transmission packet 8 (step ST2; none), the media packet extraction unit 26 sends a media packet extraction completion notification 26a to the MCT value / RCT value output unit. Then, the transmission packet 8 is excluded from the calculation target of the time counter value, and the process ends. Thereafter, the media packet extraction unit 26 proceeds to processing of the transmission packet 8 subsequently input from the RCT value acquisition unit 25.

  When there is an unexamined media packet 10 that can be processed in the transmission packet 8 (step ST2; present), the media packet extraction unit 26 extracts the media packet 10 from the transmission packet 8, and the media packet 10 A media header information part including each time counter value is extracted from the media header information 10 a and output to the SCT value extraction unit 27 as media packet time information 24. The media header information portion described above may be the entire media packet 10.

The SCT value extraction unit 27 extracts the transmission time counter value SCTn from the media packet time information 24 obtained by the media packet extraction unit 26, and sequentially stores the transmission time counter value (not shown in FIG. 3). (Step ST3).
Thereafter, the SCT value extraction unit 27 outputs the SCTn extracted from the media packet time information 24 to the virtual MCT value calculation unit 29 as a transmission time counter value (SCT value) 24a for the media packet 10 to be processed.
Furthermore, the SCT value extraction unit 27 removes the processing target SCT value (SCTn) 24a from the media packet time information 24, and includes a media header information portion that may include a media time counter value (MCT value), and a processing target. The media time count information 24c including the SCT value (SCTn) 24a is generated and output to the MCT value extraction / SCT value holding unit 28.
The media header information portion described above may be the entire media packet 10 or the entire media packet time information 24.

When the media time count information 24c is input from the SCT value extraction unit 27, the MCT value extraction / SCT value holding unit 28 determines whether the media time counter value (MCT value) 24b is stored in the media time count information 24c. Confirm (step ST4).
If the media time counter value (MCT value) 24b is stored (step ST4; present), the MCT value extraction / SCT value holding unit 28 sets the MCT value to be the newest in the transmission packet 8 to be processed. The media time counter value MCTo is held (step ST5).

  Next, the MCT value extraction / SCT value holding unit 28 sets the transmission time counter value SCTm for the transmission packet (m-th transmission packet) 8 to be processed with the transmission time counter value SCTn of the media packet 10 having the MCT value. Updated to generate virtual MCT value calculation information 28a including SCTm (transmission time counter value 24a of transmission packet 8 to be processed) and MCTo (newest media time counter value 24b of transmission packet 8 to be processed) And output to the virtual MCT value calculation unit 29 (step ST6).

  On the other hand, if the media time counter value (MCT value) 24b is not stored in the media time count information 24c (step ST4; none), the MCT value extraction / SCT value holding unit 28 includes the existing SCTm and the existing MCTo. Virtual MCT value calculation information 28 a is generated and output to the virtual MCT value calculation unit 29.

The virtual MCT value calculation unit 29 sequentially inputs the transmission time counter value SCTn for the media packet 10 currently being processed in the transmission packet 8 to be processed (m-th transmission packet 8) from the RCT value acquisition unit 25. The virtual MCT value MCTm (virtual MCT value 24d) is calculated by performing an operation according to the following equation (1) using this SCTn and each time counter value included in the virtual MCT value calculation information 28a (step S1). ST7). The MCTm is output from the virtual MCT value calculation unit 29 to the MCT value / RCT value output unit 30.
MCTm = SCTn−SCTm + MCTo (1)

  Thereafter, the MCT value / RCT value output unit 30 determines that the media packet 10 currently being processed is the transmission packet 8 to be processed depending on whether or not the media packet extraction completion notification 26a is received from the media packet extraction unit 26. It is determined whether or not it is the last media packet 10 of (mth transmission packet 8) (step ST8).

  When the media packet extraction completion notification 26a is received and it is determined that the media packet 10 currently being processed is the last media packet 10 and no media packet 10 remains in the currently processed transmission packet 8 (step ST8). MCT value / SCT value output unit 30 includes a virtual MCT value 24b for the latest media packet 10 in which the MCTm calculated last and the RCTm for this media packet 10 are included in the mth transmission packet, and The transmission time counter value 24a is determined, and transmission packet time information 15 including MCTm and RCTm is generated and output to the MCT value / RCT value storage unit 16 (step ST9). This combination of MCTm and RCTm corresponds to a time counter value for the media packet 10 indicated by a black circle symbol in FIG.

