CN107241122B - A method of video signal transmission based on power line - Google Patents

Abstract

The invention discloses a video signal transmission method based on a power line, which can transmit the video signal by using the power line. This method uses digital coding to obtain the best coding efficiency, and analog coding to obtain smooth video quality changes. Through the hybrid digital-analog coding method, the advantages of the two are effectively combined, and the power headroom in digital coding and modulation is used to transmit enhancement layer related data. information, enhance the reconstruction quality of video transmission while improving the power utilization rate; dynamically adjust the target information rate according to the channel conditions to ensure all-weather communication accessibility; and dynamically realize the transmission of different information rates under the same bandwidth conditions, maximizing the Utilize bandwidth and ensure communication rate and success rate; in the process of video data decoding, by creating ION shared memory and using a private handle structure object to directly access the video decoding data in the receiver's window buffer, the pressure on the CPU is reduced and the video quality is improved. Efficiency of signal transmission.

Description

A method of video signal transmission based on power line

technical field

The invention relates to a power carrier communication technology, in particular to a power line-based video signal transmission method.

Background technique

At present, the use of electricity has spread to thousands of households, but how to realize the intelligent management of household electricity is a problem that government departments and related manufacturers need to consider. It is a good idea and way to solve this problem through the Internet of Things, but the current research on the smart power Internet of Things system is still in the initial stage of development, and there are few studies.

Power carrier is a unique communication method for power systems. Power line Communication (PLC) refers to a technology that uses existing power lines to transmit analog or digital signals at high speed through carrier waves. In recent years, Broadband Power Line Carrier (BPLC: Broadband Power Line Carrier) technology has been widely used, especially in scenarios such as smart grid meter reading systems, energy Internet, smart home and industrial data collection.

Video surveillance has a wide range of applications in power equipment monitoring. Currently, the transmission of video signals mainly relies on optical cables or other separate transmission channels for transmission, which is costly. In the prior art, there is no report on the use of power lines for video signal transmission.

The power line carrier communication network has the advantage of not requiring repeated wiring, which can greatly reduce the construction cost of the video transmission network. Using the existing power line resources for communication can not only meet the communication needs, but also solve the wiring difficulties, and the infrastructure investment and daily maintenance costs are low. Therefore, the power line carrier communication technology has high economy, convenience and practicability. However, the original intention of power line design is to complete power distribution rather than data transmission. Therefore, power line network is not a reliable communication carrier for data communication. First, power line will cause strong attenuation to communication signals. This attenuation The amplitude is highly time-varying and depends on the signal frequency, network topology, load electronics, etc.

The frequency bands in the existing power line carrier communication systems and devices are divided into narrowband (30kHz-500kHz) and wideband (2MHz-30MHz) communication. The power line carrier communication channel is affected by various interference, attenuation, reflection, etc., which makes the frequency of the channel. And the phase response becomes very complex, resulting in a large difference in the communication success rate with time and line variation.

In addition, the difference between the video signal and the traditional network data transmission is that the video has a higher requirement for real-time performance. On the other hand, the user can tolerate some errors and distortions in the video transmission. This creates an application scenario for analog encoded transmission. Existing digital encodings have a cliff effect. After the source is entropy encoded, it is transmitted through the channel. According to Shannon's separate coding theory, this performance can be optimal for point-to-point communication. However, this optimal performance has prerequisites. First, the estimation of the channel quality must be very accurate; once the code rate of the digital encoding of the source is determined, if the channel quality changes, the channel becomes better, and the channel quality cannot be used to improve. The gain brought by, if the channel quality deteriorates to a critical point, the entire video quality will have a cliff effect.

SUMMARY OF THE INVENTION

The invention provides a video signal transmission method based on power lines, which can transmit video signals by using power lines without establishing a special video signal transmission network, realize economical communication of monitoring video signals, and ensure the reliability and timeliness of signal transmission. low cost; use digital coding to obtain the best coding efficiency, analog coding to obtain smooth video quality changes, make full use of the power headroom in digital coding and modulation to transmit information related to the enhancement layer, and improve power utilization while enhancing Reconstruction quality of video transmission; can ensure all-weather communication accessibility; and dynamically realize the transmission of different information rates under the same bandwidth conditions, can maximize the use of bandwidth, and can ensure the communication rate and success rate; reduce the pressure on the CPU , which improves the efficiency of video signal transmission.

