JPH10313448A - Moving image transmitting device and receiving device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To relate to a transmission device and a reception device for video data and audio data, and to influence data encoding and decoding by using a network asynchronous with data encoding and decoding timing. It is an object of the present invention to realize a compact and low-cost transmission system without giving a signal. SOLUTION: MPEG2 encoded data from a video signal source is stored in a video transmission buffer as TS packets. The synchronization information generator outputs a cycle start clock to the transmission controller based on synchronization information from the IEEE 1394 network. When the transmission controller receives the cycle start clock, it extracts a TS packet within the maximum TS packet calculated from the network bandwidth reserved in advance from the video transmission buffer,
Generate 94 packets. The transmitter sends this packet to IE
Output in the format specified in EE1394.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a moving picture transmitting / receiving apparatus for transmitting video information such as video data and audio data in a system in which a plurality of digital video information transmitting apparatuses and receiving apparatuses are connected to each other via a network. It is about.

[0002]

2. Description of the Related Art There have been developed a plurality of apparatuses for digitizing video data and audio data and storing and reproducing the digital data with high quality. When a video signal is digitized, the amount of data is enormous, and if it is digitized as it is, the capacity of the storage medium increases, the cost increases, and the device scale increases. Accordingly, techniques for compressing the data amount within a range that does not affect the original information have been advanced. Currently, the most effective compression method is MPEG (Moving Picture Exp
erts Group) 1 and 2 methods. In particular, MPEG2 will be used as a method for compressing high-quality video over TV.
Is expected to become mainstream. MPEG video information
The packet structure of a program stream (hereinafter, referred to as PS) and a transport stream (hereinafter, referred to as TS) is used as a format for transmitting the data to a storage medium or a remote receiving device via a network by performing the two-coding process. PS is used as a format when transmitting single video data, and TS is used when multiplexing and transmitting a plurality of video information. Since both have almost the same packet structure, the TS format will be used in the following description.

FIG. 5 shows a TS packet structure. MPEG
In the data encoded in 2, the amount of MPEG2 data generated per unit time varies because the amount of encoded data varies depending on the video content. However, when the TS packet 401 is generated, the header 402 and the payload 403 are all divided into fixed-length data of 188 bytes. That is, the number of TSs generated per unit changes with time. A PCR (Program C) is included in the header 402 as a decoding synchronization timing indicating when the decoding processing is performed on the TS packet by the decoding circuit.
lockReference) 404 is stored. This stores the encoding time at the time of encoding. By referring to the PCR 404 on the decoding side, it is possible to reproduce at the original video timing before encoding.

FIG. 6 shows a general circuit example for generating MPEG2 decoding timing from PCR. In the subtractor 501, the value of the PCR extracted from the received TS packet,
System clock 505 currently used in the decoding process
Is calculated. This error component is input to a VCO 503 via a low-pass filter (LPF) 502, the latest reception timing is determined, and a system clock 505 of a new frequency is generated. In MPEG2, the encoding timing at the time of video source encoding is set to PC
The data is transmitted to the receiving side as R data, and a decoding timing is generated from the PCR data, thereby performing reproduction in synchronization with the video source.

[0005] Since the encoding and decoding of MPEG2 are performed in the above-described procedure, the encoding device and the decoding device are connected on a one-to-one dedicated basis or from a high-speed access device such as a magnetic disk device. In the case of the decoding process of
S data is transmitted without any problem. However, when video information is transmitted between a plurality of devices connected via a network, or when asynchronous burst transfer typified by LAN occurs in addition to video information, TS data from the encoding device may be transmitted to another device. In some cases, data is not transmitted to the decoding device at a constant rate due to interference caused by data transmission. If the data transmission to the decoding device is slow, an underflow occurs and a wait occurs. If the data transmission is fast, data is lost due to an overflow in the decoding device. As one of means for avoiding this, for example, JP-A-8-1905
M over IEEE 1394 as implemented in
There is a method of synchronously transferring PEG2.