  If the media packet extraction completion notification 26a is not received from the media packet extraction unit 26, the MCT value / SCT value output unit 30 determines that the current processing target media packet 10 is not the final media packet 10 but the current processing target. It is determined that the media packet 10 remains in the transmission packet 8 (step ST8; remaining), and the transmission packet time information 15 is not output. Thereby, the process from step ST3 to step ST7 is repeated until all the media packets 10 of the transmission packet 8 currently processed are processed.

  Note that the media time counter value MCTo extracted from the last media packet 10 and the transmission time counter value SCTm of the media packet 10 in the currently processed transmission packet 8 are held by the MCT value extraction / SCT value holding unit 28. Then, the calculation processing of each time counter value in the next m + 1-th transmission packet 8 is taken over.

FIG. 8 is a diagram showing an example of the time counter value calculated by the time counter value extraction unit 9 handled in the present invention, and shows the result of calculating the virtual MCT value and the RCT value with each time counter value shown in FIG. Yes. The transmission packet time information 15 generated by determining the MCT value and the RCT value for the transmission packet 8 by the series of processes shown in FIG. 7 is sequentially held in the MCT / RCT value accumulation unit 16. As a result, the MCT / RCT value accumulation unit 16 accumulates the combination of the MCT value and the RCT value for each transmission packet 8, as shown in FIG.
The combination of the MCT value and the RCT value shown in FIG. 8 corresponds to the time counter value for the media packet 10 indicated by the black circle symbol in FIG. 6, and the relationship between the media time counter value and the reception time counter value is proportional. be able to. From this correlation, an operating frequency difference between transmission and reception between the media transmission device 1 and the media reception device 3 can be calculated.

On the other hand, the media packet 10 extracted from the transmission packet 8 by the time counter value extraction unit 9 is temporarily stored in the buffer of the media packet transmission unit 11.
The media packet transmission unit 11 determines whether or not the transmission time counter value (SCT value) 24a of the media packet 10 temporarily stored in the buffer matches the real-time time counter value 14 generated by the time counter generation unit 6. Is exceeded, the media packet 10 is taken out of the buffer and transferred to the media separation / decoding unit 13 as a media packet 12 to be decoded. Thereby, the time interval which the media transmission apparatus 1 produced | generated the said media packet is reproducible.

  The media separation / decoding unit 13 reproduces a video media signal and an audio media signal by performing media separation and decoding processing on the encoded media information from the decoding target media packet 12 based on a predetermined multiplexing method and encoding method. Then, it is output to the video display device 4 and the audio reproduction device 5.

  At this time, the peak packet selection unit 18 transmits the transmission packet 8 including the media packet 12 to be decoded from the combination of the MCT value and the RCT value accumulated in the MCT / RCT value accumulation unit 16 and the next transmission. A combination corresponding to each of the packets 8 is selected and read out as selection target transmission packet time information 17, and a combination of the MCT value and the RCT value extracted from the selection target transmission packet time information 17 is used as the calculation target transmission packet time information 19. Is output to the operating frequency difference calculation unit 20 between transmission and reception.

The operating frequency difference calculation unit 20 between transmission and reception obtains the difference between the numerical value changes in the following equation (2) using the combination of the MCT value and the RCT value extracted from the computation target transmission packet time information 19, and obtains this difference. The transmission / reception operating frequency difference 21 is calculated in terms of frequency.
Time variation of each time counter value = ((MCT [m + 1] −MCT [m]) − (RCT [m + 1] −RCT [m])) / (RCT [m + 1] −RCT [m]) ( 2)

  According to the MPEG-2 Systems standard, each time counter value is obtained as a numerical value with a precision of 27 MHz. Therefore, if the calculation result of the above equation (2) is multiplied by “27000000”, it becomes a frequency. In calculating the actual operating frequency difference, it is possible to calculate with higher accuracy by applying a calculation method such as a time average or a square error method.

Based on the transmission / reception operation frequency difference 21 calculated by the transmission / reception operation frequency difference calculation unit 20, the operation frequency control unit 22 sets the reference clock signal generated by the time counter generation unit 6 to the operation frequency of the media transmission device 1. Correct to match.
Thereby, in the media receiver 3, the operation | movement synchronized with the operating frequency of the media transmitter 1 is implement | achieved, and transmission / reception of a transmission packet and encoding / decoding of encoded media information can be performed smoothly.

