WO2012010041A1

WO2012010041A1 - Method and system for evaluating video coding performance

Info

Publication number: WO2012010041A1
Application number: PCT/CN2011/076353
Authority: WO
Inventors: 舒倩
Original assignee: 深圳市融创天下科技股份有限公司
Priority date: 2010-07-21
Filing date: 2011-06-25
Publication date: 2012-01-26
Also published as: CN101895788A; CN101895788B; HK1149408A1

Abstract

A method for evaluating video coding performance is disclosed in the present invention. The method comprises the following steps: determining that a relative error between an actual output bit rate of an encoder to be evaluated and an object bit rate is within a given range; obtaining a maximum window bit rate; obtaining an image quality index Peak Signal to Noise Rate (PSNR), i.e. PSNR-Y, PSNR-U, PSNR-V; according to values of the maximum window bit rate and the PSNR, constituting a conditional rate distortion curve graph to obtain video coding performance of the encoder. In the present invention, video compression performance and adaptability performance for network transmission of different coding techniques can be obtained via the conditional rate distortion curve graph. Network transmission performance of the encoder can also be obtained by comparing maximum window bit rate of the encoder in the case of the same PSNR value. And compression performance on the objective image quality of the encoder can be obtained by comparing the PSNR value in the case of the same maximum window bit rate.

Description

Video coding performance evaluation method and system

Technical field

The present invention relates to the field of video coding technologies, and in particular, to a video coding performance evaluation method. Background technique

The pros and cons of a video coding technique mainly depends on video compression performance and adaptability to network transmission. The video compression performance of the coding technology determines the quality of the video image after its compression processing, and the adaptability to the network transmission determines whether the compressed video code stream can be stably transmitted in the network, and the code stream is received. Whether the terminal will often get into the buffer.

On the one hand, the evaluation of video quality, the current mainstream evaluation method, is that the utilization distortion performance objectively measures the distortion of the encoded image relative to the original image, thereby obtaining the compression performance of the encoder. This is usually analyzed by signal to noise ratio data. On the other hand, the rate fluctuation characteristics are mainly used to measure the transmission performance of the encoder, that is, the adaptability of the video encoder to the network transmission, which is especially important for the mobile channel. Mobile channels have resource-limited, error-prone characteristics. The code stream output by the encoder, if the fluctuation characteristics are obvious, will cause the terminal player to frequently become buffered.

The current conventional evaluation method is to use the above two methods to evaluate the video compression performance and the adaptability to network transmission. As a result, in the need to comprehensively evaluate the coding technology at the comprehensive level of the above two performances, it is in a difficult situation.

Summary of the invention

The purpose of the embodiments of the present invention is to provide a video coding performance evaluation method, which aims to solve the problem that the prior art video coding performance evaluation method cannot comprehensively evaluate video compression performance and adaptability to network transmission.

The method of the embodiment of the invention is implemented as follows:

Get the maximum window bit rate; Obtaining an image quality indicator PSNR; constructing a condition rate distortion graph according to the maximum window bit rate and the image quality indicator PSNR, and obtaining a video encoding performance of the encoder.

Another object of the embodiments of the present invention is to provide a video coding performance evaluation system. The system shown includes:

a maximum window acquisition module, configured to obtain a maximum window bit rate;

An image quality indicator obtaining module, configured to obtain an image quality indicator PSNR; an image quality evaluation module, configured to use the maximum window bit rate and the image quality indicator

The PSNR value constructs a conditional rate distortion graph to obtain the video compression performance of different coding techniques and the adaptability to network transmission. By comparing the maximum window bit rate of the encoder under the equal image quality index PSNR value, the network transmission of the encoder is obtained. Performance, and/or by comparing the value of the image quality indicator PSNR at the same maximum window bit rate, the compression performance of the encoder on the objective quality of the image is obtained.

Advantageous Effects of the Invention: According to the conditional rate distortion graph constructed by the maximum window bit rate and the image quality index PSNR value as the abscissa and the ordinate, the video compression performance of different coding techniques and the adaptability to network transmission can be obtained. Acquiring the network transmission performance of the encoder by comparing the maximum window bit rate of the encoder under the equal image quality indicator PSNR value, and/or obtaining the encoding by comparing the value of the image quality index PSNR at the same maximum window bit rate The compression performance of the object in the objective quality of the image.

