JP2001016585A - Video storage/reproduction method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video storage/reproduction method and system with excellent quality without deteriorating the utilizing efficiency of a transmission line. SOLUTION: A storage section 16 at a receiver side stores video data after FEC decoding, a control parameter and a video frame pointer. In the case of reproducing and displaying an image with high image quality, an additional data extract section 17 extracts additional data (control parameter and video frame pointer) from the storage section 16 and transmits the data to a transmitter side. The transmitter side reads discarded data from a storage section 6 on the basis of the additional data and transmits the data to the receiver side. A video composite section 18 at the receiver side composites the data read from the storage section 16 with the received discarded data and transmits the composite data to a video decoding section 13. As a result, the image with high image quality can be reproduced and displayed without deteriorating the utilizing efficiency of a transmission line as a result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for storing and reproducing video, and more particularly, to a method for transmitting a video signal to a mobile unit such as a vehicle, for example, by transmitting a video signal to a mobile unit such as a vehicle. The present invention relates to a video storage / playback method and apparatus for temporarily storing and playing back a video signal.

[0002]

2. Description of the Related Art Conventionally, an audio / video signal (hereinafter, referred to as a video signal) transmitted through a transmission path is received,
When the received video signal is stored once and then reproduced on the receiving side, a retransmission type protocol (for example, TCP / I
P), a file is transmitted in non-real time, and the receiving side temporarily stores the received video signal in a storage medium, and then decodes and reproduces the display to display the video signal. However, a transmission path in which a transmission error is likely to occur, for example, a transmission path for transmitting to a mobile body such as a vehicle,
When a video signal is transmitted using the retransmission protocol,
Retransmission procedures occur frequently, and the throughput is greatly reduced.

Therefore, conventionally, the bit rate of a video signal to be transmitted is reduced according to specifications, and a strong error correction code is fixedly applied to the video signal to be transmitted and stored in a storage medium. ing.

[0004]

By the way, among users, there is a demand that a low-quality reproduced image is acceptable, so that the user wants to view it with a low-cost reproducing apparatus. There is a request to view the reproduced image of the. In the case of the former request, the video signal stored in the storage medium may be simply reproduced, but in the case of the latter request, retransmission by simple file transmission, that is, file transmission without reducing the bit rate, may be performed. , You can watch the video with good image quality. However, this method has a problem that the same data as the already received image data is retransmitted in a large amount, and the efficiency of use of the transmission path is reduced.

An object of the present invention is to eliminate the above-mentioned problems of the prior art and to provide a method and apparatus for storing and reproducing video with good quality without lowering the efficiency of using a transmission line.

[0006]

In order to achieve the above object, according to the present invention, a transmitting side generates a transmission data by increasing or decreasing a bit rate of a video signal in accordance with a transmission path quality, and generates the transmission data. The data is transmitted with at least a control parameter indicating the deleted video data and a video frame pointer indicating the number of frames from the start of transmission, and the receiving side stores the received data in the storage unit, and during reproduction, Extracting at least the control parameters and the video frame pointer from the data stored in the storage unit, and requesting the transmission side to transmit the video data deleted at the time of the transmission based on the extracted control parameters and the video frame pointer; It is characterized in that data and video data stored in the storage unit are combined and decoded / reproduced.

According to this feature, when reproducing the data from the storage unit that stores the data whose bit rate has been reduced according to the quality of the transmission path, the transmission side requests the transmission side to transmit the deleted data, and Since the data stored in the section and the data obtained by the transmission request can be combined and output, it is possible to reproduce a good quality video signal without lowering the transmission path utilization efficiency. become able to.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration and functions of an embodiment of the present invention. The video transmission device according to the present embodiment includes a transmission side and a reception side. The transmission side includes a stream converter 1 for reducing the bit rate of video data to be transmitted, and a variable FEC (Forward Error Correction) which is a variable error correction encoder for performing error correction encoding on the output from the stream converter 1. )
A transmitting unit 3 that packetizes the error-correction-encoded video data and transmits the packetized data to a receiving side; a control unit 4 that controls operations of the stream converting unit 1 and the variable FEC unit 2; It comprises a discard data reading unit 5, a storage unit 6 such as a hard disk for storing encoded moving image data a, and a discard data transmitting unit 7.