Next, referring to FIGS. 7 and 8, IEEE 139 will be described.
A conventional example of the MPEG2 synchronous transfer method on the C.4 will be described below. FIG. 7 is a block diagram showing a transmitting apparatus. In the figure, a signal source 701 generates compressed video data and audio data as TS packets, and outputs them as TS packets 706 to a transmitter 705. The signal source 701 stores the CTR, which is the IEEE1394 time information generated by the transmitter, in the register 703 when the TS packet is output.
A latch pulse 707 for latching a (Cicule Timer Register) value is generated. When the TS packet 706 is generated as an IEEE 1394 isochronous packet, a value obtained by adding the maximum delay time 709 on the IEEE 1394 network to the value stored in the register 703 is added as decoding timing information on the receiving side. Factors of the maximum delay time 709 include the maximum arbitration time and the maximum packetization time between a plurality of nodes. The IEEE 1394 isochronous packet generated by the transmitter 705 is output to the transmission path 712 after receiving a cycle start packet which is synchronization information output from the network master. This isochronous transfer method is defined by the IEEE 1394 standard.

FIG. 8 is a block diagram showing a receiving apparatus.
In the figure, an IEEE 1394 packet transmitted from the aforementioned transmitter is input to a receiver 801. This IEEE
The decoding timing information 808 generated on the transmission side is extracted from the E1394 packet and input to the carrier clock recovery circuit 803. The time information CTR 802 defined by IEEE 1394 also generates time information 809 on the receiving side, and the carrier clock recovery circuit 803
Is input to In the carrier clock recovery circuit 803, the value of the decoding timing information 808 and the reception side CTR information 802
Are compared, and when the two values become the same value, the counter 8
Then, the memory read control circuit 806 is driven via the control circuit 04 to start a write sequence 810 for the memory 805. This writing sequence 810 allows the receiver 8
01 is stored in the memory 805
Is written to. This write sequence 810 is completely synchronized with the encoding time generated on the transmission side. The video reproducer 807 can extract the MPEG2 stream from the TS packet data and decode and reproduce the video data and the audio data at the timing written in the memory 805.

[0008]

Since IEEE 1394 supports isochronous transfer, which is a synchronous transfer mode, MPEG-2 data is completely synchronized by using common time information CTR on the transmission side and the reception side. Although it can be transmitted, there are the following problems. First, the transmission side CTR does not add this maximum delay time, or I.
When an EEE1394 packet is transmitted, the CTR
, The CTR value on the receiving side may already be large, so that the carrier clock recovery circuit does not operate normally. Conversely, if the maximum delay time is set long, the next TS packet data is received before the previous TS packet data is stored in the memory on the receiving side, and the previous TS packet data may be lost. In addition, the maximum delay time dynamically fluctuates depending on the scale of the IEEE 1394 network and the performance of devices connected to each network, and there is a problem that it is quite difficult for the transmitting side to determine the maximum delay time.

Further, in the configuration of the transmission / reception apparatus, the transmission side needs a maximum delay time estimation sequence and an addition circuit for CTR, and the reception side needs to mount a carrier clock recovery circuit, a counter, and a memory read control circuit. However, there is a problem that the circuit scale becomes large.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. By utilizing the isochronous synchronous transfer means of the IEEE 1394 standard, it is possible to eliminate the need for a maximum delay time estimating sequence and to reduce the size. It is an object of the present invention to provide a moving picture transmitting / receiving apparatus having a circuit configuration as described above.

[0011]

According to a first aspect of the present invention, there is provided a moving image transmitting apparatus for temporarily storing a video signal source for outputting video data, audio data, or video signal synchronization data, and an output signal from the video signal source. A video transmission buffer for generating the synchronization time information, a synchronization information generating means for generating synchronization time information, and a transmission for outputting a video signal from the video transmission buffer to the transmitter based on the synchronization time information generated by the synchronization information generation means. A transmission control means for generating timing is provided.