DRAWINGS

1 is a flow chart of a preferred embodiment of a video coding performance evaluation method of the present invention;

2 is a graph showing a maximum window bit rate of different code streams obtained by different encoders and a condition rate distortion curve constructed by PSNR-Y for the first preferred embodiment of the video coding performance evaluation method of the present invention;

3 is a second preferred embodiment of the video coding performance evaluation method of the present invention for the same source, The maximum window bit rate of different code streams and the condition rate distortion curve constructed by PSNR-Y are obtained by different encoder codes;

4 is a schematic structural diagram of a preferred embodiment of a video coding performance evaluation system of the present invention; and FIG. 5 is a schematic structural diagram of a maximum window acquisition module in a preferred embodiment of the video coding performance evaluation system of the present invention.

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. For the convenience of description, only the parts related to the embodiments of the present invention are shown. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The invention obtains the video compression performance of different coding techniques and the adaptability to network transmission according to the conditional rate distortion graph of the maximum window bit rate and the PSNR value of the abscissa and the ordinate, and is used for comparing codes by equal PSNR values. The maximum window bit rate of the device, obtains the network transmission performance of the encoder, and is used to obtain the compression performance of the encoder on the objective quality of the image by comparing the value of PSNR at the same maximum window bit rate.

Embodiment 1 The condition rate distortion performance proposed by the embodiment of the present invention uses a peak signal to noise ratio (PSNR) on the one hand.

Signal to Noise Ratio) to indicate the distortion of the codec image and the original image, to measure the compression performance of the encoder in the objective quality of the video, and to replace the average bit rate in the conventional rate distortion performance with the maximum window bit rate. Evaluate the transmission performance of the encoder.

As shown in FIG. 1, a flowchart of a preferred embodiment of video coding performance evaluation of the present invention includes the following steps: S101. The encoder to be tested encodes and decodes the same source, and obtains the encoded code stream and the decoding sequence.

5102, determining, according to the code stream, whether the relative error between the actual output bit rate of the to-be-evaluated encoder and the target bit rate is within a specific range, if yes, proceeding to step S103, otherwise proceeding to step S106; considering the target bit rate and encoding of the encoding The actual output bit rate of the device is inconsistent. For equal performance testing, the relative error between the actual output bit rate and the target bit rate of all encoders is required to be within a certain range, namely:

Abs (bitrate _{i arg et} - bitrate _ac[ual ) / bitrate _{i arg et} * 100 % < Thres where Thres is the decision threshold, bitrate "_0" , is the target bit rate, is the actual output bit rate, Thres is the decision threshold, Determined by the required test accuracy, abs ^ borate _t _ bitrate _actual ) is the absolute value of bitmte _{t mg et} _ bitrate _actual .

Only when this condition is met can the substantive evaluation stage of the video condition rate distortion performance be entered.

5103, obtain the maximum window bit rate; because in the actual streaming media transmission, the client has a certain buffer duration (time window), that is, whether the client is buffered, depending on whether the maximum bit rate in the time window exceeds the actual transmission bandwidth. . The embodiment of the present invention proposes to measure the performance of the code rate fluctuation based on the time window in the actual transmission, and refers to the maximum average bit rate in the time window, which is called the maximum window bit rate MWBR. The maximum window bit rate is calculated as follows:

A): Determine the time window according to the client buffer duration in the actual transmission;

B): Calculate the average bit rate of the output in each time window as a data point (ie a window bit rate value);

0: Delete the maximum bit rate of the window, eliminating the accidental factor;

D): arranging the remaining window bit rate sequences in descending order, taking the average of the at least one window bit rate as the maximum window bit rate; 5104, obtaining image quality indicators PSNR, that is, PSNR-Y, PSNR_U, PSNR-V;

5105. Construct a condition rate distortion graph according to the maximum window bit rate and the PSNR value, and obtain the video coding performance of the encoder, END.

The conditional rate distortion curve is plotted with the maximum window bit rate MWBR as the abscissa and PSNR as the ordinate, and the image quality is compared according to the graph. The different performance curves of different encoders, the higher the curve position, the better the performance of the coding technique corresponding to the curve in the image quality quality compression and network transmission; the same image quality (PSNR values are equal), comparison The maximum window bit rate of different encoders, the lower the maximum window bit rate, the better the network transmission performance of the encoder; the same maximum window bit rate (ie the same network transmission performance), the higher the PSNR value, the encoder compression The higher the objective quality of the image.

5106, modifying the target bit rate, proceeding to step S101. FIG. 2 is a maximum window bit rate and PSNR of different code streams obtained by different encoder encodings by the first preferred embodiment of the video coding performance evaluation method of the present invention. The condition rate distortion curve constructed by Y, where two solid lines are conditional rate distortion curves of two encoders, and the dashed line is a single-sex performance comparison auxiliary line.