The receiving side includes a receiving unit 11 for receiving a packet transmitted from the transmitting side through the transmission path b, an FEC decoding unit 12 for decoding the error correction coding, and an error correcting code A video decoding unit 13 for decoding the video data that has been decoded, a video display unit 14 for displaying the output of the video decoding unit 13, and monitoring the received data of the receiving unit 11 to determine the network quality. Network quality monitoring unit 15 and F
It comprises a storage section 16 such as a hard disk for storing video data after EC decoding, an additional data extraction section 17, and a video synthesis section 18.

Next, the operation of this embodiment will be described. The stream conversion unit 1 reads encoded moving image data a, for example, MPEG-1 data from a network (not shown) or a local hard disk 6, and
Perform bit rate reduction. The bit rate reduction is
For example, Japanese Patent Application Laid-Open No. 10-2247 filed by the present applicant.
No. 94 can be used.

FIG. 2 shows an example of the above bit rate reduction method.
This will be briefly described with reference to FIG. FIG. 2 is a block diagram showing a specific example of the stream converter 1. I, P,
The B separation unit 21 separates the encoded video data a into I, P, and B pictures based on the picture header. The I, P, and B pictures separated by the I, P, and B separation unit 21 are input to first, second, and third header / low-frequency / high-frequency separation units 22, 23, and 24, respectively. The first header / low frequency / high frequency separation unit 22 separates a low frequency component of the picture header, macro block header and DCT data of the I picture, and a high frequency component of the DCT data. The header and low frequency components enter a first selector 25, and the high frequency components enter a second selector 26. Second
The header / low-frequency / high-frequency separation unit 23 separates a low-frequency component of a picture header, a macroblock header, a motion vector and DCT data of a P-picture, and a high-frequency component of the DCT data. The former is the third selection unit 2
7 and the latter enters the fourth selector 28. Further, the third header / low-frequency / high-frequency separation unit 24 separates the B-picture into a picture header, a macroblock header, a motion vector, a low-frequency component of DCT data, and a high-frequency component of the DCT data. Then, the former enters the fifth selector 29, and the latter enters the sixth selector 30. The first
The selection units 25 to 30 are controlled by a control signal from the control unit 4 and are selectively operated.

The data that has been bit-rate-converted by the stream converter 1 is input to a variable FEC unit 2. The variable FEC unit 2 performs error correction encoding with the intensity changed according to an instruction from the control unit 4. As the error correction coding, for example, Reed-Solomon with interleaving (Reed So
lomon) code can be used. As shown in FIG. 3, the Reed-Solomon code with interleaving performs data writing and application of a Reed-Solomon error correction code in the horizontal direction when the number of interleaving steps is n, and reads transmission data. The vertical direction (step direction) is used. Errors in the middle of transmission generally have the property of occurring in bursts, and if several or more errors occur consecutively, it is not possible to restore the correct data, so increase the number of interleaving stages and check By increasing the bit length and the code length of the Reed-Solomon code, error resilience can be enhanced. The Reed-Solomon code is
Other error correcting codes such as BCH (Bose-Chaudhuri-Hoch)
quenghem) of course.

The transmitting section 3 performs packetization as shown in FIG. 4 on the transmission data subjected to the error correction coding in the variable FEC section 2. The packet includes a sequence number, a control parameter, a video frame pointer, and video data. The sequence number is a value that increases by one for each packet, and the control parameter is
These parameters indicate the control that the C section 2 is following. The video frame pointer is a pointer indicating the number of the video frame counted from the start of transmission.