According to a second aspect, in the moving picture transmitting apparatus according to the first aspect, prior to outputting the video signal, a transmission band reserving means for reserving a data band required by the video signal source to a network master is provided. The video signal source stores the video signal in the video transmission buffer based on the channel information of the reserved band, and the transmission control unit generates the synchronization signal generated by the synchronization information generation unit based on the network synchronization information received from the network master. 1 according to the timing
The data transfer amount from the video transmission buffer to the transmitter in one synchronization cycle is controlled.

According to a third aspect, in the moving picture transmitting apparatus according to the second aspect, if no transmission data exists in the video transmission buffer at the time when the transmission control means receives the network synchronization information, the video data is transmitted within the synchronization cycle. Is not transmitted.

According to a fourth aspect, in the moving picture transmission apparatus according to the second aspect, the video transmission buffer has a double buffer structure comprising a buffer for storing an output signal from a video signal source and a buffer for storing a video signal to a transmitter. It is what it was.

According to a fifth aspect of the present invention, there is provided a moving image receiving apparatus comprising: receiving means for receiving data from a transmitting apparatus; receiving FIFO means for temporarily holding received data; video data, audio data, or video signal synchronization; The apparatus comprises a reception control means for generating a reproduction timing for extracting data from the reception FIFO means based on the data, and a video reproduction means for reproducing transmission-side video information in synchronization with the reproduction timing.

According to a sixth aspect of the present invention, there is provided a moving image transmitting apparatus comprising: a plurality of video signal sources for outputting video data, audio data, or video signal synchronization data; and a plurality of video signals for temporarily holding respective video signal outputs. A transmission buffer, a selector for outputting only one signal source from the plurality of video signal sources to the transmitter,
Synchronization information generating means for generating synchronization time information, and transmission control means for generating transmission timing for outputting video data from a video transmission buffer to a transmitter based on the synchronization information generated by the synchronization information generation means. It was done.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 shows a block configuration of a transmission device according to the present embodiment. The transmission device includes a video signal source 101, a video transmission buffer 102, a transmitter 103, a synchronization information generator 104, and a transmission controller 105. Prior to the transfer of the video signal source, the transmitting device sets the data transmission band required by the video signal source to IEEE.
IEEE1 to secure on E1394 network
For the network master specified in 394,
Issue a bandwidth reservation request. If there is a vacancy in the band, the network master notifies the transmitting device of the channel number of the band together with the reserved band securing notification information. If no bandwidth is available, the network master returns a busy response to the transmitting device. When the band can be secured, the video signal source 101 in the transmission device generates a TS packet at the reserved bit rate, and
02 is stored. The IEEE 1394 network master generates a cycle clock every 125 μs as network synchronization information. The reference clock in the devices connected to the network is always synchronized based on the cycle clock. Specifically, a cycle start packet is broadcast to all devices on IEEE 1394 at a period of 8 Khz. The synchronization information generator 104 in the transmission device notifies the transmission controller 105 of the TS packet transmission clock 108 synchronized with the cycle clock every 125 μs. The transmission controller 105 fetches data for the number of TS packets calculated from the reserved band from the video transmission buffer 102 and generates an IEEE 1394 isochronous transfer packet. Video transmission buffer 1
02 has a double buffer configuration. With the double buffer configuration, it is possible to store the TS packet 106 from the video signal source in one buffer and simultaneously transmit the IEEE 1394 packet to the transmitter 103 from the other buffer. The timing of transmission from the transmitter 103 is predetermined on the network by a given channel number, and the transmitter 103 transfers the isochronous transfer packet generated in the video transmission buffer 102 when its own transmission order comes. Send. For example,
The following describes an example where the transfer band of the video signal source is 16 Mbit / s. In this case, 2 Mbytes of data is transmitted in one second. Therefore, in one synchronization cycle of 125 μs, data of 2 Mbytes × 125 μs = 250 bytes is transmitted. Incidentally, the TS packet length is fixed at 188 bytes as described above, and is 250 bytes.
The packet generation / decomposition processing in units of tes becomes complicated. In the present invention, the transmission unit is a TS packet length of 18
Isochronous transfer packetization is performed in 8-byte fixed length units. Therefore, when making a bandwidth reservation, the maximum packet transfer within one synchronization cycle is secured. In this case, for the network master, 188 bytes × 2 packets = 376 bytes ≧ 2
50 bytes 376 bytes / 125 μs = 3 Mbytes / s That is, the maximum number of packets in one synchronization cycle is 2, and the reserved band is 3 Mbytes / s. Actually IEEE13
Since the overhead of 94 packets is anticipated, a band with a little margin is reserved. The TS packet transmitted in one synchronous cycle is 0 or 1 because the synchronous cycle is not synchronized with the TS packet generation timing.
Or two, and on average, a TS packet can be transmitted at a constant rate of 16 Mbits / s, the required transfer bandwidth of the video signal source. When the transmission controller receives the TS packet transmission clock 108, the video transmission buffer 10
If the TS packet has not been completely stored in No. 2, no data is output in the synchronization cycle. FIG. 3 shows the data transfer timing output from the transmitter 103. The cycle start packet 601 is a synchronization packet generated by an IEEE 1394 network master. After receiving the cycle start packet 601, the transmitter 103 transmits the TS information 602 packetized at that time at the timing specified by the channel number. In the case of the data transfer rate of 16 Mbits / s described above, one TS information 602
Two TS packets are stored in the TS information 603. 604 is a packet on another network. As mentioned above, for a transfer rate of 16 Mbits / s,
Since a band capable of transferring a maximum of two TS packets in one synchronization cycle is reserved, the transmitter 103 can always transfer the TS packets 602 and 603 at the time. The video transmission buffer amount is determined by the maximum transfer amount of the video signal source. For example, if the video signal source is HDT
If the image quality is equivalent to V, a transfer rate of at most 30 Mbits / s is secured. The amount of data transferred to the transmitter every 125 μs in IEEE 1394 is 30 Mbits × 125 μs = about 470 bytes, and it is sufficient to prepare a maximum of three TS packets. That is, the total buffer amount is (188 × 3) × 2 (for double buffer) + (IEEE
1394 headers). Therefore, the video transmission buffer 102 can be realized by mounting a buffer of a maximum of 2 KBytes.