In order to achieve the above object, the present invention provides a video signal transmission method based on a power line, which can transmit a video signal by using a power line.

An optimization scheme includes the following steps:

S1. Set up multiple carrier data transmitters between multiple power devices and set up carrier data receivers in the central control room;

S2. The original video signal is subjected to hierarchical coding of the base layer digital coding and the enhancement layer analog coding, correspondingly to obtain a digital channel coding signal and an analog coding signal, and packaging the digital channel coding signal and the analog coding signal to obtain a data packet to be sent;

S3. Obtain the data packets to be sent, and dynamically determine the target information rate;

S4. Determine an information frame according to a preset frame structure, the information frame includes an information frame header and the information data, the information frame header includes the target information rate, and the information data includes the data packet;

S5. Send the information frame to the receiving end of the central control room to complete the transmission of the video signal.

Further, wherein in S2, the basic layer digital-to-analog encoding process is: the original video signal obtains a digital bit stream through a digital source encoder based on optimal quantization parameters, and the digital bit stream obtains a digital channel encoded signal through a digital channel encoder, The analog encoding process of the enhancement layer is as follows: the digital bit stream is passed through the video decoder to obtain the reconstructed digitally encoded video, the difference between the original video signal and the reconstructed digitally encoded video is obtained to obtain the residual signal, and the residual signal is passed through the analog encoder to obtain the analog encoded signal.

Further, in the S3, it includes: sending a channel sounding frame to a receiving end according to a preset temporary information rate, instructing the receiving end to determine a first signal-to-noise ratio for receiving the channel sounding frame, and the channel sounding frame Including the transmission power; acquiring the response frame sent by the receiving end at the temporary information rate, the response frame including the first signal-to-noise ratio; determining the second signal-to-noise ratio for receiving the response frame; When both the noise ratio and the second signal-to-noise ratio are not less than a preset threshold, the temporary information rate is used as the target information rate.

Further, after the channel sounding frame is sent to the receiving end according to the preset temporary information rate, it also includes: when the response frame sent by the receiving end is not received within a preset time period, repeating the update of the temporary information. until the response frame sent by the receiving end is received; updating the temporary information rate includes: reducing the temporary information rate, and using the reduced temporary information rate as a new temporary information rate.

Further, in the step S5, during the video signal transmission process, a linear function relationship between the block variance of the sub-blocks after the residual signal is divided into blocks and the quantization parameter is also established.

Further, the linear function relationship between the block variance of the sub-blocks after the residual signal is divided into blocks and the quantization parameters, the corresponding establishment process is:

S51. within the set quantization parameter value range, select the highest value QP _min and the lowest value QP _max ;

S52. Divide the original video signal into multiple groups of pictures GoP, and obtain residual signal data corresponding to QP _min and QP _max from each GoP;

S53 carries out three-dimensional DCT transformation to the residual signal data of the two groups obtained in step S52. respectively, divides the DCT coefficients obtained by the three-dimensional DCT transformation into blocks, obtains the block variance of each sub-block after the block, and represents the i-th sub-block with λ _i the block variance of the block;

S54. Use the linear function lnλ _i = _ki ·QP+w _i to represent the curve of lnλ _i changing with QP, we can get:

和

表示在QP_min和QP_max下第i个子块的块方差，k_i和w_i为第i个子块对应的曲线参数；In the formula,

and

represents the block variance of the ith sub-block under QP _min and QP _max , and _ki and _wi are the curve parameters corresponding to the ith sub-block;

S55. For each sub-block in a GoP, a set of k _i and w _i are obtained correspondingly, then for any given value of a quantization parameter QP, the block variance λ of the i-th sub-block under the quantization parameter QP can be obtained _{i_QP} is:

λ _{i_QP} =exp(k _i ·QP+ _wi ).

Further, in the step S5, the process of video signal reconstruction is also included.

Further, the process of the video signal reconstruction is:

The information frame received by the receiving end obtains the reconstructed digital channel coded signal through the digital channel decoder, obtains the reconstructed digital bit stream from the reconstructed digital channel coded signal, and obtains the reconstructed digital bit stream through the digital source decoder. digitally encoded video;

The information frame received by the receiving end and the reconstructed digital channel coded signal are calculated to obtain a disturbed analog coded signal, and the disturbed analog coded signal obtains a reconstructed residual signal through an analog decoder;

The reconstructed digitally encoded video is superimposed with the reconstructed residual signal to obtain a reconstructed original video signal.

