JP2000358244A - Video transfer method and video transfer system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maximally utilize a transfer throughput of the entire system, to transfer video frames of a maximum number and to reduce deterioration in video image. SOLUTION: First a video interface card 6 receives a digital video signal. A frame abort section 11 abort frames at an equal interval in order to thin the frames up to the number of video frames able to be transfer-processed matching a transfer throughput of the entire video transfer system in advance. A frame FIFO 12 stores video frames after thinning out and the video frames are transferred to a main memory 2 matching the timing of transfer processing interval at which no missing frame takes place synchronously with the input video frames. The video frames stored in the main memory 2 are transferred to a network interface card 7 and a protocol processing section 18 applies protocol processing to the video frames and the resulting video frames are transmitted to a network.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a system for transferring a digital video signal, and more particularly to a video transfer system and a network for transferring a video signal to a remote place via a network. The present invention relates to a video transfer method and a video transfer system that can be used to transfer video signals efficiently.

[0002]

2. Description of the Related Art FIG. 4 shows a schematic functional configuration of an example of a conventional video transfer system. 51 is a CPU, 52 is a main memory, 53 is an internal bus, 54 is an external bus, and 55 is the internal bus 53 and an external bus. Bus bridge connecting the bus 54, 5
Reference numeral 6 denotes a video interface card for controlling input / output of a digital video signal, 57 denotes a network interface card for controlling input / output of a signal on a network, 58 denotes a video input unit for inputting an external digital video signal, 5
Reference numeral 9 denotes a video frame synchronization unit; 60, a bus control unit that controls transmission and reception of video frames to the external bus 54; 61, a video frame memory; 62, a video output unit; 63, a network interface card 57 and the external bus 54; Bus control unit for controlling transmission and reception of video frames between
Is a protocol processing unit that performs header processing and the like in accordance with a network protocol; 65 is a PDU synchronization unit that performs synchronization control of received PDUs (protocol data units); 66 is a PDU input unit that inputs PDUs from the network;
Is a PDU sending unit for sending PDUs onto the network.

[0003] The detailed specifications of digital video signals are IT
U-R BT. 601 and SMPTE259M.

When a digital video signal is transferred to a remote place via a network by the video transfer system shown in FIG. 4, the following processing is performed.

When transmitting a digital video signal over a network, a digital video signal is received from a video input unit 58 of a video interface card 56, and after a video frame is synchronized by a frame synchronization unit 59, an external bus 54 The data is transferred and stored in the memory area A of the address accessible from the video interface card 56 in the main memory 52 through the bus bridge 55 and the internal bus 53.
The video frame signal stored in the memory area A of the main memory 52 is copied to the memory area B of the address accessible from the network interface card 57 in the main memory 52, and the internal bus 53, the bus bridge 55, the external bus The data is passed to the network interface card 57 through the network interface card 57, where the protocol processing unit 64 performs network protocol processing such as adding a header such as a network address to form a PDU (protocol data unit). Sent up.

When the video transfer system receives a digital video signal from the network, the PDU received by the PDU input unit 66 of the network interface card 57 is synchronized by the PDU synchronization unit 65 in a manner opposite to the above transmission processing. Thereafter, the protocol processing unit 64 performs network protocol processing such as header removal and error checking,
The video frame signal is extracted and stored in the memory area B of the main memory 52 at an address accessible from the network interface card 57 via the external bus 54, the bus bridge 55, and the internal bus 53. The video frames stored in the memory area B of the main memory 52 are copied to the memory area A at an address accessible from the video interface card 56 in the main memory 52, and the internal bus 53, the bus bridge 55, and the external bus 54 are again copied. Is passed to the video interface card 56 through
After being temporarily stored in the video frame memory 61, the video signal is output from the video output unit 62 as a video signal of a predetermined number of video frames per unit time.

In the above-described processing, processing such as exchange of video frames between the video interface card 56 or the network interface card 57 and the main memory 52 and copying of video frame signals between different addresses in the main memory 52 are performed by the CPU 51. Do with.