Next, the operation of the receiving apparatus will be described with reference to FIG. FIG. 2 is a block diagram of the receiving apparatus. The receiving apparatus includes a receiver 201, a reception FIFO 202, a video reproducer 203, and a reception controller 204. The TS packet 207 is extracted from the IEEE 1394 packet 206 received from the receiver 201. The extracted TS packets 207 are sequentially stored in the reception FIFO 202. The timing of writing to the reception FIFO 202 is generated based on a synchronization clock on the IEEE 1394 network. After storing all the TS packet data 207 in the reception FIFO 202, the receiver 201 transmits a packet completion notification 208 to the reception controller. The reception controller 204 sends the TS to be decoded to the video reproducer 203.
A decoding start request is transmitted by a status signal 209 to notify that the packet has been received. If the receiver 201 detects a packet error, the reception controller transmits an error detection signal to the video reproducer as a status signal 209.

By using the above-described transmitter and receiver, MPEG2 data can be transferred to IEEE1394.
Can be transferred via Since the encoding timing of MPEG2 and the synchronous cycle of IEEE1394 are asynchronous, the time at which the TS packet arrives at the receiving side fluctuates with respect to the original MPEG2 decoding timing.
Since the synchronization cycle is taken every 125 μs, the maximum fluctuation width is expected to be 250 μs for two synchronization cycles.
In contrast, the PC in the TS packet header shown in FIG.
A synchronous circuit that generates a system clock 505 using R is designed to comply with the ITU-T standard, and a maximum of 4 ms
Can be sufficiently locked against jitter, that is, fluctuation. Therefore, the fluctuation component of 250 μs generated on the network can be absorbed by the decoding timing generation circuit in the video reproducer 203 of FIG.

