KR101999105B1 - Method of reliable data transmission with least video latency for real-time video streaming - Google Patents

Abstract

A method for transmitting and receiving data stably with minimum video delay time in real-time video streaming, the method comprising the steps of: setting a transmission environment factor of a communication network in a transmitter and inputting the transmission environment parameter; Setting a target restoration failure rate p for stable transmission in a transmitter and calculating and obtaining an overhead code according to the target restoration failure rate p; Generating a source symbol and a recovery symbol by a RaptorQ encoder for each source block by using data obtained by encoding a slice that is a part of one frame or frame of an image in a transmitter as one source block; Transmitting a source symbol and a recovery symbol generated for each source block in a transmitter to a communication network, and receiving a source or a recovery symbol in a receiver to recover the lost source symbol and recovering the source symbol.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for transmitting and receiving video data with a minimum delay time in a real-time video streaming,

The present invention relates to a method of transmitting and receiving data stably while minimizing a video delay time in real time video streaming. More particularly, the present invention relates to a method and apparatus for transmitting and receiving moving picture data between a transmitter which is a moving picture encoder and a receiver which is a decoder, In order to improve the existing algorithm that restores moving picture data by using the restoration data, the receiver that receives the restoration data additionally generates and transmits the stable data that minimizes the video delay time which has a significant influence on the quality of the real time video streaming And a transmission / reception algorithm.

A real-time video streaming broadcasting service in which a sender transmits real-time video data and a receiver instantly reproduces the real-time video streaming broadcast service is widely available regardless of wired or wireless.

However, the essential nature of loss and delay of data packets on the network is a major impediment to real-time video streaming services and requires a reliable data transmission method without delay.

Especially, it is more meaningful in a wireless network where transmission quality is lower than that of a wired network.

In particular, unlike the TCP (Transmission Control Protocol) transmission method, the UDP (User Datagram Protocol) transmission method does not guarantee stable transmission of data packets and does not request retransmission for lost data packets. Therefore, -FEC (Application Layer Forward Error Correction) is applied to transmit the data to guarantee the stability of the data.

The RaptorQ AL-FEC code is a fountain code, a code that can instantly create as many as you want an infinite number of encoding symbols.

The RaptorQ AL-FEC code is a systematic code, ie, the source symbol is part of an encoding symbol without modification.

This RaptorQ AL-FEC code can be used for real-time video streaming transmission.

In real-time video streaming, AL-FEC such as RaptorQ, which can recover packet loss in real-time video streaming, plays a very important role because only 1% of the packets sent to the network are lost,

However, since AL-FEC code such as RaptorQ collects data into one block until it reaches a certain size, and processes the divided blocks by dividing them into k symbols, time delay inevitably occurs in video streaming.

In the present invention, a method for reducing the delay time is proposed.

As a related art, Patent Document 1 discloses a file processing apparatus of a digital broadcast receiver, and Patent Document 2 proposes a stable data transmission / reception method in a heterogeneous LTE communication network.

1. Korea Patent No. 0848273 2. Korean Patent No. 10-1754809

Qualcomm document, TSG-SA4 # 64 meeting, 11-25 pr. 2011, San Diego, CA, USA RFC 6330 "4.2. Content Delivery Protocol Requirements "

The present invention seeks to provide an improved algorithm based on AL-FEC using RaptorQ to transmit and receive data reliably while minimizing video latency in real-time video streaming.

In order to solve the above problem, a stable data transmission / reception method for minimizing a video delay time in moving picture real time streaming includes: setting a transmission environment factor of a communication network in a transmitter and inputting the parameter; Setting a target restoration failure rate p for stable transmission in a transmitter and calculating and obtaining an overhead code according to the target restoration failure rate p; Obtaining a number of source symbols k and a number of recovered symbols r from the size of each source block, the overhead code, and the transmission environment factor, using data obtained by encoding a slice that is a part of one frame or frame of an image in a transmitter as one source block; Dividing the source block using the number of source symbols k and the number of recovered symbols r, and generating k source symbols and r recovery symbols with a RaptorQ encoder; Transmitting a source symbol and a recovery symbol generated for each source block in a transmitter to a communication network, and receiving a source or a recovery symbol in a receiver to recover the lost source symbol and recovering the source symbol.

The transmission environment factor of the communication network is a loss ratio (L) which is expected to be an average loss during transmission of data through a communication network.

If the target restoration failure rate is set to one frame per one million frames, p = 0.000001 is set.

The above overhead code is characterized by the following equation.

Equation 1

The number k of source symbols means that one source block is divided into k pieces. For example, since the Internet communication network transmits 1500 bytes in one packet, it is advantageous to prevent loss by one size smaller than k pieces of source blocks If you want to set this to 1000 bytes, divide the size of one source block by 1000 bytes and set the value to k.

The number of recovered symbols r is obtained from the overhead code, the transmission environment factor (L), k by the following equation.

Equation 2

In the real-time video streaming according to the present invention, the algorithm capable of transmitting and receiving video data stably while minimizing the video delay time is a real-time transceiver product through a wireless network having a delay time and a low stability such as a mobile router, a mobile encoder, .

In the case of using the improved RaptorQ encoder according to the present invention, when the overhead is 0, stable data is transmitted with an overhead code as low as 1 / 10,000 when the recovery failure rate is 1/100, 1 / 10,000 when 2, While reducing latency.

In addition, it has a linear time (O (n)) in the computational complexity, which is effective for large-scale file and streaming, and is also effective in memory use.