Further, the digital channel decoder reconstructs the digital channel coded signal by the following method:

Create an ION shared memory containing the file identifier through the digital channel management function;

A private handle structure object is constructed according to the file identifier, and a receiver window buffer is created according to the private handle structure object and the ION shared memory.

When the receiving end receives the information frame, the data packet in the information frame is filled into the window buffer of the receiving end;

passing the private handle structure object corresponding to the receiver window buffer filled by the data packet to a video library;

The video library accesses the data packet in the receiver window buffer according to the received private handle structure object corresponding to the receiver window buffer, and performs decoding.

The present invention has the following advantages and beneficial effects:

(1) Use digital coding to obtain the best coding efficiency, and analog coding to obtain smooth video quality changes. Through the hybrid digital-analog coding method, the advantages of the two can be effectively combined, and the power headroom in the digital coding and modulation can be fully utilized to transmit the information related to the enhancement layer, and the reconstruction quality of the video transmission can be enhanced while improving the power utilization rate;

(2) Dynamically adjust the target information rate according to the channel conditions, which can ensure all-weather communication accessibility; and dynamically realize the transmission of different information rates under the same bandwidth conditions, which can maximize the use of bandwidth and ensure the communication rate and success rate. ;

(3) During the video data decoding process, by creating the ION shared memory and using the private handle structure object to directly access the video decoding data in the receiver window buffer, the pressure on the CPU is reduced and the efficiency of video signal transmission is improved.

Description of drawings

FIG. 1 shows a flow chart of a power line-based video signal transmission method of the present invention.

Detailed ways

In order to have a clearer understanding of the technical features, objects and effects of the present invention, the specific embodiments of the present invention will now be described with reference to the accompanying drawings.

Embodiment 1 A video signal transmission method based on power line

The present invention provides a power line-based video signal transmission method, which specifically includes the following steps:

S1. Set up multiple carrier data transmitters between multiple power devices and set up carrier data receivers in the central control room;

S2. The original video signal is subjected to layered encoding of the base layer digital encoding and the enhancement layer analog encoding, correspondingly to obtain a digital channel encoded signal and an analog encoded signal, and package the digital channel encoded signal and the analog encoded signal to obtain a data packet to be sent. The invention utilizes digital encoding to obtain the best encoding efficiency, and analog encoding to obtain smooth video quality changes. The hybrid digital-analog coding method can effectively combine the advantages of the two, make full use of the power headroom in the digital coding and modulation to transmit the information related to the enhancement layer, and enhance the reconstruction quality of the video transmission while improving the power utilization rate, so as to achieve high quality Effective trade-off of scalability and coding efficiency.

S3. Acquire the data packets to be sent, and dynamically determine the target information rate.

S4. Determine an information frame according to a preset frame structure, where the information frame includes an information frame header and the information data, the information frame header includes the target information rate, and the information data includes the data packet.

S5. Send the information frame to the receiving end of the central control room to complete the transmission of the video signal. The sending rate of the information frame refers to the target information rate. The receiving end can demodulate and receive correctly without prior negotiation, without adding complex demodulation algorithms. At the same time, dynamically adjusting the target information rate according to the channel conditions can ensure all-weather communication accessibility; and dynamically realizing the transmission of different information rates under the same bandwidth conditions can maximize the utilization of the bandwidth and ensure the communication rate and success rate.

In S2, the basic layer digital-to-analog encoding process is as follows: the original video signal is passed through a digital source encoder based on optimal quantization parameters to obtain a digital bit stream, the digital bit stream is passed through a digital channel encoder to obtain a digital channel encoded signal, and the enhancement layer analog The encoding process is as follows: the digital bit stream is passed through the video decoder to obtain the reconstructed digitally encoded video, the original video signal and the reconstructed digitally encoded video are differenced to obtain the residual signal, and the residual signal is passed through the analog encoder to obtain the analog encoded signal.

Preferably, in S3, the method includes: sending a channel sounding frame to a receiving end according to a preset temporary information rate, and instructing the receiving end to determine a first signal-to-noise ratio for receiving the channel sounding frame, and the channel sounding frame Including the transmission power; acquiring the response frame sent by the receiving end at the temporary information rate, the response frame including the first signal-to-noise ratio; determining the second signal-to-noise ratio for receiving the response frame; When both the noise ratio and the second signal-to-noise ratio are not less than a preset threshold, the temporary information rate is used as the target information rate.