[0008]

In such a conventional video transfer system, an internal bus 53 and an external bus 54 are used.
Frame signals pass between the main memory 52 and the video interface card 56 and the network interface card 57 in both directions via the internal bus and the external bus in the transfer of wideband digital video signals such as uncompressed component digital video signals. And so on become transfer bottlenecks, so that the required number of video frames per unit time cannot be transferred, and so-called dropped video frames occur.

Now, the number of video frames per second is N
In the case of (30 in the case of a digital component video signal), in the video transfer system, the processing time, ie, the video processing time required until a video signal for one frame is fetched from the video interface card 56 and transmitted from the network interface card 57 to the network. If the video frame processing time in the transfer system is not less than 1 / N second, a video frame drop will occur. Further, if a frame drop occurs in the video transfer system on the transmission side, the video transfer system on the reception side cannot receive a video signal of a predetermined number of video frames per unit time. In this case, the video signal is stored in the video frame memory 61. Is output repeatedly.

In the conventional video transfer system, if the transfer processing time of the video frame in the video transfer system becomes slightly larger than 1 / N, for example, during the transfer processing of the video frame (1), the next video frame (2) ) Is discarded due to dropped frames, and dropped video frames occur for each video frame, and the maximum number of video frames that can be transferred via the network can be sent at most N / 2 per second. At most, only 1/2 of the original video information can be obtained. For this reason, unnaturalness such as the movement of a dynamic object or the like is noticeable, and image quality deteriorates rapidly.

FIG. 5 schematically shows an example of a video frame at the video input unit on the transmission side and a video output unit on the reception side. FIG. 5A shows a video frame at the video input unit on the transmission side. The configuration (b) is a video frame configuration in the video output unit on the receiving side. On the transmitting side, the transfer processing of one video frame requires slightly more than 1 / N, so that, for example, the video frame (2) input during the transfer processing of the video frame (1) is discarded. Thus, on the transmitting side, FIG.
The video frame indicated by hatching in FIG.
Transmission processing and discarding are repeated for each video frame. For this reason, the receiving side can receive only half of the originally required number of video frames per unit time, and the video frames stored in the video frame memory are repeatedly output twice each as shown in FIG. At the maximum, only half of the transmitted video frame (N / 2 video frames in the case of transmitting N video frames per second) can be received.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to make the most of the transfer throughput of the entire system of a video transfer system to maximize the number of images that can be transferred. It is an object of the present invention to provide a technique that enables a frame to be transferred and minimizes image deterioration.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a video transfer method of a video transfer system for transferring a digital video signal via a network,
A step of thinning out the video frames of the digital video signal to be transferred on the network in advance to the number of video frames that can be transferred according to the transfer throughput of the entire video transfer system, and transferring the thinned-out video frames at a timing at which no dropped frames occur. Processing step.

Alternatively, the thinning-out step includes a step of thinning out video frames of the digital video signal at equal intervals in advance at an arbitrary interval at which transfer processing can be performed in accordance with the transfer throughput of the entire video transfer system, and discarding the frames. In the transfer processing step, the thinned-out video frames are stored in a memory at an arbitrary transmission timing synchronized with the input timing of the digital video signal so that no frame drop occurs, and the stored video frames are transmitted to a network. And a step of performing the following.

Alternatively, the timing for transferring the video frame to the memory and the interval for thinning out the video frame at equal intervals are interlocked with each other.

Further, the present invention is a video transfer system for transferring a digital video signal from a video transmission side to a video reception side via a network, wherein the video transmission side and the video reception side include a video interface unit and a network interface unit. Frame synchronization means for detecting the input timing of a video frame of a digital video signal input to the video interface unit on the video transmission side,
A control means for generating an arbitrary transmission timing control signal synchronized with the input timing and causing no frame drop and an arbitrary discard timing control signal capable of performing transfer processing in advance in accordance with the transfer throughput of the entire video transfer system; A discarding unit for discarding video frames of the digital video signal at equal intervals by a control signal and discarding the video frames; and a memory space for one video frame, wherein the video frames of the digital video signal not discarded by the discarding unit are stored. A buffer memory that holds the data in a first-in first-out manner, control means for transferring the video frame held in the buffer memory to the main memory by the transmission timing control signal, and a video interface transferred and stored in the main memory to the network interface unit again Control means to input and previous Processing means for transmitting the video frame input to the network interface unit to the network, wherein the video receiving side transfers the video frame received by the network interface unit to the main memory, and transfers the video frame to the main memory. Control means for transferring the stored and stored video frames to the frame memory of the video interface unit again, and output means for outputting the video frames of the frame memory with a predetermined timing signal are provided.