Embodiment 2 A second embodiment of the present invention will be described with reference to FIG. Video signal source 301a
To 301c have the same function as the video signal source in FIG. The video transmission buffers 302a to 302c
It has the same function as the video transmission buffer in. The selector 306 controls the video transmission buffers 302a to 302
Determine which buffer data of c to output to the transmitter. The transmitter 303 and the synchronization information generator 304
Has the same function as each of the above.

Next, the operation will be described. Transmission controller 3
Reference numeral 05 denotes a video transmission buffer 3 according to a channel number specified in advance by a synchronization signal from the synchronization information generator.
02a to 302c, and generates a control signal for sequentially outputting to the transmitter. Prior to the TS packet transfer, the transmitting device acquires a transfer band requested by each video signal source from the network master as an individual channel number. The acquired channel number information is transmitted to the transmission controller 3
Hold at 05. Upon receiving the cycle start packet from the network master, the synchronization information generator 304 notifies the transmission controller 305 of the start of the synchronous transfer cycle. The transmission controller 305 sequentially sends the TS packets to be transmitted in the cycle from the video transmission buffers 302a to 302c to the transmitter 303 via the selector 306 according to the channel number. The method of determining the TS packetization unit is as follows:
This is the same as that described in the first embodiment. The transmitter 303 transmits IEEE1394 packetized data for each channel number to the network at a timing specified by IEEE1394.

[0022]

Since the present invention is constructed as described above, it has the following effects.

According to the first invention, a video signal source for outputting video signal data, a video transmission buffer for temporarily holding a video signal output, and a synchronization information generating means for generating synchronization time information are provided. Since the timing at which the video signal is output from the video transmission buffer to the transmitter is controlled by the synchronization information generated by the information generating means, the packet data can be transmitted in accordance with the IEEE 1394 synchronization timing.

According to the second aspect of the present invention, there is provided a transmission band reserving means for transmitting a data band required by a video signal source to a network master and reserving the data band before outputting the video signal. , The amount of data to be transferred from the video transmission buffer to the transmitter within one synchronization cycle is controlled. Therefore, the maximum delay time is estimated as in the conventional transmission device, and this is calculated by the IEEE.
In addition to eliminating the need to add a counter value synchronized with E1394, a processing circuit for restoring the carrier clock from the synchronization information in the received packet and performing memory read control is also implemented on the receiving device side. Thus, there is an effect that a necessary data transfer band can be secured without any need.

Further, according to the third aspect of the present invention, if there is no transmission information in the video transmission buffer when the synchronization time information is received from the network master, data transmission is not performed in this synchronization cycle. Therefore, it is possible to prevent an unnecessary increase in network traffic.

According to the fourth aspect of the present invention, the video transmission buffer has a double buffer configuration including a buffer for storing an output signal from a video signal source and a buffer for storing a video signal to a transmitter. There is an effect that a fixed amount of signal data can be transmitted in synchronization.

Further, according to the fifth invention, the receiving device includes a receiving FIFO for temporarily holding the received data,
Since the transmission-side video information is reproduced in synchronization with the reproduction timing by providing reception control means for generating reproduction timing for extracting data from the reception FIFO, the fluctuation width caused by the asynchronous between the encoding timing and the IEEE 1394 can be determined by the PCR of MPEG2. There is an effect that it can be kept within a range that can be absorbed by a jitter elimination circuit using.

In addition, according to the sixth aspect, a plurality of video signal sources, a plurality of video transmission buffers for temporarily holding respective video signal outputs, and transmission of only one signal source from the plurality of video signal sources A selector for outputting to the transmitter, a synchronization information generating means for generating synchronization time information, and a transmission timing for outputting video data from the video transmission buffer to the transmitter according to the synchronization information generated by the synchronization information generating means. Therefore, not only the transfer from a single video signal source but also the same effect as that of the first invention can be obtained in a transmission device having a plurality of video signal sources.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a transmission device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a receiving device according to the first embodiment of the present invention.