In order to easily handle the operating frequency difference 21 between transmission and reception, the operating frequency difference 21 between transmission and reception calculated by the operating frequency difference calculation unit 20 between transmission and reception is not applied as it is. “, Or“ +1 ”if the frequency difference is positive.
Also, the magnitude of the numerical value may be changed by multiplying the frequency difference by a coefficient instead of “+1” or “−1” depending on the magnitude of the frequency difference.

Furthermore, when the transmission / reception operating frequency difference 21 calculated by the transmission / reception operating frequency difference calculation unit 20 is applied as it is, the reference clock signal of the time counter generation unit 6 changes greatly, and as a result, the transition of the real-time time counter value becomes stable. Therefore, the control may fail.
In order to avoid this, the operating frequency control unit 22 may perform control so that the operating frequency difference between transmission and reception is smaller than the correction limit value. For example, according to the MPEG-2 Systems standard, the time change rate is defined as 0.075 Hz / 1 second, and the operating frequency difference 21 between transmission and reception is suppressed so as to vary within that range.
In the above description, when the transmitting side operating frequency is high and the receiving side operating frequency is low, it is calculated that there is a positive operating frequency difference, and conversely, the transmitting side operating frequency is low and the receiving side operating frequency is high. In this case, it is described that it is calculated that there is a negative operating frequency difference.

As described above, according to the first embodiment, the time counter value extraction unit 9 holds the MCT value and the SCT value extracted from the media packet 10 to which the MCT value is assigned, and stores it in the transmission packet 8. A value obtained by adding a difference value between the SCT value of the media packet 10 generated most recently and the SCT value extracted from the media packet 10 to which the MCT value is added to the MCT value among the plurality of stored media packets 10 As a virtual MCT value for the transmission packet 8, and the transmission / reception operating frequency difference calculation unit 20 calculates the virtual MCT value obtained by the time counter value extraction unit 9 and the RCT value of the transmission packet 8. The time transition amount of each value is converted into a frequency difference to calculate an operating frequency difference 21 between transmission and reception.
By configuring in this way, a plurality of media packets 10 are stored and transmitted in one transmission packet 8 in order to increase transmission efficiency, and even if the transmission interval and TS rate of the media packets 10 are not constant, It is possible to appropriately select a packet to be used for calculating the operating frequency difference 21 between transmission and reception, and it is possible to extract a time transition equivalent to the time interval at which the media transmission device 1 generates and outputs the media packet 10. As a result, even in the case of packet transmission via an IP network, it is possible to synchronize the operating frequency between transmission and reception with high accuracy and to realize a media reception device with good reception quality.

Embodiment 2. FIG.
The configuration of the media receiver according to the second embodiment is basically the same as the configuration described with reference to FIG. 1 in the first embodiment, but the generation processing of the transmission packet time information to be calculated by the peak packet selection unit Is different from the first embodiment. Therefore, in the following description, refer to FIG. 1 for the configuration of the media receiving apparatus according to the second embodiment excluding the peak packet selection unit.

  FIG. 9 is a block diagram showing the configuration of the peak packet selector of the media receiver according to Embodiment 2 of the present invention. In FIG. 9, the peak packet selection unit (selection unit) 18 includes an RCT value difference calculation unit 31, an RCT value difference average value calculation unit 32, and an RCT value difference threshold comparison unit 33. The RCT value difference calculation unit 31 extracts the selection target transmission packet time information 17 from the MCT / RCT value accumulation unit 16, and among the RCT values included in the selection target transmission packet time information 17, the transmission packet 8 that is temporally adjacent is extracted. It is a component which calculates the difference value 31a of a corresponding RCT value. The RCT value difference average value calculation unit 32 uses the RCT value difference value 31a obtained by the RCT value difference calculation unit 31, and uses the difference value 31a for N average values (N is an arbitrarily determined value). Or it is a structure part which calculates an average value within predetermined time, and the calculated average value is output as the RCT value threshold value 32a. Based on the RCT value threshold value 32a acquired by the RCT value difference average value calculation unit 32, the RCT value difference threshold value comparison unit 33 and the MCT value to be read from the MCT / RCT value accumulation unit 16 as the calculation target transmission packet time information 19 It is a component for selecting a combination of RCT values.