Alternatively, the timing for transferring the video frame to the main memory and the interval for thinning out the video frame at equal intervals are interlocked with each other.

Alternatively, the frame memory has a memory area for two video frames, and the control means for transferring the data to the frame memory alternately transfers the video frames to the memory area for the two video frames. Output the video frame of the memory area finally accumulated by the transfer with a predetermined timing signal.

According to the present invention, in the video transfer system on the transmission side, the number of video frames is reduced to a necessary minimum at equal intervals in accordance with the transfer capacity, and the transfer interval of the video frames is adjusted to cause frame drop during the transfer process. Don't do it.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram of a video transfer system showing an embodiment of the present invention, wherein 1 is a CPU, 2 is a main memory, 3 is an internal bus, 4 is an external bus, 5 is a bus bridge, 6 Reference numeral denotes a video interface card for performing input / output processing of digital video signals, and reference numeral 7 denotes a network interface card for performing processing for transmitting / receiving a PDU (protocol data unit) having a video signal as data on a network.

In the video interface card 6, 8
Is a video input unit for inputting a digital video signal from the outside, 9
Is a video frame synchronization unit for performing video frame synchronization control of an input digital video signal, 10 is a frame transmission control unit for performing timing control of transfer processing and discarding processing of an input video frame, and 11 is a frame transmission control unit. This is a frame discarding unit that performs video frame discarding processing under control. Reference numeral 12 denotes a frame FIFO for temporarily storing video frames to be transferred, which has a memory area for one frame, and the timing at which video frames are transmitted from the FIFO is based on a transmission timing signal from a frame transmission control unit. Reference numeral 13 denotes a bus control unit for controlling transmission and reception of video frames between the video interface card 6 and the main memory 2 via a bus, and 14 denotes a video frame memory for temporarily storing video frames received from a network. A double buffer type memory having a memory area for two frames and storing received video frames in alternate frame memory areas; and 15, a digital video signal having a predetermined number of video frames per unit time in the video frame memory. As a video output unit for outputting to the outside.

On the other hand, in the network interface card 7, reference numeral 16 denotes a bus control unit for controlling transmission and reception of video frames between the network interface card 7 and the main memory 2 via a bus, and reference numeral 17 denotes a bus controller in accordance with a network protocol. A protocol processing unit for performing header processing and the like; and a PDU for performing synchronous control of the received PDU
Synchronizing unit 19 is a PD for inputting PDU from the network
U input unit, 20 is a P for sending PDUs onto the network
DU sending unit.

CPU 1, main memory 2, video interface card 6, network interface card 7
Are connected to each other via an internal bus 3, an external bus 4, and a bus bridge 5. The CPU 1 controls processing of data exchange via the bus in the system and copying within the main memory. Do with.

Next, a method of transferring a digital video signal via a network in the video transfer system according to the embodiment shown in FIG. 1 will be described.

In the video transmission system on the video transmission side, when a digital video signal is input to the video input unit 8 of the video interface card 6, the video frame synchronizer 9 detects a specific pattern for synchronization in the video frame. , The frame synchronization is passed to the frame discarding unit 11, and a frame synchronization signal adjusted to the head position of the video frame is generated and sent to the frame transmission control unit 10. The frame discarding unit 11 discards the video frame from the frame synchronizing unit 9 at a fixed frame interval according to a discarding frame control signal from the frame transmission control unit 10 described later, and passes the video frame not discarded to the frame FIFO 12.

The frame FIFO 12 outputs the input video frame to the bus control unit 13 in accordance with a frame transmission timing signal from a frame transmission control unit 10 described later. The frame discarding unit 11 and the frame FIFO 12
The method of frame discarding and transmission processing under the control of the frame transmission control unit 10 will be described later in detail.