FIG. 3 shows IEEE1 according to the first embodiment of the present invention.
FIG. 6 is a diagram illustrating transfer timing on a 394 network.

FIG. 4 is a block diagram illustrating a transmission device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing an MPEG2 TS packet format.

FIG. 6 is an example of a system clock generation circuit using PCR in the MPEG2 standard.

FIG. 7 is a block diagram illustrating a transmission device according to a conventional example.

FIG. 8 is a block diagram showing a receiving device according to a conventional example.

[Explanation of symbols]

101 video signal source, 102 video signal buffer, 10
3 transmitter, 104 synchronization information generator, 105 transmission controller, 106 TS packet data, 107 IEEE13
94 packet data, 108 cycle start clock, 201 receiver, 202 reception FIFO, 203 video reproducer, 204 reception controller, 205 system clock generator, 206 IEEE 1394 packet data, 207 TS packet data, 208 packet completion notification, 209 status Signals, 301a-301c
Video signal source, 302a to 302c Video transmission buffer, 303 transmitter, 304 Synchronization information generator, 305
Transmission controller, 306 selector, 401 TS packet, 402 TS header, 403 TS payload, 4
04 PCR information, 501 Subtractor, 502 LPF
(Low-pass filter), 503 VCO (voltage controlled oscillator), 504 counter, 505 system clock,
601 cycle start packet, 602 TS packet 1, 603 TS packet 2, 604 other data packet, 701 signal source, 702 CTR (cycle time register), 703 register, 704 addition circuit, 705 transmitter, 801 receiver, 802 CT
R, 803 Carrier clock recovery circuit, 804 counter, 805 memory, 806 memory read control circuit, 807 video reproducer.

Claims (6)

[Claims] 1. A video signal source for outputting video data, audio data, or video signal synchronization data, a video transmission buffer for temporarily holding an output signal from the video signal source, and synchronization for generating synchronization time information. Information generating means, and transmission control means for generating a transmission timing for outputting a video signal from the video transmission buffer to a transmitter based on the synchronization time information generated by the synchronization information generating means. Moving image transmitting apparatus. 2. A transmission band reserving means for reserving a data band required by the video signal source to a network master prior to outputting the video signal, wherein the video signal source stores channel information of the reserved band. Storing the video signal in the video transmission buffer based on the synchronization timing generated by the synchronization information generating unit based on the network synchronization information received from the network master by the synchronization information generating unit. 2. The moving picture transmitting apparatus according to claim 1, wherein an amount of data transfer from the buffer to the transmitter is controlled. 3. The transmission control means according to claim 2, wherein when transmission data does not exist in said video transmission buffer when network synchronization information is received, data transmission is not performed in said synchronization cycle. Claim 2
The moving image transmission device according to the above. 4. The moving picture according to claim 2, wherein the video transmission buffer has a double buffer configuration including a buffer for storing an output signal from the video signal source and a buffer for storing a video signal to a transmitter. Image transmission device. 5. A receiving means for receiving data from a transmitting device; a receiving FIFO means for temporarily holding the received data; and a receiving FIFO means based on video data, audio data, or video signal synchronization data. A moving image receiving apparatus comprising: a reception control unit that generates a reproduction timing for extracting data; and a video reproduction unit that reproduces transmission-side video information in synchronization with the reproduction timing. 6. A plurality of video signal sources for outputting video data, audio data, or video signal synchronization data, a plurality of video transmission buffers for temporarily holding the respective video signal outputs, and the plurality of video signals A selector for outputting only one signal source from the source to the transmitter, a synchronization information generating means for generating synchronization time information, and the video transmission buffer to the transmitter based on the synchronization information generated by the synchronization information generating means. A moving image transmission device comprising transmission control means for generating transmission timing for outputting video data.