Next, the operation will be described.
FIG. 10 is a diagram illustrating an example of a relationship between a transmission packet to be separated in the network packet 2 and other transmission packets. As shown in FIG. 10, the network packet 2 includes a transmission packet 8 to be separated including encoded media information such as video and audio, and a transmission packet 8 that does not include such information and is not to be separated. Is transmitted.
In addition, the reception interval of the transmission packet 8 in the media receiver 3 should be synchronized with the transmission interval of the transmission packet 8 that is to be separated, but in reality, only the transmission packet 8 that is not to be separated. The reception interval of the transmission packet 8 is biased.

  FIG. 11 is a diagram showing an example of the relationship between the reception time counter value and the media time counter value. The reception time counter value (RCT value) and the media time counter value extracted for the transmission packet 8 to be separated. This schematically shows the relationship with (MCT value). When other transmission packets 8 that are not to be separated are mixed, not only the reception intervals of the transmission packets 8 to be separated are biased, but also the reception intervals are clogged locally by the amount of the mixture. The relationship between the value (RCT value) and the media time counter value (MCT value) changes. As a result, in the local period indicated by the solid line in FIG. 11, the difference in operating frequency between apparent transmission and reception is detected in an enlarged manner.

FIG. 12 is a diagram illustrating an example of a relationship between a reception time counter value and a difference value between adjacent reception time counter values in the relationship between the reception time counter value and the media time counter value in FIG. In the relationship between the RCT value and the MCT value in FIG. 11, when the difference in RCT value between temporally adjacent transmission packets 8 is calculated, as shown in FIG. 12, the difference-related threshold value is divided into two groups.
That is, when the transmission packets 8 to be separated continue, the difference between the RCT values is small, and the difference between the RCT values is large in the portion where the transmission packet 8 that is not to be separated exists.
Therefore, by selecting and paying attention to the transmission packet indicated by the black circle symbol that is the peak divided into groups (corresponding to the transmission packet similarly indicated by the black circle symbol in FIG. 11), the RCT value as shown in FIG. The MCT value is proportional. By selecting such a combination of the MCT value and the RCT value of the transmission packet 8, a highly accurate operating frequency difference can be calculated.

As described in the first embodiment, the combination of the media time counter value (MCT value) and the reception time counter value (RCT value) extracted from the transmission packet 8 is sequentially accumulated in the MCT / RCT value accumulation unit 16. ing. The peak packet selection unit 18 extracts the selection target transmission packet 17 from the MCT / RCT value accumulation unit 16.
At this time, the RCT value difference calculation unit 31 sets the difference between reception time counter values (RCT values) adjacent in time, that is, the RCT value of the mth transmission packet 8 as RCT [m], and sets the m + 1th transmission packet 8. RCT [m + 1] −RCT [m] is calculated, and the resulting difference value ΔRCT [m] is output as the RCT value difference value 31a.

In the RCT value difference average value calculation unit 32, for example, an average value of N RCT value difference values 31a (N is an arbitrarily determined value) or an RCT value difference value obtained during a predetermined time period. The average value of 31a is calculated, and this calculation result is output as the RCT value threshold value 32a.
The RCT value difference threshold value comparison unit 33 receives the RCT value difference value 31a from the RCT value difference calculation unit 31, receives the RCT value threshold value 32a from the RCT value difference average value calculation unit 32, and compares them. At this time, when the RCT value difference value 31a exceeds the RCT value threshold value 32a, the RCT value difference threshold value comparison unit 33 selects the selection target transmission packet time information including the combination of the MCT value and the RCT value corresponding to the RCT difference value 31a. 17 is selected and output as computation target transmission packet time information 19.

In the operation of the RCT value difference threshold comparison unit 33, the RCT difference value 31a whose numerical value is extremely different from the RCT value threshold 32a may be excluded.
It is also possible to specify the RCT value difference value 31a that is lower than the RCT value difference threshold value 32a and output the calculation target transmission packet time information 19 including the combination of the MCT value and the RCT value corresponding to the RCT difference value 31a. It is.

  As described above, the peak packet selection unit 18 according to the second embodiment outputs the calculation target transmission packet time information 19 selected from the selection target transmission packet time information 17 based on the RCT value difference threshold 32a. Thereby, the time counter value corresponding to the transmission packet 8 indicated by the black circle symbol in FIG. 11 is extracted, and the relationship between the media time counter value and the reception time counter value can be made proportional. From these correlations, it becomes easy to calculate the operating frequency difference between transmission and reception in the media transmission device 1 and the media reception device 3.