The video frame passed to the bus control unit 13 is an address accessible from the video interface card 6 of the main memory 2 via the external bus 4, the bus bridge 5, and the internal bus 3 under the control of the bus control unit 13. Is transferred to the memory area A.

The CPU 1 transfers a video frame sent from the video interface card 6 via the internal bus 3 to a specific memory area A of the main memory 2. When detecting that a new video frame has been stored in the memory area A of the main memory 2, the video frame in the memory area A is copied to another memory area B having an address accessible from the network interface card 7. When the copying of the video frame information to the memory area B is completed, the video frames stored therein are transferred to the network interface card 7 via the internal bus 3, the bus bridge 5, and the external bus 4, and the network interface card 7 The processing unit 17 performs a protocol process such as adding a header such as a destination address necessary for transmission and reception on the network, forms a PDU, and sends the PDU from the PDU output unit 20 to the network.

In the video transfer system on the video receiving side, the PD of the network interface card 7 is
U input unit 19 receives a PDU from the network,
After PDU synchronization using the synchronization pattern in the DU synchronization unit 18,
The protocol processing unit 17 performs protocol processing such as header removal and error checking, extracts a video frame from the PDU, and controls the external bus 4 under the control of the bus control unit 16.
The data is transferred and stored in the memory area B of an address accessible from the network interface card 7 in the main memory 2 via the bus bridge 5 and the internal bus 3. Upon detecting that a new video frame has been stored in the memory area B, the video frame is transferred to the video interface card 6.
Then, the copied video frame is transferred to the video interface card 6 via the internal bus 3, the bus bridge 5, and the external bus 4 again. In the video interface card 6, the image data is temporarily stored in an empty memory area of the video frame memory 14 through the bus control unit 13. By outputting the video frames stored in the video frame memory 14 at a fixed number per unit time, that is, N frames per second from the video output unit 15, it is possible to transfer digital video signals via a network. Become.

The video frame memory 14 is a double buffer type memory capable of storing two frames of video frames, stores video frames in alternate buffer memory areas and retrieves them, but no new video frames are stored in one buffer. In this case, the video frame stored in the other is repeatedly transmitted. The video frame memory 1
4 is provided with a counter for measuring the number of video frames before capturing the video frames, calculates the number of video frames stored in the video frame memory 14 per unit time, and based on this value, a transmission-side video transfer system described later. The frame discard unit 11 may set the video frame interval to be discarded.

Next, a method of generating a discarded frame control signal in the frame transmission control section 10 and a transmission timing signal from the frame FIFO 12 will be described in detail.

First, when a frame interval to be discarded is arbitrarily set by the frame transmission control unit 10, a discarded frame control signal and a frame A FIFO transmission timing signal is generated and output to the frame discard unit 11 and the frame FIFO 12.

FIG. 2 schematically shows the relationship between these timing control signals when the frame interval to be discarded is set to 5; FIG. 2 (a) shows a video frame input by the video input unit 8, and FIG. ) Is a timing signal indicating the start position of the input video frame generated by the frame synchronization unit 9,
(C) is a discarded frame control signal generated from the set value (5 in this case) of the discarded frame interval and the head position signal of (b), and (d) is a discarded frame interval similar to (c). (5 in this case) and the control signal for the transmission timing of the video frame from the frame FIFO 12 generated from the head position signal of (b). The control signal for the discarded frame in (c) can be easily configured by setting it to a high level every five clocks by a counter circuit using the input video frame head position signal in (b) as a clock.
The control signal of the transmission timing of (d) can be easily constituted by a multiplying circuit from the set value 5 to 4/5 of the frame interval which discards the input video frame head position signal of (b) as a clock.

By giving the control signal of the discarded frame (c) and the control signal of the transmission timing of (d) to the frame discarding unit 11 and the frame FIFO 12, respectively, the transmission control of the video frame for performing the above-described transfer processing is performed. Is possible.