Next, the receiving unit 11 receives the packet transmitted from the transmitting unit 3 via the transmission path b, and sends the received packet to the FEC decoding unit 12 and the network quality monitoring unit 15. The network quality monitoring unit 15 monitors the sequence number in the packet header, and if the sequence numbers are discontinuous, determines that a packet loss has occurred due to an error on the transmission path. The value of the transmission channel quality state or the network quality state is determined according to the degree of discontinuity of the sequence numbers. The value of the network quality state determined by the network quality monitoring unit 15 is sent to the control unit 4.

The control unit 4 controls the stream conversion unit 1 and the variable FEC unit 2 in accordance with the notified network quality state. For example, if the network quality state is expressed by an integer value from 0 to 5 (5 is the best and 0 is the worst), a control value corresponding to the value of the network quality state is determined in advance, and the control value To the stream converter 1 and the variable FEC unit 2.

For example, when the stream converter 1 has the configuration shown in FIG. 2, when the value of the network quality state is 5,
The first to sixth selectors 15 to 20 are all enabled, and all video data is transmitted as they are. When the value of the network quality state is 4, the first to fifth selectors 15 to 19 are enabled, and only the sixth selector 20 is disabled (disabled).
Only the video data of the higher order coefficient of the picture is discarded. When the value of the network quality state is 3, the first to fourth selectors 15 to 18 are enabled, and the fifth and sixth selectors 19 and 20 are enabled.
Is invalidated, and the B picture is discarded.

On the other hand, when the value of the network quality state is 5, the variable FEC unit 2 outputs data to the transmission unit 3 without performing error correction coding (FEC). When the value of the network quality state is 4, the RS (255, 2
42) The Reed-Solomon code is applied. When the value of the network quality state is 3, RS (2
55, 237) is applied. Here, “255” of RS (255, 242) indicates (original data + correction additional bit length), and “242” indicates (bit length of original data). Therefore, RS (25
5, 242) is 13 bits. The RS (255, 237) means the same contents. In this case, the additional bit length is 18 bits.

The packet sent from the receiving section 11 to the FEC decoding section 12 is FEC decoded by the FEC decoding section 12. The FEC decoding unit 6 refers to the control parameter in the packet header, determines an FEC decoding method, and performs decoding. In this decoding, received data is sequentially written in n stages in the vertical direction, and error correction decoding and data reading after decoding are performed in the horizontal direction. The data FEC-decoded by the FEC decoder 12 is sent to the video decoder 13 and sent to the storage 16 for storage.

The storage unit 16 stores data after FEC decoding, control parameters, and video frame pointers. Also, since the video bit rate is increased or decreased according to the change in the quality of the transmission path, the control parameter changes. The video decoding unit 13 decodes the FEC-decoded data into a video signal. At this time, the video decoding method is determined with reference to the control parameter in the packet header, and decoding is performed. The video display unit 14 displays the decoded video signal on a monitor.

The operation of reproducing and displaying a video signal after storing the video signal in the storage unit 16 on the receiving side as described above will be described. When reproducing and displaying a low-quality image, the video signal stored in the storage unit 16 is simply read out, decoded by the video decoding unit 13, and then displayed on the video display unit 14.

On the other hand, when reproducing and displaying a high-quality image, the data stored in the storage section 16 is read out, and the control parameters of the video frame data and the video frame pointer are extracted by the additional data extraction section 17. .
The additional data extracted by the additional data extraction unit 17 is sent to the discard data reading unit 5 on the transmission side. However, for frame data that is not normally received due to packet loss or the like, the additional data extraction unit 17 requests the discarded data reading unit 5 to retransmit all data.

The discard data reading section 5 accesses the storage section 6 in accordance with the received control parameters and the video frame pointer, and reads out the image data portion discarded in the initial transmission from the storage section 6. The read data is
It is sent from the discard data transmitting unit 7 to the receiving side. For this transmission, a protocol that enables reliable data transmission, for example, TC
Preferably, the P / IP protocol is used. Video synthesis unit 1
In step 8, the video data is reconstructed by combining the received data with the data from the storage unit 16. The reconstructed video data is sent to the video decoding unit 13, where the video data is decoded, and then displayed on the video display unit 14. In addition,
The video data reconstructed by the video synthesizing unit 18 may be stored in the storage unit 16 and viewed later.