As described above, according to the second embodiment, the difference between the RCT values of the transmission packets 8 successively received in time from among the RCT values sequentially stored in the MCT / RCT value accumulation unit 16. A peak packet selection unit 18 that detects an RCT value whose value exceeds a predetermined threshold, and selects the detected RCT value and a virtual MCT value of the transmission packet 8 corresponding to the detected RCT value from the MCT / RCT value accumulation unit 16. An inter-transmission / reception operation frequency difference calculation unit 20 converts the time transition amount of each value between the virtual MCT value selected by the peak packet selection unit 18 and the RCT value of the transmission packet 8 into a frequency difference, and the inter-transmission / transmission operation. The frequency difference 21 is calculated.
With this configuration, even when there is a deviation in the reception interval of the transmission packet 8 due to a mixture of the transmission packet 8 to be decoded and the transmission packet 8 not to be decoded in the network packet 2. It is possible to extract a time transition equivalent to the time interval at which the media transmission device 1 generates and outputs the media packet 10. Thereby, even in the case of packet transmission via the IP network, it is possible to synchronize the operating frequency between transmission and reception with high accuracy and to realize the media reception device 3 with good reception quality.

Embodiment 3 FIG.
FIG. 13 is a block diagram showing the configuration of a media receiving device according to Embodiment 3 of the present invention and its peripheral devices. As shown in FIG. 13, in the media receiver 3A according to the third embodiment, a buffer remaining amount inspection unit 34 and a control range smoothing unit 35 are added to the configuration described in the first embodiment with reference to FIG. It has been added. The buffer remaining amount inspection unit 34 is a component that inspects temporal transition of the buffer remaining amount value 11 a indicating the staying amount of the media packet 10 temporarily stored in the buffer by the media packet transmitting unit 11.
Further, the control range smoothing unit 35 is a time between the buffer remaining amount inspection result 34 a indicating the inspection result of the buffer remaining amount inspection unit 34 and the inter-transmission / reception operation frequency difference 21 input from the transmission / reception operation frequency difference calculation unit 20. This is a configuration unit that adjusts the value of the frequency difference 21 between transmission and reception based on a typical transition. The adjusted operating frequency difference between transmission and reception is output to the operating frequency control unit 22 as an adjusted operating frequency difference between transmission and reception 21a.

Next, the operation will be described.
In the following, description of operations that are the same as those in the first and second embodiments will be omitted, and operations unique to the third embodiment will be described.
The media packet transmission unit 11 temporarily stores the media packet 10 extracted by the time counter value extraction unit 9 in a buffer, and the real-time time counter value 14 generated by the time counter generation unit 6 temporarily stores it. When the transmission time counter value (SCT value) assigned to the media packet 10 is matched or exceeded, the media packet 10 is output to the media separation / decoding unit 13 as a media packet 12 to be decoded.
At this time, the media packet transmission unit 11 sets the buffer retention amount corresponding to the difference between the fetch of the media packet 10 and the fetch of the media packet 12 to be decoded as the buffer remaining amount value 11a, and the buffer remaining amount checking unit 34. Output to.

  Note that as the buffer remaining amount value 11a, a result obtained by measuring the difference in the number of packets between the media packet 10 and the media packet 12 to be decoded may be used. That is, every time the media packet 10 is fetched, “+1” is added to the packet remaining amount value, and every time the media packet 12 to be decoded is taken out, the packet residual amount value is subtracted to “−1”. Can be measured.

  In addition, since the buffer is configured by a so-called memory, the buffer remaining amount value 11a is obtained by using the result measured by the data amount of the media packet waiting for processing existing in the memory on the buffer. Also good. In other words, the write address is updated each time the media packet 10 is fetched and sequentially written to the buffer, and the read address is updated each time the media packet 12 to be decoded is fetched and sequentially read from the buffer. The total data amount of media packets staying in the buffer can be measured based on the address difference.