The set value of the frame interval to be discarded (5 in this example) is first set to a value that does not discard anything, and the video is actually transferred.
If only half of the transmission frame can be received on the receiving side in the same way as in the conventional system, if a value is sequentially set to narrow the discarding frame interval, 1 /
More than two video frames can be received. In this state, frames are not dropped during the transfer process, and video transfer is performed by making the most of the transfer throughput of the entire system.

The number of frames received on the receiving side may be measured using a video frame counter connected outside the video transfer system, or calculated from the video frame counter input to the frame memory 14 described above. You may.
Further, in this example, the discarding frame interval is described as 5, but it can be easily analogized from this description that the same processing can be performed even if this value is an arbitrary value.

In the video transfer system according to the above embodiment of the present invention, when the speed of the video transfer process is slightly lower than the input video frame speed due to a transfer bottleneck of the external bus 4 or the internal bus 2 or the like. Will be described in detail below.

FIG. 3 illustrates a case where only four frames can be transferred from a five-frame input video frame in order to describe a video frame in a transfer process in a video transfer system according to an embodiment of the present invention. , (A)
Is a transmission-side input video frame, (b) is a discarded frame control signal generated by the frame transmission control unit 10, (c) is a transmission timing control signal also generated by the frame transmission control unit 10, and (d) is a transfer process. (E) the transmission timing of the video frame from the frame FIFO 12 where
Is a timing signal of a video frame output from the frame memory 14 on the receiving side, and (f) is a video output unit 1 on the receiving side.
5 shows a video frame output from the fifth frame.

Here, a case is shown in which transmission processing can be performed for only four frames with respect to five input video frames, but when the transfer throughput of the video transfer system is different, for example, when only five out of six frames can be transferred. The transfer method can be easily inferred from this description. As described above, the transfer throughput of the video transfer system can be detected by changing the set value of the discarded frame interval.

Since the transfer throughput of the video transfer system shown in this example is 4/5 of the input video speed, the discard frame control signal of FIG. Are discarded, that is, the video frame of the shaded portion in (a) is discarded. A video frame which is not discarded, that is, a video frame without hatching in FIG.
It is sent to O12 and sent to the bus control unit 13 in accordance with the sending timing signal (c). Frame FIFO12
Output speed is 4/5 of the input speed of video frame
When the frames (1) to (4) of (a) are input to the frame FIFO 12, (4/5) of the memory space for one frame is filled. However, since the next frame (5) is discarded, the video frames remaining in the frame FIFO 12 during this time are also passed to the bus control unit 13, and the frame FIFO 12 becomes empty. That is, the frame FIFO 12 is initialized every five frames, and a video transfer process becomes possible. Bus control unit 1
3 is transferred to the PDU input unit 19 of the video transfer system on the receiving side by the above-described video transfer processing, and is stored in the double buffer type frame memory 14 through protocol processing and main memory copy. e)
Video output unit 1 according to the video frame transmission timing
5 is output. At this time, since the transfer processing speed of the video frame, that is, the speed input to the frame memory 14 is 4/5 lower than the output speed of the video frame, the next time the video frame (1) is transmitted, Video frames are not stored. Therefore, the video frame of the frame (1) is output again as shown in (f),
Thereafter, the frames (2), (3), and (4) sequentially stored in the frame memory 14 are output, and the video output unit 1 outputs the video frame of the pattern (f) having a cycle of five frames.
Send out from 5.

[0042]

The effects obtained by the representative inventions among the inventions disclosed in the present invention will be briefly described.
It is as follows.

According to the present invention, even when the transfer processing speed of the video frame is slightly lower than the input video frame speed as in the conventional system, the reception side causes only one half of the input video frame due to the occurrence of dropped frames. Unlike the case where transfer is not possible, the thinning of the video frames and the control of the transfer interval are performed before the transfer process in accordance with the transfer throughput of the video transfer system, so that there is no frame drop in the video transfer process, and the video transfer system has It is possible to transfer a video frame by making maximum use of the transfer throughput, and to express a dynamic object or the like more finely, and to receive a video signal with relatively little image degradation.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a video transfer system according to an embodiment of the present invention.