The corresponding curve of the encoder 1 is higher than the curve corresponding to the encoder 2, that is, the encoder 1 is superior to the encoder 2 in the comprehensive index of the objective quality of the image and the network transmission;

Network transmission performance comparison under the same image quality: When the PSNR-Y of the two encoders is equal, the maximum window bit rate of the encoder 1 is smaller than the maximum window bit rate of the encoder 2, that is, under the same image quality, the encoder 1 is encoded. 2 has better network transmission performance;

3 is a second preferred embodiment of the video coding performance evaluation method of the present invention. For the same source, the maximum window bit rate of different code streams obtained by different encoders and the condition rate distortion curve constructed by PSNR-Y are shown. The solid line is the condition rate distortion curve of the two encoders, and the dashed line is the single sex performance comparison guide line. Under the same maximum window bit rate (as shown in Figure 3), the objective quality performance comparison of the image: When the maximum window bit rate of the two encoders is equal, the PSNR-Y of the encoder 1 is greater than the PSNR-Y of the encoder 2, ie At the same maximum window bit rate, the objective quality of the encoder 1 is superior to that of the encoder 2.

The embodiment of the invention provides a video coding performance evaluation method to comprehensively evaluate the compression performance and network transmission performance of the coding technology in the objective quality of the video. The embodiment of the present invention firstly establishes a condition rate distortion graph with a maximum window bit rate as an abscissa and a PSNR value as an ordinate, and then according to the graph, on the one hand, can obtain video compression performance of different coding technologies and network transmission. Adaptability, that is, the higher the curve, the better the performance of the corresponding coding technology; on the other hand, the comparison of individual performance can also be obtained: By comparing the maximum window bit rate of the encoder under the equal PSNR value, the network transmission performance of the encoder is obtained. By comparing the value of PSNR at the same maximum window bit rate, the compression performance of the encoder on the objective quality of the image is obtained. Embodiment 2

4 is a schematic structural diagram of a preferred embodiment of a video coding performance evaluation system according to the present invention. The system includes: a codec module, an average code rate determination module, a maximum window acquisition module, an image quality indicator acquisition module, and an image quality evaluation. Module.

a codec module, configured to encode and decode the same source and obtain the encoded code stream and the decoding sequence; and an average rate determining module, configured to determine, according to the code stream, an actual output bit rate and a target bit of the to-be-evaluated encoder Whether the relative error of the rate is within a specific range, wherein the specific range is:

Abs (bitrate _{t aig et} - bitrate _actual ) / bitrate _{t aig et} * 100 % < Thres where Thres is the decision threshold, bitrate _ot is the target bit rate, is the actual output bit rate, Thres is the decision threshold, which is required The accuracy of the test achieved is determined, abs "itrate _{t 3lg et} ~ bitrate , ) is the absolute value of bitrate _{t mg et} ~ titrate .

a target bit rate modification module, configured to modify the target bit rate such that a relative error between the actual output bit rate and the target bit rate is within the specific range;

a maximum window acquisition module for determining a maximum average bit rate in the time window (ie, a maximum window bit rate MWBR );

An image quality indicator obtaining module for obtaining an image quality index PSNR, that is, PSNR-Y, PSNR-U, PSNR-V;

An image quality evaluation module, configured to obtain video compression performance and adaptability to network transmission by using a condition rate distortion graph constructed with a maximum window bit rate, a PSNR value, and an ordinate, and is used to obtain different Coding technology Network transmission performance and video compression performance single-item performance comparison (that is, comparing the maximum window bit rate of the encoder under the equal PSNR value, obtaining the network transmission performance of the encoder, the lower the maximum window bit rate, the encoder network The better the transmission performance is; at the same maximum window bit rate, the value of PSNR is compared to obtain the compression performance of the encoder on the objective quality of the image. The higher the PSNR value, the better the compression performance of the encoder on the objective quality of the image).

Figure 5 is a block diagram showing the structure of a maximum window acquisition module in a preferred embodiment of the video coding performance evaluation system of the present invention. The maximum window acquisition module includes a time window determination module, a data point acquisition module, an accidental factor elimination module, and a maximum window selection module. The time window determining module is configured to determine a time window according to a client buffering duration in actual transmission; the data point obtaining module is configured to calculate an output average bit rate in each time window as a data point (ie, a window bit The accidental factor elimination module is configured to delete the window bit rate maximum value and eliminate the accidental factor; the maximum window selection module is configured to arrange the remaining window bit rate sequences in descending order, and take the average value of the at least one window bit rate as Maximum window bit rate.