Further, the media packet transmission unit 11 waits for the media packet 12 to be decoded until the media packet 10 stays at the intermediate value of the buffer, and the counter value corresponding to this waiting time is set as the transmission time counter value. And the real-time time counter value may be offset to adjust the extraction timing of the media packet 12 to be decoded. That is, when the relationship of the following expression (3) is satisfied, the media packet transmission unit 11 extracts the media packet 12 to be decoded from the buffer and outputs it to the media separation / decoding unit 12.
(Transmission time counter value + standby time) ≤ Real-time time counter value (3)

The buffer remaining amount checking unit 34 determines whether the retention amount of the media packet in the buffer of the media packet transmitting unit 11 is increasing or decreasing by measuring temporal transition of the buffer remaining amount value 11a. To do.
As described above, since a plurality of media packets 10 are stored together in the transmission packet 8, the media packets 10 are captured in bursts by the media packet transmitter 11. Further, since the transmission packet 8 to be decoded and the transmission packet 8 not to be decoded are mixed and transmitted between the media transmission device 1 and the media reception device 3, the reception interval of the transmission packet 8 itself to be decoded is transmitted. Is not constant. On the other hand, the transmission time counter value (SCT value) is given to the media packet 10 in a relatively constant increment.
For this reason, the buffer remaining amount value 11a of the media packet transmission unit 11 changes greatly increased or decreased.
Therefore, the buffer remaining amount checking unit 34 obtains the buffer remaining amount value 11a from the media packet transmitting unit 11 at any time, obtains a time average of the buffer remaining amount value 11a at a predetermined time interval, and obtains an average buffer remaining amount value. calculate. If this average buffer remaining amount value has increased from the previous calculation period, it is determined to be increasing, and if it has decreased, it is determined to be decreasing, and the difference from the previous calculation period is within a predetermined range. If it falls within the range, it is determined that there is no steady increase / decrease.

The determination result is output to the control range smoothing unit 35 as the buffer remaining amount inspection result 34a.
At this time, in order to make the calculation accuracy (unit) coincide with the operation frequency difference 21 between transmission and reception calculated by the operation frequency difference calculation unit 20 between transmission and reception, the buffer remaining amount inspection result 34a is calculated as the buffer remaining amount inspection result 34a. It is converted into a frequency difference based on the time average period and treated as a media packet input / output frequency difference.
In order to easily handle the buffer remaining amount inspection result (media packet input / output frequency difference) 34a, the media packet input / output frequency difference is set to “−1” if it is increasing, and if it is decreasing, the media packet is determined. The input / output frequency difference may be “+1” and the media packet input / output frequency difference may be ± 0 in a steady state with no increase / decrease.
Alternatively, depending on the amount of change in the time average when the time average is calculated, the increasing tendency is not “+1” and the decreasing tendency is not “−1”, but the numerical value of the media packet input / output frequency difference is changed. May be.

The control range smoothing unit 35 adjusts the transmission / reception operating frequency difference from the temporal transition of the transmission / reception operating frequency difference 21. When the value of the operating frequency difference 21 between transmission / reception notified last time tends to be constant, for example, when the result that the reception side operating frequency is high is continuously obtained, the operating frequency difference 21 between transmission / reception remains as it is. Is continuously reflected in the operating frequency control unit 22, the operating frequency in the time counter generating unit 6 is cumulatively increased.
Accordingly, the control range smoothing unit 35 corrects the inter-transmission / reception operating frequency difference 21 to “0” when the inter-transmission / reception operating frequency difference 21 is smaller than the previous time. When the inter-transmission / reception operating frequency difference 21 is equal to the previous time, the inter-transmission / reception operating frequency difference 21 is corrected to a value that is suppressed to ½ or the like.

Further, the control range smoothing unit 35 temporarily saves the media packet transmission unit 11 by adding the buffer remaining amount inspection result 34 a calculated by the buffer remaining amount inspection unit 34 to the operating frequency difference 21 between transmission and reception. It is also possible to adjust the staying amount of the media packet 10 being processed. For example, it is set as the relationship of following formula (4).
Operation frequency difference between transmission and reception + buffer remaining amount inspection result → adjusted operation frequency difference between transmission and reception (4)

The control range smoothing unit 35 corrects the operating frequency difference 21 between transmission and reception to be higher when the buffer remaining amount inspection result 34a is increasing, that is, when the receiving side operating frequency is low, and the buffer remaining amount inspection result 34a is decreasing, that is, receiving. When the side operating frequency is high, the operating frequency difference 21 between transmission and reception is corrected to be low.
At this time, if the operating frequency difference 21 between transmission and reception is larger than the media packet input / output frequency difference obtained by frequency conversion of the buffer remaining amount inspection result 34a, the buffer remaining amount inspection result 34a is invalidated to “0”, and control is performed. You may control so that it may not fail.
When the inter-transmission / reception operating frequency difference 21 is equal to or smaller than the media packet input / output frequency difference obtained by frequency conversion of the buffer remaining amount inspection result 34a, the correction amount is increased by multiplying the inter-transmission / reception operating frequency difference 21 by a predetermined coefficient. Thus, the control may be converged.