Preferably, after the channel sounding frame is sent to the receiving end according to the preset temporary information rate, the method further includes: when the response frame sent by the receiving end is not received within a preset time period, repeating updating the temporary information until the response frame sent by the receiving end is received; the updating the temporary information rate includes: reducing the temporary information rate, and using the reduced temporary information rate as a new temporary information rate.

Preferably, in the step S5, during the video signal transmission process, a linear function relationship between the block variance of the sub-blocks after the residual signal is divided into blocks and the quantization parameters is also established, and the corresponding establishment process is:

S51. within the set quantization parameter value range, select the highest value QP _min and the lowest value QP _max ;

S52. Divide the original video signal into multiple groups of pictures GoP, and obtain residual signal data corresponding to QP _min and QP _max from each GoP;

S53 respectively performs three-dimensional DCT transformation on the residual signal data of the two groups obtained in step S52, divides the DCT coefficients obtained by the three-dimensional DCT transformation into blocks, obtains the block variance of each sub-block after the block, and uses λ _i to represent the ith sub-block The block variance of ;

S54. Use the linear function lnλ _i = _ki ·QP+w _i to represent the curve of lnλ _i changing with QP, we can get:

和

表示在QP_min和QP_max下第i个子块的块方差，k_i和w_i为第i个子块对应的曲线参数；In the formula,

and

represents the block variance of the ith sub-block under QP _min and QP _max , and _ki and _wi are the curve parameters corresponding to the ith sub-block;

S55. For each sub-block in a GoP, a set of k _i and w _i are obtained correspondingly, then for any given value of a quantization parameter QP, the block variance λ of the i-th sub-block under the quantization parameter QP can be obtained _{i_QP} is:

λ _{i_QP} =exp(k _i ·QP+ _wi ).

Preferably, in the step S5, the process of video signal reconstruction is also included:

The information frame received by the receiving end obtains a reconstructed digital channel coded signal through a digital channel decoder, a reconstructed digital bit stream is obtained from the reconstructed digital channel coded signal, and the reconstructed digital bit stream is reconstructed through a digital source decoder. digitally encoded video.

The information frame received by the receiving end and the reconstructed digital channel coded signal are calculated to obtain an analog coded signal with noise, and the analog coded signal with noise is obtained through an analog decoder to obtain a reconstructed residual signal. Specifically, LLSE is used for analog decoding of the noisy analog coded signal to obtain the reconstructed residual signal (LLSE is an important part of the decoder, LLSE uses an algorithm called least linear square estimation to analyze the received signal from the PHY physical layer. Data is de-whitened, inverse energy distribution process).

The reconstructed digitally encoded video is superimposed with the reconstructed residual signal to obtain a reconstructed original video signal.

Preferably, the digital channel decoder reconstructs the digital channel coded signal by the following method:

Create an ION shared memory containing the file identifier through the digital channel management function;

A private handle structure object is constructed according to the file identifier, and a receiver window buffer is created according to the private handle structure object and the ION shared memory.

When the receiving end receives the information frame, filling the data packet in the information frame into the window buffer of the receiving end;

passing the private handle structure object corresponding to the receiver window buffer filled by the data packet to a video library;

The video library accesses the data packet in the receiver window buffer according to the received private handle structure object corresponding to the receiver window buffer, and performs decoding.

Preferably, the private handle is defined as:

In data I/O, if data is to be read from a packet, the application first calls the operating system function and passes the file name, and selects a path to the file to open the file; the above operating system function retrieves a sequence number, that is, the private handle (file handle), which is the only identification basis for the opened file; to read a piece of data from the data packet, the application needs to call the function ReadFile, and combine the address of the private handle in memory with the The number of bytes to be copied is transmitted to the operating system; the buffer (buffer register, also called a buffer) can coordinate and buffer the high-speed CPU and the slow-speed peripherals to achieve synchronization of data transmission.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention. The exemplary embodiments were chosen and described for the purpose of explaining certain principles of the invention and their practical applications, to thereby enable one skilled in the art to make and utilize various exemplary embodiments and various different aspects of the invention. Choose and change. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims (3)