As described above, according to the present embodiment, a low-quality image and a high-quality image can be selectively and easily reproduced and displayed. Further, when reproducing and displaying a high-quality image, only the image data portion discarded in the initial transmission and the image data portion not normally received due to packet loss or the like need be retransmitted. There is no decrease in the efficiency of use.

[0024]

As is apparent from the above description, according to the present invention, when a video signal transmitted using a transmission path whose transmission path quality changes is temporarily recorded on the receiving side and reproduced. It is possible to combine the data deleted at the time of transmission and the recorded data obtained from the transmission side based on the transmission request from the reception side and reproduce the data, so that the utilization efficiency of the transmission path is reduced. And a high-quality image can be reproduced and displayed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration and functions of an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a specific example of a stream converter.

FIG. 3 is an explanatory diagram of Reed-Solomon encoding with interleaving.

FIG. 4 is an explanatory diagram of a packet configuration.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Stream conversion part, 2 ... Variable FEC part, 3 ... Transmission part, 4 ... Control part, 5 ... Discard data reading part, 6 ... Storage part,
7: Discarded data transmitter, 11: Receiver, 12: FEC decoder, 13: Video decoder, 14: Video display, 15
... Network quality monitoring unit, 16 storage unit, 17 additional data extraction unit, 18 video synthesis unit.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Wada 2-1-15 Ohara, Kamifukuoka-shi, Saitama F-term in Kadidi Laboratory Co., Ltd. (Reference) 5C053 FA23 GB14 GB15 GB23 GB28 GB37 JA21 KA08 KA17 LA14 5C059 KK00 MA00 MA05 MA14 MA23 PP05 PP06 PP07 RA04 RA08 RB14 RC12 RF05 RF23 SS06 SS11 TA73 TA76 TB04 TC22 TD07 UA02 UA05 UA31 5D044 AB07 BC01 CC04 DE14 DE38 DE43 DE49 GK07 GK10 GK11 HL14 5K014 AA01 AA05 BA07 BA08 DA01 FA01 FA03 FA03 FA03

Claims (4)

[Claims] In the method of storing and reproducing a video signal, a transmitting side generates transmission data by increasing or decreasing a bit rate of a video signal according to a transmission path quality, and adds the deleted video data to the transmission data. Control parameters and a video frame pointer indicating the number of frames from the start of transmission, and transmit the data. The receiving side stores the received data in the storage unit,
Extracting at least the control parameters and the video frame pointer from the data stored in the storage unit, and requesting the transmission side to transmit the video data deleted at the time of the transmission based on the extracted control parameters and the video frame pointer; A video storage / reproduction method, comprising combining data and video data stored in the storage unit, and decoding / reproducing the data. 2. The video signal storage / reproduction method according to claim 1, wherein the transmitting side converts the bit stream compressed by MPEG into a B picture and a P picture and a DCT low frequency A video storage / reproducing method characterized in that the bit rate is increased or decreased by deleting a combination of a component and a DCT high-frequency component. 3. A video signal storage / reproduction device, comprising: a storage unit for storing received data; extracting additional data in the received data from the storage unit; and transmitting the video data deleted during transmission to a transmission side. And a video synthesizing unit for synthesizing the video data received from the transmitting side based on the transmission request by the additional data extracting unit and the video data stored in the storage unit. A video storage / playback apparatus characterized in that: 4. A discard data reading section for reading out video data deleted at the time of transmission from a transmission data storage section based on additional data sent from a receiving side, in the video signal storage / playback apparatus, A discard data transmitting unit for transmitting video data read from the unit to a receiving side by using a retransmission type protocol.