As described above, according to the third embodiment, the number of media packets stored in the buffer or the data amount of media packets waiting to be processed is periodically fetched from the media packet transmission unit 11, and the number of media packets or data The media packet input / output frequency difference obtained by converting the media packet input / output rate difference defined by the difference between the frequency of writing media packets to the buffer and the frequency of reading media packets from the buffer into the frequency difference The buffer remaining amount inspection unit 34 for calculating the remaining buffer amount inspection result 34a and the inter-transmission / reception operating frequency difference calculation unit 20 calculated by adding the media packet input / output frequency difference to the transmission / reception operating frequency difference 21 are adjusted. A control range smoothing unit 35 for outputting as a transmission / reception operating frequency difference 21a, Provided, the operating frequency control unit 22, based on the adjusted transmission and reception between the operating frequency difference 21a, to match the operating frequency of the media transmitter 1, corrects the generation of operating frequency due to the time counter generating unit 6.
In this way, by considering the temporal transition between the transmission / reception operating frequency difference 21 and the buffer remaining amount value 11a, a device such as a crystal oscillator serving as a reference clock of the time counter generating unit 6 can It is possible to synchronize the operating frequency between transmission and reception with high accuracy even when transmission fluctuation occurs in the transmission packet 8 due to the phenomenon that the operating frequency changes due to the influence or the processing delay of various network devices in the IP network. In addition, it is possible to realize the media reception device 3A with good reception quality.

  DESCRIPTION OF SYMBOLS 1 Media transmitter, 2 Network packet, 2a Network header information, 3,3A Media receiver, 4 Video display apparatus, 5 Audio | voice reproduction apparatus, 6 Time counter production | generation part, 7 Transmission packet reception part, 8, 8-1-8 -3 transmission packet, 8a transmission packet header information, 9 time counter value extraction unit, 10, 10-0 to 10-11, 12 media packet, 10a media header information, 10b media packet payload, 11 media packet transmission unit, 11a buffer Remaining value, 13 Media separation / decoding unit, 14 Real-time time counter value, 15 Transmission packet time information, 16 MCT / RCT value accumulation unit (time counter value accumulation unit), 17 Selection target transmission packet time information, 18 Peak packet selection Part (selection part), 19 Transmission packet time information, 20 Transmission / reception operating frequency difference calculation unit, 21 Transmission / reception operation frequency difference, 21a Adjusted transmission / reception operation frequency difference, 22 Operation frequency control unit, 23 Time counter control value, 24 Media packet time information, 24a transmission Time counter value (SCT value), 24b media time counter value (MCT value), 24c media time count information, 24d virtual MCT value, 25 RCT value fetching unit, 26 media packet extraction unit, 26a media packet extraction completion notification, 27 SCT value extraction unit, 28 MCT value extraction / SCT value holding unit, 28a virtual MCT value calculation information, 29 virtual MCT value calculation unit, 30 MCT value / RCT value output unit, 31 RCT value difference calculation unit, 31a RCT value difference value 32 RCT value difference average value calculation unit, 32a RCT value threshold , 33 RCT value difference threshold comparing unit, 34 a buffer remaining capacity checking section, 34a remaining buffer capacity test results, 35 control range smoothing unit.

Claims (9)