1. A power line-based video signal transmission method, the method comprising the steps: S1. Set up multiple carrier data transmitters between multiple power devices and set up carrier data receivers in the central control room; S2. The original video signal is subjected to layered encoding of the base layer digital encoding and the enhancement layer analog encoding, correspondingly to obtain a digital channel encoded signal and an analog encoded signal, and package the digital channel encoded signal and the analog encoded signal to obtain a data packet to be sent; S3. Obtain the data packets to be sent, and dynamically determine the target information rate; S4. Determine an information frame according to a preset frame structure, the information frame includes an information frame header and information data, the information frame header includes the target information rate, and the information data includes the data packet; S5. Send the information frame to the receiving end of the central control room to complete the transmission of the video signal; In S2, the basic layer digital-to-analog encoding process is as follows: the original video signal is passed through a digital source encoder based on optimal quantization parameters to obtain a digital bit stream, the digital bit stream is passed through a digital channel encoder to obtain a digital channel encoded signal, and the enhancement layer analog The encoding process is as follows: the digital bit stream is passed through the video decoder to obtain the reconstructed digitally encoded video, the difference between the original video signal and the reconstructed digitally encoded video is obtained to obtain a residual signal, and the residual signal is passed through the analog encoder to obtain an analog encoded signal; The step S3 includes: sending a channel sounding frame to a receiving end according to a preset temporary information rate, and instructing the receiving end to determine a first signal-to-noise ratio for receiving the channel sounding frame, where the channel sounding frame includes transmission power; Obtain a response frame sent by the receiving end at the temporary information rate, where the response frame includes the first signal-to-noise ratio; determine a second signal-to-noise ratio for receiving the response frame; When the second signal-to-noise ratio is not less than a preset threshold, the temporary information rate is used as the target information rate; After the sending the channel sounding frame to the receiving end according to the preset temporary information rate, the method further includes: when the response frame sent by the receiving end is not received within the preset time period, repeating the updating of the temporary information rate until Receive the response frame sent by the receiving end; the updating the temporary information rate includes: reducing the temporary information rate, and using the reduced temporary information rate as a new temporary information rate; In the step S5, during the video signal transmission process, a linear function relationship between the block variance of the sub-blocks after the residual signal is divided and the quantization parameter is also established, and the corresponding establishment process is: S51. within the set quantization parameter value range, select the highest value QP _min and the lowest value QP _max ; S52. Divide the original video signal into multiple groups of pictures GoP, and obtain residual signal data corresponding to QP _min and QP _max from each GoP; S53. respectively carry out 3-dimensional DCT transformation to the residual signal data of the two groups obtained in step S52., divide the DCT coefficients obtained by the 3-dimensional DCT transformation into blocks, and obtain the block variance of each sub-block after the block, represented by λ _i block variance of the i-th subblock; S54. Use the linear function lnλ _i = _ki ·QP+w _i to represent the curve of lnλ _i changing with QP, we can get:

In the formula,

and

represents the block variance of the ith sub-block under QP _min and QP _max , and _ki and _wi are the curve parameters corresponding to the ith sub-block; S55. For each sub-block in a GoP, a set of k _i and w _i are obtained correspondingly, then for any given value of a quantization parameter QP, the block variance λ of the i-th sub-block under the quantization parameter QP can be obtained _{i_QP} is: λ _{i_QP} =exp(k _i ·QP+ _wi ). 2. method as claimed in claim 1, in described step S5, also comprise the process of video signal reconstruction: The information frame received by the receiving end obtains the reconstructed digital channel coded signal through the digital channel decoder, obtains the reconstructed digital bit stream from the reconstructed digital channel coded signal, and obtains the reconstructed digital bit stream through the digital source decoder. digitally encoded video; The information frame received by the receiving end and the reconstructed digital channel coded signal are calculated to obtain a disturbed analog coded signal, and the disturbed analog coded signal obtains a reconstructed residual signal through an analog decoder; The reconstructed digitally encoded video is superimposed with the reconstructed residual signal to obtain a reconstructed original video signal. 3. The method of claim 2, wherein the digital channel decoder reconstructs the digital channel coded signal by: Create an ION shared memory containing the file identifier through the digital channel management function; Build a private handle structure object according to the file identifier and create a receiver window buffer according to the private handle structure object and the ION shared memory; When the receiving end receives the information frame, the data packet in the information frame is filled into the window buffer of the receiving end; The private handle structure object corresponding to the receiver window buffer filled by the data packet is delivered to a video library; The video library accesses the data packet in the receiver window buffer according to the received private handle structure object corresponding to the receiver window buffer, and performs decoding.

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