FIG. 2 shows a video transfer system according to the embodiment.
FIG. 3 is a diagram illustrating timing signals necessary for video frame transfer control.

FIG. 3 illustrates a video transfer system according to the embodiment.
It is a figure which shows from a transmission side input video frame to a reception side output video frame.

FIG. 4 is a diagram showing a schematic configuration of an example of a conventional video transfer system.

FIG. 5 is a schematic configuration diagram of a video frame when a video frame is dropped in a conventional video transfer system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... CPU 2 ... Main memory 3 ... Internal bus 4 ... External bus 5 ... Bus bridge 6 ... Video interface card 7 ... Network interface card 10 ... Frame transmission control part 11 ... Frame discarding part 12 ... Frame FIFO 13, 16 ... Bus control unit 14 Frame memory 15 Video output unit 17 Protocol processing unit 18 PDU synchronization unit 19 PDU input unit 20 PDU output unit

Continued on the front page (72) Inventor Daiki Uesono 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Co., Ltd. (72) Inventor Tomohiko Nagase 1-9-8 Shibuya, Shibuya-ku, Tokyo Stock Within Photoron (72) Inventor Shigeru Yamada 1-9-9 Shibuya, Shibuya-ku, Tokyo F-term within Photoron Corporation (reference) 5C059 KK34 LB07 LB11 RB02 SS06 TA07 TB04 TC37 UA01 UA04 UA10 UA29 UA34 UA39 5C064 AA01 BA07 BB05 BC10 BC20 BD08

Claims (6)

[Claims] 1. A video transfer method for a video transfer system for transferring a digital video signal via a network, wherein a video frame of the digital video signal transferred on the network is transferred in advance according to the transfer throughput of the entire video transfer system. A video transfer method comprising: a step of thinning out the number of video frames that can be processed; and a step of transferring the thinned-out video frames at a timing at which frame dropout does not occur. 2. The thinning-out step includes a step of thinning out video frames of a digital video signal at equal intervals in advance at an arbitrary interval that allows transfer processing in accordance with the transfer throughput of the entire video transfer system and discarding the frames in advance. In the transfer processing step, storing the thinned-out video frame in a memory at an arbitrary transmission timing synchronized with the input timing of the video frame of the digital video signal so that no frame drop occurs; and Transmitting the image to a network. 3. The video transfer method according to claim 2, wherein a timing of transferring the video frame to the memory and an interval for thinning out the video frame at equal intervals are linked to each other. 4. A video transfer system for transferring a digital video signal from a video transmission side to a video reception side via a network, wherein the video transmission side and the video reception side include a video interface unit and a network interface unit in a main memory. A video synchronizing means for detecting an input timing of a video frame of a digital video signal input to the video interface unit; and an optional device which synchronizes with the input timing and does not cause a frame drop. Control means for generating a discard timing control signal capable of performing transfer processing in advance according to the transmission timing control signal of the digital video signal and the transfer throughput of the entire video transfer system; and arbitrarily setting a video frame of the digital video signal by the discard timing control signal. At regular intervals and discard A discarding unit, a buffer memory having a memory space for one video frame, and holding a video frame of a digital video signal which is not discarded by the discarding unit on a first-in first-out basis; and controlling the transmission timing of the video frame held in the buffer memory. Control means for transferring the video frames transferred and stored in the main memory to the network interface unit again, and processing for transmitting the video frames input to the network interface unit to the network On the video receiving side, control means for transferring the video frame received by the network interface unit to the main memory; and transferring the video frame transferred and accumulated in the main memory to the frame memory of the video interface unit again. Forward Image transfer system characterized by comprising a control means, and output means for outputting a video frame of the frame memory at a predetermined timing signal. 5. The video transfer system according to claim 4, wherein a timing of transferring the video frame to the main memory and an interval for thinning out the video frame at equal intervals are linked to each other. 6. The frame memory includes a memory area for two video frames, the control means for transferring the image data to the frame memory alternately transfers video frames to the memory area for the two video frames, and the output means. 6. The video transfer system according to claim 4, wherein the video output unit outputs a video frame in a memory area lastly stored by the transfer at a predetermined timing signal.