A transmission packet receiver for receiving a transmission packet transmitted from the media transmission device;
A time counter generation unit that generates an operation frequency serving as an operation reference of the own device and a time counter value synchronized with the operation frequency;
A time counter value at the time when the transmission packet is received by the transmission packet reception unit is acquired from the time counter generation unit as a reception time counter value, and the media transmission device is obtained from a plurality of media packets stored in the transmission packet. The transmission time counter value indicating the transmission timing according to each of the media packets is extracted, and the media packet is counted corresponding to the operating frequency of the media transmission device involved in generating the encoded media information stored in the media packet. If a media time counter value is given, a time counter value extraction unit that extracts the media time counter value;
Time counter value accumulation for sequentially storing the transmission time counter value, the reception time counter value, and the media time counter value acquired by the time counter value extraction unit for the transmission packets sequentially received by the transmission packet reception unit. And
Converting the time transition amount of each value in the transmission time counter value, the reception time counter value, and the media time counter value stored in the time counter value accumulation unit into a frequency difference, the media transmission device and the device itself An operating frequency difference calculation unit between transmission and reception that calculates an operating frequency difference between
Based on the operating frequency difference calculated by the transmitting / receiving operating frequency difference calculating unit, the operating frequency control unit corrects the generation of the operating frequency by the time counter generating unit so as to match the operating frequency of the media transmitting device. And
The time counter value extraction unit
Holding the media time counter value and the transmission time counter value extracted from the media packet to which the media time counter value is assigned;
Among the plurality of media packets stored in the transmission packet, the transmission time counter value of the most recently generated media packet and the transmission time counter value extracted from the media packet to which the media time counter value is assigned A value obtained by adding the difference value to the media time counter value is calculated as a virtual media time counter value for the transmission packet ,
From the reception time counter values stored in the time counter value accumulation unit, a reception time counter value in which the difference value of the reception time counter values of each transmission packet received continuously in time exceeds a predetermined threshold is detected. And a selection unit that selects the detected reception time counter value and the virtual media time counter value of the transmission packet corresponding to the detected reception time counter value from the time counter value accumulation unit,
The operating frequency difference calculation unit between transmission and reception converts a time transition amount between each value of the virtual media time counter value selected by the selection unit and the reception time counter value of the transmission packet into a frequency difference. A media receiving apparatus that calculates an operating frequency difference between the transmission and reception. The operating frequency control unit, as changes in the operating frequency generated by said time counter generating unit is within a predetermined range, according to claim 1 Symbol placement and controls the transmission and reception between the operating frequency difference Media receiver. A buffer for temporarily storing a media packet, and when the time counter value generated by the time counter generator matches or exceeds the transmission time counter value assigned to the media packet, 3. The media receiving apparatus according to claim 1, further comprising a media packet transmitting unit that extracts a packet from the buffer and outputs the packet to media separation and decoding processing. From the media packet transmission unit, the number of media packets stored in the buffer or the amount of media packets waiting to be processed is periodically fetched, and the time variation of the number of media packets or the amount of data is transferred to the buffer. A buffer remaining amount inspection unit for calculating a media packet input / output frequency difference by converting a media packet input / output rate difference defined by a difference between a media packet write frequency and a read frequency of the media packet from the buffer into a frequency difference; ,
A control range smoothing unit that outputs a value obtained by adding the media packet input / output frequency difference to the operation frequency difference between transmission and reception calculated by the operation frequency difference calculation unit between transmission and reception as an adjusted operation frequency difference between transmission and reception; ,
The operating frequency control unit corrects the generation of the operating frequency by the time counter generating unit based on the adjusted operating frequency difference between transmission and reception so as to match the operating frequency of the media transmission device. The media receiving device according to claim 3 . The control range smoothing unit invalidates the media packet input / output frequency difference to 0 when the transmission / reception operating frequency difference calculated by the transmission / reception operating frequency difference calculation unit is larger than the media packet input / output frequency difference; 5. The media receiving apparatus according to claim 4, wherein when the operating frequency difference between transmission and reception is less than or equal to the media packet input / output frequency difference, the operating frequency difference between transmission and reception is increased by multiplying by a predetermined coefficient. The control range smoothing unit determines that the current transmission / reception operation frequency difference calculated by the transmission / reception operating frequency difference calculation unit is less than the value used in the previous correction when the current value is less than the transmission / reception operation frequency difference. 5. The media receiving apparatus according to claim 4, wherein the difference in operating frequency is considered as zero. The control range smoothing unit, when the transmission / reception operating frequency difference calculated by the transmission / reception operating frequency difference calculation unit is the same as the value used in the previous correction and the current value, 5. The media receiver according to claim 4, wherein the difference is multiplied by a predetermined coefficient to suppress the value. If the media packet input / output frequency difference is a positive value, the control range smoothing unit changes the transmission / reception operating frequency difference calculated by the transmission / reception operating frequency difference calculation unit to +1 and sets a negative value. 5. The media receiving apparatus according to claim 4 , wherein if there is, the operating frequency difference between transmission and reception is changed to -1. The operating frequency control unit changes the operating frequency difference between transmission and reception to +1 if the operating frequency difference between transmission and reception is a positive value, and sets the operating frequency difference between transmission and reception to -1 if the operating frequency difference is a negative value. the media receiving apparatus according to any one of claims 1 to 8, characterized in that to change.

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