1 is a method of transmitting and receiving data by AL-FEC.
2 is a conceptual diagram of data transmission / reception in a wired / wireless communication network according to the present invention.
Figure 3 is an improvement over the prior art according to the present invention.
4 is a block diagram of a data transmission / reception system according to the present invention.
5 is a flowchart of data transmission and reception according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the particular forms disclosed. And shall not interpret it.

A method of eliminating a retransmission request causing an overload of a network in a unidirectional multicast and providing asynchronous reception to a receiver includes generating and transmitting a constantly encoded packet using a file to be transmitted by the transmitter, And decodes the received packet only to the extent that decoding is possible.

As shown in FIG. 1, the AL-FEC sends a recovery symbol generated from the source block and the source block over the network in order to reliably transmit data on the network where data loss occurs. In a network, loss of source symbols and recovery symbols may occur due to packet loss. Finally, when the source symbol and the recovery symbol arrive, they are used to recover the lost source block and restore the original block.

RaptorQ is a method of AL-FEC that divides the fixed size data to be sent by the transmitter into block units, generates r recovery symbols using k source symbols in each block, generates k original source symbols, r, and recover the lost source symbol from the received source symbol or recovery symbol equal to or greater than the source symbol number k at the receiver.

Conventionally, FEC technology for preventing packet loss prevents error in data coding in normal hardware. However, RaptorQ compensates conventional error coding. It can be implemented by software only. In the case of decoding, Luby Transform) code.

A fountain code is a property that can generate infinite number of recovery symbols from a given source symbol, so that the amount of encoded data is rateless. The fractional code can be implemented in LT code and later developed into Raptor code. The Raptor code is pre-coding the source symbols in advance, generating intermediate symbols from the source symbols for encoding and decoding, and replacing the (lost) source or recovery symbols with a small number of exclusive It is an efficient fractional code that can be generated as a sum (XOR).

가 되는 아주 뛰어난 특성을 갖고 있다. (참고문헌: Qualcomm document, TSG-SA4#64 meeting, 11-25 pr. 2011, San Diego, CA, USA)RaptorQ has the probability of failing to recover all lost source symbols when (k + Δ) source or recovery symbols are received for k source symbols in a block

And has excellent characteristics. (Reference: Qualcomm document, TSG-SA4 # 64 meeting, 11-25 pr. 2011, San Diego, CA, USA)

For example, when the number of source symbols in one block is k and the number of source or recovery symbols received when the source symbol and the recovery symbol for this block are sent to the network is k, k + 1, k + 2, the probability of failure to recover the lost source symbol is as shown in Table 1.

Number of source symbols and probability of restoration failure
Number of received source or recovery symbols

Restoration failure probability
k

1/100
k + 1

1 / 10,000
k + 2

1 / 1000,000

Equation 1

In the RaptorQ AL-FEC algorithm, the recovery failure probability p is

, The overhead code [Delta] is given by

Can be written as.

Equation 2

In order to meet the above restoration failure rate, k source symbols and r recovery symbols must start from the transmitter and reach a minimum k + Δ over the communication network with a loss rate of L. Therefore,

Therefore, if the minimum r is obtained by using this,

.

In the present invention, an existing method of transmitting data using RaptorQ AL-FEC is improved as follows so that transmission can be performed stably and efficiently while reducing delay time in a communication network. (See Fig. 3)

1) The conventional RaptorQ AL-FEC algorithm transmits the RaptorQ AL-FEC algorithm by transmitting the data to be transmitted until it reaches a predetermined size. However, the RaptorQ AL-FEC algorithm generates data by a frame or a slice of the image For the encoder, the time taken for the data of a certain size to converge was a delay time.

2) Our improved RaptorQ AL-FEC algorithm is based on the existing RaptorQ AL-FEC algorithm by applying the RaptorQ AL-FEC algorithm as a source block as soon as the encoded data of one frame is generated by the encoder. The time required for data gathering up to a predetermined size is prevented from becoming a delay time.

3) The conventional RaptorQ AL-FEC algorithm requires that the transmitter collects the necessary parameters for recovering the source block using the recovery symbol generation and recovery symbols, assuming that the data is always collected until it reaches the same size. However, according to the improved RaptorQ AL-FEC algorithm, since the size of data is not constant for each source block, the parameters required for each source block are different for each source block, and these parameters are transmitted together with every source block to solve the problem.

The parameters required to be exchanged between the transmitter and the receiver are as follows. (See RFC 6330 "4.2 Content Delivery Protocol Requirements")

① F: the transfer length of the object, in octets

(2) Al: the symbol alignment parameter

③ T: the symbol size in octets, which MUST be a multiple of Al

④ Z: the number of source blocks

⑤ N: the number of sub-blocks in each source block

⑥ Source Block Number (SBN)

⑦ Encoding Symbol ID (ESI)

⑧ Encoding symbol (s)

Claims (1)

A method for stably transmitting and receiving data between a transmitter and a receiver in real time video streaming while minimizing a video delay time,
Setting a transmission environment factor of a communication network in a transmitter and inputting the parameter;
Setting a target restoration failure rate p for stable transmission in a transmitter and calculating and obtaining an overhead code according to the target restoration failure rate p;
The transmitter encodes the slice, which is a part of an image frame or a frame, as one source block. The number of source symbols k and the number of recovered symbols r from the size of each source block, the overhead code, Obtaining;
Dividing the source block using the number of source symbols k and the number of recovered symbols r, and generating k source symbols and r recovery symbols with a RaptorQ encoder;
Calculating and transmitting a RaptorQ parameter for each source block from the source block size and the number of source symbols k;
Transmitting a source and a symbol generated in the transmitter by a communication network; and
And recovering the lost source symbol by receiving at least k source or recovery symbols at the receiver.

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