The embodiment of the present invention obtains a comprehensive evaluation of video coding performance and adaptability to network transmission by using a condition rate distortion graph according to a maximum window bit rate and a PSNR value of an abscissa and an ordinate, and is used for Comparing the maximum window bit rate of the encoder with equal PSNR values, Get the network transmission performance of the encoder, and use it to compare at the same maximum window bit rate

The value of PSNR, the compression performance of the encoder on the objective quality of the image.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims

Rights request

A video coding performance evaluation method, characterized in that the method comprises the following steps: obtaining a maximum window bit rate;

Acquiring an image quality indicator PSNR; constructing a condition rate distortion graph according to the maximum window bit rate and the image quality indicator PSNR, and obtaining a video encoding performance of the encoder.

2. The video coding performance evaluation method according to claim 1, wherein the step of: "acquiring the maximum window bit rate" further comprises the steps of: determining that the relative error between the actual output bit rate of the encoder to be evaluated and the target bit rate is specific Within the scope.

3. The video coding performance evaluation method according to claim 1, wherein the step further comprises the step of: determining that the relative error between the actual output bit rate of the encoder to be evaluated and the target bit rate is within a specific range: The evaluation encoder encodes and decodes the same source to obtain the encoded code stream and the decoding sequence.

4. The video coding performance evaluation method according to claim 2 or 3, wherein the specific range is:

Abs (bitrate _{t 3Ig et} — bitrate _actual ) / bitrate _{t 3Ig et} * 100 % < Thres where Thres is the decision threshold, bitrate „, is the target bit rate, bitrate is the actual output bit rate, Thres is the decision threshold, abs ( _{Toraie t} ^ _et ~ bitrate _actual ) is the absolute value of bitmte - bitmte _actual .

5. The video coding performance evaluation method according to claim 1, wherein the obtaining The method for maximizing the window bit rate specifically includes: determining a time window according to a client buffer duration of the actual transmission;

Calculating an output average bit rate within each time window as a window bit rate value;

Delete the maximum bit rate of the window;

The remaining window bit rate sequences are arranged in descending order, and the average of the at least one window bit rate is taken as the maximum window bit rate.

The video coding performance evaluation method according to claim 1, wherein the step of: constructing a condition rate distortion graph according to a maximum window bit rate and the image quality indicator PSNR value, and acquiring a video coding of the encoder "Performance" includes: obtaining video compression performance and adaptability to network transmission according to the condition rate distortion graph; obtaining the coding by comparing the maximum window bit rate of the encoder under the equal image quality index PSNR value The network transmission performance of the device, and / or by comparing the value of the image quality indicator PSNR at the same maximum window bit rate, to obtain the compression performance of the encoder on the objective quality of the image.

7. A video coding performance evaluation system, characterized in that the system shown comprises:

An image quality indicator obtaining module, configured to obtain an image quality indicator PSNR; an image quality evaluation module, configured to construct a condition rate distortion graph according to the maximum window bit rate and the image quality indicator PSNR value, and obtain video compression of different encoding technologies Performance and adaptability to network transmission; Compare the encoder's network transmission performance by comparing the encoder's maximum window bit rate at equal image quality indicator PSNR values, and/or compare images by the same maximum window bit rate The value of the quality indicator PSNR, which obtains the compression performance of the encoder on the objective quality of the image.

8. The video coding performance evaluation system of claim 7, wherein the system is further Includes:

The average rate decision module is connected to the maximum window acquisition module for determining whether the relative error between the actual output bit rate of the encoder to be tested and the target bit rate is within a specific range.

9. The video coding performance evaluation system of claim 7, wherein the system further comprises: a target bit rate modification module coupled to the average rate decision module for modifying the target bit rate to enable The relative error between the actual output bit rate and the target bit rate is within the specific range.

10. The video coding performance evaluation system of claim 7, wherein the system further comprises:

The codec module is connected to the average rate decision module and the target bit rate modification module, and is configured to encode and decode the same source and obtain the encoded code stream and the decoding sequence.

The video coding performance evaluation system of claim 7, wherein the maximum window acquisition module comprises:

a time window determining module, configured to determine a time window according to a client buffering duration of the actual transmission; a data point obtaining module, configured to calculate an output average bit rate in each time window as a window bit rate value;

An accidental factor elimination module for deleting a window bit rate maximum;

The maximum window selection module is configured to sort the remaining window bit rate sequences in descending order, and take the average of the at least one window bit rate as the maximum window bit rate.

12. The video coding performance evaluation system of claim 7, wherein the specific range is:

Abs (bitrate _{t aig et} - bitrate _actual ) / bitrate _{t aig et} * 100 % < Thres where Thres is the decision threshold, bitrate _ot is the target bit rate, is the actual output bit rate, Thres is the decision threshold, abs ( _toraie — Bitrate _actual ) is the absolute value of bitmte - bitmte _actual .